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-rwxr-xr-x.ci/scripts/test_export_data_command.sh2
-rwxr-xr-x.ci/scripts/test_synapse_port_db.sh2
-rw-r--r--.github/PULL_REQUEST_TEMPLATE.md9
-rw-r--r--CHANGES.md110
-rw-r--r--contrib/purge_api/purge_history.sh6
-rwxr-xr-xdebian/build_virtualenv11
-rw-r--r--debian/changelog26
-rw-r--r--debian/control2
-rwxr-xr-xdebian/matrix-synapse-py3.config1
-rw-r--r--debian/matrix-synapse-py3.postinst1
-rw-r--r--debian/matrix-synapse.service2
-rw-r--r--debian/test/.gitignore2
-rw-r--r--debian/test/provision.sh23
-rw-r--r--debian/test/stretch/Vagrantfile13
-rw-r--r--debian/test/xenial/Vagrantfile10
-rwxr-xr-xdemo/clean.sh8
-rwxr-xr-xdemo/start.sh154
-rwxr-xr-xdemo/stop.sh2
-rw-r--r--docker/README.md13
-rw-r--r--docker/build_debian.sh4
-rwxr-xr-xdocker/start.py37
-rw-r--r--docs/CAPTCHA_SETUP.md4
-rw-r--r--docs/SUMMARY.md1
-rw-r--r--docs/admin_api/event_reports.md4
-rw-r--r--docs/admin_api/purge_history_api.md2
-rw-r--r--docs/admin_api/room_membership.md2
-rw-r--r--docs/admin_api/rooms.md31
-rw-r--r--docs/code_style.md78
-rw-r--r--docs/consent_tracking.md2
-rw-r--r--docs/delegate.md82
-rw-r--r--docs/development/cas.md8
-rw-r--r--docs/development/contributing_guide.md11
-rw-r--r--docs/development/database_schema.md4
-rw-r--r--docs/development/saml.md2
-rw-r--r--docs/message_retention_policies.md26
-rw-r--r--docs/modules/password_auth_provider_callbacks.md4
-rw-r--r--docs/modules/spam_checker_callbacks.md36
-rw-r--r--docs/modules/third_party_rules_callbacks.md29
-rw-r--r--docs/openid.md72
-rw-r--r--docs/postgres.md50
-rw-r--r--docs/reverse_proxy.md8
-rw-r--r--docs/sample_config.yaml31
-rw-r--r--docs/setup/installation.md14
-rw-r--r--docs/synctl_workers.md8
-rw-r--r--docs/systemd-with-workers/system/matrix-synapse-worker@.service2
-rw-r--r--docs/systemd-with-workers/system/matrix-synapse.service2
-rw-r--r--docs/turn-howto.md70
-rw-r--r--docs/upgrade.md127
-rw-r--r--docs/usage/administration/admin_api/background_updates.md84
-rw-r--r--docs/workers.md18
-rw-r--r--mypy.ini21
-rwxr-xr-xscripts-dev/check-newsfragment6
-rwxr-xr-xscripts-dev/check_line_terminators.sh2
-rwxr-xr-xscripts-dev/complement.sh6
-rwxr-xr-xscripts-dev/config-lint.sh2
-rwxr-xr-xscripts-dev/docker_update_debian_changelog.sh2
-rwxr-xr-xscripts-dev/generate_sample_config2
-rwxr-xr-xscripts-dev/next_github_number.sh2
-rwxr-xr-xscripts/synapse_port_db2
-rwxr-xr-xsetup.py3
-rw-r--r--synapse/__init__.py2
-rw-r--r--synapse/_scripts/review_recent_signups.py9
-rw-r--r--synapse/api/errors.py7
-rw-r--r--synapse/api/filtering.py139
-rw-r--r--synapse/api/urls.py3
-rw-r--r--synapse/app/_base.py5
-rw-r--r--synapse/app/admin_cmd.py14
-rw-r--r--synapse/app/generic_worker.py3
-rw-r--r--synapse/app/homeserver.py4
-rw-r--r--synapse/config/account_validity.py4
-rw-r--r--synapse/config/cas.py10
-rw-r--r--synapse/config/emailconfig.py8
-rw-r--r--synapse/config/oidc.py2
-rw-r--r--synapse/config/registration.py15
-rw-r--r--synapse/config/saml2.py5
-rw-r--r--synapse/config/server.py64
-rw-r--r--synapse/config/sso.py18
-rw-r--r--synapse/config/workers.py18
-rw-r--r--synapse/crypto/keyring.py74
-rw-r--r--synapse/events/__init__.py227
-rw-r--r--synapse/events/third_party_rules.py40
-rw-r--r--synapse/events/validator.py2
-rw-r--r--synapse/federation/federation_client.py17
-rw-r--r--synapse/federation/federation_server.py19
-rw-r--r--synapse/federation/sender/transaction_manager.py1
-rw-r--r--synapse/federation/transport/client.py25
-rw-r--r--synapse/handlers/admin.py22
-rw-r--r--synapse/handlers/appservice.py91
-rw-r--r--synapse/handlers/auth.py4
-rw-r--r--synapse/handlers/directory.py2
-rw-r--r--synapse/handlers/e2e_keys.py211
-rw-r--r--synapse/handlers/federation_event.py6
-rw-r--r--synapse/handlers/identity.py6
-rw-r--r--synapse/handlers/message.py23
-rw-r--r--synapse/handlers/pagination.py2
-rw-r--r--synapse/handlers/presence.py2
-rw-r--r--synapse/handlers/profile.py4
-rw-r--r--synapse/handlers/room.py4
-rw-r--r--synapse/handlers/room_batch.py2
-rw-r--r--synapse/handlers/room_member.py4
-rw-r--r--synapse/handlers/search.py12
-rw-r--r--synapse/handlers/typing.py6
-rw-r--r--synapse/http/connectproxyclient.py12
-rw-r--r--synapse/http/request_metrics.py50
-rw-r--r--synapse/logging/context.py4
-rw-r--r--synapse/logging/utils.py8
-rw-r--r--synapse/metrics/__init__.py51
-rw-r--r--synapse/module_api/__init__.py149
-rw-r--r--synapse/notifier.py55
-rw-r--r--synapse/push/bulk_push_rule_evaluator.py4
-rw-r--r--synapse/push/push_rule_evaluator.py10
-rw-r--r--synapse/replication/tcp/client.py3
-rw-r--r--synapse/replication/tcp/handler.py2
-rw-r--r--synapse/replication/tcp/streams/_base.py3
-rw-r--r--synapse/rest/admin/__init__.py8
-rw-r--r--synapse/rest/admin/background_updates.py107
-rw-r--r--synapse/rest/admin/rooms.py141
-rw-r--r--synapse/rest/client/receipts.py12
-rw-r--r--synapse/rest/client/room.py2
-rw-r--r--synapse/rest/client/room_batch.py33
-rw-r--r--synapse/rest/client/versions.py1
-rw-r--r--synapse/rest/media/v1/media_repository.py12
-rw-r--r--synapse/rest/media/v1/upload_resource.py2
-rw-r--r--synapse/rest/well_known.py50
-rw-r--r--synapse/server.py4
-rw-r--r--synapse/state/__init__.py7
-rw-r--r--synapse/storage/background_updates.py65
-rw-r--r--synapse/storage/database.py11
-rw-r--r--synapse/storage/databases/main/deviceinbox.py189
-rw-r--r--synapse/storage/databases/main/devices.py39
-rw-r--r--synapse/storage/databases/main/events.py7
-rw-r--r--synapse/storage/databases/main/events_worker.py56
-rw-r--r--synapse/storage/databases/main/group_server.py17
-rw-r--r--synapse/storage/databases/main/lock.py31
-rw-r--r--synapse/storage/databases/main/presence.py2
-rw-r--r--synapse/storage/databases/main/profile.py2
-rw-r--r--synapse/storage/databases/main/relations.py38
-rw-r--r--synapse/storage/databases/main/room.py29
-rw-r--r--synapse/storage/databases/main/room_batch.py2
-rw-r--r--synapse/storage/databases/main/roommember.py8
-rw-r--r--synapse/storage/prepare_database.py27
-rw-r--r--synapse/storage/schema/main/delta/65/03remove_hidden_devices_from_device_inbox.sql22
-rw-r--r--synapse/storage/schema/main/delta/65/04_local_group_updates.sql18
-rw-r--r--synapse/storage/schema/main/delta/65/06remove_deleted_devices_from_device_inbox.sql34
-rw-r--r--synapse/util/async_helpers.py34
-rw-r--r--sytest-blacklist3
-rw-r--r--tests/crypto/test_keyring.py12
-rw-r--r--tests/handlers/test_admin.py35
-rw-r--r--tests/handlers/test_appservice.py51
-rw-r--r--tests/handlers/test_device.py31
-rw-r--r--tests/handlers/test_e2e_keys.py151
-rw-r--r--tests/module_api/test_api.py152
-rw-r--r--tests/push/test_email.py2
-rw-r--r--tests/rest/admin/test_background_updates.py218
-rw-r--r--tests/rest/admin/test_room.py131
-rw-r--r--tests/rest/client/test_consent.py1
-rw-r--r--tests/rest/client/test_register.py1
-rw-r--r--tests/rest/client/test_sync.py30
-rw-r--r--tests/rest/client/test_third_party_rules.py109
-rw-r--r--tests/rest/client/utils.py29
-rw-r--r--tests/rest/media/v1/test_media_storage.py18
-rw-r--r--tests/rest/test_well_known.py32
-rw-r--r--tests/storage/databases/main/test_deviceinbox.py164
-rw-r--r--tests/storage/test_client_ips.py206
-rw-r--r--tests/storage/test_rollback_worker.py119
-rw-r--r--tests/util/caches/test_deferred_cache.py4
-rw-r--r--tests/util/caches/test_descriptors.py43
-rw-r--r--tests/util/test_async_helpers.py (renamed from tests/util/test_async_utils.py)69
168 files changed, 4113 insertions, 1293 deletions
diff --git a/.ci/scripts/test_export_data_command.sh b/.ci/scripts/test_export_data_command.sh
index 75f5811d10..ab96387a0a 100755
--- a/.ci/scripts/test_export_data_command.sh
+++ b/.ci/scripts/test_export_data_command.sh
@@ -3,7 +3,7 @@
 # Test for the export-data admin command against sqlite and postgres
 
 set -xe
-cd `dirname $0`/../..
+cd "$(dirname "$0")/../.."
 
 echo "--- Install dependencies"
 
diff --git a/.ci/scripts/test_synapse_port_db.sh b/.ci/scripts/test_synapse_port_db.sh
index 50115b3079..797904e64c 100755
--- a/.ci/scripts/test_synapse_port_db.sh
+++ b/.ci/scripts/test_synapse_port_db.sh
@@ -7,7 +7,7 @@
 
 
 set -xe
-cd `dirname $0`/../..
+cd "$(dirname "$0")/../.."
 
 echo "--- Install dependencies"
 
diff --git a/.github/PULL_REQUEST_TEMPLATE.md b/.github/PULL_REQUEST_TEMPLATE.md
index fc22d89426..6c3a998499 100644
--- a/.github/PULL_REQUEST_TEMPLATE.md
+++ b/.github/PULL_REQUEST_TEMPLATE.md
@@ -1,12 +1,13 @@
 ### Pull Request Checklist
 
-<!-- Please read CONTRIBUTING.md before submitting your pull request -->
+<!-- Please read https://matrix-org.github.io/synapse/latest/development/contributing_guide.html before submitting your pull request -->
 
 * [ ] Pull request is based on the develop branch
-* [ ] Pull request includes a [changelog file](https://github.com/matrix-org/synapse/blob/master/CONTRIBUTING.md#changelog). The entry should:
+* [ ] Pull request includes a [changelog file](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#changelog). The entry should:
   - Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
   - Use markdown where necessary, mostly for `code blocks`.
   - End with either a period (.) or an exclamation mark (!).
   - Start with a capital letter.
-* [ ] Pull request includes a [sign off](https://github.com/matrix-org/synapse/blob/master/CONTRIBUTING.md#sign-off)
-* [ ] Code style is correct (run the [linters](https://github.com/matrix-org/synapse/blob/master/CONTRIBUTING.md#code-style))
+* [ ] Pull request includes a [sign off](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#sign-off)
+* [ ] [Code style](https://matrix-org.github.io/synapse/latest/code_style.html) is correct
+  (run the [linters](https://matrix-org.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))
diff --git a/CHANGES.md b/CHANGES.md
index e74544f489..a435d9c592 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,113 @@
+Synapse 1.47.0 (2021-11-17)
+===========================
+
+No significant changes since 1.47.0rc3.
+
+
+Synapse 1.47.0rc3 (2021-11-16)
+==============================
+
+Bugfixes
+--------
+
+- Fix a bug introduced in 1.47.0rc1 which caused worker processes to not halt startup in the presence of outstanding database migrations. ([\#11346](https://github.com/matrix-org/synapse/issues/11346))
+- Fix a bug introduced in 1.47.0rc1 which prevented the 'remove deleted devices from `device_inbox` column' background process from running when updating from a recent Synapse version. ([\#11303](https://github.com/matrix-org/synapse/issues/11303), [\#11353](https://github.com/matrix-org/synapse/issues/11353))
+
+
+Synapse 1.47.0rc2 (2021-11-10)
+==============================
+
+This fixes an issue with publishing the Debian packages for 1.47.0rc1.
+It is otherwise identical to 1.47.0rc1.
+
+
+Synapse 1.47.0rc1 (2021-11-09)
+==============================
+
+Deprecations and Removals
+-------------------------
+
+- The `user_may_create_room_with_invites` module callback is now deprecated. Please refer to the [upgrade notes](https://matrix-org.github.io/synapse/develop/upgrade#upgrading-to-v1470) for more information. ([\#11206](https://github.com/matrix-org/synapse/issues/11206))
+- Remove deprecated admin API to delete rooms (`POST /_synapse/admin/v1/rooms/<room_id>/delete`). ([\#11213](https://github.com/matrix-org/synapse/issues/11213))
+
+
+Features
+--------
+
+- Advertise support for Client-Server API r0.6.1. ([\#11097](https://github.com/matrix-org/synapse/issues/11097))
+- Add search by room ID and room alias to the List Room admin API. ([\#11099](https://github.com/matrix-org/synapse/issues/11099))
+- Add an `on_new_event` third-party rules callback to allow Synapse modules to act after an event has been sent into a room. ([\#11126](https://github.com/matrix-org/synapse/issues/11126))
+- Add a module API method to update a user's membership in a room. ([\#11147](https://github.com/matrix-org/synapse/issues/11147))
+- Add metrics for thread pool usage. ([\#11178](https://github.com/matrix-org/synapse/issues/11178))
+- Support the stable room type field for [MSC3288](https://github.com/matrix-org/matrix-doc/pull/3288). ([\#11187](https://github.com/matrix-org/synapse/issues/11187))
+- Add a module API method to retrieve the current state of a room. ([\#11204](https://github.com/matrix-org/synapse/issues/11204))
+- Calculate a default value for `public_baseurl` based on `server_name`. ([\#11210](https://github.com/matrix-org/synapse/issues/11210))
+- Add support for serving `/.well-known/matrix/server` files, to redirect federation traffic to port 443. ([\#11211](https://github.com/matrix-org/synapse/issues/11211))
+- Add admin APIs to pause, start and check the status of background updates. ([\#11263](https://github.com/matrix-org/synapse/issues/11263))
+
+
+Bugfixes
+--------
+
+- Fix a long-standing bug which allowed hidden devices to receive to-device messages, resulting in unnecessary database bloat. ([\#10097](https://github.com/matrix-org/synapse/issues/10097))
+- Fix a long-standing bug where messages in the `device_inbox` table for deleted devices would persist indefinitely. Contributed by @dklimpel and @JohannesKleine. ([\#10969](https://github.com/matrix-org/synapse/issues/10969), [\#11212](https://github.com/matrix-org/synapse/issues/11212))
+- Do not accept events if a third-party rule `check_event_allowed` callback raises an exception. ([\#11033](https://github.com/matrix-org/synapse/issues/11033))
+- Fix long-standing bug where verification requests could fail in certain cases if a federation whitelist was in place but did not include your own homeserver. ([\#11129](https://github.com/matrix-org/synapse/issues/11129))
+- Allow an empty list of `state_events_at_start` to be sent when using the [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) `/batch_send` endpoint and the author of the historical messages is already part of the current room state at the given `?prev_event_id`. ([\#11188](https://github.com/matrix-org/synapse/issues/11188))
+- Fix a bug introduced in Synapse 1.45.0 which prevented the `synapse_review_recent_signups` script from running. Contributed by @samuel-p. ([\#11191](https://github.com/matrix-org/synapse/issues/11191))
+- Delete `to_device` messages for hidden devices that will never be read, reducing database size. ([\#11199](https://github.com/matrix-org/synapse/issues/11199))
+- Fix a long-standing bug wherein a missing `Content-Type` header when downloading remote media would cause Synapse to throw an error. ([\#11200](https://github.com/matrix-org/synapse/issues/11200))
+- Fix a long-standing bug which could result in serialization errors and potentially duplicate transaction data when sending ephemeral events to application services. Contributed by @Fizzadar at Beeper. ([\#11207](https://github.com/matrix-org/synapse/issues/11207))
+- Fix a bug introduced in Synapse 1.35.0 which made it impossible to join rooms that return a `send_join` response containing floats. ([\#11217](https://github.com/matrix-org/synapse/issues/11217))
+- Fix long-standing bug where cross signing keys were not included in the response to `/r0/keys/query` the first time a remote user was queried. ([\#11234](https://github.com/matrix-org/synapse/issues/11234))
+- Fix a long-standing bug where all requests that read events from the database could get stuck as a result of losing the database connection. ([\#11240](https://github.com/matrix-org/synapse/issues/11240))
+- Fix a bug preventing Synapse from being rolled back to an earlier version when using workers. ([\#11255](https://github.com/matrix-org/synapse/issues/11255), [\#11276](https://github.com/matrix-org/synapse/issues/11276))
+- Fix a bug introduced in Synapse 1.37.1 which caused a remote event being processed by a worker to not get processed on restart if the worker was killed. ([\#11262](https://github.com/matrix-org/synapse/issues/11262))
+- Only allow old Element/Riot Android clients to send read receipts without a request body. All other clients must include a request body as required by the specification. Contributed by @rogersheu. ([\#11157](https://github.com/matrix-org/synapse/issues/11157))
+
+
+Updates to the Docker image
+---------------------------
+
+- Avoid changing user ID when started as a non-root user, and no explicit `UID` is set. ([\#11209](https://github.com/matrix-org/synapse/issues/11209))
+
+
+Improved Documentation
+----------------------
+
+- Improve example HAProxy config in the docs to properly handle HTTP `Host` headers with port information. This is required for federation over port 443 to work correctly. ([\#11128](https://github.com/matrix-org/synapse/issues/11128))
+- Add documentation for using Authentik as an OpenID Connect Identity Provider. Contributed by @samip5. ([\#11151](https://github.com/matrix-org/synapse/issues/11151))
+- Clarify lack of support for Windows. ([\#11198](https://github.com/matrix-org/synapse/issues/11198))
+- Improve code formatting and fix a few typos in docs. Contributed by @sumnerevans at Beeper. ([\#11221](https://github.com/matrix-org/synapse/issues/11221))
+- Add documentation for using LemonLDAP as an OpenID Connect Identity Provider. Contributed by @l00ptr. ([\#11257](https://github.com/matrix-org/synapse/issues/11257))
+
+
+Internal Changes
+----------------
+
+- Add type annotations for the `log_function` decorator. ([\#10943](https://github.com/matrix-org/synapse/issues/10943))
+- Add type hints to `synapse.events`. ([\#11098](https://github.com/matrix-org/synapse/issues/11098))
+- Remove and document unnecessary `RoomStreamToken` checks in application service ephemeral event code. ([\#11137](https://github.com/matrix-org/synapse/issues/11137))
+- Add type hints so that `synapse.http` passes `mypy` checks. ([\#11164](https://github.com/matrix-org/synapse/issues/11164))
+- Update scripts to pass Shellcheck lints. ([\#11166](https://github.com/matrix-org/synapse/issues/11166))
+- Add knock information in admin export. Contributed by Rafael Gonçalves. ([\#11171](https://github.com/matrix-org/synapse/issues/11171))
+- Add tests to check that `ClientIpStore.get_last_client_ip_by_device` and `get_user_ip_and_agents` combine database and in-memory data correctly. ([\#11179](https://github.com/matrix-org/synapse/issues/11179))
+- Refactor `Filter` to check different fields depending on the data type. ([\#11194](https://github.com/matrix-org/synapse/issues/11194))
+- Improve type hints for the relations datastore. ([\#11205](https://github.com/matrix-org/synapse/issues/11205))
+- Replace outdated links in the pull request checklist with links to the rendered documentation. ([\#11225](https://github.com/matrix-org/synapse/issues/11225))
+- Fix a bug in unit test `test_block_room_and_not_purge`. ([\#11226](https://github.com/matrix-org/synapse/issues/11226))
+- In `ObservableDeferred`, run observers in the order they were registered. ([\#11229](https://github.com/matrix-org/synapse/issues/11229))
+- Minor speed up to start up times and getting updates for groups by adding missing index to `local_group_updates.stream_id`. ([\#11231](https://github.com/matrix-org/synapse/issues/11231))
+- Add `twine` and `towncrier` as dev dependencies, as they're used by the release script. ([\#11233](https://github.com/matrix-org/synapse/issues/11233))
+- Allow `stream_writers.typing` config to be a list of one worker. ([\#11237](https://github.com/matrix-org/synapse/issues/11237))
+- Remove debugging statement in tests. ([\#11239](https://github.com/matrix-org/synapse/issues/11239))
+- Fix [MSC2716](https://github.com/matrix-org/matrix-doc/pull/2716) historical messages backfilling in random order on remote homeservers. ([\#11244](https://github.com/matrix-org/synapse/issues/11244))
+- Add an additional test for the `cachedList` method decorator. ([\#11246](https://github.com/matrix-org/synapse/issues/11246))
+- Make minor correction to the type of `auth_checkers` callbacks. ([\#11253](https://github.com/matrix-org/synapse/issues/11253))
+- Clean up trivial aspects of the Debian package build tooling. ([\#11269](https://github.com/matrix-org/synapse/issues/11269), [\#11273](https://github.com/matrix-org/synapse/issues/11273))
+- Blacklist new SyTest that checks that key uploads are valid pending the validation being implemented in Synapse. ([\#11270](https://github.com/matrix-org/synapse/issues/11270))
+
+
 Synapse 1.46.0 (2021-11-02)
 ===========================
 
diff --git a/contrib/purge_api/purge_history.sh b/contrib/purge_api/purge_history.sh
index 9d5324ea1c..de58dcdbb7 100644
--- a/contrib/purge_api/purge_history.sh
+++ b/contrib/purge_api/purge_history.sh
@@ -84,7 +84,9 @@ AUTH="Authorization: Bearer $TOKEN"
 ###################################################################################################
 # finally start pruning the room:
 ###################################################################################################
-POSTDATA='{"delete_local_events":"true"}' # this will really delete local events, so the messages in the room really disappear unless they are restored by remote federation
+# this will really delete local events, so the messages in the room really
+# disappear unless they are restored by remote federation. This is because
+# we pass {"delete_local_events":true} to the curl invocation below.
 
 for ROOM in "${ROOMS_ARRAY[@]}"; do
     echo "########################################### $(date) ################# "
@@ -104,7 +106,7 @@ for ROOM in "${ROOMS_ARRAY[@]}"; do
       SLEEP=2
       set -x
       # call purge
-      OUT=$(curl --header "$AUTH" -s -d $POSTDATA POST "$API_URL/admin/purge_history/$ROOM/$EVENT_ID")
+      OUT=$(curl --header "$AUTH" -s -d '{"delete_local_events":true}' POST "$API_URL/admin/purge_history/$ROOM/$EVENT_ID")
       PURGE_ID=$(echo "$OUT" |grep purge_id|cut -d'"' -f4 )
       if [ "$PURGE_ID" == "" ]; then
         # probably the history purge is already in progress for $ROOM
diff --git a/debian/build_virtualenv b/debian/build_virtualenv
index 801ecb9086..e691163619 100755
--- a/debian/build_virtualenv
+++ b/debian/build_virtualenv
@@ -15,7 +15,7 @@ export DH_VIRTUALENV_INSTALL_ROOT=/opt/venvs
 # python won't look in the right directory. At least this way, the error will
 # be a *bit* more obvious.
 #
-SNAKE=`readlink -e /usr/bin/python3`
+SNAKE=$(readlink -e /usr/bin/python3)
 
 # try to set the CFLAGS so any compiled C extensions are compiled with the most
 # generic as possible x64 instructions, so that compiling it on a new Intel chip
@@ -24,7 +24,7 @@ SNAKE=`readlink -e /usr/bin/python3`
 # TODO: add similar things for non-amd64, or figure out a more generic way to
 # do this.
 
-case `dpkg-architecture -q DEB_HOST_ARCH` in
+case $(dpkg-architecture -q DEB_HOST_ARCH) in
     amd64)
         export CFLAGS=-march=x86-64
         ;;
@@ -40,6 +40,7 @@ dh_virtualenv \
     --upgrade-pip \
     --preinstall="lxml" \
     --preinstall="mock" \
+    --preinstall="wheel" \
     --extra-pip-arg="--no-cache-dir" \
     --extra-pip-arg="--compile" \
     --extras="all,systemd,test"
@@ -56,8 +57,8 @@ case "$DEB_BUILD_OPTIONS" in
     *)
         # Copy tests to a temporary directory so that we can put them on the
         # PYTHONPATH without putting the uninstalled synapse on the pythonpath.
-        tmpdir=`mktemp -d`
-        trap "rm -r $tmpdir" EXIT
+        tmpdir=$(mktemp -d)
+        trap 'rm -r $tmpdir' EXIT
 
         cp -r tests "$tmpdir"
 
@@ -98,7 +99,7 @@ esac
         --output-file="${PACKAGE_BUILD_DIR}/etc/matrix-synapse/log.yaml"
 
 # add a dependency on the right version of python to substvars.
-PYPKG=`basename $SNAKE`
+PYPKG=$(basename "$SNAKE")
 echo "synapse:pydepends=$PYPKG" >> debian/matrix-synapse-py3.substvars
 
 
diff --git a/debian/changelog b/debian/changelog
index 06e7a0862d..ba75d0b251 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,29 @@
+matrix-synapse-py3 (1.47.0) stable; urgency=medium
+
+  * New synapse release 1.47.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 17 Nov 2021 13:09:43 +0000
+
+matrix-synapse-py3 (1.47.0~rc3) stable; urgency=medium
+
+  * New synapse release 1.47.0~rc3.
+
+ -- Synapse Packaging team <packages@matrix.org>  Tue, 16 Nov 2021 14:32:47 +0000
+
+matrix-synapse-py3 (1.47.0~rc2) stable; urgency=medium
+
+  [ Dan Callahan ]
+  * Update scripts to pass Shellcheck lints.
+  * Remove unused Vagrant scripts from debian/ directory.
+  * Allow building Debian packages for any architecture, not just amd64.
+  * Preinstall the "wheel" package when building virtualenvs.
+  * Do not error if /etc/default/matrix-synapse is missing.
+
+  [ Synapse Packaging team ]
+  * New synapse release 1.47.0~rc2.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 10 Nov 2021 09:41:01 +0000
+
 matrix-synapse-py3 (1.46.0) stable; urgency=medium
 
   [ Richard van der Hoff ]
diff --git a/debian/control b/debian/control
index 763fabd6f6..412a9e1d4c 100644
--- a/debian/control
+++ b/debian/control
@@ -19,7 +19,7 @@ Standards-Version: 3.9.8
 Homepage: https://github.com/matrix-org/synapse
 
 Package: matrix-synapse-py3
-Architecture: amd64
+Architecture: any
 Provides: matrix-synapse
 Conflicts:
  matrix-synapse (<< 0.34.0.1-0matrix2),
diff --git a/debian/matrix-synapse-py3.config b/debian/matrix-synapse-py3.config
index 37a781b3e8..3b2f469e15 100755
--- a/debian/matrix-synapse-py3.config
+++ b/debian/matrix-synapse-py3.config
@@ -2,6 +2,7 @@
 
 set -e
 
+# shellcheck disable=SC1091
 . /usr/share/debconf/confmodule
 
 # try to update the debconf db according to whatever is in the config files
diff --git a/debian/matrix-synapse-py3.postinst b/debian/matrix-synapse-py3.postinst
index c0dd7e5534..a8dde1e082 100644
--- a/debian/matrix-synapse-py3.postinst
+++ b/debian/matrix-synapse-py3.postinst
@@ -1,5 +1,6 @@
 #!/bin/sh -e
 
+# shellcheck disable=SC1091
 . /usr/share/debconf/confmodule
 
 CONFIGFILE_SERVERNAME="/etc/matrix-synapse/conf.d/server_name.yaml"
diff --git a/debian/matrix-synapse.service b/debian/matrix-synapse.service
index 553babf549..bde1c6cb9f 100644
--- a/debian/matrix-synapse.service
+++ b/debian/matrix-synapse.service
@@ -5,7 +5,7 @@ Description=Synapse Matrix homeserver
 Type=notify
 User=matrix-synapse
 WorkingDirectory=/var/lib/matrix-synapse
-EnvironmentFile=/etc/default/matrix-synapse
+EnvironmentFile=-/etc/default/matrix-synapse
 ExecStartPre=/opt/venvs/matrix-synapse/bin/python -m synapse.app.homeserver --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/ --generate-keys
 ExecStart=/opt/venvs/matrix-synapse/bin/python -m synapse.app.homeserver --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/
 ExecReload=/bin/kill -HUP $MAINPID
diff --git a/debian/test/.gitignore b/debian/test/.gitignore
deleted file mode 100644
index 95eda73fcc..0000000000
--- a/debian/test/.gitignore
+++ /dev/null
@@ -1,2 +0,0 @@
-.vagrant
-*.log
diff --git a/debian/test/provision.sh b/debian/test/provision.sh
deleted file mode 100644
index a5c7f59712..0000000000
--- a/debian/test/provision.sh
+++ /dev/null
@@ -1,23 +0,0 @@
-#!/bin/bash
-#
-# provisioning script for vagrant boxes for testing the matrix-synapse debs.
-#
-# Will install the most recent matrix-synapse-py3 deb for this platform from
-# the /debs directory.
-
-set -e
-
-apt-get update
-apt-get install -y lsb-release
-
-deb=`ls /debs/matrix-synapse-py3_*+$(lsb_release -cs)*.deb | sort | tail -n1`
-
-debconf-set-selections <<EOF
-matrix-synapse matrix-synapse/report-stats boolean false
-matrix-synapse matrix-synapse/server-name string localhost:18448
-EOF
-
-dpkg -i "$deb"
-
-sed -i -e '/port: 8...$/{s/8448/18448/; s/8008/18008/}' -e '$aregistration_shared_secret: secret' /etc/matrix-synapse/homeserver.yaml
-systemctl restart matrix-synapse
diff --git a/debian/test/stretch/Vagrantfile b/debian/test/stretch/Vagrantfile
deleted file mode 100644
index d8eff6fe11..0000000000
--- a/debian/test/stretch/Vagrantfile
+++ /dev/null
@@ -1,13 +0,0 @@
-# -*- mode: ruby -*-
-# vi: set ft=ruby :
-
-ver = `cd ../../..; dpkg-parsechangelog -S Version`.strip()
-
-Vagrant.configure("2") do |config|
-  config.vm.box = "debian/stretch64"
-
-  config.vm.synced_folder ".", "/vagrant", disabled: true
-  config.vm.synced_folder "../../../../debs", "/debs", type: "nfs"
-
-  config.vm.provision "shell", path: "../provision.sh"
-end
diff --git a/debian/test/xenial/Vagrantfile b/debian/test/xenial/Vagrantfile
deleted file mode 100644
index 189236da17..0000000000
--- a/debian/test/xenial/Vagrantfile
+++ /dev/null
@@ -1,10 +0,0 @@
-# -*- mode: ruby -*-
-# vi: set ft=ruby :
-
-Vagrant.configure("2") do |config|
-  config.vm.box = "ubuntu/xenial64"
-
-  config.vm.synced_folder ".", "/vagrant", disabled: true
-  config.vm.synced_folder "../../../../debs", "/debs"
-  config.vm.provision "shell", path: "../provision.sh"
-end
diff --git a/demo/clean.sh b/demo/clean.sh
index 6b809f6e83..e9b440d90d 100755
--- a/demo/clean.sh
+++ b/demo/clean.sh
@@ -6,14 +6,14 @@ DIR="$( cd "$( dirname "$0" )" && pwd )"
 
 PID_FILE="$DIR/servers.pid"
 
-if [ -f $PID_FILE ]; then
+if [ -f "$PID_FILE" ]; then
     echo "servers.pid exists!"
     exit 1
 fi
 
 for port in 8080 8081 8082; do
-    rm -rf $DIR/$port
-    rm -rf $DIR/media_store.$port
+    rm -rf "${DIR:?}/$port"
+    rm -rf "$DIR/media_store.$port"
 done
 
-rm -rf $DIR/etc
+rm -rf "${DIR:?}/etc"
diff --git a/demo/start.sh b/demo/start.sh
index bc4854091b..8ffb14e30a 100755
--- a/demo/start.sh
+++ b/demo/start.sh
@@ -4,21 +4,22 @@ DIR="$( cd "$( dirname "$0" )" && pwd )"
 
 CWD=$(pwd)
 
-cd "$DIR/.."
+cd "$DIR/.." || exit
 
 mkdir -p demo/etc
 
-export PYTHONPATH=$(readlink -f $(pwd))
+PYTHONPATH=$(readlink -f "$(pwd)")
+export PYTHONPATH
 
 
-echo $PYTHONPATH
+echo "$PYTHONPATH"
 
 for port in 8080 8081 8082; do
     echo "Starting server on port $port... "
 
     https_port=$((port + 400))
     mkdir -p demo/$port
-    pushd demo/$port
+    pushd demo/$port || exit
 
     #rm $DIR/etc/$port.config
     python3 -m synapse.app.homeserver \
@@ -27,75 +28,78 @@ for port in 8080 8081 8082; do
         --config-path "$DIR/etc/$port.config" \
         --report-stats no
 
-    if ! grep -F "Customisation made by demo/start.sh" -q  $DIR/etc/$port.config; then
-        printf '\n\n# Customisation made by demo/start.sh\n' >> $DIR/etc/$port.config
-
-        echo "public_baseurl: http://localhost:$port/" >> $DIR/etc/$port.config
-
-        echo 'enable_registration: true' >> $DIR/etc/$port.config
-
-        # Warning, this heredoc depends on the interaction of tabs and spaces. Please don't
-        # accidentaly bork me with your fancy settings.
-		listeners=$(cat <<-PORTLISTENERS
-		# Configure server to listen on both $https_port and $port
-		# This overides some of the default settings above
-		listeners:
-		  - port: $https_port
-		    type: http
-		    tls: true
-		    resources:
-		      - names: [client, federation]
-
-		  - port: $port
-		    tls: false
-		    bind_addresses: ['::1', '127.0.0.1']
-		    type: http
-		    x_forwarded: true
-		    resources:
-		      - names: [client, federation]
-		        compress: false
-		PORTLISTENERS
-		)
-        echo "${listeners}" >> $DIR/etc/$port.config
-
-        # Disable tls for the servers
-        printf '\n\n# Disable tls on the servers.' >> $DIR/etc/$port.config
-        echo '# DO NOT USE IN PRODUCTION' >> $DIR/etc/$port.config
-        echo 'use_insecure_ssl_client_just_for_testing_do_not_use: true' >> $DIR/etc/$port.config
-        echo 'federation_verify_certificates: false' >> $DIR/etc/$port.config
-
-        # Set tls paths
-        echo "tls_certificate_path: \"$DIR/etc/localhost:$https_port.tls.crt\"" >> $DIR/etc/$port.config
-        echo "tls_private_key_path: \"$DIR/etc/localhost:$https_port.tls.key\"" >> $DIR/etc/$port.config
-
+    if ! grep -F "Customisation made by demo/start.sh" -q "$DIR/etc/$port.config"; then
         # Generate tls keys
-        openssl req -x509 -newkey rsa:4096 -keyout $DIR/etc/localhost\:$https_port.tls.key -out $DIR/etc/localhost\:$https_port.tls.crt -days 365 -nodes -subj "/O=matrix"
-
-        # Ignore keys from the trusted keys server
-        echo '# Ignore keys from the trusted keys server' >> $DIR/etc/$port.config
-        echo 'trusted_key_servers:' >> $DIR/etc/$port.config
-        echo '  - server_name: "matrix.org"' >> $DIR/etc/$port.config
-        echo '    accept_keys_insecurely: true' >> $DIR/etc/$port.config
-
-        # Reduce the blacklist
-        blacklist=$(cat <<-BLACK
-		# Set the blacklist so that it doesn't include 127.0.0.1, ::1
-		federation_ip_range_blacklist:
-		  - '10.0.0.0/8'
-		  - '172.16.0.0/12'
-		  - '192.168.0.0/16'
-		  - '100.64.0.0/10'
-		  - '169.254.0.0/16'
-		  - 'fe80::/64'
-		  - 'fc00::/7'
-		BLACK
-		)
-        echo "${blacklist}" >> $DIR/etc/$port.config
+        openssl req -x509 -newkey rsa:4096 -keyout "$DIR/etc/localhost:$https_port.tls.key" -out "$DIR/etc/localhost:$https_port.tls.crt" -days 365 -nodes -subj "/O=matrix"
+
+        # Regenerate configuration
+        {
+            printf '\n\n# Customisation made by demo/start.sh\n'
+            echo "public_baseurl: http://localhost:$port/"
+            echo 'enable_registration: true'
+
+			# Warning, this heredoc depends on the interaction of tabs and spaces.
+			# Please don't accidentaly bork me with your fancy settings.
+			listeners=$(cat <<-PORTLISTENERS
+			# Configure server to listen on both $https_port and $port
+			# This overides some of the default settings above
+			listeners:
+			  - port: $https_port
+			    type: http
+			    tls: true
+			    resources:
+			      - names: [client, federation]
+
+			  - port: $port
+			    tls: false
+			    bind_addresses: ['::1', '127.0.0.1']
+			    type: http
+			    x_forwarded: true
+			    resources:
+			      - names: [client, federation]
+			        compress: false
+			PORTLISTENERS
+			)
+
+            echo "${listeners}"
+
+            # Disable tls for the servers
+            printf '\n\n# Disable tls on the servers.'
+            echo '# DO NOT USE IN PRODUCTION'
+            echo 'use_insecure_ssl_client_just_for_testing_do_not_use: true'
+            echo 'federation_verify_certificates: false'
+
+            # Set tls paths
+            echo "tls_certificate_path: \"$DIR/etc/localhost:$https_port.tls.crt\""
+            echo "tls_private_key_path: \"$DIR/etc/localhost:$https_port.tls.key\""
+
+            # Ignore keys from the trusted keys server
+            echo '# Ignore keys from the trusted keys server'
+            echo 'trusted_key_servers:'
+            echo '  - server_name: "matrix.org"'
+            echo '    accept_keys_insecurely: true'
+
+			# Reduce the blacklist
+			blacklist=$(cat <<-BLACK
+			# Set the blacklist so that it doesn't include 127.0.0.1, ::1
+			federation_ip_range_blacklist:
+			  - '10.0.0.0/8'
+			  - '172.16.0.0/12'
+			  - '192.168.0.0/16'
+			  - '100.64.0.0/10'
+			  - '169.254.0.0/16'
+			  - 'fe80::/64'
+			  - 'fc00::/7'
+			BLACK
+			)
+
+            echo "${blacklist}"
+        } >> "$DIR/etc/$port.config"
     fi
 
     # Check script parameters
     if [ $# -eq 1 ]; then
-        if [ $1 = "--no-rate-limit" ]; then
+        if [ "$1" = "--no-rate-limit" ]; then
 
             # Disable any rate limiting
             ratelimiting=$(cat <<-RC
@@ -137,22 +141,22 @@ for port in 8080 8081 8082; do
 			    burst_count: 1000
 			RC
 			)
-            echo "${ratelimiting}" >> $DIR/etc/$port.config
+            echo "${ratelimiting}" >> "$DIR/etc/$port.config"
         fi
     fi
 
-    if ! grep -F "full_twisted_stacktraces" -q  $DIR/etc/$port.config; then
-        echo "full_twisted_stacktraces: true" >> $DIR/etc/$port.config
+    if ! grep -F "full_twisted_stacktraces" -q  "$DIR/etc/$port.config"; then
+        echo "full_twisted_stacktraces: true" >> "$DIR/etc/$port.config"
     fi
-    if ! grep -F "report_stats" -q  $DIR/etc/$port.config ; then
-        echo "report_stats: false" >> $DIR/etc/$port.config
+    if ! grep -F "report_stats" -q  "$DIR/etc/$port.config" ; then
+        echo "report_stats: false" >> "$DIR/etc/$port.config"
     fi
 
     python3 -m synapse.app.homeserver \
         --config-path "$DIR/etc/$port.config" \
         -D \
 
-    popd
+    popd || exit
 done
 
-cd "$CWD"
+cd "$CWD" || exit
diff --git a/demo/stop.sh b/demo/stop.sh
index f9dddc5914..c97e4b8d00 100755
--- a/demo/stop.sh
+++ b/demo/stop.sh
@@ -8,7 +8,7 @@ for pid_file in $FILES; do
     pid=$(cat "$pid_file")
     if [[ $pid ]]; then
         echo "Killing $pid_file with $pid"
-        kill $pid
+        kill "$pid"
     fi
 done
 
diff --git a/docker/README.md b/docker/README.md
index 38d182bf45..4349e71f87 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -65,7 +65,8 @@ The following environment variables are supported in `generate` mode:
 * `SYNAPSE_DATA_DIR`: where the generated config will put persistent data
   such as the database and media store. Defaults to `/data`.
 * `UID`, `GID`: the user id and group id to use for creating the data
-  directories. Defaults to `991`, `991`.
+  directories. If unset, and no user is set via `docker run --user`, defaults
+  to `991`, `991`.
 
 ## Running synapse
 
@@ -97,7 +98,9 @@ The following environment variables are supported in `run` mode:
   `<SYNAPSE_CONFIG_DIR>/homeserver.yaml`.
 * `SYNAPSE_WORKER`: module to execute, used when running synapse with workers.
    Defaults to `synapse.app.homeserver`, which is suitable for non-worker mode.
-* `UID`, `GID`: the user and group id to run Synapse as. Defaults to `991`, `991`.
+* `UID`, `GID`: the user and group id to run Synapse as. If unset, and no user
+  is set via `docker run --user`, defaults to `991`, `991`. Note that this user
+  must have permission to read the config files, and write to the data directories.
 * `TZ`: the [timezone](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones) the container will run with. Defaults to `UTC`.
 
 For more complex setups (e.g. for workers) you can also pass your args directly to synapse using `run` mode. For example like this:
@@ -186,7 +189,7 @@ point to another Dockerfile.
 ## Disabling the healthcheck
 
 If you are using a non-standard port or tls inside docker you can disable the healthcheck
-whilst running the above `docker run` commands. 
+whilst running the above `docker run` commands.
 
 ```
    --no-healthcheck
@@ -212,7 +215,7 @@ If you wish to point the healthcheck at a different port with docker command, ad
 ## Setting the healthcheck in docker-compose file
 
 You can add the following to set a custom healthcheck in a docker compose file.
-You will need docker-compose version >2.1 for this to work. 
+You will need docker-compose version >2.1 for this to work.
 
 ```
 healthcheck:
@@ -226,5 +229,5 @@ healthcheck:
 ## Using jemalloc
 
 Jemalloc is embedded in the image and will be used instead of the default allocator.
-You can read about jemalloc by reading the Synapse 
+You can read about jemalloc by reading the Synapse
 [README](https://github.com/matrix-org/synapse/blob/HEAD/README.rst#help-synapse-is-slow-and-eats-all-my-ram-cpu).
diff --git a/docker/build_debian.sh b/docker/build_debian.sh
index 801ff45471..9eae38af91 100644
--- a/docker/build_debian.sh
+++ b/docker/build_debian.sh
@@ -5,7 +5,7 @@
 set -ex
 
 # Get the codename from distro env
-DIST=`cut -d ':' -f2 <<< $distro`
+DIST=$(cut -d ':' -f2 <<< "${distro:?}")
 
 # we get a read-only copy of the source: make a writeable copy
 cp -aT /synapse/source /synapse/build
@@ -17,7 +17,7 @@ cd /synapse/build
 # Section to determine which "component" it should go into (see
 # https://manpages.debian.org/stretch/reprepro/reprepro.1.en.html#GUESSING)
 
-DEB_VERSION=`dpkg-parsechangelog -SVersion`
+DEB_VERSION=$(dpkg-parsechangelog -SVersion)
 case $DEB_VERSION in
     *~rc*|*~a*|*~b*|*~c*)
         sed -ie '/^Section:/c\Section: prerelease' debian/control
diff --git a/docker/start.py b/docker/start.py
index 16d6a8208a..ec9eeb49ae 100755
--- a/docker/start.py
+++ b/docker/start.py
@@ -120,6 +120,7 @@ def generate_config_from_template(config_dir, config_path, environ, ownership):
     ]
 
     if ownership is not None:
+        log(f"Setting ownership on /data to {ownership}")
         subprocess.check_output(["chown", "-R", ownership, "/data"])
         args = ["gosu", ownership] + args
 
@@ -144,12 +145,18 @@ def run_generate_config(environ, ownership):
     config_path = environ.get("SYNAPSE_CONFIG_PATH", config_dir + "/homeserver.yaml")
     data_dir = environ.get("SYNAPSE_DATA_DIR", "/data")
 
+    if ownership is not None:
+        # make sure that synapse has perms to write to the data dir.
+        log(f"Setting ownership on {data_dir} to {ownership}")
+        subprocess.check_output(["chown", ownership, data_dir])
+
     # create a suitable log config from our template
     log_config_file = "%s/%s.log.config" % (config_dir, server_name)
     if not os.path.exists(log_config_file):
         log("Creating log config %s" % (log_config_file,))
         convert("/conf/log.config", log_config_file, environ)
 
+    # generate the main config file, and a signing key.
     args = [
         "python",
         "-m",
@@ -168,29 +175,23 @@ def run_generate_config(environ, ownership):
         "--open-private-ports",
     ]
     # log("running %s" % (args, ))
-
-    if ownership is not None:
-        # make sure that synapse has perms to write to the data dir.
-        subprocess.check_output(["chown", ownership, data_dir])
-
-        args = ["gosu", ownership] + args
-        os.execv("/usr/sbin/gosu", args)
-    else:
-        os.execv("/usr/local/bin/python", args)
+    os.execv("/usr/local/bin/python", args)
 
 
 def main(args, environ):
     mode = args[1] if len(args) > 1 else "run"
-    desired_uid = int(environ.get("UID", "991"))
-    desired_gid = int(environ.get("GID", "991"))
-    synapse_worker = environ.get("SYNAPSE_WORKER", "synapse.app.homeserver")
-    if (desired_uid == os.getuid()) and (desired_gid == os.getgid()):
-        ownership = None
-    else:
-        ownership = "{}:{}".format(desired_uid, desired_gid)
 
-    if ownership is None:
-        log("Will not perform chmod/gosu as UserID already matches request")
+    # if we were given an explicit user to switch to, do so
+    ownership = None
+    if "UID" in environ:
+        desired_uid = int(environ["UID"])
+        desired_gid = int(environ.get("GID", "991"))
+        ownership = f"{desired_uid}:{desired_gid}"
+    elif os.getuid() == 0:
+        # otherwise, if we are running as root, use user 991
+        ownership = "991:991"
+
+    synapse_worker = environ.get("SYNAPSE_WORKER", "synapse.app.homeserver")
 
     # In generate mode, generate a configuration and missing keys, then exit
     if mode == "generate":
diff --git a/docs/CAPTCHA_SETUP.md b/docs/CAPTCHA_SETUP.md
index fabdd7b726..49419ce8df 100644
--- a/docs/CAPTCHA_SETUP.md
+++ b/docs/CAPTCHA_SETUP.md
@@ -15,12 +15,12 @@ in `homeserver.yaml`, to the list of authorized domains. If you have not set
 1. Agree to the terms of service and submit.
 1. Copy your site key and secret key and add them to your `homeserver.yaml`
 configuration file
-    ```
+    ```yaml
     recaptcha_public_key: YOUR_SITE_KEY
     recaptcha_private_key: YOUR_SECRET_KEY
     ```
 1. Enable the CAPTCHA for new registrations
-    ```
+    ```yaml
     enable_registration_captcha: true
     ```
 1. Go to the settings page for the CAPTCHA you just created
diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
index 35412ea92c..04320ab07b 100644
--- a/docs/SUMMARY.md
+++ b/docs/SUMMARY.md
@@ -51,6 +51,7 @@
   - [Administration](usage/administration/README.md)
     - [Admin API](usage/administration/admin_api/README.md)
       - [Account Validity](admin_api/account_validity.md)
+      - [Background Updates](usage/administration/admin_api/background_updates.md)
       - [Delete Group](admin_api/delete_group.md)
       - [Event Reports](admin_api/event_reports.md)
       - [Media](admin_api/media_admin_api.md)
diff --git a/docs/admin_api/event_reports.md b/docs/admin_api/event_reports.md
index 3abb06099c..f523774ba8 100644
--- a/docs/admin_api/event_reports.md
+++ b/docs/admin_api/event_reports.md
@@ -99,7 +99,7 @@ server admin: see [Admin API](../usage/administration/admin_api).
 
 It returns a JSON body like the following:
 
-```jsonc
+```json
 {
     "event_id": "$bNUFCwGzWca1meCGkjp-zwslF-GfVcXukvRLI1_FaVY",
     "event_json": {
@@ -132,7 +132,7 @@ It returns a JSON body like the following:
         },
         "type": "m.room.message",
         "unsigned": {
-            "age_ts": 1592291711430,
+            "age_ts": 1592291711430
         }
     },
     "id": <report_id>,
diff --git a/docs/admin_api/purge_history_api.md b/docs/admin_api/purge_history_api.md
index 13b991eacf..bd29e29ab8 100644
--- a/docs/admin_api/purge_history_api.md
+++ b/docs/admin_api/purge_history_api.md
@@ -27,7 +27,7 @@ Room state data (such as joins, leaves, topic) is always preserved.
 
 To delete local message events as well, set `delete_local_events` in the body:
 
-```
+```json
 {
    "delete_local_events": true
 }
diff --git a/docs/admin_api/room_membership.md b/docs/admin_api/room_membership.md
index 8a5ce191df..548b790a5c 100644
--- a/docs/admin_api/room_membership.md
+++ b/docs/admin_api/room_membership.md
@@ -28,7 +28,7 @@ server admin: see [Admin API](../usage/administration/admin_api).
 
 Response:
 
-```
+```json
 {
   "room_id": "!636q39766251:server.com"
 }
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 8e524e6509..ab6b82a082 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -38,9 +38,14 @@ The following query parameters are available:
   - `history_visibility` - Rooms are ordered alphabetically by visibility of history of the room.
   - `state_events` - Rooms are ordered by number of state events. Largest to smallest.
 * `dir` - Direction of room order. Either `f` for forwards or `b` for backwards. Setting
-          this value to `b` will reverse the above sort order. Defaults to `f`.
-* `search_term` - Filter rooms by their room name. Search term can be contained in any
-                  part of the room name. Defaults to no filtering.
+  this value to `b` will reverse the above sort order. Defaults to `f`.
+* `search_term` - Filter rooms by their room name, canonical alias and room id.
+  Specifically, rooms are selected if the search term is contained in
+  - the room's name,
+  - the local part of the room's canonical alias, or
+  - the complete (local and server part) room's id (case sensitive).
+
+  Defaults to no filtering.
 
 **Response**
 
@@ -87,7 +92,7 @@ GET /_synapse/admin/v1/rooms
 
 A response body like the following is returned:
 
-```jsonc
+```json
 {
   "rooms": [
     {
@@ -170,7 +175,7 @@ GET /_synapse/admin/v1/rooms?order_by=size
 
 A response body like the following is returned:
 
-```jsonc
+```json
 {
   "rooms": [
     {
@@ -208,7 +213,7 @@ A response body like the following is returned:
     }
   ],
   "offset": 0,
-  "total_rooms": 150
+  "total_rooms": 150,
   "next_token": 100
 }
 ```
@@ -224,7 +229,7 @@ GET /_synapse/admin/v1/rooms?order_by=size&from=100
 
 A response body like the following is returned:
 
-```jsonc
+```json
 {
   "rooms": [
     {
@@ -380,7 +385,7 @@ A response body like the following is returned:
 
 # Delete Room API
 
-The Delete Room admin API allows server admins to remove rooms from server
+The Delete Room admin API allows server admins to remove rooms from the server
 and block these rooms.
 
 Shuts down a room. Moves all local users and room aliases automatically to a
@@ -520,16 +525,6 @@ With all that being said, if you still want to try and recover the room:
 4. If `new_room_user_id` was given, a 'Content Violation' will have been
    created. Consider whether you want to delete that roomm.
 
-## Deprecated endpoint
-
-The previous deprecated API will be removed in a future release, it was:
-
-```
-POST /_synapse/admin/v1/rooms/<room_id>/delete
-```
-
-It behaves the same way than the current endpoint except the path and the method.
-
 # Make Room Admin API
 
 Grants another user the highest power available to a local user who is in the room.
diff --git a/docs/code_style.md b/docs/code_style.md
index 28fb7277c4..4d8e7c973d 100644
--- a/docs/code_style.md
+++ b/docs/code_style.md
@@ -10,7 +10,9 @@ The necessary tools are detailed below.
 
 First install them with:
 
-    pip install -e ".[lint,mypy]"
+```sh
+pip install -e ".[lint,mypy]"
+```
 
 -   **black**
 
@@ -21,7 +23,9 @@ First install them with:
     Have `black` auto-format your code (it shouldn't change any
     functionality) with:
 
-        black . --exclude="\.tox|build|env"
+    ```sh
+    black . --exclude="\.tox|build|env"
+    ```
 
 -   **flake8**
 
@@ -30,7 +34,9 @@ First install them with:
 
     Check all application and test code with:
 
-        flake8 synapse tests
+    ```sh
+    flake8 synapse tests
+    ```
 
 -   **isort**
 
@@ -39,7 +45,9 @@ First install them with:
 
     Auto-fix imports with:
 
-        isort -rc synapse tests
+    ```sh
+    isort -rc synapse tests
+    ```
 
     `-rc` means to recursively search the given directories.
 
@@ -66,15 +74,19 @@ save as it takes a while and is very resource intensive.
 
         Example:
 
-            from synapse.types import UserID
-            ...
-            user_id = UserID(local, server)
+        ```python
+        from synapse.types import UserID
+        ...
+        user_id = UserID(local, server)
+        ```
 
         is preferred over:
 
-            from synapse import types
-            ...
-            user_id = types.UserID(local, server)
+        ```python
+        from synapse import types
+        ...
+        user_id = types.UserID(local, server)
+        ```
 
         (or any other variant).
 
@@ -134,28 +146,30 @@ Some guidelines follow:
 
 Example:
 
-    ## Frobnication ##
-
-    # The frobnicator will ensure that all requests are fully frobnicated.
-    # To enable it, uncomment the following.
-    #
-    #frobnicator_enabled: true
-
-    # By default, the frobnicator will frobnicate with the default frobber.
-    # The following will make it use an alternative frobber.
-    #
-    #frobincator_frobber: special_frobber
-
-    # Settings for the frobber
-    #
-    frobber:
-      # frobbing speed. Defaults to 1.
-      #
-      #speed: 10
-
-      # frobbing distance. Defaults to 1000.
-      #
-      #distance: 100
+```yaml
+## Frobnication ##
+
+# The frobnicator will ensure that all requests are fully frobnicated.
+# To enable it, uncomment the following.
+#
+#frobnicator_enabled: true
+
+# By default, the frobnicator will frobnicate with the default frobber.
+# The following will make it use an alternative frobber.
+#
+#frobincator_frobber: special_frobber
+
+# Settings for the frobber
+#
+frobber:
+  # frobbing speed. Defaults to 1.
+  #
+  #speed: 10
+
+  # frobbing distance. Defaults to 1000.
+  #
+  #distance: 100
+```
 
 Note that the sample configuration is generated from the synapse code
 and is maintained by a script, `scripts-dev/generate_sample_config`.
diff --git a/docs/consent_tracking.md b/docs/consent_tracking.md
index 911a1f95db..fb1fec80fe 100644
--- a/docs/consent_tracking.md
+++ b/docs/consent_tracking.md
@@ -99,7 +99,7 @@ construct URIs where users can give their consent.
    see if an unauthenticated user is viewing the page. This is typically
    wrapped around the form that would be used to actually agree to the document:
 
-   ```
+   ```html
    {% if not public_version %}
      <!-- The variables used here are only provided when the 'u' param is given to the homeserver -->
      <form method="post" action="consent">
diff --git a/docs/delegate.md b/docs/delegate.md
index 05cb635047..ee9cbb3b1c 100644
--- a/docs/delegate.md
+++ b/docs/delegate.md
@@ -1,4 +1,8 @@
-# Delegation
+# Delegation of incoming federation traffic
+
+In the following documentation, we use the term `server_name` to refer to that setting
+in your homeserver configuration file. It appears at the ends of user ids, and tells
+other homeservers where they can find your server.
 
 By default, other homeservers will expect to be able to reach yours via
 your `server_name`, on port 8448. For example, if you set your `server_name`
@@ -12,13 +16,21 @@ to a different server and/or port (e.g. `synapse.example.com:443`).
 
 ## .well-known delegation
 
-To use this method, you need to be able to alter the
-`server_name` 's https server to serve the `/.well-known/matrix/server`
-URL. Having an active server (with a valid TLS certificate) serving your
-`server_name` domain is out of the scope of this documentation.
+To use this method, you need to be able to configure the server at
+`https://<server_name>` to serve a file at
+`https://<server_name>/.well-known/matrix/server`.  There are two ways to do this, shown below.
+
+Note that the `.well-known` file is hosted on the default port for `https` (port 443).
+
+### External server
+
+For maximum flexibility, you need to configure an external server such as nginx, Apache
+or HAProxy to serve the `https://<server_name>/.well-known/matrix/server` file. Setting
+up such a server is out of the scope of this documentation, but note that it is often
+possible to configure your [reverse proxy](reverse_proxy.md) for this.
 
-The URL `https://<server_name>/.well-known/matrix/server` should
-return a JSON structure containing the key `m.server` like so:
+The URL `https://<server_name>/.well-known/matrix/server` should be configured
+return a JSON structure containing the key `m.server` like this:
 
 ```json
 {
@@ -26,8 +38,9 @@ return a JSON structure containing the key `m.server` like so:
 }
 ```
 
-In our example, this would mean that URL `https://example.com/.well-known/matrix/server`
-should return:
+In our example (where we want federation traffic to be routed to
+`https://synapse.example.com`, on port 443), this would mean that
+`https://example.com/.well-known/matrix/server` should return:
 
 ```json
 {
@@ -38,16 +51,29 @@ should return:
 Note, specifying a port is optional. If no port is specified, then it defaults
 to 8448.
 
-With .well-known delegation, federating servers will check for a valid TLS
-certificate for the delegated hostname (in our example: `synapse.example.com`).
+### Serving a `.well-known/matrix/server` file with Synapse
+
+If you are able to set up your domain so that `https://<server_name>` is routed to
+Synapse (i.e., the only change needed is to direct federation traffic to port 443
+instead of port 8448), then it is possible to configure Synapse to serve a suitable
+`.well-known/matrix/server` file. To do so, add the following to your `homeserver.yaml`
+file:
+
+```yaml
+serve_server_wellknown: true
+```
+
+**Note**: this *only* works if `https://<server_name>` is routed to Synapse, so is
+generally not suitable if Synapse is hosted at a subdomain such as
+`https://synapse.example.com`.
 
 ## SRV DNS record delegation
 
-It is also possible to do delegation using a SRV DNS record. However, that is
-considered an advanced topic since it's a bit complex to set up, and `.well-known`
-delegation is already enough in most cases.
+It is also possible to do delegation using a SRV DNS record. However, that is generally
+not recommended, as it can be difficult to configure the TLS certificates correctly in
+this case, and it offers little advantage over `.well-known` delegation.
 
-However, if you really need it, you can find some documentation on how such a
+However, if you really need it, you can find some documentation on what such a
 record should look like and how Synapse will use it in [the Matrix
 specification](https://matrix.org/docs/spec/server_server/latest#resolving-server-names).
 
@@ -68,27 +94,9 @@ wouldn't need any delegation set up.
 domain `server_name` points to, you will need to let other servers know how to
 find it using delegation.
 
-### Do you still recommend against using a reverse proxy on the federation port?
-
-We no longer actively recommend against using a reverse proxy. Many admins will
-find it easier to direct federation traffic to a reverse proxy and manage their
-own TLS certificates, and this is a supported configuration.
+### Should I use a reverse proxy for federation traffic?
 
-See [the reverse proxy documentation](reverse_proxy.md) for information on setting up a
+Generally, using a reverse proxy for both the federation and client traffic is a good
+idea, since it saves handling TLS traffic in Synapse. See
+[the reverse proxy documentation](reverse_proxy.md) for information on setting up a
 reverse proxy.
-
-### Do I still need to give my TLS certificates to Synapse if I am using a reverse proxy?
-
-This is no longer necessary. If you are using a reverse proxy for all of your
-TLS traffic, then you can set `no_tls: True` in the Synapse config.
-
-In that case, the only reason Synapse needs the certificate is to populate a legacy
-`tls_fingerprints` field in the federation API. This is ignored by Synapse 0.99.0
-and later, and the only time pre-0.99 Synapses will check it is when attempting to
-fetch the server keys - and generally this is delegated via `matrix.org`, which
-is running a modern version of Synapse.
-
-### Do I need the same certificate for the client and federation port?
-
-No. There is nothing stopping you from using different certificates,
-particularly if you are using a reverse proxy.
\ No newline at end of file
diff --git a/docs/development/cas.md b/docs/development/cas.md
index 592b2d8d4f..7c0668e034 100644
--- a/docs/development/cas.md
+++ b/docs/development/cas.md
@@ -8,23 +8,23 @@ easy to run CAS implementation built on top of Django.
 1. Create a new virtualenv: `python3 -m venv <your virtualenv>`
 2. Activate your virtualenv: `source /path/to/your/virtualenv/bin/activate`
 3. Install Django and django-mama-cas:
-   ```
+   ```sh
    python -m pip install "django<3" "django-mama-cas==2.4.0"
    ```
 4. Create a Django project in the current directory:
-   ```
+   ```sh
    django-admin startproject cas_test .
    ```
 5. Follow the [install directions](https://django-mama-cas.readthedocs.io/en/latest/installation.html#configuring) for django-mama-cas
 6. Setup the SQLite database: `python manage.py migrate`
 7. Create a user:
-   ```
+   ```sh
    python manage.py createsuperuser
    ```
    1. Use whatever you want as the username and password.
    2. Leave the other fields blank.
 8. Use the built-in Django test server to serve the CAS endpoints on port 8000:
-   ```
+   ```sh
    python manage.py runserver
    ```
 
diff --git a/docs/development/contributing_guide.md b/docs/development/contributing_guide.md
index 3bf08a72bb..abdb808438 100644
--- a/docs/development/contributing_guide.md
+++ b/docs/development/contributing_guide.md
@@ -15,6 +15,11 @@ license - in our case, this is almost always Apache Software License v2 (see
 
 # 2. What do I need?
 
+If you are running Windows, the Windows Subsystem for Linux (WSL) is strongly
+recommended for development. More information about WSL can be found at
+<https://docs.microsoft.com/en-us/windows/wsl/install>. Running Synapse natively
+on Windows is not officially supported.
+
 The code of Synapse is written in Python 3. To do pretty much anything, you'll need [a recent version of Python 3](https://wiki.python.org/moin/BeginnersGuide/Download).
 
 The source code of Synapse is hosted on GitHub. You will also need [a recent version of git](https://github.com/git-guides/install-git).
@@ -41,8 +46,6 @@ can find many good git tutorials on the web.
 
 # 4. Install the dependencies
 
-## Under Unix (macOS, Linux, BSD, ...)
-
 Once you have installed Python 3 and added the source, please open a terminal and
 setup a *virtualenv*, as follows:
 
@@ -56,10 +59,6 @@ pip install tox
 
 This will install the developer dependencies for the project.
 
-## Under Windows
-
-TBD
-
 
 # 5. Get in touch.
 
diff --git a/docs/development/database_schema.md b/docs/development/database_schema.md
index 20740cf5ac..256a629210 100644
--- a/docs/development/database_schema.md
+++ b/docs/development/database_schema.md
@@ -89,7 +89,9 @@ To do so, use `scripts-dev/make_full_schema.sh`. This will produce new
 
 Ensure postgres is installed, then run:
 
-    ./scripts-dev/make_full_schema.sh -p postgres_username -o output_dir/
+```sh
+./scripts-dev/make_full_schema.sh -p postgres_username -o output_dir/
+```
 
 NB at the time of writing, this script predates the split into separate `state`/`main`
 databases so will require updates to handle that correctly.
diff --git a/docs/development/saml.md b/docs/development/saml.md
index 60a431d686..b08bcb7419 100644
--- a/docs/development/saml.md
+++ b/docs/development/saml.md
@@ -15,7 +15,7 @@ To make Synapse (and therefore Element) use it:
      sp_config:
        allow_unknown_attributes: true  # Works around a bug with AVA Hashes: https://github.com/IdentityPython/pysaml2/issues/388
        metadata:
-         local: ["samling.xml"]   
+         local: ["samling.xml"]
    ```
 5. Ensure that your `homeserver.yaml` has a setting for `public_baseurl`:
    ```yaml
diff --git a/docs/message_retention_policies.md b/docs/message_retention_policies.md
index ea3d46cc10..9214d6d7e9 100644
--- a/docs/message_retention_policies.md
+++ b/docs/message_retention_policies.md
@@ -69,9 +69,9 @@ A default policy can be defined as such, in the `retention` section of
 the configuration file:
 
 ```yaml
-  default_policy:
-    min_lifetime: 1d
-    max_lifetime: 1y
+default_policy:
+  min_lifetime: 1d
+  max_lifetime: 1y
 ```
 
 Here, `min_lifetime` and `max_lifetime` have the same meaning and level
@@ -95,14 +95,14 @@ depending on an event's room's policy. This can be done by setting the
 file. An example of such configuration could be:
 
 ```yaml
-  purge_jobs:
-    - longest_max_lifetime: 3d
-      interval: 12h
-    - shortest_max_lifetime: 3d
-      longest_max_lifetime: 1w
-      interval: 1d
-    - shortest_max_lifetime: 1w
-      interval: 2d
+purge_jobs:
+  - longest_max_lifetime: 3d
+    interval: 12h
+  - shortest_max_lifetime: 3d
+    longest_max_lifetime: 1w
+    interval: 1d
+  - shortest_max_lifetime: 1w
+    interval: 2d
 ```
 
 In this example, we define three jobs:
@@ -141,8 +141,8 @@ purging old events in a room. These limits can be defined as such in the
 `retention` section of the configuration file:
 
 ```yaml
-  allowed_lifetime_min: 1d
-  allowed_lifetime_max: 1y
+allowed_lifetime_min: 1d
+allowed_lifetime_max: 1y
 ```
 
 The limits are considered when running purge jobs. If necessary, the
diff --git a/docs/modules/password_auth_provider_callbacks.md b/docs/modules/password_auth_provider_callbacks.md
index 9dddfdfaaa..e53abf6409 100644
--- a/docs/modules/password_auth_provider_callbacks.md
+++ b/docs/modules/password_auth_provider_callbacks.md
@@ -10,8 +10,8 @@ registered by using the Module API's `register_password_auth_provider_callbacks`
 
 _First introduced in Synapse v1.46.0_
 
-```
- auth_checkers: Dict[Tuple[str,Tuple], Callable]
+```python
+auth_checkers: Dict[Tuple[str, Tuple[str, ...]], Callable]
 ```
 
 A dict mapping from tuples of a login type identifier (such as `m.login.password`) and a
diff --git a/docs/modules/spam_checker_callbacks.md b/docs/modules/spam_checker_callbacks.md
index 534ea196e0..2eb9032f41 100644
--- a/docs/modules/spam_checker_callbacks.md
+++ b/docs/modules/spam_checker_callbacks.md
@@ -123,42 +123,6 @@ callback returns `True`, Synapse falls through to the next one. The value of the
 callback that does not return `True` will be used. If this happens, Synapse will not call
 any of the subsequent implementations of this callback.
 
-### `user_may_create_room_with_invites`
-
-_First introduced in Synapse v1.44.0_
-
-```python
-async def user_may_create_room_with_invites(
-    user: str,
-    invites: List[str],
-    threepid_invites: List[Dict[str, str]],
-) -> bool
-```
-
-Called when processing a room creation request (right after `user_may_create_room`).
-The module is given the Matrix user ID of the user trying to create a room, as well as a
-list of Matrix users to invite and a list of third-party identifiers (3PID, e.g. email
-addresses) to invite.
-
-An invited Matrix user to invite is represented by their Matrix user IDs, and an invited
-3PIDs is represented by a dict that includes the 3PID medium (e.g. "email") through its
-`medium` key and its address (e.g. "alice@example.com") through its `address` key.
-
-See [the Matrix specification](https://matrix.org/docs/spec/appendices#pid-types) for more
-information regarding third-party identifiers.
-
-If no invite and/or 3PID invite were specified in the room creation request, the
-corresponding list(s) will be empty.
-
-**Note**: This callback is not called when a room is cloned (e.g. during a room upgrade)
-since no invites are sent when cloning a room. To cover this case, modules also need to
-implement `user_may_create_room`.
-
-If multiple modules implement this callback, they will be considered in order. If a
-callback returns `True`, Synapse falls through to the next one. The value of the first
-callback that does not return `True` will be used. If this happens, Synapse will not call
-any of the subsequent implementations of this callback.
-
 ### `user_may_create_room_alias`
 
 _First introduced in Synapse v1.37.0_
diff --git a/docs/modules/third_party_rules_callbacks.md b/docs/modules/third_party_rules_callbacks.md
index 034923da0f..a3a17096a8 100644
--- a/docs/modules/third_party_rules_callbacks.md
+++ b/docs/modules/third_party_rules_callbacks.md
@@ -43,6 +43,14 @@ event with new data by returning the new event's data as a dictionary. In order
 that, it is recommended the module calls `event.get_dict()` to get the current event as a
 dictionary, and modify the returned dictionary accordingly.
 
+If `check_event_allowed` raises an exception, the module is assumed to have failed.
+The event will not be accepted but is not treated as explicitly rejected, either.
+An HTTP request causing the module check will likely result in a 500 Internal
+Server Error.
+
+When the boolean returned by the module is `False`, the event is rejected.
+(Module developers should not use exceptions for rejection.)
+
 Note that replacing the event only works for events sent by local users, not for events
 received over federation.
 
@@ -119,6 +127,27 @@ callback returns `True`, Synapse falls through to the next one. The value of the
 callback that does not return `True` will be used. If this happens, Synapse will not call
 any of the subsequent implementations of this callback.
 
+### `on_new_event`
+
+_First introduced in Synapse v1.47.0_
+
+```python
+async def on_new_event(
+    event: "synapse.events.EventBase",
+    state_events: "synapse.types.StateMap",
+) -> None:
+```
+
+Called after sending an event into a room. The module is passed the event, as well
+as the state of the room _after_ the event. This means that if the event is a state event,
+it will be included in this state.
+
+Note that this callback is called when the event has already been processed and stored
+into the room, which means this callback cannot be used to deny persisting the event. To
+deny an incoming event, see [`check_event_for_spam`](spam_checker_callbacks.md#check_event_for_spam) instead.
+
+If multiple modules implement this callback, Synapse runs them all in order.
+
 ## Example
 
 The example below is a module that implements the third-party rules callback
diff --git a/docs/openid.md b/docs/openid.md
index 49180eec52..c74e8bda60 100644
--- a/docs/openid.md
+++ b/docs/openid.md
@@ -21,6 +21,8 @@ such as [Github][github-idp].
 
 [google-idp]: https://developers.google.com/identity/protocols/oauth2/openid-connect
 [auth0]: https://auth0.com/
+[authentik]: https://goauthentik.io/
+[lemonldap]: https://lemonldap-ng.org/
 [okta]: https://www.okta.com/
 [dex-idp]: https://github.com/dexidp/dex
 [keycloak-idp]: https://www.keycloak.org/docs/latest/server_admin/#sso-protocols
@@ -209,6 +211,76 @@ oidc_providers:
         display_name_template: "{{ user.name }}"
 ```
 
+### Authentik
+
+[Authentik][authentik] is an open-source IdP solution.
+
+1. Create a provider in Authentik, with type OAuth2/OpenID.
+2. The parameters are:
+- Client Type: Confidential
+- JWT Algorithm: RS256
+- Scopes: OpenID, Email and Profile
+- RSA Key: Select any available key
+- Redirect URIs: `[synapse public baseurl]/_synapse/client/oidc/callback`
+3. Create an application for synapse in Authentik and link it to the provider.
+4. Note the slug of your application, Client ID and Client Secret.
+
+Synapse config:
+```yaml
+oidc_providers:
+  - idp_id: authentik
+    idp_name: authentik
+    discover: true
+    issuer: "https://your.authentik.example.org/application/o/your-app-slug/" # TO BE FILLED: domain and slug
+    client_id: "your client id" # TO BE FILLED
+    client_secret: "your client secret" # TO BE FILLED
+    scopes:
+      - "openid"
+      - "profile"
+      - "email"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}}"
+        display_name_template: "{{ user.preferred_username|capitalize }}" # TO BE FILLED: If your users have names in Authentik and you want those in Synapse, this should be replaced with user.name|capitalize.
+```
+
+### LemonLDAP
+
+[LemonLDAP::NG][lemonldap] is an open-source IdP solution.
+
+1. Create an OpenID Connect Relying Parties in LemonLDAP::NG
+2. The parameters are:
+- Client ID under the basic menu of the new Relying Parties (`Options > Basic >
+  Client ID`)
+- Client secret (`Options > Basic > Client secret`)
+- JWT Algorithm: RS256 within the security menu of the new Relying Parties
+  (`Options > Security > ID Token signature algorithm` and `Options > Security >
+  Access Token signature algorithm`)
+- Scopes: OpenID, Email and Profile
+- Allowed redirection addresses for login (`Options > Basic > Allowed
+  redirection addresses for login` ) :
+  `[synapse public baseurl]/_synapse/client/oidc/callback`
+
+Synapse config:
+```yaml
+oidc_providers:
+  - idp_id: lemonldap
+    idp_name: lemonldap
+    discover: true
+    issuer: "https://auth.example.org/" # TO BE FILLED: replace with your domain
+    client_id: "your client id" # TO BE FILLED
+    client_secret: "your client secret" # TO BE FILLED
+    scopes:
+      - "openid"
+      - "profile"
+      - "email"
+    user_mapping_provider:
+      config:
+        localpart_template: "{{ user.preferred_username }}}"
+        # TO BE FILLED: If your users have names in LemonLDAP::NG and you want those in Synapse, this should be replaced with user.name|capitalize or any valid filter.
+        display_name_template: "{{ user.preferred_username|capitalize }}"
+```
+
 ### GitHub
 
 [GitHub][github-idp] is a bit special as it is not an OpenID Connect compliant provider, but
diff --git a/docs/postgres.md b/docs/postgres.md
index 2c0a5b803a..083b0aaff0 100644
--- a/docs/postgres.md
+++ b/docs/postgres.md
@@ -29,16 +29,20 @@ connect to a postgres database.
 
 Assuming your PostgreSQL database user is called `postgres`, first authenticate as the database user with:
 
-    su - postgres
-    # Or, if your system uses sudo to get administrative rights
-    sudo -u postgres bash
+```sh
+su - postgres
+# Or, if your system uses sudo to get administrative rights
+sudo -u postgres bash
+```
 
 Then, create a postgres user and a database with:
 
-    # this will prompt for a password for the new user
-    createuser --pwprompt synapse_user
+```sh
+# this will prompt for a password for the new user
+createuser --pwprompt synapse_user
 
-    createdb --encoding=UTF8 --locale=C --template=template0 --owner=synapse_user synapse
+createdb --encoding=UTF8 --locale=C --template=template0 --owner=synapse_user synapse
+```
 
 The above will create a user called `synapse_user`, and a database called
 `synapse`.
@@ -145,20 +149,26 @@ Firstly, shut down the currently running synapse server and copy its
 database file (typically `homeserver.db`) to another location. Once the
 copy is complete, restart synapse. For instance:
 
-    ./synctl stop
-    cp homeserver.db homeserver.db.snapshot
-    ./synctl start
+```sh
+./synctl stop
+cp homeserver.db homeserver.db.snapshot
+./synctl start
+```
 
 Copy the old config file into a new config file:
 
-    cp homeserver.yaml homeserver-postgres.yaml
+```sh
+cp homeserver.yaml homeserver-postgres.yaml
+```
 
 Edit the database section as described in the section *Synapse config*
 above and with the SQLite snapshot located at `homeserver.db.snapshot`
 simply run:
 
-    synapse_port_db --sqlite-database homeserver.db.snapshot \
-        --postgres-config homeserver-postgres.yaml
+```sh
+synapse_port_db --sqlite-database homeserver.db.snapshot \
+    --postgres-config homeserver-postgres.yaml
+```
 
 The flag `--curses` displays a coloured curses progress UI.
 
@@ -170,16 +180,20 @@ To complete the conversion shut down the synapse server and run the port
 script one last time, e.g. if the SQLite database is at `homeserver.db`
 run:
 
-    synapse_port_db --sqlite-database homeserver.db \
-        --postgres-config homeserver-postgres.yaml
+```sh
+synapse_port_db --sqlite-database homeserver.db \
+    --postgres-config homeserver-postgres.yaml
+```
 
 Once that has completed, change the synapse config to point at the
 PostgreSQL database configuration file `homeserver-postgres.yaml`:
 
-    ./synctl stop
-    mv homeserver.yaml homeserver-old-sqlite.yaml
-    mv homeserver-postgres.yaml homeserver.yaml
-    ./synctl start
+```sh
+./synctl stop
+mv homeserver.yaml homeserver-old-sqlite.yaml
+mv homeserver-postgres.yaml homeserver.yaml
+./synctl start
+```
 
 Synapse should now be running against PostgreSQL.
 
diff --git a/docs/reverse_proxy.md b/docs/reverse_proxy.md
index bc351d604e..f3b3aea732 100644
--- a/docs/reverse_proxy.md
+++ b/docs/reverse_proxy.md
@@ -52,7 +52,7 @@ to proxied traffic.)
 
 ### nginx
 
-```
+```nginx
 server {
     listen 443 ssl http2;
     listen [::]:443 ssl http2;
@@ -141,7 +141,7 @@ matrix.example.com {
 
 ### Apache
 
-```
+```apache
 <VirtualHost *:443>
     SSLEngine on
     ServerName matrix.example.com
@@ -170,7 +170,7 @@ matrix.example.com {
 
 **NOTE 2**: It appears that Synapse is currently incompatible with the ModSecurity module for Apache (`mod_security2`). If you need it enabled for other services on your web server, you can disable it for Synapse's two VirtualHosts by including the following lines before each of the two `</VirtualHost>` above:
 
-```
+```apache
 <IfModule security2_module>
     SecRuleEngine off
 </IfModule>
@@ -188,7 +188,7 @@ frontend https
   http-request set-header X-Forwarded-For %[src]
 
   # Matrix client traffic
-  acl matrix-host hdr(host) -i matrix.example.com
+  acl matrix-host hdr(host) -i matrix.example.com matrix.example.com:443
   acl matrix-path path_beg /_matrix
   acl matrix-path path_beg /_synapse/client
 
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index b90ed62d61..d48c08f1d9 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -91,8 +91,28 @@ pid_file: DATADIR/homeserver.pid
 # Otherwise, it should be the URL to reach Synapse's client HTTP listener (see
 # 'listeners' below).
 #
+# Defaults to 'https://<server_name>/'.
+#
 #public_baseurl: https://example.com/
 
+# Uncomment the following to tell other servers to send federation traffic on
+# port 443.
+#
+# By default, other servers will try to reach our server on port 8448, which can
+# be inconvenient in some environments.
+#
+# Provided 'https://<server_name>/' on port 443 is routed to Synapse, this
+# option configures Synapse to serve a file at
+# 'https://<server_name>/.well-known/matrix/server'. This will tell other
+# servers to send traffic to port 443 instead.
+#
+# See https://matrix-org.github.io/synapse/latest/delegate.html for more
+# information.
+#
+# Defaults to 'false'.
+#
+#serve_server_wellknown: true
+
 # Set the soft limit on the number of file descriptors synapse can use
 # Zero is used to indicate synapse should set the soft limit to the
 # hard limit.
@@ -1247,7 +1267,7 @@ oembed:
 # in on this server.
 #
 # (By default, no suggestion is made, so it is left up to the client.
-# This setting is ignored unless public_baseurl is also set.)
+# This setting is ignored unless public_baseurl is also explicitly set.)
 #
 #default_identity_server: https://matrix.org
 
@@ -1272,8 +1292,6 @@ oembed:
 # by the Matrix Identity Service API specification:
 # https://matrix.org/docs/spec/identity_service/latest
 #
-# If a delegate is specified, the config option public_baseurl must also be filled out.
-#
 account_threepid_delegates:
     #email: https://example.com     # Delegate email sending to example.com
     #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
@@ -1963,11 +1981,10 @@ sso:
     # phishing attacks from evil.site. To avoid this, include a slash after the
     # hostname: "https://my.client/".
     #
-    # If public_baseurl is set, then the login fallback page (used by clients
-    # that don't natively support the required login flows) is whitelisted in
-    # addition to any URLs in this list.
+    # The login fallback page (used by clients that don't natively support the
+    # required login flows) is whitelisted in addition to any URLs in this list.
     #
-    # By default, this list is empty.
+    # By default, this list contains only the login fallback page.
     #
     #client_whitelist:
     #  - https://riot.im/develop
diff --git a/docs/setup/installation.md b/docs/setup/installation.md
index 874925e927..3e08024441 100644
--- a/docs/setup/installation.md
+++ b/docs/setup/installation.md
@@ -356,12 +356,14 @@ make install
 
 ##### Windows
 
-If you wish to run or develop Synapse on Windows, the Windows Subsystem For
-Linux provides a Linux environment on Windows 10 which is capable of using the
-Debian, Fedora, or source installation methods. More information about WSL can
-be found at <https://docs.microsoft.com/en-us/windows/wsl/install-win10> for
-Windows 10 and <https://docs.microsoft.com/en-us/windows/wsl/install-on-server>
-for Windows Server.
+Running Synapse natively on Windows is not officially supported.
+
+If you wish to run or develop Synapse on Windows, the Windows Subsystem for
+Linux provides a Linux environment which is capable of using the Debian, Fedora,
+or source installation methods. More information about WSL can be found at
+<https://docs.microsoft.com/en-us/windows/wsl/install> for Windows 10/11 and
+<https://docs.microsoft.com/en-us/windows/wsl/install-on-server> for
+Windows Server.
 
 ## Setting up Synapse
 
diff --git a/docs/synctl_workers.md b/docs/synctl_workers.md
index 8da4a31852..15e37f608d 100644
--- a/docs/synctl_workers.md
+++ b/docs/synctl_workers.md
@@ -20,7 +20,9 @@ Finally, to actually run your worker-based synapse, you must pass synctl the `-a
 commandline option to tell it to operate on all the worker configurations found
 in the given directory, e.g.:
 
-    synctl -a $CONFIG/workers start
+```sh
+synctl -a $CONFIG/workers start
+```
 
 Currently one should always restart all workers when restarting or upgrading
 synapse, unless you explicitly know it's safe not to.  For instance, restarting
@@ -29,4 +31,6 @@ notifications.
 
 To manipulate a specific worker, you pass the -w option to synctl:
 
-    synctl -w $CONFIG/workers/worker1.yaml restart
+```sh
+synctl -w $CONFIG/workers/worker1.yaml restart
+```
diff --git a/docs/systemd-with-workers/system/matrix-synapse-worker@.service b/docs/systemd-with-workers/system/matrix-synapse-worker@.service
index d164e8ce1f..8f5c44c9d4 100644
--- a/docs/systemd-with-workers/system/matrix-synapse-worker@.service
+++ b/docs/systemd-with-workers/system/matrix-synapse-worker@.service
@@ -15,7 +15,7 @@ Type=notify
 NotifyAccess=main
 User=matrix-synapse
 WorkingDirectory=/var/lib/matrix-synapse
-EnvironmentFile=/etc/default/matrix-synapse
+EnvironmentFile=-/etc/default/matrix-synapse
 ExecStart=/opt/venvs/matrix-synapse/bin/python -m synapse.app.generic_worker --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/ --config-path=/etc/matrix-synapse/workers/%i.yaml
 ExecReload=/bin/kill -HUP $MAINPID
 Restart=always
diff --git a/docs/systemd-with-workers/system/matrix-synapse.service b/docs/systemd-with-workers/system/matrix-synapse.service
index f6b6dfd3ce..0c73fb55fb 100644
--- a/docs/systemd-with-workers/system/matrix-synapse.service
+++ b/docs/systemd-with-workers/system/matrix-synapse.service
@@ -10,7 +10,7 @@ Type=notify
 NotifyAccess=main
 User=matrix-synapse
 WorkingDirectory=/var/lib/matrix-synapse
-EnvironmentFile=/etc/default/matrix-synapse
+EnvironmentFile=-/etc/default/matrix-synapse
 ExecStartPre=/opt/venvs/matrix-synapse/bin/python -m synapse.app.homeserver --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/ --generate-keys
 ExecStart=/opt/venvs/matrix-synapse/bin/python -m synapse.app.homeserver --config-path=/etc/matrix-synapse/homeserver.yaml --config-path=/etc/matrix-synapse/conf.d/
 ExecReload=/bin/kill -HUP $MAINPID
diff --git a/docs/turn-howto.md b/docs/turn-howto.md
index 5d282099e3..e2f66f60e2 100644
--- a/docs/turn-howto.md
+++ b/docs/turn-howto.md
@@ -40,7 +40,9 @@ This will install and start a systemd service called `coturn`.
 
 1.  Configure it:
 
-        ./configure
+    ```sh
+    ./configure
+    ```
 
     You may need to install `libevent2`: if so, you should do so in
     the way recommended by your operating system. You can ignore
@@ -49,22 +51,28 @@ This will install and start a systemd service called `coturn`.
 
 1.  Build and install it:
 
-        make
-        make install
+    ```sh
+    make
+    make install
+    ```
 
 ### Configuration
 
 1.  Create or edit the config file in `/etc/turnserver.conf`. The relevant
     lines, with example values, are:
 
-        use-auth-secret
-        static-auth-secret=[your secret key here]
-        realm=turn.myserver.org
+    ```
+    use-auth-secret
+    static-auth-secret=[your secret key here]
+    realm=turn.myserver.org
+    ```
 
     See `turnserver.conf` for explanations of the options. One way to generate
     the `static-auth-secret` is with `pwgen`:
 
-        pwgen -s 64 1
+    ```sh
+    pwgen -s 64 1
+    ```
 
     A `realm` must be specified, but its value is somewhat arbitrary. (It is
     sent to clients as part of the authentication flow.) It is conventional to
@@ -73,7 +81,9 @@ This will install and start a systemd service called `coturn`.
 1.  You will most likely want to configure coturn to write logs somewhere. The
     easiest way is normally to send them to the syslog:
 
-        syslog
+    ```sh
+    syslog
+    ```
 
     (in which case, the logs will be available via `journalctl -u coturn` on a
     systemd system). Alternatively, coturn can be configured to write to a
@@ -83,31 +93,35 @@ This will install and start a systemd service called `coturn`.
     connect to arbitrary IP addresses and ports. The following configuration is
     suggested as a minimum starting point:
 
-        # VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
-        no-tcp-relay
+    ```
+    # VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
+    no-tcp-relay
 
-        # don't let the relay ever try to connect to private IP address ranges within your network (if any)
-        # given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
-        denied-peer-ip=10.0.0.0-10.255.255.255
-        denied-peer-ip=192.168.0.0-192.168.255.255
-        denied-peer-ip=172.16.0.0-172.31.255.255
+    # don't let the relay ever try to connect to private IP address ranges within your network (if any)
+    # given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
+    denied-peer-ip=10.0.0.0-10.255.255.255
+    denied-peer-ip=192.168.0.0-192.168.255.255
+    denied-peer-ip=172.16.0.0-172.31.255.255
 
-        # special case the turn server itself so that client->TURN->TURN->client flows work
-        allowed-peer-ip=10.0.0.1
+    # special case the turn server itself so that client->TURN->TURN->client flows work
+    allowed-peer-ip=10.0.0.1
 
-        # consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
-        user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
-        total-quota=1200
+    # consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
+    user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
+    total-quota=1200
+    ```
 
 1.  Also consider supporting TLS/DTLS. To do this, add the following settings
     to `turnserver.conf`:
 
-        # TLS certificates, including intermediate certs.
-        # For Let's Encrypt certificates, use `fullchain.pem` here.
-        cert=/path/to/fullchain.pem
+    ```
+    # TLS certificates, including intermediate certs.
+    # For Let's Encrypt certificates, use `fullchain.pem` here.
+    cert=/path/to/fullchain.pem
 
-        # TLS private key file
-        pkey=/path/to/privkey.pem
+    # TLS private key file
+    pkey=/path/to/privkey.pem
+    ```
 
     In this case, replace the `turn:` schemes in the `turn_uri` settings below
     with `turns:`.
@@ -126,7 +140,9 @@ This will install and start a systemd service called `coturn`.
     If you want to try it anyway, you will at least need to tell coturn its
     external IP address:
 
-        external-ip=192.88.99.1
+    ```
+    external-ip=192.88.99.1
+    ```
 
     ... and your NAT gateway must forward all of the relayed ports directly
     (eg, port 56789 on the external IP must be always be forwarded to port
@@ -186,7 +202,7 @@ After updating the homeserver configuration, you must restart synapse:
     ./synctl restart
     ```
   * If you use systemd:
-    ```
+    ```sh
     systemctl restart matrix-synapse.service
     ```
 ... and then reload any clients (or wait an hour for them to refresh their
diff --git a/docs/upgrade.md b/docs/upgrade.md
index c47eef1a20..136c806c41 100644
--- a/docs/upgrade.md
+++ b/docs/upgrade.md
@@ -85,6 +85,29 @@ process, for example:
     dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
     ```
 
+# Upgrading to v1.47.0
+
+## Removal of old Room Admin API
+
+The following admin APIs were deprecated in [Synapse 1.34](https://github.com/matrix-org/synapse/blob/v1.34.0/CHANGES.md#deprecations-and-removals)
+(released on 2021-05-17) and have now been removed:
+
+- `POST /_synapse/admin/v1/<room_id>/delete`
+
+Any scripts still using the above APIs should be converted to use the
+[Delete Room API](https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#delete-room-api).
+
+## Deprecation of the `user_may_create_room_with_invites` module callback
+
+The `user_may_create_room_with_invites` is deprecated and will be removed in a future
+version of Synapse. Modules implementing this callback can instead implement
+[`user_may_invite`](https://matrix-org.github.io/synapse/latest/modules/spam_checker_callbacks.html#user_may_invite)
+and use the [`get_room_state`](https://github.com/matrix-org/synapse/blob/872f23b95fa980a61b0866c1475e84491991fa20/synapse/module_api/__init__.py#L869-L876)
+module API method to infer whether the invite is happening in the context of creating a
+room.
+
+We plan to remove this callback in January 2022.
+
 # Upgrading to v1.45.0
 
 ## Changes required to media storage provider modules when reading from the Synapse configuration object
@@ -1163,16 +1186,20 @@ For more information on configuring TLS certificates see the
     For users who have installed Synapse into a virtualenv, we recommend
     doing this by creating a new virtualenv. For example:
 
-        virtualenv -p python3 ~/synapse/env3
-        source ~/synapse/env3/bin/activate
-        pip install matrix-synapse
+    ```sh
+    virtualenv -p python3 ~/synapse/env3
+    source ~/synapse/env3/bin/activate
+    pip install matrix-synapse
+    ```
 
     You can then start synapse as normal, having activated the new
     virtualenv:
 
-        cd ~/synapse
-        source env3/bin/activate
-        synctl start
+    ```sh
+    cd ~/synapse
+    source env3/bin/activate
+    synctl start
+    ```
 
     Users who have installed from distribution packages should see the
     relevant package documentation. See below for notes on Debian
@@ -1184,34 +1211,38 @@ For more information on configuring TLS certificates see the
         `<server>.log.config` file. For example, if your `log.config`
         file contains:
 
-            handlers:
-              file:
-                class: logging.handlers.RotatingFileHandler
-                formatter: precise
-                filename: homeserver.log
-                maxBytes: 104857600
-                backupCount: 10
-                filters: [context]
-              console:
-                class: logging.StreamHandler
-                formatter: precise
-                filters: [context]
+        ```yaml
+        handlers:
+          file:
+            class: logging.handlers.RotatingFileHandler
+            formatter: precise
+            filename: homeserver.log
+            maxBytes: 104857600
+            backupCount: 10
+            filters: [context]
+          console:
+            class: logging.StreamHandler
+            formatter: precise
+            filters: [context]
+        ```
 
         Then you should update this to be:
 
-            handlers:
-              file:
-                class: logging.handlers.RotatingFileHandler
-                formatter: precise
-                filename: homeserver.log
-                maxBytes: 104857600
-                backupCount: 10
-                filters: [context]
-                encoding: utf8
-              console:
-                class: logging.StreamHandler
-                formatter: precise
-                filters: [context]
+        ```yaml
+        handlers:
+          file:
+            class: logging.handlers.RotatingFileHandler
+            formatter: precise
+            filename: homeserver.log
+            maxBytes: 104857600
+            backupCount: 10
+            filters: [context]
+            encoding: utf8
+          console:
+            class: logging.StreamHandler
+            formatter: precise
+            filters: [context]
+        ```
 
         There is no need to revert this change if downgrading to
         Python 2.
@@ -1297,24 +1328,28 @@ with the HS remotely has been removed.
 It has been replaced by specifying a list of application service
 registrations in `homeserver.yaml`:
 
-    app_service_config_files: ["registration-01.yaml", "registration-02.yaml"]
+```yaml
+app_service_config_files: ["registration-01.yaml", "registration-02.yaml"]
+```
 
 Where `registration-01.yaml` looks like:
 
-    url: <String>  # e.g. "https://my.application.service.com"
-    as_token: <String>
-    hs_token: <String>
-    sender_localpart: <String>  # This is a new field which denotes the user_id localpart when using the AS token
-    namespaces:
-      users:
-        - exclusive: <Boolean>
-          regex: <String>  # e.g. "@prefix_.*"
-      aliases:
-        - exclusive: <Boolean>
-          regex: <String>
-      rooms:
-        - exclusive: <Boolean>
-          regex: <String>
+```yaml
+url: <String>  # e.g. "https://my.application.service.com"
+as_token: <String>
+hs_token: <String>
+sender_localpart: <String>  # This is a new field which denotes the user_id localpart when using the AS token
+namespaces:
+  users:
+    - exclusive: <Boolean>
+      regex: <String>  # e.g. "@prefix_.*"
+  aliases:
+    - exclusive: <Boolean>
+      regex: <String>
+  rooms:
+    - exclusive: <Boolean>
+      regex: <String>
+```
 
 # Upgrading to v0.8.0
 
diff --git a/docs/usage/administration/admin_api/background_updates.md b/docs/usage/administration/admin_api/background_updates.md
new file mode 100644
index 0000000000..b36d7fe398
--- /dev/null
+++ b/docs/usage/administration/admin_api/background_updates.md
@@ -0,0 +1,84 @@
+# Background Updates API
+
+This API allows a server administrator to manage the background updates being
+run against the database.
+
+## Status
+
+This API gets the current status of the background updates.
+
+
+The API is:
+
+```
+GET /_synapse/admin/v1/background_updates/status
+```
+
+Returning:
+
+```json
+{
+    "enabled": true,
+    "current_updates": {
+        "<db_name>": {
+            "name": "<background_update_name>",
+            "total_item_count": 50,
+            "total_duration_ms": 10000.0,
+            "average_items_per_ms": 2.2,
+        },
+    }
+}
+```
+
+`enabled` whether the background updates are enabled or disabled.
+
+`db_name` the database name (usually Synapse is configured with a single database named 'master').
+
+For each update:
+
+`name` the name of the update.
+`total_item_count` total number of "items" processed (the meaning of 'items' depends on the update in question).
+`total_duration_ms` how long the background process has been running, not including time spent sleeping.
+`average_items_per_ms` how many items are processed per millisecond based on an exponential average.
+
+
+
+## Enabled
+
+This API allow pausing background updates.
+
+Background updates should *not* be paused for significant periods of time, as
+this can affect the performance of Synapse.
+
+*Note*: This won't persist over restarts.
+
+*Note*: This won't cancel any update query that is currently running. This is
+usually fine since most queries are short lived, except for `CREATE INDEX`
+background updates which won't be cancelled once started.
+
+
+The API is:
+
+```
+POST /_synapse/admin/v1/background_updates/enabled
+```
+
+with the following body:
+
+```json
+{
+    "enabled": false
+}
+```
+
+`enabled` sets whether the background updates are enabled or disabled.
+
+The API returns the `enabled` param.
+
+```json
+{
+    "enabled": false
+}
+```
+
+There is also a `GET` version which returns the `enabled` state.
diff --git a/docs/workers.md b/docs/workers.md
index f1673d67d0..f88e2c1de3 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -443,19 +443,19 @@ In the `media_repository` worker configuration file, configure the http listener
 expose the `media` resource. For example:
 
 ```yaml
-    worker_listeners:
-     - type: http
-       port: 8085
-       resources:
-         - names:
-           - media
+worker_listeners:
+ - type: http
+   port: 8085
+   resources:
+     - names:
+       - media
 ```
 
 Note that if running multiple media repositories they must be on the same server
 and you must configure a single instance to run the background tasks, e.g.:
 
 ```yaml
-    media_instance_running_background_jobs: "media-repository-1"
+media_instance_running_background_jobs: "media-repository-1"
 ```
 
 Note that if a reverse proxy is used , then `/_matrix/media/` must be routed for both inbound client and federation requests (if they are handled separately).
@@ -492,7 +492,9 @@ must therefore be configured with the location of the main instance, via
 the `worker_main_http_uri` setting in the `frontend_proxy` worker configuration
 file. For example:
 
-    worker_main_http_uri: http://127.0.0.1:8008
+```yaml
+worker_main_http_uri: http://127.0.0.1:8008
+```
 
 ### Historical apps
 
diff --git a/mypy.ini b/mypy.ini
index c5f44aea39..600402a5d3 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -16,31 +16,17 @@ no_implicit_optional = True
 
 files =
   scripts-dev/sign_json,
+  synapse/__init__.py,
   synapse/api,
   synapse/appservice,
   synapse/config,
   synapse/crypto,
   synapse/event_auth.py,
-  synapse/events/builder.py,
-  synapse/events/presence_router.py,
-  synapse/events/snapshot.py,
-  synapse/events/spamcheck.py,
-  synapse/events/third_party_rules.py,
-  synapse/events/utils.py,
-  synapse/events/validator.py,
+  synapse/events,
   synapse/federation,
   synapse/groups,
   synapse/handlers,
-  synapse/http/additional_resource.py,
-  synapse/http/client.py,
-  synapse/http/federation/matrix_federation_agent.py,
-  synapse/http/federation/srv_resolver.py,
-  synapse/http/federation/well_known_resolver.py,
-  synapse/http/matrixfederationclient.py,
-  synapse/http/proxyagent.py,
-  synapse/http/servlet.py,
-  synapse/http/server.py,
-  synapse/http/site.py,
+  synapse/http,
   synapse/logging,
   synapse/metrics,
   synapse/module_api,
@@ -61,6 +47,7 @@ files =
   synapse/storage/databases/main/keys.py,
   synapse/storage/databases/main/pusher.py,
   synapse/storage/databases/main/registration.py,
+  synapse/storage/databases/main/relations.py,
   synapse/storage/databases/main/session.py,
   synapse/storage/databases/main/stream.py,
   synapse/storage/databases/main/ui_auth.py,
diff --git a/scripts-dev/check-newsfragment b/scripts-dev/check-newsfragment
index 393a548d58..af4de345df 100755
--- a/scripts-dev/check-newsfragment
+++ b/scripts-dev/check-newsfragment
@@ -42,10 +42,10 @@ echo "--------------------------"
 echo
 
 matched=0
-for f in `git diff --name-only FETCH_HEAD... -- changelog.d`; do
+for f in $(git diff --name-only FETCH_HEAD... -- changelog.d); do
     # check that any modified newsfiles on this branch end with a full stop.
-    lastchar=`tr -d '\n' < $f | tail -c 1`
-    if [ $lastchar != '.' -a $lastchar != '!' ]; then
+    lastchar=$(tr -d '\n' < "$f" | tail -c 1)
+    if [ "$lastchar" != '.' ] && [ "$lastchar" != '!' ]; then
         echo -e "\e[31mERROR: newsfragment $f does not end with a '.' or '!'\e[39m" >&2
         echo -e "$CONTRIBUTING_GUIDE_TEXT" >&2
         exit 1
diff --git a/scripts-dev/check_line_terminators.sh b/scripts-dev/check_line_terminators.sh
index c983956231..fffa24e01e 100755
--- a/scripts-dev/check_line_terminators.sh
+++ b/scripts-dev/check_line_terminators.sh
@@ -25,7 +25,7 @@
 # terminators are found, 0 otherwise.
 
 # cd to the root of the repository
-cd `dirname $0`/..
+cd "$(dirname "$0")/.." || exit
 
 # Find and print files with non-unix line terminators
 if find . -path './.git/*' -prune -o -type f -print0 | xargs -0 grep -I -l $'\r$'; then
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index 89af7a4fde..7d38b39e90 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -24,7 +24,7 @@
 set -e
 
 # Change to the repository root
-cd "$(dirname $0)/.."
+cd "$(dirname "$0")/.."
 
 # Check for a user-specified Complement checkout
 if [[ -z "$COMPLEMENT_DIR" ]]; then
@@ -61,8 +61,8 @@ cd "$COMPLEMENT_DIR"
 EXTRA_COMPLEMENT_ARGS=""
 if [[ -n "$1" ]]; then
   # A test name regex has been set, supply it to Complement
-  EXTRA_COMPLEMENT_ARGS+="-run $1 "
+  EXTRA_COMPLEMENT_ARGS=(-run "$1")
 fi
 
 # Run the tests!
-go test -v -tags synapse_blacklist,msc2946,msc3083,msc2403,msc2716 -count=1 $EXTRA_COMPLEMENT_ARGS ./tests/...
+go test -v -tags synapse_blacklist,msc2946,msc3083,msc2403,msc2716 -count=1 "${EXTRA_COMPLEMENT_ARGS[@]}" ./tests/...
diff --git a/scripts-dev/config-lint.sh b/scripts-dev/config-lint.sh
index 8c6323e59a..6ce030b819 100755
--- a/scripts-dev/config-lint.sh
+++ b/scripts-dev/config-lint.sh
@@ -3,7 +3,7 @@
 # Exits with 0 if there are no problems, or another code otherwise.
 
 # cd to the root of the repository
-cd `dirname $0`/..
+cd "$(dirname "$0")/.." || exit
 
 # Restore backup of sample config upon script exit
 trap "mv docs/sample_config.yaml.bak docs/sample_config.yaml" EXIT
diff --git a/scripts-dev/docker_update_debian_changelog.sh b/scripts-dev/docker_update_debian_changelog.sh
index 89821bba72..729f8fc467 100755
--- a/scripts-dev/docker_update_debian_changelog.sh
+++ b/scripts-dev/docker_update_debian_changelog.sh
@@ -60,5 +60,5 @@ DEBIAN_FRONTEND=noninteractive apt-get install -y devscripts
 
 # Update the Debian changelog.
 ver=${1}
-dch -M -v $(sed -Ee 's/(rc|a|b|c)/~\1/' <<<$ver) "New synapse release $ver."
+dch -M -v "$(sed -Ee 's/(rc|a|b|c)/~\1/' <<<"$ver")" "New synapse release $ver."
 dch -M -r -D stable ""
diff --git a/scripts-dev/generate_sample_config b/scripts-dev/generate_sample_config
index 02739894b5..4cd1d1d5b8 100755
--- a/scripts-dev/generate_sample_config
+++ b/scripts-dev/generate_sample_config
@@ -4,7 +4,7 @@
 
 set -e
 
-cd `dirname $0`/..
+cd "$(dirname "$0")/.."
 
 SAMPLE_CONFIG="docs/sample_config.yaml"
 SAMPLE_LOG_CONFIG="docs/sample_log_config.yaml"
diff --git a/scripts-dev/next_github_number.sh b/scripts-dev/next_github_number.sh
index 00e9b14569..5ecd515127 100755
--- a/scripts-dev/next_github_number.sh
+++ b/scripts-dev/next_github_number.sh
@@ -4,6 +4,6 @@ set -e
 
 # Fetch the current GitHub issue number, add one to it -- presto! The likely
 # next PR number.
-CURRENT_NUMBER=`curl -s "https://api.github.com/repos/matrix-org/synapse/issues?state=all&per_page=1" | jq -r ".[0].number"`
+CURRENT_NUMBER=$(curl -s "https://api.github.com/repos/matrix-org/synapse/issues?state=all&per_page=1" | jq -r ".[0].number")
 CURRENT_NUMBER=$((CURRENT_NUMBER+1))
 echo $CURRENT_NUMBER
diff --git a/scripts/synapse_port_db b/scripts/synapse_port_db
index 349866eb9a..640ff15277 100755
--- a/scripts/synapse_port_db
+++ b/scripts/synapse_port_db
@@ -43,6 +43,7 @@ from synapse.storage.databases.main.end_to_end_keys import EndToEndKeyBackground
 from synapse.storage.databases.main.events_bg_updates import (
     EventsBackgroundUpdatesStore,
 )
+from synapse.storage.databases.main.group_server import GroupServerWorkerStore
 from synapse.storage.databases.main.media_repository import (
     MediaRepositoryBackgroundUpdateStore,
 )
@@ -181,6 +182,7 @@ class Store(
     StatsStore,
     PusherWorkerStore,
     PresenceBackgroundUpdateStore,
+    GroupServerWorkerStore,
 ):
     def execute(self, f, *args, **kwargs):
         return self.db_pool.runInteraction(f.__name__, f, *args, **kwargs)
diff --git a/setup.py b/setup.py
index 220084a49d..345cff09c3 100755
--- a/setup.py
+++ b/setup.py
@@ -132,6 +132,9 @@ CONDITIONAL_REQUIREMENTS["dev"] = (
         "GitPython==3.1.14",
         "commonmark==0.9.1",
         "pygithub==1.55",
+        # The following are executed as commands by the release script.
+        "twine",
+        "towncrier",
     ]
 )
 
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 5ef34bce40..aa964afb5e 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -47,7 +47,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.46.0"
+__version__ = "1.47.0"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when
diff --git a/synapse/_scripts/review_recent_signups.py b/synapse/_scripts/review_recent_signups.py
index 9de913db88..8e66a38421 100644
--- a/synapse/_scripts/review_recent_signups.py
+++ b/synapse/_scripts/review_recent_signups.py
@@ -20,7 +20,12 @@ from typing import List
 
 import attr
 
-from synapse.config._base import RootConfig, find_config_files, read_config_files
+from synapse.config._base import (
+    Config,
+    RootConfig,
+    find_config_files,
+    read_config_files,
+)
 from synapse.config.database import DatabaseConfig
 from synapse.storage.database import DatabasePool, LoggingTransaction, make_conn
 from synapse.storage.engines import create_engine
@@ -126,7 +131,7 @@ def main():
         config_dict,
     )
 
-    since_ms = time.time() * 1000 - config.parse_duration(config_args.since)
+    since_ms = time.time() * 1000 - Config.parse_duration(config_args.since)
     exclude_users_with_email = config_args.exclude_emails
     include_context = not config_args.only_users
 
diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index 685d1c25cf..85302163da 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -596,3 +596,10 @@ class ShadowBanError(Exception):
 
     This should be caught and a proper "fake" success response sent to the user.
     """
+
+
+class ModuleFailedException(Exception):
+    """
+    Raised when a module API callback fails, for example because it raised an
+    exception.
+    """
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index bc550ae646..4b0a9b2974 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -18,7 +18,8 @@ import json
 from typing import (
     TYPE_CHECKING,
     Awaitable,
-    Container,
+    Callable,
+    Dict,
     Iterable,
     List,
     Optional,
@@ -217,19 +218,19 @@ class FilterCollection:
         return self._filter_json
 
     def timeline_limit(self) -> int:
-        return self._room_timeline_filter.limit()
+        return self._room_timeline_filter.limit
 
     def presence_limit(self) -> int:
-        return self._presence_filter.limit()
+        return self._presence_filter.limit
 
     def ephemeral_limit(self) -> int:
-        return self._room_ephemeral_filter.limit()
+        return self._room_ephemeral_filter.limit
 
     def lazy_load_members(self) -> bool:
-        return self._room_state_filter.lazy_load_members()
+        return self._room_state_filter.lazy_load_members
 
     def include_redundant_members(self) -> bool:
-        return self._room_state_filter.include_redundant_members()
+        return self._room_state_filter.include_redundant_members
 
     def filter_presence(
         self, events: Iterable[UserPresenceState]
@@ -276,19 +277,25 @@ class Filter:
     def __init__(self, filter_json: JsonDict):
         self.filter_json = filter_json
 
-        self.types = self.filter_json.get("types", None)
-        self.not_types = self.filter_json.get("not_types", [])
+        self.limit = filter_json.get("limit", 10)
+        self.lazy_load_members = filter_json.get("lazy_load_members", False)
+        self.include_redundant_members = filter_json.get(
+            "include_redundant_members", False
+        )
+
+        self.types = filter_json.get("types", None)
+        self.not_types = filter_json.get("not_types", [])
 
-        self.rooms = self.filter_json.get("rooms", None)
-        self.not_rooms = self.filter_json.get("not_rooms", [])
+        self.rooms = filter_json.get("rooms", None)
+        self.not_rooms = filter_json.get("not_rooms", [])
 
-        self.senders = self.filter_json.get("senders", None)
-        self.not_senders = self.filter_json.get("not_senders", [])
+        self.senders = filter_json.get("senders", None)
+        self.not_senders = filter_json.get("not_senders", [])
 
-        self.contains_url = self.filter_json.get("contains_url", None)
+        self.contains_url = filter_json.get("contains_url", None)
 
-        self.labels = self.filter_json.get("org.matrix.labels", None)
-        self.not_labels = self.filter_json.get("org.matrix.not_labels", [])
+        self.labels = filter_json.get("org.matrix.labels", None)
+        self.not_labels = filter_json.get("org.matrix.not_labels", [])
 
     def filters_all_types(self) -> bool:
         return "*" in self.not_types
@@ -302,76 +309,95 @@ class Filter:
     def check(self, event: FilterEvent) -> bool:
         """Checks whether the filter matches the given event.
 
+        Args:
+            event: The event, account data, or presence to check against this
+                filter.
+
         Returns:
-            True if the event matches
+            True if the event matches the filter.
         """
         # We usually get the full "events" as dictionaries coming through,
         # except for presence which actually gets passed around as its own
         # namedtuple type.
         if isinstance(event, UserPresenceState):
-            sender: Optional[str] = event.user_id
-            room_id = None
-            ev_type = "m.presence"
-            contains_url = False
-            labels: List[str] = []
+            user_id = event.user_id
+            field_matchers = {
+                "senders": lambda v: user_id == v,
+                "types": lambda v: "m.presence" == v,
+            }
+            return self._check_fields(field_matchers)
         else:
+            content = event.get("content")
+            # Content is assumed to be a dict below, so ensure it is. This should
+            # always be true for events, but account_data has been allowed to
+            # have non-dict content.
+            if not isinstance(content, dict):
+                content = {}
+
             sender = event.get("sender", None)
             if not sender:
                 # Presence events had their 'sender' in content.user_id, but are
                 # now handled above. We don't know if anything else uses this
                 # form. TODO: Check this and probably remove it.
-                content = event.get("content")
-                # account_data has been allowed to have non-dict content, so
-                # check type first
-                if isinstance(content, dict):
-                    sender = content.get("user_id")
+                sender = content.get("user_id")
 
             room_id = event.get("room_id", None)
             ev_type = event.get("type", None)
 
-            content = event.get("content") or {}
             # check if there is a string url field in the content for filtering purposes
-            contains_url = isinstance(content.get("url"), str)
             labels = content.get(EventContentFields.LABELS, [])
 
-        return self.check_fields(room_id, sender, ev_type, labels, contains_url)
+            field_matchers = {
+                "rooms": lambda v: room_id == v,
+                "senders": lambda v: sender == v,
+                "types": lambda v: _matches_wildcard(ev_type, v),
+                "labels": lambda v: v in labels,
+            }
+
+            result = self._check_fields(field_matchers)
+            if not result:
+                return result
+
+            contains_url_filter = self.contains_url
+            if contains_url_filter is not None:
+                contains_url = isinstance(content.get("url"), str)
+                if contains_url_filter != contains_url:
+                    return False
+
+            return True
 
-    def check_fields(
-        self,
-        room_id: Optional[str],
-        sender: Optional[str],
-        event_type: Optional[str],
-        labels: Container[str],
-        contains_url: bool,
-    ) -> bool:
+    def _check_fields(self, field_matchers: Dict[str, Callable[[str], bool]]) -> bool:
         """Checks whether the filter matches the given event fields.
 
+        Args:
+            field_matchers: A map of attribute name to callable to use for checking
+                particular fields.
+
+                The attribute name and an inverse (not_<attribute name>) must
+                exist on the Filter.
+
+                The callable should return true if the event's value matches the
+                filter's value.
+
         Returns:
             True if the event fields match
         """
-        literal_keys = {
-            "rooms": lambda v: room_id == v,
-            "senders": lambda v: sender == v,
-            "types": lambda v: _matches_wildcard(event_type, v),
-            "labels": lambda v: v in labels,
-        }
-
-        for name, match_func in literal_keys.items():
+
+        for name, match_func in field_matchers.items():
+            # If the event matches one of the disallowed values, reject it.
             not_name = "not_%s" % (name,)
             disallowed_values = getattr(self, not_name)
             if any(map(match_func, disallowed_values)):
                 return False
 
+            # Other the event does not match at least one of the allowed values,
+            # reject it.
             allowed_values = getattr(self, name)
             if allowed_values is not None:
                 if not any(map(match_func, allowed_values)):
                     return False
 
-        contains_url_filter = self.filter_json.get("contains_url")
-        if contains_url_filter is not None:
-            if contains_url_filter != contains_url:
-                return False
-
+        # Otherwise, accept it.
         return True
 
     def filter_rooms(self, room_ids: Iterable[str]) -> Set[str]:
@@ -385,10 +411,10 @@ class Filter:
         """
         room_ids = set(room_ids)
 
-        disallowed_rooms = set(self.filter_json.get("not_rooms", []))
+        disallowed_rooms = set(self.not_rooms)
         room_ids -= disallowed_rooms
 
-        allowed_rooms = self.filter_json.get("rooms", None)
+        allowed_rooms = self.rooms
         if allowed_rooms is not None:
             room_ids &= set(allowed_rooms)
 
@@ -397,15 +423,6 @@ class Filter:
     def filter(self, events: Iterable[FilterEvent]) -> List[FilterEvent]:
         return list(filter(self.check, events))
 
-    def limit(self) -> int:
-        return self.filter_json.get("limit", 10)
-
-    def lazy_load_members(self) -> bool:
-        return self.filter_json.get("lazy_load_members", False)
-
-    def include_redundant_members(self) -> bool:
-        return self.filter_json.get("include_redundant_members", False)
-
     def with_room_ids(self, room_ids: Iterable[str]) -> "Filter":
         """Returns a new filter with the given room IDs appended.
 
diff --git a/synapse/api/urls.py b/synapse/api/urls.py
index 6e84b1524f..4486b3bc7d 100644
--- a/synapse/api/urls.py
+++ b/synapse/api/urls.py
@@ -38,9 +38,6 @@ class ConsentURIBuilder:
     def __init__(self, hs_config: HomeServerConfig):
         if hs_config.key.form_secret is None:
             raise ConfigError("form_secret not set in config")
-        if hs_config.server.public_baseurl is None:
-            raise ConfigError("public_baseurl not set in config")
-
         self._hmac_secret = hs_config.key.form_secret.encode("utf-8")
         self._public_baseurl = hs_config.server.public_baseurl
 
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index f4c3f867a8..f2c1028b5d 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -45,6 +45,7 @@ from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.handlers.auth import load_legacy_password_auth_providers
 from synapse.logging.context import PreserveLoggingContext
+from synapse.metrics import register_threadpool
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.metrics.jemalloc import setup_jemalloc_stats
 from synapse.util.caches.lrucache import setup_expire_lru_cache_entries
@@ -351,6 +352,10 @@ async def start(hs: "HomeServer"):
         GAIResolver(reactor, getThreadPool=lambda: resolver_threadpool)
     )
 
+    # Register the threadpools with our metrics.
+    register_threadpool("default", reactor.getThreadPool())
+    register_threadpool("gai_resolver", resolver_threadpool)
+
     # Set up the SIGHUP machinery.
     if hasattr(signal, "SIGHUP"):
 
diff --git a/synapse/app/admin_cmd.py b/synapse/app/admin_cmd.py
index 2fc848596d..ad20b1d6aa 100644
--- a/synapse/app/admin_cmd.py
+++ b/synapse/app/admin_cmd.py
@@ -145,6 +145,20 @@ class FileExfiltrationWriter(ExfiltrationWriter):
             for event in state.values():
                 print(json.dumps(event), file=f)
 
+    def write_knock(self, room_id, event, state):
+        self.write_events(room_id, [event])
+
+        # We write the knock state somewhere else as they aren't full events
+        # and are only a subset of the state at the event.
+        room_directory = os.path.join(self.base_directory, "rooms", room_id)
+        os.makedirs(room_directory, exist_ok=True)
+
+        knock_state = os.path.join(room_directory, "knock_state")
+
+        with open(knock_state, "a") as f:
+            for event in state.values():
+                print(json.dumps(event), file=f)
+
     def finished(self):
         return self.base_directory
 
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index 51eadf122d..218826741e 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -100,6 +100,7 @@ from synapse.rest.client.register import (
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyApiV2Resource
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
+from synapse.rest.well_known import well_known_resource
 from synapse.server import HomeServer
 from synapse.storage.databases.main.censor_events import CensorEventsStore
 from synapse.storage.databases.main.client_ips import ClientIpWorkerStore
@@ -318,6 +319,8 @@ class GenericWorkerServer(HomeServer):
                     resources.update({CLIENT_API_PREFIX: resource})
 
                     resources.update(build_synapse_client_resource_tree(self))
+                    resources.update({"/.well-known": well_known_resource(self)})
+
                 elif name == "federation":
                     resources.update({FEDERATION_PREFIX: TransportLayerServer(self)})
                 elif name == "media":
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 93e2299266..336c279a44 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -66,7 +66,7 @@ from synapse.rest.admin import AdminRestResource
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyApiV2Resource
 from synapse.rest.synapse.client import build_synapse_client_resource_tree
-from synapse.rest.well_known import WellKnownResource
+from synapse.rest.well_known import well_known_resource
 from synapse.server import HomeServer
 from synapse.storage import DataStore
 from synapse.util.httpresourcetree import create_resource_tree
@@ -189,7 +189,7 @@ class SynapseHomeServer(HomeServer):
                     "/_matrix/client/unstable": client_resource,
                     "/_matrix/client/v2_alpha": client_resource,
                     "/_matrix/client/versions": client_resource,
-                    "/.well-known/matrix/client": WellKnownResource(self),
+                    "/.well-known": well_known_resource(self),
                     "/_synapse/admin": AdminRestResource(self),
                     **build_synapse_client_resource_tree(self),
                 }
diff --git a/synapse/config/account_validity.py b/synapse/config/account_validity.py
index b56c2a24df..c533452cab 100644
--- a/synapse/config/account_validity.py
+++ b/synapse/config/account_validity.py
@@ -75,10 +75,6 @@ class AccountValidityConfig(Config):
                 self.account_validity_period * 10.0 / 100.0
             )
 
-        if self.account_validity_renew_by_email_enabled:
-            if not self.root.server.public_baseurl:
-                raise ConfigError("Can't send renewal emails without 'public_baseurl'")
-
         # Load account validity templates.
         account_validity_template_dir = account_validity_config.get("template_dir")
         if account_validity_template_dir is not None:
diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index 9b58ecf3d8..3f81814043 100644
--- a/synapse/config/cas.py
+++ b/synapse/config/cas.py
@@ -16,7 +16,7 @@ from typing import Any, List
 
 from synapse.config.sso import SsoAttributeRequirement
 
-from ._base import Config, ConfigError
+from ._base import Config
 from ._util import validate_config
 
 
@@ -35,14 +35,10 @@ class CasConfig(Config):
         if self.cas_enabled:
             self.cas_server_url = cas_config["server_url"]
 
-            # The public baseurl is required because it is used by the redirect
-            # template.
-            public_baseurl = self.root.server.public_baseurl
-            if not public_baseurl:
-                raise ConfigError("cas_config requires a public_baseurl to be set")
-
             # TODO Update this to a _synapse URL.
+            public_baseurl = self.root.server.public_baseurl
             self.cas_service_url = public_baseurl + "_matrix/client/r0/login/cas/ticket"
+
             self.cas_displayname_attribute = cas_config.get("displayname_attribute")
             required_attributes = cas_config.get("required_attributes") or {}
             self.cas_required_attributes = _parsed_required_attributes_def(
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index 8ff59aa2f8..afd65fecd3 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -186,11 +186,6 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
-            # public_baseurl is required to build password reset and validation links that
-            # will be emailed to users
-            if config.get("public_baseurl") is None:
-                missing.append("public_baseurl")
-
             if missing:
                 raise ConfigError(
                     MISSING_PASSWORD_RESET_CONFIG_ERROR % (", ".join(missing),)
@@ -296,9 +291,6 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
-            if config.get("public_baseurl") is None:
-                missing.append("public_baseurl")
-
             if missing:
                 raise ConfigError(
                     "email.enable_notifs is True but required keys are missing: %s"
diff --git a/synapse/config/oidc.py b/synapse/config/oidc.py
index 10f5796330..42f113cd24 100644
--- a/synapse/config/oidc.py
+++ b/synapse/config/oidc.py
@@ -59,8 +59,6 @@ class OIDCConfig(Config):
                 )
 
         public_baseurl = self.root.server.public_baseurl
-        if public_baseurl is None:
-            raise ConfigError("oidc_config requires a public_baseurl to be set")
         self.oidc_callback_url = public_baseurl + "_synapse/client/oidc/callback"
 
     @property
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index a3d2a38c4c..5379e80715 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -45,17 +45,6 @@ class RegistrationConfig(Config):
         account_threepid_delegates = config.get("account_threepid_delegates") or {}
         self.account_threepid_delegate_email = account_threepid_delegates.get("email")
         self.account_threepid_delegate_msisdn = account_threepid_delegates.get("msisdn")
-        if (
-            self.account_threepid_delegate_msisdn
-            and not self.root.server.public_baseurl
-        ):
-            raise ConfigError(
-                "The configuration option `public_baseurl` is required if "
-                "`account_threepid_delegate.msisdn` is set, such that "
-                "clients know where to submit validation tokens to. Please "
-                "configure `public_baseurl`."
-            )
-
         self.default_identity_server = config.get("default_identity_server")
         self.allow_guest_access = config.get("allow_guest_access", False)
 
@@ -240,7 +229,7 @@ class RegistrationConfig(Config):
         # in on this server.
         #
         # (By default, no suggestion is made, so it is left up to the client.
-        # This setting is ignored unless public_baseurl is also set.)
+        # This setting is ignored unless public_baseurl is also explicitly set.)
         #
         #default_identity_server: https://matrix.org
 
@@ -265,8 +254,6 @@ class RegistrationConfig(Config):
         # by the Matrix Identity Service API specification:
         # https://matrix.org/docs/spec/identity_service/latest
         #
-        # If a delegate is specified, the config option public_baseurl must also be filled out.
-        #
         account_threepid_delegates:
             #email: https://example.com     # Delegate email sending to example.com
             #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
diff --git a/synapse/config/saml2.py b/synapse/config/saml2.py
index 9c51b6a25a..ba2b0905ff 100644
--- a/synapse/config/saml2.py
+++ b/synapse/config/saml2.py
@@ -199,14 +199,11 @@ class SAML2Config(Config):
         """
         import saml2
 
-        public_baseurl = self.root.server.public_baseurl
-        if public_baseurl is None:
-            raise ConfigError("saml2_config requires a public_baseurl to be set")
-
         if self.saml2_grandfathered_mxid_source_attribute:
             optional_attributes.add(self.saml2_grandfathered_mxid_source_attribute)
         optional_attributes -= required_attributes
 
+        public_baseurl = self.root.server.public_baseurl
         metadata_url = public_baseurl + "_synapse/client/saml2/metadata.xml"
         response_url = public_baseurl + "_synapse/client/saml2/authn_response"
         return {
diff --git a/synapse/config/server.py b/synapse/config/server.py
index ed094bdc44..7bc0030a9e 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -16,6 +16,7 @@ import itertools
 import logging
 import os.path
 import re
+import urllib.parse
 from textwrap import indent
 from typing import Any, Dict, Iterable, List, Optional, Set, Tuple, Union
 
@@ -262,11 +263,46 @@ class ServerConfig(Config):
         self.print_pidfile = config.get("print_pidfile")
         self.user_agent_suffix = config.get("user_agent_suffix")
         self.use_frozen_dicts = config.get("use_frozen_dicts", False)
+        self.serve_server_wellknown = config.get("serve_server_wellknown", False)
+
+        # Whether we should serve a "client well-known":
+        #  (a) at .well-known/matrix/client on our client HTTP listener
+        #  (b) in the response to /login
+        #
+        # ... which together help ensure that clients use our public_baseurl instead of
+        # whatever they were told by the user.
+        #
+        # For the sake of backwards compatibility with existing installations, this is
+        # True if public_baseurl is specified explicitly, and otherwise False. (The
+        # reasoning here is that we have no way of knowing that the default
+        # public_baseurl is actually correct for existing installations - many things
+        # will not work correctly, but that's (probably?) better than sending clients
+        # to a completely broken URL.
+        self.serve_client_wellknown = False
+
+        public_baseurl = config.get("public_baseurl")
+        if public_baseurl is None:
+            public_baseurl = f"https://{self.server_name}/"
+            logger.info("Using default public_baseurl %s", public_baseurl)
+        else:
+            self.serve_client_wellknown = True
+            if public_baseurl[-1] != "/":
+                public_baseurl += "/"
+        self.public_baseurl = public_baseurl
 
-        self.public_baseurl = config.get("public_baseurl")
-        if self.public_baseurl is not None:
-            if self.public_baseurl[-1] != "/":
-                self.public_baseurl += "/"
+        # check that public_baseurl is valid
+        try:
+            splits = urllib.parse.urlsplit(self.public_baseurl)
+        except Exception as e:
+            raise ConfigError(f"Unable to parse URL: {e}", ("public_baseurl",))
+        if splits.scheme not in ("https", "http"):
+            raise ConfigError(
+                f"Invalid scheme '{splits.scheme}': only https and http are supported"
+            )
+        if splits.query or splits.fragment:
+            raise ConfigError(
+                "public_baseurl cannot contain query parameters or a #-fragment"
+            )
 
         # Whether to enable user presence.
         presence_config = config.get("presence") or {}
@@ -772,8 +808,28 @@ class ServerConfig(Config):
         # Otherwise, it should be the URL to reach Synapse's client HTTP listener (see
         # 'listeners' below).
         #
+        # Defaults to 'https://<server_name>/'.
+        #
         #public_baseurl: https://example.com/
 
+        # Uncomment the following to tell other servers to send federation traffic on
+        # port 443.
+        #
+        # By default, other servers will try to reach our server on port 8448, which can
+        # be inconvenient in some environments.
+        #
+        # Provided 'https://<server_name>/' on port 443 is routed to Synapse, this
+        # option configures Synapse to serve a file at
+        # 'https://<server_name>/.well-known/matrix/server'. This will tell other
+        # servers to send traffic to port 443 instead.
+        #
+        # See https://matrix-org.github.io/synapse/latest/delegate.html for more
+        # information.
+        #
+        # Defaults to 'false'.
+        #
+        #serve_server_wellknown: true
+
         # Set the soft limit on the number of file descriptors synapse can use
         # Zero is used to indicate synapse should set the soft limit to the
         # hard limit.
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 11a9b76aa0..60aacb13ea 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -101,13 +101,10 @@ class SSOConfig(Config):
         # gracefully to the client). This would make it pointless to ask the user for
         # confirmation, since the URL the confirmation page would be showing wouldn't be
         # the client's.
-        # public_baseurl is an optional setting, so we only add the fallback's URL to the
-        # list if it's provided (because we can't figure out what that URL is otherwise).
-        if self.root.server.public_baseurl:
-            login_fallback_url = (
-                self.root.server.public_baseurl + "_matrix/static/client/login"
-            )
-            self.sso_client_whitelist.append(login_fallback_url)
+        login_fallback_url = (
+            self.root.server.public_baseurl + "_matrix/static/client/login"
+        )
+        self.sso_client_whitelist.append(login_fallback_url)
 
     def generate_config_section(self, **kwargs):
         return """\
@@ -128,11 +125,10 @@ class SSOConfig(Config):
             # phishing attacks from evil.site. To avoid this, include a slash after the
             # hostname: "https://my.client/".
             #
-            # If public_baseurl is set, then the login fallback page (used by clients
-            # that don't natively support the required login flows) is whitelisted in
-            # addition to any URLs in this list.
+            # The login fallback page (used by clients that don't natively support the
+            # required login flows) is whitelisted in addition to any URLs in this list.
             #
-            # By default, this list is empty.
+            # By default, this list contains only the login fallback page.
             #
             #client_whitelist:
             #  - https://riot.im/develop
diff --git a/synapse/config/workers.py b/synapse/config/workers.py
index 462630201d..4507992031 100644
--- a/synapse/config/workers.py
+++ b/synapse/config/workers.py
@@ -63,7 +63,8 @@ class WriterLocations:
 
     Attributes:
         events: The instances that write to the event and backfill streams.
-        typing: The instance that writes to the typing stream.
+        typing: The instances that write to the typing stream. Currently
+            can only be a single instance.
         to_device: The instances that write to the to_device stream. Currently
             can only be a single instance.
         account_data: The instances that write to the account data streams. Currently
@@ -75,9 +76,15 @@ class WriterLocations:
     """
 
     events = attr.ib(
-        default=["master"], type=List[str], converter=_instance_to_list_converter
+        default=["master"],
+        type=List[str],
+        converter=_instance_to_list_converter,
+    )
+    typing = attr.ib(
+        default=["master"],
+        type=List[str],
+        converter=_instance_to_list_converter,
     )
-    typing = attr.ib(default="master", type=str)
     to_device = attr.ib(
         default=["master"],
         type=List[str],
@@ -217,6 +224,11 @@ class WorkerConfig(Config):
                         % (instance, stream)
                     )
 
+        if len(self.writers.typing) != 1:
+            raise ConfigError(
+                "Must only specify one instance to handle `typing` messages."
+            )
+
         if len(self.writers.to_device) != 1:
             raise ConfigError(
                 "Must only specify one instance to handle `to_device` messages."
diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 8628e951c4..f641ab7ef5 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -22,6 +22,7 @@ import attr
 from signedjson.key import (
     decode_verify_key_bytes,
     encode_verify_key_base64,
+    get_verify_key,
     is_signing_algorithm_supported,
 )
 from signedjson.sign import (
@@ -30,6 +31,7 @@ from signedjson.sign import (
     signature_ids,
     verify_signed_json,
 )
+from signedjson.types import VerifyKey
 from unpaddedbase64 import decode_base64
 
 from twisted.internet import defer
@@ -177,6 +179,8 @@ class Keyring:
             clock=hs.get_clock(),
             process_batch_callback=self._inner_fetch_key_requests,
         )
+        self.verify_key = get_verify_key(hs.signing_key)
+        self.hostname = hs.hostname
 
     async def verify_json_for_server(
         self,
@@ -196,6 +200,7 @@ class Keyring:
             validity_time: timestamp at which we require the signing key to
                 be valid. (0 implies we don't care)
         """
+
         request = VerifyJsonRequest.from_json_object(
             server_name,
             json_object,
@@ -262,6 +267,11 @@ class Keyring:
                 Codes.UNAUTHORIZED,
             )
 
+        # If we are the originating server don't fetch verify key for self over federation
+        if verify_request.server_name == self.hostname:
+            await self._process_json(self.verify_key, verify_request)
+            return
+
         # Add the keys we need to verify to the queue for retrieval. We queue
         # up requests for the same server so we don't end up with many in flight
         # requests for the same keys.
@@ -285,35 +295,8 @@ class Keyring:
             if key_result.valid_until_ts < verify_request.minimum_valid_until_ts:
                 continue
 
-            verify_key = key_result.verify_key
-            json_object = verify_request.get_json_object()
-            try:
-                verify_signed_json(
-                    json_object,
-                    verify_request.server_name,
-                    verify_key,
-                )
-                verified = True
-            except SignatureVerifyException as e:
-                logger.debug(
-                    "Error verifying signature for %s:%s:%s with key %s: %s",
-                    verify_request.server_name,
-                    verify_key.alg,
-                    verify_key.version,
-                    encode_verify_key_base64(verify_key),
-                    str(e),
-                )
-                raise SynapseError(
-                    401,
-                    "Invalid signature for server %s with key %s:%s: %s"
-                    % (
-                        verify_request.server_name,
-                        verify_key.alg,
-                        verify_key.version,
-                        str(e),
-                    ),
-                    Codes.UNAUTHORIZED,
-                )
+            await self._process_json(key_result.verify_key, verify_request)
+            verified = True
 
         if not verified:
             raise SynapseError(
@@ -322,6 +305,39 @@ class Keyring:
                 Codes.UNAUTHORIZED,
             )
 
+    async def _process_json(
+        self, verify_key: VerifyKey, verify_request: VerifyJsonRequest
+    ) -> None:
+        """Processes the `VerifyJsonRequest`. Raises if the signature can't be
+        verified.
+        """
+        try:
+            verify_signed_json(
+                verify_request.get_json_object(),
+                verify_request.server_name,
+                verify_key,
+            )
+        except SignatureVerifyException as e:
+            logger.debug(
+                "Error verifying signature for %s:%s:%s with key %s: %s",
+                verify_request.server_name,
+                verify_key.alg,
+                verify_key.version,
+                encode_verify_key_base64(verify_key),
+                str(e),
+            )
+            raise SynapseError(
+                401,
+                "Invalid signature for server %s with key %s:%s: %s"
+                % (
+                    verify_request.server_name,
+                    verify_key.alg,
+                    verify_key.version,
+                    str(e),
+                ),
+                Codes.UNAUTHORIZED,
+            )
+
     async def _inner_fetch_key_requests(
         self, requests: List[_FetchKeyRequest]
     ) -> Dict[str, Dict[str, FetchKeyResult]]:
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 157669ea88..38f3cf4d33 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -16,8 +16,23 @@
 
 import abc
 import os
-from typing import Dict, Optional, Tuple, Type
-
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Dict,
+    Generic,
+    Iterable,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Type,
+    TypeVar,
+    Union,
+    overload,
+)
+
+from typing_extensions import Literal
 from unpaddedbase64 import encode_base64
 
 from synapse.api.room_versions import EventFormatVersions, RoomVersion, RoomVersions
@@ -26,6 +41,9 @@ from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
 from synapse.util.stringutils import strtobool
 
+if TYPE_CHECKING:
+    from synapse.events.builder import EventBuilder
+
 # Whether we should use frozen_dict in FrozenEvent. Using frozen_dicts prevents
 # bugs where we accidentally share e.g. signature dicts. However, converting a
 # dict to frozen_dicts is expensive.
@@ -37,7 +55,23 @@ from synapse.util.stringutils import strtobool
 USE_FROZEN_DICTS = strtobool(os.environ.get("SYNAPSE_USE_FROZEN_DICTS", "0"))
 
 
-class DictProperty:
+T = TypeVar("T")
+
+
+# DictProperty (and DefaultDictProperty) require the classes they're used with to
+# have a _dict property to pull properties from.
+#
+# TODO _DictPropertyInstance should not include EventBuilder but due to
+# https://github.com/python/mypy/issues/5570 it thinks the DictProperty and
+# DefaultDictProperty get applied to EventBuilder when it is in a Union with
+# EventBase. This is the least invasive hack to get mypy to comply.
+#
+# Note that DictProperty/DefaultDictProperty cannot actually be used with
+# EventBuilder as it lacks a _dict property.
+_DictPropertyInstance = Union["_EventInternalMetadata", "EventBase", "EventBuilder"]
+
+
+class DictProperty(Generic[T]):
     """An object property which delegates to the `_dict` within its parent object."""
 
     __slots__ = ["key"]
@@ -45,12 +79,33 @@ class DictProperty:
     def __init__(self, key: str):
         self.key = key
 
-    def __get__(self, instance, owner=None):
+    @overload
+    def __get__(
+        self,
+        instance: Literal[None],
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> "DictProperty":
+        ...
+
+    @overload
+    def __get__(
+        self,
+        instance: _DictPropertyInstance,
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> T:
+        ...
+
+    def __get__(
+        self,
+        instance: Optional[_DictPropertyInstance],
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> Union[T, "DictProperty"]:
         # if the property is accessed as a class property rather than an instance
         # property, return the property itself rather than the value
         if instance is None:
             return self
         try:
+            assert isinstance(instance, (EventBase, _EventInternalMetadata))
             return instance._dict[self.key]
         except KeyError as e1:
             # We want this to look like a regular attribute error (mostly so that
@@ -65,10 +120,12 @@ class DictProperty:
                 "'%s' has no '%s' property" % (type(instance), self.key)
             ) from e1.__context__
 
-    def __set__(self, instance, v):
+    def __set__(self, instance: _DictPropertyInstance, v: T) -> None:
+        assert isinstance(instance, (EventBase, _EventInternalMetadata))
         instance._dict[self.key] = v
 
-    def __delete__(self, instance):
+    def __delete__(self, instance: _DictPropertyInstance) -> None:
+        assert isinstance(instance, (EventBase, _EventInternalMetadata))
         try:
             del instance._dict[self.key]
         except KeyError as e1:
@@ -77,7 +134,7 @@ class DictProperty:
             ) from e1.__context__
 
 
-class DefaultDictProperty(DictProperty):
+class DefaultDictProperty(DictProperty, Generic[T]):
     """An extension of DictProperty which provides a default if the property is
     not present in the parent's _dict.
 
@@ -86,13 +143,34 @@ class DefaultDictProperty(DictProperty):
 
     __slots__ = ["default"]
 
-    def __init__(self, key, default):
+    def __init__(self, key: str, default: T):
         super().__init__(key)
         self.default = default
 
-    def __get__(self, instance, owner=None):
+    @overload
+    def __get__(
+        self,
+        instance: Literal[None],
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> "DefaultDictProperty":
+        ...
+
+    @overload
+    def __get__(
+        self,
+        instance: _DictPropertyInstance,
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> T:
+        ...
+
+    def __get__(
+        self,
+        instance: Optional[_DictPropertyInstance],
+        owner: Optional[Type[_DictPropertyInstance]] = None,
+    ) -> Union[T, "DefaultDictProperty"]:
         if instance is None:
             return self
+        assert isinstance(instance, (EventBase, _EventInternalMetadata))
         return instance._dict.get(self.key, self.default)
 
 
@@ -111,22 +189,22 @@ class _EventInternalMetadata:
         # in the DAG)
         self.outlier = False
 
-    out_of_band_membership: bool = DictProperty("out_of_band_membership")
-    send_on_behalf_of: str = DictProperty("send_on_behalf_of")
-    recheck_redaction: bool = DictProperty("recheck_redaction")
-    soft_failed: bool = DictProperty("soft_failed")
-    proactively_send: bool = DictProperty("proactively_send")
-    redacted: bool = DictProperty("redacted")
-    txn_id: str = DictProperty("txn_id")
-    token_id: int = DictProperty("token_id")
-    historical: bool = DictProperty("historical")
+    out_of_band_membership: DictProperty[bool] = DictProperty("out_of_band_membership")
+    send_on_behalf_of: DictProperty[str] = DictProperty("send_on_behalf_of")
+    recheck_redaction: DictProperty[bool] = DictProperty("recheck_redaction")
+    soft_failed: DictProperty[bool] = DictProperty("soft_failed")
+    proactively_send: DictProperty[bool] = DictProperty("proactively_send")
+    redacted: DictProperty[bool] = DictProperty("redacted")
+    txn_id: DictProperty[str] = DictProperty("txn_id")
+    token_id: DictProperty[int] = DictProperty("token_id")
+    historical: DictProperty[bool] = DictProperty("historical")
 
     # XXX: These are set by StreamWorkerStore._set_before_and_after.
     # I'm pretty sure that these are never persisted to the database, so shouldn't
     # be here
-    before: RoomStreamToken = DictProperty("before")
-    after: RoomStreamToken = DictProperty("after")
-    order: Tuple[int, int] = DictProperty("order")
+    before: DictProperty[RoomStreamToken] = DictProperty("before")
+    after: DictProperty[RoomStreamToken] = DictProperty("after")
+    order: DictProperty[Tuple[int, int]] = DictProperty("order")
 
     def get_dict(self) -> JsonDict:
         return dict(self._dict)
@@ -162,9 +240,6 @@ class _EventInternalMetadata:
 
         If the sender of the redaction event is allowed to redact any event
         due to auth rules, then this will always return false.
-
-        Returns:
-            bool
         """
         return self._dict.get("recheck_redaction", False)
 
@@ -176,32 +251,23 @@ class _EventInternalMetadata:
                sent to clients.
             2. They should not be added to the forward extremities (and
                therefore not to current state).
-
-        Returns:
-            bool
         """
         return self._dict.get("soft_failed", False)
 
-    def should_proactively_send(self):
+    def should_proactively_send(self) -> bool:
         """Whether the event, if ours, should be sent to other clients and
         servers.
 
         This is used for sending dummy events internally. Servers and clients
         can still explicitly fetch the event.
-
-        Returns:
-            bool
         """
         return self._dict.get("proactively_send", True)
 
-    def is_redacted(self):
+    def is_redacted(self) -> bool:
         """Whether the event has been redacted.
 
         This is used for efficiently checking whether an event has been
         marked as redacted without needing to make another database call.
-
-        Returns:
-            bool
         """
         return self._dict.get("redacted", False)
 
@@ -241,29 +307,31 @@ class EventBase(metaclass=abc.ABCMeta):
 
         self.internal_metadata = _EventInternalMetadata(internal_metadata_dict)
 
-    auth_events = DictProperty("auth_events")
-    depth = DictProperty("depth")
-    content = DictProperty("content")
-    hashes = DictProperty("hashes")
-    origin = DictProperty("origin")
-    origin_server_ts = DictProperty("origin_server_ts")
-    prev_events = DictProperty("prev_events")
-    redacts = DefaultDictProperty("redacts", None)
-    room_id = DictProperty("room_id")
-    sender = DictProperty("sender")
-    state_key = DictProperty("state_key")
-    type = DictProperty("type")
-    user_id = DictProperty("sender")
+    depth: DictProperty[int] = DictProperty("depth")
+    content: DictProperty[JsonDict] = DictProperty("content")
+    hashes: DictProperty[Dict[str, str]] = DictProperty("hashes")
+    origin: DictProperty[str] = DictProperty("origin")
+    origin_server_ts: DictProperty[int] = DictProperty("origin_server_ts")
+    redacts: DefaultDictProperty[Optional[str]] = DefaultDictProperty("redacts", None)
+    room_id: DictProperty[str] = DictProperty("room_id")
+    sender: DictProperty[str] = DictProperty("sender")
+    # TODO state_key should be Optional[str], this is generally asserted in Synapse
+    # by calling is_state() first (which ensures this), but it is hard (not possible?)
+    # to properly annotate that calling is_state() asserts that state_key exists
+    # and is non-None.
+    state_key: DictProperty[str] = DictProperty("state_key")
+    type: DictProperty[str] = DictProperty("type")
+    user_id: DictProperty[str] = DictProperty("sender")
 
     @property
     def event_id(self) -> str:
         raise NotImplementedError()
 
     @property
-    def membership(self):
+    def membership(self) -> str:
         return self.content["membership"]
 
-    def is_state(self):
+    def is_state(self) -> bool:
         return hasattr(self, "state_key") and self.state_key is not None
 
     def get_dict(self) -> JsonDict:
@@ -272,13 +340,13 @@ class EventBase(metaclass=abc.ABCMeta):
 
         return d
 
-    def get(self, key, default=None):
+    def get(self, key: str, default: Optional[Any] = None) -> Any:
         return self._dict.get(key, default)
 
-    def get_internal_metadata_dict(self):
+    def get_internal_metadata_dict(self) -> JsonDict:
         return self.internal_metadata.get_dict()
 
-    def get_pdu_json(self, time_now=None) -> JsonDict:
+    def get_pdu_json(self, time_now: Optional[int] = None) -> JsonDict:
         pdu_json = self.get_dict()
 
         if time_now is not None and "age_ts" in pdu_json["unsigned"]:
@@ -305,49 +373,46 @@ class EventBase(metaclass=abc.ABCMeta):
 
         return template_json
 
-    def __set__(self, instance, value):
-        raise AttributeError("Unrecognized attribute %s" % (instance,))
-
-    def __getitem__(self, field):
+    def __getitem__(self, field: str) -> Optional[Any]:
         return self._dict[field]
 
-    def __contains__(self, field):
+    def __contains__(self, field: str) -> bool:
         return field in self._dict
 
-    def items(self):
+    def items(self) -> List[Tuple[str, Optional[Any]]]:
         return list(self._dict.items())
 
-    def keys(self):
+    def keys(self) -> Iterable[str]:
         return self._dict.keys()
 
-    def prev_event_ids(self):
+    def prev_event_ids(self) -> Sequence[str]:
         """Returns the list of prev event IDs. The order matches the order
         specified in the event, though there is no meaning to it.
 
         Returns:
-            list[str]: The list of event IDs of this event's prev_events
+            The list of event IDs of this event's prev_events
         """
-        return [e for e, _ in self.prev_events]
+        return [e for e, _ in self._dict["prev_events"]]
 
-    def auth_event_ids(self):
+    def auth_event_ids(self) -> Sequence[str]:
         """Returns the list of auth event IDs. The order matches the order
         specified in the event, though there is no meaning to it.
 
         Returns:
-            list[str]: The list of event IDs of this event's auth_events
+            The list of event IDs of this event's auth_events
         """
-        return [e for e, _ in self.auth_events]
+        return [e for e, _ in self._dict["auth_events"]]
 
-    def freeze(self):
+    def freeze(self) -> None:
         """'Freeze' the event dict, so it cannot be modified by accident"""
 
         # this will be a no-op if the event dict is already frozen.
         self._dict = freeze(self._dict)
 
-    def __str__(self):
+    def __str__(self) -> str:
         return self.__repr__()
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         rejection = f"REJECTED={self.rejected_reason}, " if self.rejected_reason else ""
 
         return (
@@ -443,7 +508,7 @@ class FrozenEventV2(EventBase):
         else:
             frozen_dict = event_dict
 
-        self._event_id = None
+        self._event_id: Optional[str] = None
 
         super().__init__(
             frozen_dict,
@@ -455,7 +520,7 @@ class FrozenEventV2(EventBase):
         )
 
     @property
-    def event_id(self):
+    def event_id(self) -> str:
         # We have to import this here as otherwise we get an import loop which
         # is hard to break.
         from synapse.crypto.event_signing import compute_event_reference_hash
@@ -465,23 +530,23 @@ class FrozenEventV2(EventBase):
         self._event_id = "$" + encode_base64(compute_event_reference_hash(self)[1])
         return self._event_id
 
-    def prev_event_ids(self):
+    def prev_event_ids(self) -> Sequence[str]:
         """Returns the list of prev event IDs. The order matches the order
         specified in the event, though there is no meaning to it.
 
         Returns:
-            list[str]: The list of event IDs of this event's prev_events
+            The list of event IDs of this event's prev_events
         """
-        return self.prev_events
+        return self._dict["prev_events"]
 
-    def auth_event_ids(self):
+    def auth_event_ids(self) -> Sequence[str]:
         """Returns the list of auth event IDs. The order matches the order
         specified in the event, though there is no meaning to it.
 
         Returns:
-            list[str]: The list of event IDs of this event's auth_events
+            The list of event IDs of this event's auth_events
         """
-        return self.auth_events
+        return self._dict["auth_events"]
 
 
 class FrozenEventV3(FrozenEventV2):
@@ -490,7 +555,7 @@ class FrozenEventV3(FrozenEventV2):
     format_version = EventFormatVersions.V3  # All events of this type are V3
 
     @property
-    def event_id(self):
+    def event_id(self) -> str:
         # We have to import this here as otherwise we get an import loop which
         # is hard to break.
         from synapse.crypto.event_signing import compute_event_reference_hash
@@ -503,12 +568,14 @@ class FrozenEventV3(FrozenEventV2):
         return self._event_id
 
 
-def _event_type_from_format_version(format_version: int) -> Type[EventBase]:
+def _event_type_from_format_version(
+    format_version: int,
+) -> Type[Union[FrozenEvent, FrozenEventV2, FrozenEventV3]]:
     """Returns the python type to use to construct an Event object for the
     given event format version.
 
     Args:
-        format_version (int): The event format version
+        format_version: The event format version
 
     Returns:
         type: A type that can be initialized as per the initializer of
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py
index 2a6dabdab6..1bb8ca7145 100644
--- a/synapse/events/third_party_rules.py
+++ b/synapse/events/third_party_rules.py
@@ -14,7 +14,7 @@
 import logging
 from typing import TYPE_CHECKING, Any, Awaitable, Callable, List, Optional, Tuple
 
-from synapse.api.errors import SynapseError
+from synapse.api.errors import ModuleFailedException, SynapseError
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.types import Requester, StateMap
@@ -36,6 +36,7 @@ CHECK_THREEPID_CAN_BE_INVITED_CALLBACK = Callable[
 CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK = Callable[
     [str, StateMap[EventBase], str], Awaitable[bool]
 ]
+ON_NEW_EVENT_CALLBACK = Callable[[EventBase, StateMap[EventBase]], Awaitable]
 
 
 def load_legacy_third_party_event_rules(hs: "HomeServer") -> None:
@@ -152,6 +153,7 @@ class ThirdPartyEventRules:
         self._check_visibility_can_be_modified_callbacks: List[
             CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK
         ] = []
+        self._on_new_event_callbacks: List[ON_NEW_EVENT_CALLBACK] = []
 
     def register_third_party_rules_callbacks(
         self,
@@ -163,6 +165,7 @@ class ThirdPartyEventRules:
         check_visibility_can_be_modified: Optional[
             CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK
         ] = None,
+        on_new_event: Optional[ON_NEW_EVENT_CALLBACK] = None,
     ) -> None:
         """Register callbacks from modules for each hook."""
         if check_event_allowed is not None:
@@ -181,6 +184,9 @@ class ThirdPartyEventRules:
                 check_visibility_can_be_modified,
             )
 
+        if on_new_event is not None:
+            self._on_new_event_callbacks.append(on_new_event)
+
     async def check_event_allowed(
         self, event: EventBase, context: EventContext
     ) -> Tuple[bool, Optional[dict]]:
@@ -227,9 +233,10 @@ class ThirdPartyEventRules:
                 # This module callback needs a rework so that hacks such as
                 # this one are not necessary.
                 raise e
-            except Exception as e:
-                logger.warning("Failed to run module API callback %s: %s", callback, e)
-                continue
+            except Exception:
+                raise ModuleFailedException(
+                    "Failed to run `check_event_allowed` module API callback"
+                )
 
             # Return if the event shouldn't be allowed or if the module came up with a
             # replacement dict for the event.
@@ -321,6 +328,31 @@ class ThirdPartyEventRules:
 
         return True
 
+    async def on_new_event(self, event_id: str) -> None:
+        """Let modules act on events after they've been sent (e.g. auto-accepting
+        invites, etc.)
+
+        Args:
+            event_id: The ID of the event.
+
+        Raises:
+            ModuleFailureError if a callback raised any exception.
+        """
+        # Bail out early without hitting the store if we don't have any callbacks
+        if len(self._on_new_event_callbacks) == 0:
+            return
+
+        event = await self.store.get_event(event_id)
+        state_events = await self._get_state_map_for_room(event.room_id)
+
+        for callback in self._on_new_event_callbacks:
+            try:
+                await callback(event, state_events)
+            except Exception as e:
+                logger.exception(
+                    "Failed to run module API callback %s: %s", callback, e
+                )
+
     async def _get_state_map_for_room(self, room_id: str) -> StateMap[EventBase]:
         """Given a room ID, return the state events of that room.
 
diff --git a/synapse/events/validator.py b/synapse/events/validator.py
index 4d459c17f1..cf86934968 100644
--- a/synapse/events/validator.py
+++ b/synapse/events/validator.py
@@ -55,7 +55,7 @@ class EventValidator:
         ]
 
         for k in required:
-            if not hasattr(event, k):
+            if k not in event:
                 raise SynapseError(400, "Event does not have key %s" % (k,))
 
         # Check that the following keys have string values
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 2ab4dec88f..670186f548 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -227,7 +227,7 @@ class FederationClient(FederationBase):
         )
 
     async def backfill(
-        self, dest: str, room_id: str, limit: int, extremities: Iterable[str]
+        self, dest: str, room_id: str, limit: int, extremities: Collection[str]
     ) -> Optional[List[EventBase]]:
         """Requests some more historic PDUs for the given room from the
         given destination server.
@@ -237,6 +237,8 @@ class FederationClient(FederationBase):
             room_id: The room_id to backfill.
             limit: The maximum number of events to return.
             extremities: our current backwards extremities, to backfill from
+                Must be a Collection that is falsy when empty.
+                (Iterable is not enough here!)
         """
         logger.debug("backfill extrem=%s", extremities)
 
@@ -250,11 +252,22 @@ class FederationClient(FederationBase):
 
         logger.debug("backfill transaction_data=%r", transaction_data)
 
+        if not isinstance(transaction_data, dict):
+            # TODO we probably want an exception type specific to federation
+            # client validation.
+            raise TypeError("Backfill transaction_data is not a dict.")
+
+        transaction_data_pdus = transaction_data.get("pdus")
+        if not isinstance(transaction_data_pdus, list):
+            # TODO we probably want an exception type specific to federation
+            # client validation.
+            raise TypeError("transaction_data.pdus is not a list.")
+
         room_version = await self.store.get_room_version(room_id)
 
         pdus = [
             event_from_pdu_json(p, room_version, outlier=False)
-            for p in transaction_data["pdus"]
+            for p in transaction_data_pdus
         ]
 
         # Check signatures and hash of pdus, removing any from the list that fail checks
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 0d66034f44..9a8758e9a6 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -213,6 +213,11 @@ class FederationServer(FederationBase):
             self._started_handling_of_staged_events = True
             self._handle_old_staged_events()
 
+            # Start a periodic check for old staged events. This is to handle
+            # the case where locks time out, e.g. if another process gets killed
+            # without dropping its locks.
+            self._clock.looping_call(self._handle_old_staged_events, 60 * 1000)
+
         # keep this as early as possible to make the calculated origin ts as
         # accurate as possible.
         request_time = self._clock.time_msec()
@@ -295,14 +300,16 @@ class FederationServer(FederationBase):
         Returns:
             HTTP response code and body
         """
-        response = await self.transaction_actions.have_responded(origin, transaction)
+        existing_response = await self.transaction_actions.have_responded(
+            origin, transaction
+        )
 
-        if response:
+        if existing_response:
             logger.debug(
                 "[%s] We've already responded to this request",
                 transaction.transaction_id,
             )
-            return response
+            return existing_response
 
         logger.debug("[%s] Transaction is new", transaction.transaction_id)
 
@@ -632,7 +639,7 @@ class FederationServer(FederationBase):
 
     async def on_make_knock_request(
         self, origin: str, room_id: str, user_id: str, supported_versions: List[str]
-    ) -> Dict[str, Union[EventBase, str]]:
+    ) -> JsonDict:
         """We've received a /make_knock/ request, so we create a partial knock
         event for the room and hand that back, along with the room version, to the knocking
         homeserver. We do *not* persist or process this event until the other server has
@@ -1230,10 +1237,6 @@ class FederationHandlerRegistry:
 
         self.query_handlers[query_type] = handler
 
-    def register_instance_for_edu(self, edu_type: str, instance_name: str) -> None:
-        """Register that the EDU handler is on a different instance than master."""
-        self._edu_type_to_instance[edu_type] = [instance_name]
-
     def register_instances_for_edu(
         self, edu_type: str, instance_names: List[str]
     ) -> None:
diff --git a/synapse/federation/sender/transaction_manager.py b/synapse/federation/sender/transaction_manager.py
index dc555cca0b..ab935e5a7e 100644
--- a/synapse/federation/sender/transaction_manager.py
+++ b/synapse/federation/sender/transaction_manager.py
@@ -149,7 +149,6 @@ class TransactionManager:
                 )
             except HttpResponseException as e:
                 code = e.code
-                response = e.response
 
                 set_tag(tags.ERROR, True)
 
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 8b247fe206..10b5aa5af8 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -15,7 +15,19 @@
 
 import logging
 import urllib
-from typing import Any, Callable, Dict, Iterable, List, Mapping, Optional, Tuple, Union
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    Collection,
+    Dict,
+    Iterable,
+    List,
+    Mapping,
+    Optional,
+    Tuple,
+    Union,
+)
 
 import attr
 import ijson
@@ -100,7 +112,7 @@ class TransportLayerClient:
 
     @log_function
     async def backfill(
-        self, destination: str, room_id: str, event_tuples: Iterable[str], limit: int
+        self, destination: str, room_id: str, event_tuples: Collection[str], limit: int
     ) -> Optional[JsonDict]:
         """Requests `limit` previous PDUs in a given context before list of
         PDUs.
@@ -108,7 +120,9 @@ class TransportLayerClient:
         Args:
             destination
             room_id
-            event_tuples
+            event_tuples:
+                Must be a Collection that is falsy when empty.
+                (Iterable is not enough here!)
             limit
 
         Returns:
@@ -786,7 +800,7 @@ class TransportLayerClient:
     @log_function
     def join_group(
         self, destination: str, group_id: str, user_id: str, content: JsonDict
-    ) -> JsonDict:
+    ) -> Awaitable[JsonDict]:
         """Attempts to join a group"""
         path = _create_v1_path("/groups/%s/users/%s/join", group_id, user_id)
 
@@ -1296,14 +1310,17 @@ class SendJoinParser(ByteParser[SendJoinResponse]):
         self._coro_state = ijson.items_coro(
             _event_list_parser(room_version, self._response.state),
             prefix + "state.item",
+            use_float=True,
         )
         self._coro_auth = ijson.items_coro(
             _event_list_parser(room_version, self._response.auth_events),
             prefix + "auth_chain.item",
+            use_float=True,
         )
         self._coro_event = ijson.kvitems_coro(
             _event_parser(self._response.event_dict),
             prefix + "org.matrix.msc3083.v2.event",
+            use_float=True,
         )
 
     def write(self, data: bytes) -> int:
diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index a53cd62d3c..be3203ac80 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -90,6 +90,7 @@ class AdminHandler:
                 Membership.LEAVE,
                 Membership.BAN,
                 Membership.INVITE,
+                Membership.KNOCK,
             ),
         )
 
@@ -122,6 +123,13 @@ class AdminHandler:
                         invited_state = invite.unsigned["invite_room_state"]
                         writer.write_invite(room_id, invite, invited_state)
 
+                if room.membership == Membership.KNOCK:
+                    event_id = room.event_id
+                    knock = await self.store.get_event(event_id, allow_none=True)
+                    if knock:
+                        knock_state = knock.unsigned["knock_room_state"]
+                        writer.write_knock(room_id, knock, knock_state)
+
                 continue
 
             # We only want to bother fetching events up to the last time they
@@ -239,6 +247,20 @@ class ExfiltrationWriter(metaclass=abc.ABCMeta):
         raise NotImplementedError()
 
     @abc.abstractmethod
+    def write_knock(
+        self, room_id: str, event: EventBase, state: StateMap[dict]
+    ) -> None:
+        """Write a knock for the room, with associated knock state.
+
+        Args:
+            room_id: The room ID the knock is for.
+            event: The knock event.
+            state: A subset of the state at the knock, with a subset of the
+                event keys (type, state_key content and sender).
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
     def finished(self) -> Any:
         """Called when all data has successfully been exported and written.
 
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 36c206dae6..ddc9105ee9 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -34,6 +34,7 @@ from synapse.metrics.background_process_metrics import (
 )
 from synapse.storage.databases.main.directory import RoomAliasMapping
 from synapse.types import JsonDict, RoomAlias, RoomStreamToken, UserID
+from synapse.util.async_helpers import Linearizer
 from synapse.util.metrics import Measure
 
 if TYPE_CHECKING:
@@ -58,6 +59,10 @@ class ApplicationServicesHandler:
         self.current_max = 0
         self.is_processing = False
 
+        self._ephemeral_events_linearizer = Linearizer(
+            name="appservice_ephemeral_events"
+        )
+
     def notify_interested_services(self, max_token: RoomStreamToken) -> None:
         """Notifies (pushes) all application services interested in this event.
 
@@ -182,7 +187,7 @@ class ApplicationServicesHandler:
     def notify_interested_services_ephemeral(
         self,
         stream_key: str,
-        new_token: Optional[int],
+        new_token: Union[int, RoomStreamToken],
         users: Optional[Collection[Union[str, UserID]]] = None,
     ) -> None:
         """
@@ -203,7 +208,7 @@ class ApplicationServicesHandler:
                 Appservices will only receive ephemeral events that fall within their
                 registered user and room namespaces.
 
-            new_token: The latest stream token.
+            new_token: The stream token of the event.
             users: The users that should be informed of the new event, if any.
         """
         if not self.notify_appservices:
@@ -212,6 +217,19 @@ class ApplicationServicesHandler:
         if stream_key not in ("typing_key", "receipt_key", "presence_key"):
             return
 
+        # Assert that new_token is an integer (and not a RoomStreamToken).
+        # All of the supported streams that this function handles use an
+        # integer to track progress (rather than a RoomStreamToken - a
+        # vector clock implementation) as they don't support multiple
+        # stream writers.
+        #
+        # As a result, we simply assert that new_token is an integer.
+        # If we do end up needing to pass a RoomStreamToken down here
+        # in the future, using RoomStreamToken.stream (the minimum stream
+        # position) to convert to an ascending integer value should work.
+        # Additional context: https://github.com/matrix-org/synapse/pull/11137
+        assert isinstance(new_token, int)
+
         services = [
             service
             for service in self.store.get_app_services()
@@ -231,14 +249,13 @@ class ApplicationServicesHandler:
         self,
         services: List[ApplicationService],
         stream_key: str,
-        new_token: Optional[int],
+        new_token: int,
         users: Collection[Union[str, UserID]],
     ) -> None:
         logger.debug("Checking interested services for %s" % (stream_key))
         with Measure(self.clock, "notify_interested_services_ephemeral"):
             for service in services:
-                # Only handle typing if we have the latest token
-                if stream_key == "typing_key" and new_token is not None:
+                if stream_key == "typing_key":
                     # Note that we don't persist the token (via set_type_stream_id_for_appservice)
                     # for typing_key due to performance reasons and due to their highly
                     # ephemeral nature.
@@ -248,26 +265,37 @@ class ApplicationServicesHandler:
                     events = await self._handle_typing(service, new_token)
                     if events:
                         self.scheduler.submit_ephemeral_events_for_as(service, events)
+                    continue
 
-                elif stream_key == "receipt_key":
-                    events = await self._handle_receipts(service)
-                    if events:
-                        self.scheduler.submit_ephemeral_events_for_as(service, events)
-
-                    # Persist the latest handled stream token for this appservice
-                    await self.store.set_type_stream_id_for_appservice(
-                        service, "read_receipt", new_token
+                # Since we read/update the stream position for this AS/stream
+                with (
+                    await self._ephemeral_events_linearizer.queue(
+                        (service.id, stream_key)
                     )
+                ):
+                    if stream_key == "receipt_key":
+                        events = await self._handle_receipts(service, new_token)
+                        if events:
+                            self.scheduler.submit_ephemeral_events_for_as(
+                                service, events
+                            )
+
+                        # Persist the latest handled stream token for this appservice
+                        await self.store.set_type_stream_id_for_appservice(
+                            service, "read_receipt", new_token
+                        )
 
-                elif stream_key == "presence_key":
-                    events = await self._handle_presence(service, users)
-                    if events:
-                        self.scheduler.submit_ephemeral_events_for_as(service, events)
+                    elif stream_key == "presence_key":
+                        events = await self._handle_presence(service, users, new_token)
+                        if events:
+                            self.scheduler.submit_ephemeral_events_for_as(
+                                service, events
+                            )
 
-                    # Persist the latest handled stream token for this appservice
-                    await self.store.set_type_stream_id_for_appservice(
-                        service, "presence", new_token
-                    )
+                        # Persist the latest handled stream token for this appservice
+                        await self.store.set_type_stream_id_for_appservice(
+                            service, "presence", new_token
+                        )
 
     async def _handle_typing(
         self, service: ApplicationService, new_token: int
@@ -304,7 +332,9 @@ class ApplicationServicesHandler:
         )
         return typing
 
-    async def _handle_receipts(self, service: ApplicationService) -> List[JsonDict]:
+    async def _handle_receipts(
+        self, service: ApplicationService, new_token: Optional[int]
+    ) -> List[JsonDict]:
         """
         Return the latest read receipts that the given application service should receive.
 
@@ -323,6 +353,12 @@ class ApplicationServicesHandler:
         from_key = await self.store.get_type_stream_id_for_appservice(
             service, "read_receipt"
         )
+        if new_token is not None and new_token <= from_key:
+            logger.debug(
+                "Rejecting token lower than or equal to stored: %s" % (new_token,)
+            )
+            return []
+
         receipts_source = self.event_sources.sources.receipt
         receipts, _ = await receipts_source.get_new_events_as(
             service=service, from_key=from_key
@@ -330,7 +366,10 @@ class ApplicationServicesHandler:
         return receipts
 
     async def _handle_presence(
-        self, service: ApplicationService, users: Collection[Union[str, UserID]]
+        self,
+        service: ApplicationService,
+        users: Collection[Union[str, UserID]],
+        new_token: Optional[int],
     ) -> List[JsonDict]:
         """
         Return the latest presence updates that the given application service should receive.
@@ -353,6 +392,12 @@ class ApplicationServicesHandler:
         from_key = await self.store.get_type_stream_id_for_appservice(
             service, "presence"
         )
+        if new_token is not None and new_token <= from_key:
+            logger.debug(
+                "Rejecting token lower than or equal to stored: %s" % (new_token,)
+            )
+            return []
+
         for user in users:
             if isinstance(user, str):
                 user = UserID.from_string(user)
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index d508d7d32a..60e59d11a0 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -1989,7 +1989,9 @@ class PasswordAuthProvider:
         self,
         check_3pid_auth: Optional[CHECK_3PID_AUTH_CALLBACK] = None,
         on_logged_out: Optional[ON_LOGGED_OUT_CALLBACK] = None,
-        auth_checkers: Optional[Dict[Tuple[str, Tuple], CHECK_AUTH_CALLBACK]] = None,
+        auth_checkers: Optional[
+            Dict[Tuple[str, Tuple[str, ...]], CHECK_AUTH_CALLBACK]
+        ] = None,
     ) -> None:
         # Register check_3pid_auth callback
         if check_3pid_auth is not None:
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index 8567cb0e00..8ca5f60b1c 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -245,7 +245,7 @@ class DirectoryHandler:
                 servers = result.servers
         else:
             try:
-                fed_result = await self.federation.make_query(
+                fed_result: Optional[JsonDict] = await self.federation.make_query(
                     destination=room_alias.domain,
                     query_type="directory",
                     args={"room_alias": room_alias.to_string()},
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index d0fb2fc7dc..60c11e3d21 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -201,95 +201,19 @@ class E2eKeysHandler:
                     r[user_id] = remote_queries[user_id]
 
             # Now fetch any devices that we don't have in our cache
-            @trace
-            async def do_remote_query(destination: str) -> None:
-                """This is called when we are querying the device list of a user on
-                a remote homeserver and their device list is not in the device list
-                cache. If we share a room with this user and we're not querying for
-                specific user we will update the cache with their device list.
-                """
-
-                destination_query = remote_queries_not_in_cache[destination]
-
-                # We first consider whether we wish to update the device list cache with
-                # the users device list. We want to track a user's devices when the
-                # authenticated user shares a room with the queried user and the query
-                # has not specified a particular device.
-                # If we update the cache for the queried user we remove them from further
-                # queries. We use the more efficient batched query_client_keys for all
-                # remaining users
-                user_ids_updated = []
-                for (user_id, device_list) in destination_query.items():
-                    if user_id in user_ids_updated:
-                        continue
-
-                    if device_list:
-                        continue
-
-                    room_ids = await self.store.get_rooms_for_user(user_id)
-                    if not room_ids:
-                        continue
-
-                    # We've decided we're sharing a room with this user and should
-                    # probably be tracking their device lists. However, we haven't
-                    # done an initial sync on the device list so we do it now.
-                    try:
-                        if self._is_master:
-                            user_devices = await self.device_handler.device_list_updater.user_device_resync(
-                                user_id
-                            )
-                        else:
-                            user_devices = await self._user_device_resync_client(
-                                user_id=user_id
-                            )
-
-                        user_devices = user_devices["devices"]
-                        user_results = results.setdefault(user_id, {})
-                        for device in user_devices:
-                            user_results[device["device_id"]] = device["keys"]
-                        user_ids_updated.append(user_id)
-                    except Exception as e:
-                        failures[destination] = _exception_to_failure(e)
-
-                if len(destination_query) == len(user_ids_updated):
-                    # We've updated all the users in the query and we do not need to
-                    # make any further remote calls.
-                    return
-
-                # Remove all the users from the query which we have updated
-                for user_id in user_ids_updated:
-                    destination_query.pop(user_id)
-
-                try:
-                    remote_result = await self.federation.query_client_keys(
-                        destination, {"device_keys": destination_query}, timeout=timeout
-                    )
-
-                    for user_id, keys in remote_result["device_keys"].items():
-                        if user_id in destination_query:
-                            results[user_id] = keys
-
-                    if "master_keys" in remote_result:
-                        for user_id, key in remote_result["master_keys"].items():
-                            if user_id in destination_query:
-                                cross_signing_keys["master_keys"][user_id] = key
-
-                    if "self_signing_keys" in remote_result:
-                        for user_id, key in remote_result["self_signing_keys"].items():
-                            if user_id in destination_query:
-                                cross_signing_keys["self_signing_keys"][user_id] = key
-
-                except Exception as e:
-                    failure = _exception_to_failure(e)
-                    failures[destination] = failure
-                    set_tag("error", True)
-                    set_tag("reason", failure)
-
             await make_deferred_yieldable(
                 defer.gatherResults(
                     [
-                        run_in_background(do_remote_query, destination)
-                        for destination in remote_queries_not_in_cache
+                        run_in_background(
+                            self._query_devices_for_destination,
+                            results,
+                            cross_signing_keys,
+                            failures,
+                            destination,
+                            queries,
+                            timeout,
+                        )
+                        for destination, queries in remote_queries_not_in_cache.items()
                     ],
                     consumeErrors=True,
                 ).addErrback(unwrapFirstError)
@@ -301,6 +225,121 @@ class E2eKeysHandler:
 
             return ret
 
+    @trace
+    async def _query_devices_for_destination(
+        self,
+        results: JsonDict,
+        cross_signing_keys: JsonDict,
+        failures: Dict[str, JsonDict],
+        destination: str,
+        destination_query: Dict[str, Iterable[str]],
+        timeout: int,
+    ) -> None:
+        """This is called when we are querying the device list of a user on
+        a remote homeserver and their device list is not in the device list
+        cache. If we share a room with this user and we're not querying for
+        specific user we will update the cache with their device list.
+
+        Args:
+            results: A map from user ID to their device keys, which gets
+                updated with the newly fetched keys.
+            cross_signing_keys: Map from user ID to their cross signing keys,
+                which gets updated with the newly fetched keys.
+            failures: Map of destinations to failures that have occurred while
+                attempting to fetch keys.
+            destination: The remote server to query
+            destination_query: The query dict of devices to query the remote
+                server for.
+            timeout: The timeout for remote HTTP requests.
+        """
+
+        # We first consider whether we wish to update the device list cache with
+        # the users device list. We want to track a user's devices when the
+        # authenticated user shares a room with the queried user and the query
+        # has not specified a particular device.
+        # If we update the cache for the queried user we remove them from further
+        # queries. We use the more efficient batched query_client_keys for all
+        # remaining users
+        user_ids_updated = []
+        for (user_id, device_list) in destination_query.items():
+            if user_id in user_ids_updated:
+                continue
+
+            if device_list:
+                continue
+
+            room_ids = await self.store.get_rooms_for_user(user_id)
+            if not room_ids:
+                continue
+
+            # We've decided we're sharing a room with this user and should
+            # probably be tracking their device lists. However, we haven't
+            # done an initial sync on the device list so we do it now.
+            try:
+                if self._is_master:
+                    resync_results = await self.device_handler.device_list_updater.user_device_resync(
+                        user_id
+                    )
+                else:
+                    resync_results = await self._user_device_resync_client(
+                        user_id=user_id
+                    )
+
+                # Add the device keys to the results.
+                user_devices = resync_results["devices"]
+                user_results = results.setdefault(user_id, {})
+                for device in user_devices:
+                    user_results[device["device_id"]] = device["keys"]
+                user_ids_updated.append(user_id)
+
+                # Add any cross signing keys to the results.
+                master_key = resync_results.get("master_key")
+                self_signing_key = resync_results.get("self_signing_key")
+
+                if master_key:
+                    cross_signing_keys["master_keys"][user_id] = master_key
+
+                if self_signing_key:
+                    cross_signing_keys["self_signing_keys"][user_id] = self_signing_key
+            except Exception as e:
+                failures[destination] = _exception_to_failure(e)
+
+        if len(destination_query) == len(user_ids_updated):
+            # We've updated all the users in the query and we do not need to
+            # make any further remote calls.
+            return
+
+        # Remove all the users from the query which we have updated
+        for user_id in user_ids_updated:
+            destination_query.pop(user_id)
+
+        try:
+            remote_result = await self.federation.query_client_keys(
+                destination, {"device_keys": destination_query}, timeout=timeout
+            )
+
+            for user_id, keys in remote_result["device_keys"].items():
+                if user_id in destination_query:
+                    results[user_id] = keys
+
+            if "master_keys" in remote_result:
+                for user_id, key in remote_result["master_keys"].items():
+                    if user_id in destination_query:
+                        cross_signing_keys["master_keys"][user_id] = key
+
+            if "self_signing_keys" in remote_result:
+                for user_id, key in remote_result["self_signing_keys"].items():
+                    if user_id in destination_query:
+                        cross_signing_keys["self_signing_keys"][user_id] = key
+
+        except Exception as e:
+            failure = _exception_to_failure(e)
+            failures[destination] = failure
+            set_tag("error", True)
+            set_tag("reason", failure)
+
+        return
+
     async def get_cross_signing_keys_from_cache(
         self, query: Iterable[str], from_user_id: Optional[str]
     ) -> Dict[str, Dict[str, dict]]:
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 9584d5bd46..1a1cd93b1a 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -477,7 +477,7 @@ class FederationEventHandler:
 
     @log_function
     async def backfill(
-        self, dest: str, room_id: str, limit: int, extremities: Iterable[str]
+        self, dest: str, room_id: str, limit: int, extremities: Collection[str]
     ) -> None:
         """Trigger a backfill request to `dest` for the given `room_id`
 
@@ -1643,7 +1643,7 @@ class FederationEventHandler:
             event: the event whose auth_events we want
 
         Returns:
-            all of the events in `event.auth_events`, after deduplication
+            all of the events listed in `event.auth_events_ids`, after deduplication
 
         Raises:
             AuthError if we were unable to fetch the auth_events for any reason.
@@ -1916,7 +1916,7 @@ class FederationEventHandler:
         event_pos = PersistedEventPosition(
             self._instance_name, event.internal_metadata.stream_ordering
         )
-        self._notifier.on_new_room_event(
+        await self._notifier.on_new_room_event(
             event, event_pos, max_stream_token, extra_users=extra_users
         )
 
diff --git a/synapse/handlers/identity.py b/synapse/handlers/identity.py
index 7ef8698a5e..3dbe611f95 100644
--- a/synapse/handlers/identity.py
+++ b/synapse/handlers/identity.py
@@ -537,10 +537,6 @@ class IdentityHandler:
         except RequestTimedOutError:
             raise SynapseError(500, "Timed out contacting identity server")
 
-        # It is already checked that public_baseurl is configured since this code
-        # should only be used if account_threepid_delegate_msisdn is true.
-        assert self.hs.config.server.public_baseurl
-
         # we need to tell the client to send the token back to us, since it doesn't
         # otherwise know where to send it, so add submit_url response parameter
         # (see also MSC2078)
@@ -879,6 +875,8 @@ class IdentityHandler:
         }
 
         if room_type is not None:
+            invite_config["room_type"] = room_type
+            # TODO The unstable field is deprecated and should be removed in the future.
             invite_config["org.matrix.msc3288.room_type"] = room_type
 
         # If a custom web client location is available, include it in the request.
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 2e024b551f..d4c2a6ab7a 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -1318,6 +1318,8 @@ class EventCreationHandler:
             # user is actually admin or not).
             is_admin_redaction = False
             if event.type == EventTypes.Redaction:
+                assert event.redacts is not None
+
                 original_event = await self.store.get_event(
                     event.redacts,
                     redact_behaviour=EventRedactBehaviour.AS_IS,
@@ -1413,6 +1415,8 @@ class EventCreationHandler:
                 )
 
         if event.type == EventTypes.Redaction:
+            assert event.redacts is not None
+
             original_event = await self.store.get_event(
                 event.redacts,
                 redact_behaviour=EventRedactBehaviour.AS_IS,
@@ -1500,11 +1504,13 @@ class EventCreationHandler:
                 next_batch_id = event.content.get(
                     EventContentFields.MSC2716_NEXT_BATCH_ID
                 )
-                conflicting_insertion_event_id = (
-                    await self.store.get_insertion_event_by_batch_id(
-                        event.room_id, next_batch_id
+                conflicting_insertion_event_id = None
+                if next_batch_id:
+                    conflicting_insertion_event_id = (
+                        await self.store.get_insertion_event_id_by_batch_id(
+                            event.room_id, next_batch_id
+                        )
                     )
-                )
                 if conflicting_insertion_event_id is not None:
                     # The current insertion event that we're processing is invalid
                     # because an insertion event already exists in the room with the
@@ -1537,13 +1543,16 @@ class EventCreationHandler:
             # If there's an expiry timestamp on the event, schedule its expiry.
             self._message_handler.maybe_schedule_expiry(event)
 
-        def _notify() -> None:
+        async def _notify() -> None:
             try:
-                self.notifier.on_new_room_event(
+                await self.notifier.on_new_room_event(
                     event, event_pos, max_stream_token, extra_users=extra_users
                 )
             except Exception:
-                logger.exception("Error notifying about new room event")
+                logger.exception(
+                    "Error notifying about new room event %s",
+                    event.event_id,
+                )
 
         run_in_background(_notify)
 
diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 60ff896386..abfe7be0e3 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -438,7 +438,7 @@ class PaginationHandler:
             }
 
         state = None
-        if event_filter and event_filter.lazy_load_members() and len(events) > 0:
+        if event_filter and event_filter.lazy_load_members and len(events) > 0:
             # TODO: remove redundant members
 
             # FIXME: we also care about invite targets etc.
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index fdab50da37..3df872c578 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -52,6 +52,7 @@ import synapse.metrics
 from synapse.api.constants import EventTypes, Membership, PresenceState
 from synapse.api.errors import SynapseError
 from synapse.api.presence import UserPresenceState
+from synapse.appservice import ApplicationService
 from synapse.events.presence_router import PresenceRouter
 from synapse.logging.context import run_in_background
 from synapse.logging.utils import log_function
@@ -1551,6 +1552,7 @@ class PresenceEventSource(EventSource[int, UserPresenceState]):
         is_guest: bool = False,
         explicit_room_id: Optional[str] = None,
         include_offline: bool = True,
+        service: Optional[ApplicationService] = None,
     ) -> Tuple[List[UserPresenceState], int]:
         # The process for getting presence events are:
         #  1. Get the rooms the user is in.
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index e6c3cf585b..6b5a6ded8b 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -456,7 +456,11 @@ class ProfileHandler:
                 continue
 
             new_name = profile.get("displayname")
+            if not isinstance(new_name, str):
+                new_name = None
             new_avatar = profile.get("avatar_url")
+            if not isinstance(new_avatar, str):
+                new_avatar = None
 
             # We always hit update to update the last_check timestamp
             await self.store.update_remote_profile_cache(user_id, new_name, new_avatar)
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index cf01d58ea1..969eb3b9b0 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -525,7 +525,7 @@ class RoomCreationHandler:
             ):
                 await self.room_member_handler.update_membership(
                     requester,
-                    UserID.from_string(old_event["state_key"]),
+                    UserID.from_string(old_event.state_key),
                     new_room_id,
                     "ban",
                     ratelimit=False,
@@ -1173,7 +1173,7 @@ class RoomContextHandler:
         else:
             last_event_id = event_id
 
-        if event_filter and event_filter.lazy_load_members():
+        if event_filter and event_filter.lazy_load_members:
             state_filter = StateFilter.from_lazy_load_member_list(
                 ev.sender
                 for ev in itertools.chain(
diff --git a/synapse/handlers/room_batch.py b/synapse/handlers/room_batch.py
index 2f5a3e4d19..0723286383 100644
--- a/synapse/handlers/room_batch.py
+++ b/synapse/handlers/room_batch.py
@@ -355,7 +355,7 @@ class RoomBatchHandler:
         for (event, context) in reversed(events_to_persist):
             await self.event_creation_handler.handle_new_client_event(
                 await self.create_requester_for_user_id_from_app_service(
-                    event["sender"], app_service_requester.app_service
+                    event.sender, app_service_requester.app_service
                 ),
                 event=event,
                 context=context,
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 74e6c7eca6..08244b690d 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -1669,7 +1669,9 @@ class RoomMemberMasterHandler(RoomMemberHandler):
         #
         # the prev_events consist solely of the previous membership event.
         prev_event_ids = [previous_membership_event.event_id]
-        auth_event_ids = previous_membership_event.auth_event_ids() + prev_event_ids
+        auth_event_ids = (
+            list(previous_membership_event.auth_event_ids()) + prev_event_ids
+        )
 
         event, context = await self.event_creation_handler.create_event(
             requester,
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index a3ffa26be8..6e4dff8056 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -249,7 +249,7 @@ class SearchHandler:
             )
 
             events.sort(key=lambda e: -rank_map[e.event_id])
-            allowed_events = events[: search_filter.limit()]
+            allowed_events = events[: search_filter.limit]
 
             for e in allowed_events:
                 rm = room_groups.setdefault(
@@ -271,13 +271,13 @@ class SearchHandler:
             # We keep looping and we keep filtering until we reach the limit
             # or we run out of things.
             # But only go around 5 times since otherwise synapse will be sad.
-            while len(room_events) < search_filter.limit() and i < 5:
+            while len(room_events) < search_filter.limit and i < 5:
                 i += 1
                 search_result = await self.store.search_rooms(
                     room_ids,
                     search_term,
                     keys,
-                    search_filter.limit() * 2,
+                    search_filter.limit * 2,
                     pagination_token=pagination_token,
                 )
 
@@ -299,9 +299,9 @@ class SearchHandler:
                 )
 
                 room_events.extend(events)
-                room_events = room_events[: search_filter.limit()]
+                room_events = room_events[: search_filter.limit]
 
-                if len(results) < search_filter.limit() * 2:
+                if len(results) < search_filter.limit * 2:
                     pagination_token = None
                     break
                 else:
@@ -311,7 +311,7 @@ class SearchHandler:
                 group = room_groups.setdefault(event.room_id, {"results": []})
                 group["results"].append(event.event_id)
 
-            if room_events and len(room_events) >= search_filter.limit():
+            if room_events and len(room_events) >= search_filter.limit:
                 last_event_id = room_events[-1].event_id
                 pagination_token = results_map[last_event_id]["pagination_token"]
 
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index c411d69924..22c6174821 100644
--- a/synapse/handlers/typing.py
+++ b/synapse/handlers/typing.py
@@ -62,8 +62,8 @@ class FollowerTypingHandler:
         if hs.should_send_federation():
             self.federation = hs.get_federation_sender()
 
-        if hs.config.worker.writers.typing != hs.get_instance_name():
-            hs.get_federation_registry().register_instance_for_edu(
+        if hs.get_instance_name() not in hs.config.worker.writers.typing:
+            hs.get_federation_registry().register_instances_for_edu(
                 "m.typing",
                 hs.config.worker.writers.typing,
             )
@@ -205,7 +205,7 @@ class TypingWriterHandler(FollowerTypingHandler):
     def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
-        assert hs.config.worker.writers.typing == hs.get_instance_name()
+        assert hs.get_instance_name() in hs.config.worker.writers.typing
 
         self.auth = hs.get_auth()
         self.notifier = hs.get_notifier()
diff --git a/synapse/http/connectproxyclient.py b/synapse/http/connectproxyclient.py
index c577142268..fbafffd69b 100644
--- a/synapse/http/connectproxyclient.py
+++ b/synapse/http/connectproxyclient.py
@@ -84,7 +84,11 @@ class HTTPConnectProxyEndpoint:
     def __repr__(self):
         return "<HTTPConnectProxyEndpoint %s>" % (self._proxy_endpoint,)
 
-    def connect(self, protocolFactory: ClientFactory):
+    # Mypy encounters a false positive here: it complains that ClientFactory
+    # is incompatible with IProtocolFactory. But ClientFactory inherits from
+    # Factory, which implements IProtocolFactory. So I think this is a bug
+    # in mypy-zope.
+    def connect(self, protocolFactory: ClientFactory):  # type: ignore[override]
         f = HTTPProxiedClientFactory(
             self._host, self._port, protocolFactory, self._proxy_creds
         )
@@ -119,13 +123,15 @@ class HTTPProxiedClientFactory(protocol.ClientFactory):
         self.dst_port = dst_port
         self.wrapped_factory = wrapped_factory
         self.proxy_creds = proxy_creds
-        self.on_connection = defer.Deferred()
+        self.on_connection: "defer.Deferred[None]" = defer.Deferred()
 
     def startedConnecting(self, connector):
         return self.wrapped_factory.startedConnecting(connector)
 
     def buildProtocol(self, addr):
         wrapped_protocol = self.wrapped_factory.buildProtocol(addr)
+        if wrapped_protocol is None:
+            raise TypeError("buildProtocol produced None instead of a Protocol")
 
         return HTTPConnectProtocol(
             self.dst_host,
@@ -235,7 +241,7 @@ class HTTPConnectSetupClient(http.HTTPClient):
         self.host = host
         self.port = port
         self.proxy_creds = proxy_creds
-        self.on_connected = defer.Deferred()
+        self.on_connected: "defer.Deferred[None]" = defer.Deferred()
 
     def connectionMade(self):
         logger.debug("Connected to proxy, sending CONNECT")
diff --git a/synapse/http/request_metrics.py b/synapse/http/request_metrics.py
index 602f93c497..4886626d50 100644
--- a/synapse/http/request_metrics.py
+++ b/synapse/http/request_metrics.py
@@ -15,6 +15,8 @@
 
 import logging
 import threading
+import traceback
+from typing import Dict, Mapping, Set, Tuple
 
 from prometheus_client.core import Counter, Histogram
 
@@ -105,19 +107,14 @@ in_flight_requests_db_sched_duration = Counter(
     ["method", "servlet"],
 )
 
-# The set of all in flight requests, set[RequestMetrics]
-_in_flight_requests = set()
+_in_flight_requests: Set["RequestMetrics"] = set()
 
 # Protects the _in_flight_requests set from concurrent access
 _in_flight_requests_lock = threading.Lock()
 
 
-def _get_in_flight_counts():
-    """Returns a count of all in flight requests by (method, server_name)
-
-    Returns:
-        dict[tuple[str, str], int]
-    """
+def _get_in_flight_counts() -> Mapping[Tuple[str, ...], int]:
+    """Returns a count of all in flight requests by (method, server_name)"""
     # Cast to a list to prevent it changing while the Prometheus
     # thread is collecting metrics
     with _in_flight_requests_lock:
@@ -127,8 +124,9 @@ def _get_in_flight_counts():
         rm.update_metrics()
 
     # Map from (method, name) -> int, the number of in flight requests of that
-    # type
-    counts = {}
+    # type. The key type is Tuple[str, str], but we leave the length unspecified
+    # for compatability with LaterGauge's annotations.
+    counts: Dict[Tuple[str, ...], int] = {}
     for rm in reqs:
         key = (rm.method, rm.name)
         counts[key] = counts.get(key, 0) + 1
@@ -145,15 +143,21 @@ LaterGauge(
 
 
 class RequestMetrics:
-    def start(self, time_sec, name, method):
-        self.start = time_sec
+    def start(self, time_sec: float, name: str, method: str) -> None:
+        self.start_ts = time_sec
         self.start_context = current_context()
         self.name = name
         self.method = method
 
-        # _request_stats records resource usage that we have already added
-        # to the "in flight" metrics.
-        self._request_stats = self.start_context.get_resource_usage()
+        if self.start_context:
+            # _request_stats records resource usage that we have already added
+            # to the "in flight" metrics.
+            self._request_stats = self.start_context.get_resource_usage()
+        else:
+            logger.error(
+                "Tried to start a RequestMetric from the sentinel context.\n%s",
+                "".join(traceback.format_stack()),
+            )
 
         with _in_flight_requests_lock:
             _in_flight_requests.add(self)
@@ -169,12 +173,18 @@ class RequestMetrics:
             tag = context.tag
 
             if context != self.start_context:
-                logger.warning(
+                logger.error(
                     "Context have unexpectedly changed %r, %r",
                     context,
                     self.start_context,
                 )
                 return
+        else:
+            logger.error(
+                "Trying to stop RequestMetrics in the sentinel context.\n%s",
+                "".join(traceback.format_stack()),
+            )
+            return
 
         response_code = str(response_code)
 
@@ -183,7 +193,7 @@ class RequestMetrics:
         response_count.labels(self.method, self.name, tag).inc()
 
         response_timer.labels(self.method, self.name, tag, response_code).observe(
-            time_sec - self.start
+            time_sec - self.start_ts
         )
 
         resource_usage = context.get_resource_usage()
@@ -213,6 +223,12 @@ class RequestMetrics:
 
     def update_metrics(self):
         """Updates the in flight metrics with values from this request."""
+        if not self.start_context:
+            logger.error(
+                "Tried to update a RequestMetric from the sentinel context.\n%s",
+                "".join(traceback.format_stack()),
+            )
+            return
         new_stats = self.start_context.get_resource_usage()
 
         diff = new_stats - self._request_stats
diff --git a/synapse/logging/context.py b/synapse/logging/context.py
index bdc0187743..d8ae3188b7 100644
--- a/synapse/logging/context.py
+++ b/synapse/logging/context.py
@@ -220,7 +220,7 @@ class _Sentinel:
         self.scope = None
         self.tag = None
 
-    def __str__(self):
+    def __str__(self) -> str:
         return "sentinel"
 
     def copy_to(self, record):
@@ -241,7 +241,7 @@ class _Sentinel:
     def record_event_fetch(self, event_count):
         pass
 
-    def __bool__(self):
+    def __bool__(self) -> Literal[False]:
         return False
 
 
diff --git a/synapse/logging/utils.py b/synapse/logging/utils.py
index 08895e72ee..4a01b902c2 100644
--- a/synapse/logging/utils.py
+++ b/synapse/logging/utils.py
@@ -16,6 +16,7 @@
 import logging
 from functools import wraps
 from inspect import getcallargs
+from typing import Callable, TypeVar, cast
 
 _TIME_FUNC_ID = 0
 
@@ -41,7 +42,10 @@ def _log_debug_as_f(f, msg, msg_args):
         logger.handle(record)
 
 
-def log_function(f):
+F = TypeVar("F", bound=Callable)
+
+
+def log_function(f: F) -> F:
     """Function decorator that logs every call to that function."""
     func_name = f.__name__
 
@@ -69,4 +73,4 @@ def log_function(f):
         return f(*args, **kwargs)
 
     wrapped.__name__ = func_name
-    return wrapped
+    return cast(F, wrapped)
diff --git a/synapse/metrics/__init__.py b/synapse/metrics/__init__.py
index f237b8a236..91ee5c8193 100644
--- a/synapse/metrics/__init__.py
+++ b/synapse/metrics/__init__.py
@@ -20,7 +20,7 @@ import os
 import platform
 import threading
 import time
-from typing import Callable, Dict, Iterable, Optional, Tuple, Union
+from typing import Callable, Dict, Iterable, Mapping, Optional, Tuple, Union
 
 import attr
 from prometheus_client import Counter, Gauge, Histogram
@@ -32,6 +32,7 @@ from prometheus_client.core import (
 )
 
 from twisted.internet import reactor
+from twisted.python.threadpool import ThreadPool
 
 import synapse
 from synapse.metrics._exposition import (
@@ -67,7 +68,11 @@ class LaterGauge:
     labels = attr.ib(hash=False, type=Optional[Iterable[str]])
     # callback: should either return a value (if there are no labels for this metric),
     # or dict mapping from a label tuple to a value
-    caller = attr.ib(type=Callable[[], Union[Dict[Tuple[str, ...], float], float]])
+    caller = attr.ib(
+        type=Callable[
+            [], Union[Mapping[Tuple[str, ...], Union[int, float]], Union[int, float]]
+        ]
+    )
 
     def collect(self):
 
@@ -80,11 +85,11 @@ class LaterGauge:
             yield g
             return
 
-        if isinstance(calls, dict):
+        if isinstance(calls, (int, float)):
+            g.add_metric([], calls)
+        else:
             for k, v in calls.items():
                 g.add_metric(k, v)
-        else:
-            g.add_metric([], calls)
 
         yield g
 
@@ -522,6 +527,42 @@ threepid_send_requests = Histogram(
     labelnames=("type", "reason"),
 )
 
+threadpool_total_threads = Gauge(
+    "synapse_threadpool_total_threads",
+    "Total number of threads currently in the threadpool",
+    ["name"],
+)
+
+threadpool_total_working_threads = Gauge(
+    "synapse_threadpool_working_threads",
+    "Number of threads currently working in the threadpool",
+    ["name"],
+)
+
+threadpool_total_min_threads = Gauge(
+    "synapse_threadpool_min_threads",
+    "Minimum number of threads configured in the threadpool",
+    ["name"],
+)
+
+threadpool_total_max_threads = Gauge(
+    "synapse_threadpool_max_threads",
+    "Maximum number of threads configured in the threadpool",
+    ["name"],
+)
+
+
+def register_threadpool(name: str, threadpool: ThreadPool) -> None:
+    """Add metrics for the threadpool."""
+
+    threadpool_total_min_threads.labels(name).set(threadpool.min)
+    threadpool_total_max_threads.labels(name).set(threadpool.max)
+
+    threadpool_total_threads.labels(name).set_function(lambda: len(threadpool.threads))
+    threadpool_total_working_threads.labels(name).set_function(
+        lambda: len(threadpool.working)
+    )
+
 
 class ReactorLastSeenMetric:
     def collect(self):
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index d707a9325d..6e7f5238fe 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -33,6 +33,7 @@ import jinja2
 from twisted.internet import defer
 from twisted.web.resource import IResource
 
+from synapse.api.errors import SynapseError
 from synapse.events import EventBase
 from synapse.events.presence_router import PresenceRouter
 from synapse.http.client import SimpleHttpClient
@@ -54,6 +55,7 @@ from synapse.types import (
     DomainSpecificString,
     JsonDict,
     Requester,
+    StateMap,
     UserID,
     UserInfo,
     create_requester,
@@ -88,6 +90,8 @@ __all__ = [
     "PRESENCE_ALL_USERS",
     "LoginResponse",
     "JsonDict",
+    "EventBase",
+    "StateMap",
 ]
 
 logger = logging.getLogger(__name__)
@@ -625,8 +629,105 @@ class ModuleApi:
         state = yield defer.ensureDeferred(self._store.get_events(state_ids.values()))
         return state.values()
 
+    async def update_room_membership(
+        self,
+        sender: str,
+        target: str,
+        room_id: str,
+        new_membership: str,
+        content: Optional[JsonDict] = None,
+    ) -> EventBase:
+        """Updates the membership of a user to the given value.
+
+        Added in Synapse v1.46.0.
+
+        Args:
+            sender: The user performing the membership change. Must be a user local to
+                this homeserver.
+            target: The user whose membership is changing. This is often the same value
+                as `sender`, but it might differ in some cases (e.g. when kicking a user,
+                the `sender` is the user performing the kick and the `target` is the user
+                being kicked).
+            room_id: The room in which to change the membership.
+            new_membership: The new membership state of `target` after this operation. See
+                https://spec.matrix.org/unstable/client-server-api/#mroommember for the
+                list of allowed values.
+            content: Additional values to include in the resulting event's content.
+
+        Returns:
+            The newly created membership event.
+
+        Raises:
+            RuntimeError if the `sender` isn't a local user.
+            ShadowBanError if a shadow-banned requester attempts to send an invite.
+            SynapseError if the module attempts to send a membership event that isn't
+                allowed, either by the server's configuration (e.g. trying to set a
+                per-room display name that's too long) or by the validation rules around
+                membership updates (e.g. the `membership` value is invalid).
+        """
+        if not self.is_mine(sender):
+            raise RuntimeError(
+                "Tried to send an event as a user that isn't local to this homeserver",
+            )
+
+        requester = create_requester(sender)
+        target_user_id = UserID.from_string(target)
+
+        if content is None:
+            content = {}
+
+        # Set the profile if not already done by the module.
+        if "avatar_url" not in content or "displayname" not in content:
+            try:
+                # Try to fetch the user's profile.
+                profile = await self._hs.get_profile_handler().get_profile(
+                    target_user_id.to_string(),
+                )
+            except SynapseError as e:
+                # If the profile couldn't be found, use default values.
+                profile = {
+                    "displayname": target_user_id.localpart,
+                    "avatar_url": None,
+                }
+
+                if e.code != 404:
+                    # If the error isn't 404, it means we tried to fetch the profile over
+                    # federation but the remote server responded with a non-standard
+                    # status code.
+                    logger.error(
+                        "Got non-404 error status when fetching profile for %s",
+                        target_user_id.to_string(),
+                    )
+
+            # Set the profile where it needs to be set.
+            if "avatar_url" not in content:
+                content["avatar_url"] = profile["avatar_url"]
+
+            if "displayname" not in content:
+                content["displayname"] = profile["displayname"]
+
+        event_id, _ = await self._hs.get_room_member_handler().update_membership(
+            requester=requester,
+            target=target_user_id,
+            room_id=room_id,
+            action=new_membership,
+            content=content,
+        )
+
+        # Try to retrieve the resulting event.
+        event = await self._hs.get_datastore().get_event(event_id)
+
+        # update_membership is supposed to always return after the event has been
+        # successfully persisted.
+        assert event is not None
+
+        return event
+
     async def create_and_send_event_into_room(self, event_dict: JsonDict) -> EventBase:
-        """Create and send an event into a room. Membership events are currently not supported.
+        """Create and send an event into a room.
+
+        Membership events are not supported by this method. To update a user's membership
+        in a room, please use the `update_room_membership` method instead.
 
         Added in Synapse v1.22.0.
 
@@ -866,6 +967,52 @@ class ModuleApi:
         else:
             return []
 
+    async def get_room_state(
+        self,
+        room_id: str,
+        event_filter: Optional[Iterable[Tuple[str, Optional[str]]]] = None,
+    ) -> StateMap[EventBase]:
+        """Returns the current state of the given room.
+
+        The events are returned as a mapping, in which the key for each event is a tuple
+        which first element is the event's type and the second one is its state key.
+
+        Added in Synapse v1.47.0
+
+        Args:
+            room_id: The ID of the room to get state from.
+            event_filter: A filter to apply when retrieving events. None if no filter
+                should be applied. If provided, must be an iterable of tuples. A tuple's
+                first element is the event type and the second is the state key, or is
+                None if the state key should not be filtered on.
+                An example of a filter is:
+                    [
+                        ("m.room.member", "@alice:example.com"),  # Member event for @alice:example.com
+                        ("org.matrix.some_event", ""),  # State event of type "org.matrix.some_event"
+                                                        # with an empty string as its state key
+                        ("org.matrix.some_other_event", None),  # State events of type "org.matrix.some_other_event"
+                                                                # regardless of their state key
+                    ]
+        """
+        if event_filter:
+            # If a filter was provided, turn it into a StateFilter and retrieve a filtered
+            # view of the state.
+            state_filter = StateFilter.from_types(event_filter)
+            state_ids = await self._store.get_filtered_current_state_ids(
+                room_id,
+                state_filter,
+            )
+        else:
+            # If no filter was provided, get the whole state. We could also reuse the call
+            # to get_filtered_current_state_ids above, with `state_filter = StateFilter.all()`,
+            # but get_filtered_current_state_ids isn't cached and `get_current_state_ids`
+            # is, so using the latter when we can is better for perf.
+            state_ids = await self._store.get_current_state_ids(room_id)
+
+        state_events = await self._store.get_events(state_ids.values())
+
+        return {key: state_events[event_id] for key, event_id in state_ids.items()}
+
 
 class PublicRoomListManager:
     """Contains methods for adding to, removing from and querying whether a room
diff --git a/synapse/notifier.py b/synapse/notifier.py
index 1acd899fab..60e5409895 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -220,6 +220,8 @@ class Notifier:
         # down.
         self.remote_server_up_callbacks: List[Callable[[str], None]] = []
 
+        self._third_party_rules = hs.get_third_party_event_rules()
+
         self.clock = hs.get_clock()
         self.appservice_handler = hs.get_application_service_handler()
         self._pusher_pool = hs.get_pusherpool()
@@ -267,7 +269,7 @@ class Notifier:
         """
         self.replication_callbacks.append(cb)
 
-    def on_new_room_event(
+    async def on_new_room_event(
         self,
         event: EventBase,
         event_pos: PersistedEventPosition,
@@ -275,9 +277,10 @@ class Notifier:
         extra_users: Optional[Collection[UserID]] = None,
     ):
         """Unwraps event and calls `on_new_room_event_args`."""
-        self.on_new_room_event_args(
+        await self.on_new_room_event_args(
             event_pos=event_pos,
             room_id=event.room_id,
+            event_id=event.event_id,
             event_type=event.type,
             state_key=event.get("state_key"),
             membership=event.content.get("membership"),
@@ -285,9 +288,10 @@ class Notifier:
             extra_users=extra_users or [],
         )
 
-    def on_new_room_event_args(
+    async def on_new_room_event_args(
         self,
         room_id: str,
+        event_id: str,
         event_type: str,
         state_key: Optional[str],
         membership: Optional[str],
@@ -302,7 +306,10 @@ class Notifier:
         listening to the room, and any listeners for the users in the
         `extra_users` param.
 
-        The events can be peristed out of order. The notifier will wait
+        This also notifies modules listening on new events via the
+        `on_new_event` callback.
+
+        The events can be persisted out of order. The notifier will wait
         until all previous events have been persisted before notifying
         the client streams.
         """
@@ -318,6 +325,8 @@ class Notifier:
         )
         self._notify_pending_new_room_events(max_room_stream_token)
 
+        await self._third_party_rules.on_new_event(event_id)
+
         self.notify_replication()
 
     def _notify_pending_new_room_events(self, max_room_stream_token: RoomStreamToken):
@@ -374,29 +383,6 @@ class Notifier:
         except Exception:
             logger.exception("Error notifying application services of event")
 
-    def _notify_app_services_ephemeral(
-        self,
-        stream_key: str,
-        new_token: Union[int, RoomStreamToken],
-        users: Optional[Collection[Union[str, UserID]]] = None,
-    ) -> None:
-        """Notify application services of ephemeral event activity.
-
-        Args:
-            stream_key: The stream the event came from.
-            new_token: The value of the new stream token.
-            users: The users that should be informed of the new event, if any.
-        """
-        try:
-            stream_token = None
-            if isinstance(new_token, int):
-                stream_token = new_token
-            self.appservice_handler.notify_interested_services_ephemeral(
-                stream_key, stream_token, users or []
-            )
-        except Exception:
-            logger.exception("Error notifying application services of event")
-
     def _notify_pusher_pool(self, max_room_stream_token: RoomStreamToken):
         try:
             self._pusher_pool.on_new_notifications(max_room_stream_token)
@@ -458,12 +444,15 @@ class Notifier:
 
             self.notify_replication()
 
-            # Notify appservices
-            self._notify_app_services_ephemeral(
-                stream_key,
-                new_token,
-                users,
-            )
+            # Notify appservices.
+            try:
+                self.appservice_handler.notify_interested_services_ephemeral(
+                    stream_key,
+                    new_token,
+                    users,
+                )
+            except Exception:
+                logger.exception("Error notifying application services of event")
 
     def on_new_replication_data(self) -> None:
         """Used to inform replication listeners that something has happened
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 0622a37ae8..009d8e77b0 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -232,6 +232,8 @@ class BulkPushRuleEvaluator:
                 # that user, as they might not be already joined.
                 if event.type == EventTypes.Member and event.state_key == uid:
                     display_name = event.content.get("displayname", None)
+                    if not isinstance(display_name, str):
+                        display_name = None
 
             if count_as_unread:
                 # Add an element for the current user if the event needs to be marked as
@@ -268,7 +270,7 @@ def _condition_checker(
     evaluator: PushRuleEvaluatorForEvent,
     conditions: List[dict],
     uid: str,
-    display_name: str,
+    display_name: Optional[str],
     cache: Dict[str, bool],
 ) -> bool:
     for cond in conditions:
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index 7a8dc63976..7f68092ec5 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -18,7 +18,7 @@ import re
 from typing import Any, Dict, List, Optional, Pattern, Tuple, Union
 
 from synapse.events import EventBase
-from synapse.types import UserID
+from synapse.types import JsonDict, UserID
 from synapse.util import glob_to_regex, re_word_boundary
 from synapse.util.caches.lrucache import LruCache
 
@@ -129,7 +129,7 @@ class PushRuleEvaluatorForEvent:
         self._value_cache = _flatten_dict(event)
 
     def matches(
-        self, condition: Dict[str, Any], user_id: str, display_name: str
+        self, condition: Dict[str, Any], user_id: str, display_name: Optional[str]
     ) -> bool:
         if condition["kind"] == "event_match":
             return self._event_match(condition, user_id)
@@ -172,7 +172,7 @@ class PushRuleEvaluatorForEvent:
 
             return _glob_matches(pattern, haystack)
 
-    def _contains_display_name(self, display_name: str) -> bool:
+    def _contains_display_name(self, display_name: Optional[str]) -> bool:
         if not display_name:
             return False
 
@@ -222,7 +222,7 @@ def _glob_matches(glob: str, value: str, word_boundary: bool = False) -> bool:
 
 
 def _flatten_dict(
-    d: Union[EventBase, dict],
+    d: Union[EventBase, JsonDict],
     prefix: Optional[List[str]] = None,
     result: Optional[Dict[str, str]] = None,
 ) -> Dict[str, str]:
@@ -233,7 +233,7 @@ def _flatten_dict(
     for key, value in d.items():
         if isinstance(value, str):
             result[".".join(prefix + [key])] = value.lower()
-        elif hasattr(value, "items"):
+        elif isinstance(value, dict):
             _flatten_dict(value, prefix=(prefix + [key]), result=result)
 
     return result
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 961c17762e..e29ae1e375 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -207,11 +207,12 @@ class ReplicationDataHandler:
 
                 max_token = self.store.get_room_max_token()
                 event_pos = PersistedEventPosition(instance_name, token)
-                self.notifier.on_new_room_event_args(
+                await self.notifier.on_new_room_event_args(
                     event_pos=event_pos,
                     max_room_stream_token=max_token,
                     extra_users=extra_users,
                     room_id=row.data.room_id,
+                    event_id=row.data.event_id,
                     event_type=row.data.type,
                     state_key=row.data.state_key,
                     membership=row.data.membership,
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index 06fd06fdf3..21293038ef 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -138,7 +138,7 @@ class ReplicationCommandHandler:
             if isinstance(stream, TypingStream):
                 # Only add TypingStream as a source on the instance in charge of
                 # typing.
-                if hs.config.worker.writers.typing == hs.get_instance_name():
+                if hs.get_instance_name() in hs.config.worker.writers.typing:
                     self._streams_to_replicate.append(stream)
 
                 continue
diff --git a/synapse/replication/tcp/streams/_base.py b/synapse/replication/tcp/streams/_base.py
index c8b188ae4e..743a01da08 100644
--- a/synapse/replication/tcp/streams/_base.py
+++ b/synapse/replication/tcp/streams/_base.py
@@ -328,8 +328,7 @@ class TypingStream(Stream):
     ROW_TYPE = TypingStreamRow
 
     def __init__(self, hs: "HomeServer"):
-        writer_instance = hs.config.worker.writers.typing
-        if writer_instance == hs.get_instance_name():
+        if hs.get_instance_name() in hs.config.worker.writers.typing:
             # On the writer, query the typing handler
             typing_writer_handler = hs.get_typing_writer_handler()
             update_function: Callable[
diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index e1506deb2b..81e98f81d6 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -25,6 +25,10 @@ from synapse.http.server import HttpServer, JsonResource
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.http.site import SynapseRequest
 from synapse.rest.admin._base import admin_patterns, assert_requester_is_admin
+from synapse.rest.admin.background_updates import (
+    BackgroundUpdateEnabledRestServlet,
+    BackgroundUpdateRestServlet,
+)
 from synapse.rest.admin.devices import (
     DeleteDevicesRestServlet,
     DeviceRestServlet,
@@ -42,7 +46,6 @@ from synapse.rest.admin.registration_tokens import (
     RegistrationTokenRestServlet,
 )
 from synapse.rest.admin.rooms import (
-    DeleteRoomRestServlet,
     ForwardExtremitiesRestServlet,
     JoinRoomAliasServlet,
     ListRoomRestServlet,
@@ -221,7 +224,6 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RoomStateRestServlet(hs).register(http_server)
     RoomRestServlet(hs).register(http_server)
     RoomMembersRestServlet(hs).register(http_server)
-    DeleteRoomRestServlet(hs).register(http_server)
     JoinRoomAliasServlet(hs).register(http_server)
     VersionServlet(hs).register(http_server)
     UserAdminServlet(hs).register(http_server)
@@ -249,6 +251,8 @@ def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     # Some servlets only get registered for the main process.
     if hs.config.worker.worker_app is None:
         SendServerNoticeServlet(hs).register(http_server)
+        BackgroundUpdateEnabledRestServlet(hs).register(http_server)
+        BackgroundUpdateRestServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(
diff --git a/synapse/rest/admin/background_updates.py b/synapse/rest/admin/background_updates.py
new file mode 100644
index 0000000000..0d0183bf20
--- /dev/null
+++ b/synapse/rest/admin/background_updates.py
@@ -0,0 +1,107 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+from typing import TYPE_CHECKING, Tuple
+
+from synapse.api.errors import SynapseError
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.rest.admin._base import admin_patterns, assert_user_is_admin
+from synapse.types import JsonDict
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class BackgroundUpdateEnabledRestServlet(RestServlet):
+    """Allows temporarily disabling background updates"""
+
+    PATTERNS = admin_patterns("/background_updates/enabled")
+
+    def __init__(self, hs: "HomeServer"):
+        self.group_server = hs.get_groups_server_handler()
+        self.is_mine_id = hs.is_mine_id
+        self.auth = hs.get_auth()
+
+        self.data_stores = hs.get_datastores()
+
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        # We need to check that all configured databases have updates enabled.
+        # (They *should* all be in sync.)
+        enabled = all(db.updates.enabled for db in self.data_stores.databases)
+
+        return 200, {"enabled": enabled}
+
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        body = parse_json_object_from_request(request)
+
+        enabled = body.get("enabled", True)
+
+        if not isinstance(enabled, bool):
+            raise SynapseError(400, "'enabled' parameter must be a boolean")
+
+        for db in self.data_stores.databases:
+            db.updates.enabled = enabled
+
+            # If we're re-enabling them ensure that we start the background
+            # process again.
+            if enabled:
+                db.updates.start_doing_background_updates()
+
+        return 200, {"enabled": enabled}
+
+
+class BackgroundUpdateRestServlet(RestServlet):
+    """Fetch information about background updates"""
+
+    PATTERNS = admin_patterns("/background_updates/status")
+
+    def __init__(self, hs: "HomeServer"):
+        self.group_server = hs.get_groups_server_handler()
+        self.is_mine_id = hs.is_mine_id
+        self.auth = hs.get_auth()
+
+        self.data_stores = hs.get_datastores()
+
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        # We need to check that all configured databases have updates enabled.
+        # (They *should* all be in sync.)
+        enabled = all(db.updates.enabled for db in self.data_stores.databases)
+
+        current_updates = {}
+
+        for db in self.data_stores.databases:
+            update = db.updates.get_current_update()
+            if not update:
+                continue
+
+            current_updates[db.name()] = {
+                "name": update.name,
+                "total_item_count": update.total_item_count,
+                "total_duration_ms": update.total_duration_ms,
+                "average_items_per_ms": update.average_items_per_ms(),
+            }
+
+        return 200, {"enabled": enabled, "current_updates": current_updates}
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index a4823ca6e7..05c5b4bf0c 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -46,41 +46,6 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class DeleteRoomRestServlet(RestServlet):
-    """Delete a room from server.
-
-    It is a combination and improvement of shutdown and purge room.
-
-    Shuts down a room by removing all local users from the room.
-    Blocking all future invites and joins to the room is optional.
-
-    If desired any local aliases will be repointed to a new room
-    created by `new_room_user_id` and kicked users will be auto-
-    joined to the new room.
-
-    If 'purge' is true, it will remove all traces of a room from the database.
-    """
-
-    PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)/delete$")
-
-    def __init__(self, hs: "HomeServer"):
-        self.hs = hs
-        self.auth = hs.get_auth()
-        self.room_shutdown_handler = hs.get_room_shutdown_handler()
-        self.pagination_handler = hs.get_pagination_handler()
-
-    async def on_POST(
-        self, request: SynapseRequest, room_id: str
-    ) -> Tuple[int, JsonDict]:
-        return await _delete_room(
-            request,
-            room_id,
-            self.auth,
-            self.room_shutdown_handler,
-            self.pagination_handler,
-        )
-
-
 class ListRoomRestServlet(RestServlet):
     """
     List all rooms that are known to the homeserver. Results are returned
@@ -218,7 +183,7 @@ class RoomRestServlet(RestServlet):
     async def on_DELETE(
         self, request: SynapseRequest, room_id: str
     ) -> Tuple[int, JsonDict]:
-        return await _delete_room(
+        return await self._delete_room(
             request,
             room_id,
             self.auth,
@@ -226,6 +191,58 @@ class RoomRestServlet(RestServlet):
             self.pagination_handler,
         )
 
+    async def _delete_room(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        auth: "Auth",
+        room_shutdown_handler: "RoomShutdownHandler",
+        pagination_handler: "PaginationHandler",
+    ) -> Tuple[int, JsonDict]:
+        requester = await auth.get_user_by_req(request)
+        await assert_user_is_admin(auth, requester.user)
+
+        content = parse_json_object_from_request(request)
+
+        block = content.get("block", False)
+        if not isinstance(block, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'block' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        purge = content.get("purge", True)
+        if not isinstance(purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        force_purge = content.get("force_purge", False)
+        if not isinstance(force_purge, bool):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Param 'force_purge' must be a boolean, if given",
+                Codes.BAD_JSON,
+            )
+
+        ret = await room_shutdown_handler.shutdown_room(
+            room_id=room_id,
+            new_room_user_id=content.get("new_room_user_id"),
+            new_room_name=content.get("room_name"),
+            message=content.get("message"),
+            requester_user_id=requester.user.to_string(),
+            block=block,
+        )
+
+        # Purge room
+        if purge:
+            await pagination_handler.purge_room(room_id, force=force_purge)
+
+        return 200, ret
+
 
 class RoomMembersRestServlet(RestServlet):
     """
@@ -617,55 +634,3 @@ class RoomEventContextServlet(RestServlet):
         )
 
         return 200, results
-
-
-async def _delete_room(
-    request: SynapseRequest,
-    room_id: str,
-    auth: "Auth",
-    room_shutdown_handler: "RoomShutdownHandler",
-    pagination_handler: "PaginationHandler",
-) -> Tuple[int, JsonDict]:
-    requester = await auth.get_user_by_req(request)
-    await assert_user_is_admin(auth, requester.user)
-
-    content = parse_json_object_from_request(request)
-
-    block = content.get("block", False)
-    if not isinstance(block, bool):
-        raise SynapseError(
-            HTTPStatus.BAD_REQUEST,
-            "Param 'block' must be a boolean, if given",
-            Codes.BAD_JSON,
-        )
-
-    purge = content.get("purge", True)
-    if not isinstance(purge, bool):
-        raise SynapseError(
-            HTTPStatus.BAD_REQUEST,
-            "Param 'purge' must be a boolean, if given",
-            Codes.BAD_JSON,
-        )
-
-    force_purge = content.get("force_purge", False)
-    if not isinstance(force_purge, bool):
-        raise SynapseError(
-            HTTPStatus.BAD_REQUEST,
-            "Param 'force_purge' must be a boolean, if given",
-            Codes.BAD_JSON,
-        )
-
-    ret = await room_shutdown_handler.shutdown_room(
-        room_id=room_id,
-        new_room_user_id=content.get("new_room_user_id"),
-        new_room_name=content.get("room_name"),
-        message=content.get("message"),
-        requester_user_id=requester.user.to_string(),
-        block=block,
-    )
-
-    # Purge room
-    if purge:
-        await pagination_handler.purge_room(room_id, force=force_purge)
-
-    return 200, ret
diff --git a/synapse/rest/client/receipts.py b/synapse/rest/client/receipts.py
index 9770413c61..2b25b9aad6 100644
--- a/synapse/rest/client/receipts.py
+++ b/synapse/rest/client/receipts.py
@@ -13,10 +13,12 @@
 # limitations under the License.
 
 import logging
+import re
 from typing import TYPE_CHECKING, Tuple
 
 from synapse.api.constants import ReadReceiptEventFields
 from synapse.api.errors import Codes, SynapseError
+from synapse.http import get_request_user_agent
 from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.http.site import SynapseRequest
@@ -24,6 +26,8 @@ from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+pattern = re.compile(r"(?:Element|SchildiChat)/1\.[012]\.")
+
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
@@ -52,7 +56,13 @@ class ReceiptRestServlet(RestServlet):
         if receipt_type != "m.read":
             raise SynapseError(400, "Receipt type must be 'm.read'")
 
-        body = parse_json_object_from_request(request, allow_empty_body=True)
+        # Do not allow older SchildiChat and Element Android clients (prior to Element/1.[012].x) to send an empty body.
+        user_agent = get_request_user_agent(request)
+        allow_empty_body = False
+        if "Android" in user_agent:
+            if pattern.match(user_agent) or "Riot" in user_agent:
+                allow_empty_body = True
+        body = parse_json_object_from_request(request, allow_empty_body)
         hidden = body.get(ReadReceiptEventFields.MSC2285_HIDDEN, False)
 
         if not isinstance(hidden, bool):
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index ed95189b6d..6a876cfa2f 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -914,7 +914,7 @@ class RoomTypingRestServlet(RestServlet):
         # If we're not on the typing writer instance we should scream if we get
         # requests.
         self._is_typing_writer = (
-            hs.config.worker.writers.typing == hs.get_instance_name()
+            hs.get_instance_name() in hs.config.worker.writers.typing
         )
 
     async def on_PUT(
diff --git a/synapse/rest/client/room_batch.py b/synapse/rest/client/room_batch.py
index 99f8156ad0..e4c9451ae0 100644
--- a/synapse/rest/client/room_batch.py
+++ b/synapse/rest/client/room_batch.py
@@ -112,7 +112,7 @@ class RoomBatchSendEventRestServlet(RestServlet):
         # and have the batch connected.
         if batch_id_from_query:
             corresponding_insertion_event_id = (
-                await self.store.get_insertion_event_by_batch_id(
+                await self.store.get_insertion_event_id_by_batch_id(
                     room_id, batch_id_from_query
                 )
             )
@@ -131,20 +131,22 @@ class RoomBatchSendEventRestServlet(RestServlet):
             prev_event_ids_from_query
         )
 
+        state_event_ids_at_start = []
         # Create and persist all of the state events that float off on their own
         # before the batch. These will most likely be all of the invite/member
         # state events used to auth the upcoming historical messages.
-        state_event_ids_at_start = (
-            await self.room_batch_handler.persist_state_events_at_start(
-                state_events_at_start=body["state_events_at_start"],
-                room_id=room_id,
-                initial_auth_event_ids=auth_event_ids,
-                app_service_requester=requester,
+        if body["state_events_at_start"]:
+            state_event_ids_at_start = (
+                await self.room_batch_handler.persist_state_events_at_start(
+                    state_events_at_start=body["state_events_at_start"],
+                    room_id=room_id,
+                    initial_auth_event_ids=auth_event_ids,
+                    app_service_requester=requester,
+                )
             )
-        )
-        # Update our ongoing auth event ID list with all of the new state we
-        # just created
-        auth_event_ids.extend(state_event_ids_at_start)
+            # Update our ongoing auth event ID list with all of the new state we
+            # just created
+            auth_event_ids.extend(state_event_ids_at_start)
 
         inherited_depth = await self.room_batch_handler.inherit_depth_from_prev_ids(
             prev_event_ids_from_query
@@ -191,14 +193,17 @@ class RoomBatchSendEventRestServlet(RestServlet):
                 depth=inherited_depth,
             )
 
-            batch_id_to_connect_to = base_insertion_event["content"][
+            batch_id_to_connect_to = base_insertion_event.content[
                 EventContentFields.MSC2716_NEXT_BATCH_ID
             ]
 
         # Also connect the historical event chain to the end of the floating
         # state chain, which causes the HS to ask for the state at the start of
-        # the batch later.
-        prev_event_ids = [state_event_ids_at_start[-1]]
+        # the batch later. If there is no state chain to connect to, just make
+        # the insertion event float itself.
+        prev_event_ids = []
+        if len(state_event_ids_at_start):
+            prev_event_ids = [state_event_ids_at_start[-1]]
 
         # Create and persist all of the historical events as well as insertion
         # and batch meta events to make the batch navigable in the DAG.
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index b52a296d8f..8d888f4565 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -72,6 +72,7 @@ class VersionsRestServlet(RestServlet):
                     "r0.4.0",
                     "r0.5.0",
                     "r0.6.0",
+                    "r0.6.1",
                 ],
                 # as per MSC1497:
                 "unstable_features": {
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index abd88a2d4f..244ba261bb 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -215,6 +215,8 @@ class MediaRepository:
         self.mark_recently_accessed(None, media_id)
 
         media_type = media_info["media_type"]
+        if not media_type:
+            media_type = "application/octet-stream"
         media_length = media_info["media_length"]
         upload_name = name if name else media_info["upload_name"]
         url_cache = media_info["url_cache"]
@@ -333,6 +335,9 @@ class MediaRepository:
                 logger.info("Media is quarantined")
                 raise NotFoundError()
 
+            if not media_info["media_type"]:
+                media_info["media_type"] = "application/octet-stream"
+
             responder = await self.media_storage.fetch_media(file_info)
             if responder:
                 return responder, media_info
@@ -354,6 +359,8 @@ class MediaRepository:
                 raise e
 
         file_id = media_info["filesystem_id"]
+        if not media_info["media_type"]:
+            media_info["media_type"] = "application/octet-stream"
         file_info = FileInfo(server_name, file_id)
 
         # We generate thumbnails even if another process downloaded the media
@@ -445,7 +452,10 @@ class MediaRepository:
 
             await finish()
 
-            media_type = headers[b"Content-Type"][0].decode("ascii")
+            if b"Content-Type" in headers:
+                media_type = headers[b"Content-Type"][0].decode("ascii")
+            else:
+                media_type = "application/octet-stream"
             upload_name = get_filename_from_headers(headers)
             time_now_ms = self.clock.time_msec()
 
diff --git a/synapse/rest/media/v1/upload_resource.py b/synapse/rest/media/v1/upload_resource.py
index 7dcb1428e4..8162094cf6 100644
--- a/synapse/rest/media/v1/upload_resource.py
+++ b/synapse/rest/media/v1/upload_resource.py
@@ -80,7 +80,7 @@ class UploadResource(DirectServeJsonResource):
             assert content_type_headers  # for mypy
             media_type = content_type_headers[0].decode("ascii")
         else:
-            raise SynapseError(msg="Upload request missing 'Content-Type'", code=400)
+            media_type = "application/octet-stream"
 
         # if headers.hasHeader(b"Content-Disposition"):
         #     disposition = headers.getRawHeaders(b"Content-Disposition")[0]
diff --git a/synapse/rest/well_known.py b/synapse/rest/well_known.py
index 7ac01faab4..04b035a1b1 100644
--- a/synapse/rest/well_known.py
+++ b/synapse/rest/well_known.py
@@ -21,6 +21,7 @@ from twisted.web.server import Request
 from synapse.http.server import set_cors_headers
 from synapse.types import JsonDict
 from synapse.util import json_encoder
+from synapse.util.stringutils import parse_server_name
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -33,8 +34,7 @@ class WellKnownBuilder:
         self._config = hs.config
 
     def get_well_known(self) -> Optional[JsonDict]:
-        # if we don't have a public_baseurl, we can't help much here.
-        if self._config.server.public_baseurl is None:
+        if not self._config.server.serve_client_wellknown:
             return None
 
         result = {"m.homeserver": {"base_url": self._config.server.public_baseurl}}
@@ -47,8 +47,8 @@ class WellKnownBuilder:
         return result
 
 
-class WellKnownResource(Resource):
-    """A Twisted web resource which renders the .well-known file"""
+class ClientWellKnownResource(Resource):
+    """A Twisted web resource which renders the .well-known/matrix/client file"""
 
     isLeaf = 1
 
@@ -67,3 +67,45 @@ class WellKnownResource(Resource):
         logger.debug("returning: %s", r)
         request.setHeader(b"Content-Type", b"application/json")
         return json_encoder.encode(r).encode("utf-8")
+
+
+class ServerWellKnownResource(Resource):
+    """Resource for .well-known/matrix/server, redirecting to port 443"""
+
+    isLeaf = 1
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self._serve_server_wellknown = hs.config.server.serve_server_wellknown
+
+        host, port = parse_server_name(hs.config.server.server_name)
+
+        # If we've got this far, then https://<server_name>/ must route to us, so
+        # we just redirect the traffic to port 443 instead of 8448.
+        if port is None:
+            port = 443
+
+        self._response = json_encoder.encode({"m.server": f"{host}:{port}"}).encode(
+            "utf-8"
+        )
+
+    def render_GET(self, request: Request) -> bytes:
+        if not self._serve_server_wellknown:
+            request.setResponseCode(404)
+            request.setHeader(b"Content-Type", b"text/plain")
+            return b"404. Is anything ever truly *well* known?\n"
+
+        request.setHeader(b"Content-Type", b"application/json")
+        return self._response
+
+
+def well_known_resource(hs: "HomeServer") -> Resource:
+    """Returns a Twisted web resource which handles '.well-known' requests"""
+    res = Resource()
+    matrix_resource = Resource()
+    res.putChild(b"matrix", matrix_resource)
+
+    matrix_resource.putChild(b"server", ServerWellKnownResource(hs))
+    matrix_resource.putChild(b"client", ClientWellKnownResource(hs))
+
+    return res
diff --git a/synapse/server.py b/synapse/server.py
index 0fbf36ba99..013a7bacaa 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -463,7 +463,7 @@ class HomeServer(metaclass=abc.ABCMeta):
 
     @cache_in_self
     def get_typing_writer_handler(self) -> TypingWriterHandler:
-        if self.config.worker.writers.typing == self.get_instance_name():
+        if self.get_instance_name() in self.config.worker.writers.typing:
             return TypingWriterHandler(self)
         else:
             raise Exception("Workers cannot write typing")
@@ -474,7 +474,7 @@ class HomeServer(metaclass=abc.ABCMeta):
 
     @cache_in_self
     def get_typing_handler(self) -> FollowerTypingHandler:
-        if self.config.worker.writers.typing == self.get_instance_name():
+        if self.get_instance_name() in self.config.worker.writers.typing:
             # Use get_typing_writer_handler to ensure that we use the same
             # cached version.
             return self.get_typing_writer_handler()
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 5cf2e12575..1605411b00 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -26,6 +26,7 @@ from typing import (
     FrozenSet,
     Iterable,
     List,
+    Mapping,
     Optional,
     Sequence,
     Set,
@@ -246,7 +247,7 @@ class StateHandler:
         return await self.get_hosts_in_room_at_events(room_id, event_ids)
 
     async def get_hosts_in_room_at_events(
-        self, room_id: str, event_ids: List[str]
+        self, room_id: str, event_ids: Iterable[str]
     ) -> Set[str]:
         """Get the hosts that were in a room at the given event ids
 
@@ -519,7 +520,7 @@ class StateResolutionHandler:
         self,
         room_id: str,
         room_version: str,
-        state_groups_ids: Dict[int, StateMap[str]],
+        state_groups_ids: Mapping[int, StateMap[str]],
         event_map: Optional[Dict[str, EventBase]],
         state_res_store: "StateResolutionStore",
     ) -> _StateCacheEntry:
@@ -703,7 +704,7 @@ class StateResolutionHandler:
 
 
 def _make_state_cache_entry(
-    new_state: StateMap[str], state_groups_ids: Dict[int, StateMap[str]]
+    new_state: StateMap[str], state_groups_ids: Mapping[int, StateMap[str]]
 ) -> _StateCacheEntry:
     """Given a resolved state, and a set of input state groups, pick one to base
     a new state group on (if any), and return an appropriately-constructed
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 82b31d24f1..b9a8ca997e 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -100,29 +100,58 @@ class BackgroundUpdater:
         ] = {}
         self._all_done = False
 
+        # Whether we're currently running updates
+        self._running = False
+
+        # Whether background updates are enabled. This allows us to
+        # enable/disable background updates via the admin API.
+        self.enabled = True
+
+    def get_current_update(self) -> Optional[BackgroundUpdatePerformance]:
+        """Returns the current background update, if any."""
+
+        update_name = self._current_background_update
+        if not update_name:
+            return None
+
+        perf = self._background_update_performance.get(update_name)
+        if not perf:
+            perf = BackgroundUpdatePerformance(update_name)
+
+        return perf
+
     def start_doing_background_updates(self) -> None:
-        run_as_background_process("background_updates", self.run_background_updates)
+        if self.enabled:
+            run_as_background_process("background_updates", self.run_background_updates)
 
     async def run_background_updates(self, sleep: bool = True) -> None:
-        logger.info("Starting background schema updates")
-        while True:
-            if sleep:
-                await self._clock.sleep(self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0)
+        if self._running or not self.enabled:
+            return
 
-            try:
-                result = await self.do_next_background_update(
-                    self.BACKGROUND_UPDATE_DURATION_MS
-                )
-            except Exception:
-                logger.exception("Error doing update")
-            else:
-                if result:
-                    logger.info(
-                        "No more background updates to do."
-                        " Unscheduling background update task."
+        self._running = True
+
+        try:
+            logger.info("Starting background schema updates")
+            while self.enabled:
+                if sleep:
+                    await self._clock.sleep(self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0)
+
+                try:
+                    result = await self.do_next_background_update(
+                        self.BACKGROUND_UPDATE_DURATION_MS
                     )
-                    self._all_done = True
-                    return None
+                except Exception:
+                    logger.exception("Error doing update")
+                else:
+                    if result:
+                        logger.info(
+                            "No more background updates to do."
+                            " Unscheduling background update task."
+                        )
+                        self._all_done = True
+                        return None
+        finally:
+            self._running = False
 
     async def has_completed_background_updates(self) -> bool:
         """Check if all the background updates have completed
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index fa4e89d35c..d4cab69ebf 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -48,6 +48,7 @@ from synapse.logging.context import (
     current_context,
     make_deferred_yieldable,
 )
+from synapse.metrics import register_threadpool
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.background_updates import BackgroundUpdater
 from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
@@ -104,13 +105,17 @@ def make_pool(
                 LoggingDatabaseConnection(conn, engine, "on_new_connection")
             )
 
-    return adbapi.ConnectionPool(
+    connection_pool = adbapi.ConnectionPool(
         db_config.config["name"],
         cp_reactor=reactor,
         cp_openfun=_on_new_connection,
         **db_args,
     )
 
+    register_threadpool(f"database-{db_config.name}", connection_pool.threadpool)
+
+    return connection_pool
+
 
 def make_conn(
     db_config: DatabaseConnectionConfig,
@@ -441,6 +446,10 @@ class DatabasePool:
                 self._check_safe_to_upsert,
             )
 
+    def name(self) -> str:
+        "Return the name of this database"
+        return self._database_config.name
+
     def is_running(self) -> bool:
         """Is the database pool currently running"""
         return self._db_pool.running
diff --git a/synapse/storage/databases/main/deviceinbox.py b/synapse/storage/databases/main/deviceinbox.py
index 8143168107..264e625bd7 100644
--- a/synapse/storage/databases/main/deviceinbox.py
+++ b/synapse/storage/databases/main/deviceinbox.py
@@ -19,9 +19,10 @@ from synapse.logging import issue9533_logger
 from synapse.logging.opentracing import log_kv, set_tag, trace
 from synapse.replication.tcp.streams import ToDeviceStream
 from synapse.storage._base import SQLBaseStore, db_to_json
-from synapse.storage.database import DatabasePool
+from synapse.storage.database import DatabasePool, LoggingTransaction
 from synapse.storage.engines import PostgresEngine
 from synapse.storage.util.id_generators import MultiWriterIdGenerator, StreamIdGenerator
+from synapse.types import JsonDict
 from synapse.util import json_encoder
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.caches.stream_change_cache import StreamChangeCache
@@ -488,10 +489,12 @@ class DeviceInboxWorkerStore(SQLBaseStore):
             devices = list(messages_by_device.keys())
             if len(devices) == 1 and devices[0] == "*":
                 # Handle wildcard device_ids.
+                # We exclude hidden devices (such as cross-signing keys) here as they are
+                # not expected to receive to-device messages.
                 devices = self.db_pool.simple_select_onecol_txn(
                     txn,
                     table="devices",
-                    keyvalues={"user_id": user_id},
+                    keyvalues={"user_id": user_id, "hidden": False},
                     retcol="device_id",
                 )
 
@@ -504,10 +507,12 @@ class DeviceInboxWorkerStore(SQLBaseStore):
                 if not devices:
                     continue
 
+                # We exclude hidden devices (such as cross-signing keys) here as they are
+                # not expected to receive to-device messages.
                 rows = self.db_pool.simple_select_many_txn(
                     txn,
                     table="devices",
-                    keyvalues={"user_id": user_id},
+                    keyvalues={"user_id": user_id, "hidden": False},
                     column="device_id",
                     iterable=devices,
                     retcols=("device_id",),
@@ -555,6 +560,8 @@ class DeviceInboxWorkerStore(SQLBaseStore):
 
 class DeviceInboxBackgroundUpdateStore(SQLBaseStore):
     DEVICE_INBOX_STREAM_ID = "device_inbox_stream_drop"
+    REMOVE_DELETED_DEVICES = "remove_deleted_devices_from_device_inbox"
+    REMOVE_HIDDEN_DEVICES = "remove_hidden_devices_from_device_inbox"
 
     def __init__(self, database: DatabasePool, db_conn, hs: "HomeServer"):
         super().__init__(database, db_conn, hs)
@@ -570,6 +577,16 @@ class DeviceInboxBackgroundUpdateStore(SQLBaseStore):
             self.DEVICE_INBOX_STREAM_ID, self._background_drop_index_device_inbox
         )
 
+        self.db_pool.updates.register_background_update_handler(
+            self.REMOVE_DELETED_DEVICES,
+            self._remove_deleted_devices_from_device_inbox,
+        )
+
+        self.db_pool.updates.register_background_update_handler(
+            self.REMOVE_HIDDEN_DEVICES,
+            self._remove_hidden_devices_from_device_inbox,
+        )
+
     async def _background_drop_index_device_inbox(self, progress, batch_size):
         def reindex_txn(conn):
             txn = conn.cursor()
@@ -582,6 +599,172 @@ class DeviceInboxBackgroundUpdateStore(SQLBaseStore):
 
         return 1
 
+    async def _remove_deleted_devices_from_device_inbox(
+        self, progress: JsonDict, batch_size: int
+    ) -> int:
+        """A background update that deletes all device_inboxes for deleted devices.
+
+        This should only need to be run once (when users upgrade to v1.47.0)
+
+        Args:
+            progress: JsonDict used to store progress of this background update
+            batch_size: the maximum number of rows to retrieve in a single select query
+
+        Returns:
+            The number of deleted rows
+        """
+
+        def _remove_deleted_devices_from_device_inbox_txn(
+            txn: LoggingTransaction,
+        ) -> int:
+            """stream_id is not unique
+            we need to use an inclusive `stream_id >= ?` clause,
+            since we might not have deleted all dead device messages for the stream_id
+            returned from the previous query
+
+            Then delete only rows matching the `(user_id, device_id, stream_id)` tuple,
+            to avoid problems of deleting a large number of rows all at once
+            due to a single device having lots of device messages.
+            """
+
+            last_stream_id = progress.get("stream_id", 0)
+
+            sql = """
+                SELECT device_id, user_id, stream_id
+                FROM device_inbox
+                WHERE
+                    stream_id >= ?
+                    AND (device_id, user_id) NOT IN (
+                        SELECT device_id, user_id FROM devices
+                    )
+                ORDER BY stream_id
+                LIMIT ?
+            """
+
+            txn.execute(sql, (last_stream_id, batch_size))
+            rows = txn.fetchall()
+
+            num_deleted = 0
+            for row in rows:
+                num_deleted += self.db_pool.simple_delete_txn(
+                    txn,
+                    "device_inbox",
+                    {"device_id": row[0], "user_id": row[1], "stream_id": row[2]},
+                )
+
+            if rows:
+                # send more than stream_id to progress
+                # otherwise it can happen in large deployments that
+                # no change of status is visible in the log file
+                # it may be that the stream_id does not change in several runs
+                self.db_pool.updates._background_update_progress_txn(
+                    txn,
+                    self.REMOVE_DELETED_DEVICES,
+                    {
+                        "device_id": rows[-1][0],
+                        "user_id": rows[-1][1],
+                        "stream_id": rows[-1][2],
+                    },
+                )
+
+            return num_deleted
+
+        number_deleted = await self.db_pool.runInteraction(
+            "_remove_deleted_devices_from_device_inbox",
+            _remove_deleted_devices_from_device_inbox_txn,
+        )
+
+        # The task is finished when no more lines are deleted.
+        if not number_deleted:
+            await self.db_pool.updates._end_background_update(
+                self.REMOVE_DELETED_DEVICES
+            )
+
+        return number_deleted
+
+    async def _remove_hidden_devices_from_device_inbox(
+        self, progress: JsonDict, batch_size: int
+    ) -> int:
+        """A background update that deletes all device_inboxes for hidden devices.
+
+        This should only need to be run once (when users upgrade to v1.47.0)
+
+        Args:
+            progress: JsonDict used to store progress of this background update
+            batch_size: the maximum number of rows to retrieve in a single select query
+
+        Returns:
+            The number of deleted rows
+        """
+
+        def _remove_hidden_devices_from_device_inbox_txn(
+            txn: LoggingTransaction,
+        ) -> int:
+            """stream_id is not unique
+            we need to use an inclusive `stream_id >= ?` clause,
+            since we might not have deleted all hidden device messages for the stream_id
+            returned from the previous query
+
+            Then delete only rows matching the `(user_id, device_id, stream_id)` tuple,
+            to avoid problems of deleting a large number of rows all at once
+            due to a single device having lots of device messages.
+            """
+
+            last_stream_id = progress.get("stream_id", 0)
+
+            sql = """
+                SELECT device_id, user_id, stream_id
+                FROM device_inbox
+                WHERE
+                    stream_id >= ?
+                    AND (device_id, user_id) IN (
+                        SELECT device_id, user_id FROM devices WHERE hidden = ?
+                    )
+                ORDER BY stream_id
+                LIMIT ?
+            """
+
+            txn.execute(sql, (last_stream_id, True, batch_size))
+            rows = txn.fetchall()
+
+            num_deleted = 0
+            for row in rows:
+                num_deleted += self.db_pool.simple_delete_txn(
+                    txn,
+                    "device_inbox",
+                    {"device_id": row[0], "user_id": row[1], "stream_id": row[2]},
+                )
+
+            if rows:
+                # We don't just save the `stream_id` in progress as
+                # otherwise it can happen in large deployments that
+                # no change of status is visible in the log file, as
+                # it may be that the stream_id does not change in several runs
+                self.db_pool.updates._background_update_progress_txn(
+                    txn,
+                    self.REMOVE_HIDDEN_DEVICES,
+                    {
+                        "device_id": rows[-1][0],
+                        "user_id": rows[-1][1],
+                        "stream_id": rows[-1][2],
+                    },
+                )
+
+            return num_deleted
+
+        number_deleted = await self.db_pool.runInteraction(
+            "_remove_hidden_devices_from_device_inbox",
+            _remove_hidden_devices_from_device_inbox_txn,
+        )
+
+        # The task is finished when no more lines are deleted.
+        if not number_deleted:
+            await self.db_pool.updates._end_background_update(
+                self.REMOVE_HIDDEN_DEVICES
+            )
+
+        return number_deleted
+
 
 class DeviceInboxStore(DeviceInboxWorkerStore, DeviceInboxBackgroundUpdateStore):
     pass
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index a01bf2c5b7..9ccc66e589 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -427,7 +427,7 @@ class DeviceWorkerStore(SQLBaseStore):
             user_ids: the users who were signed
 
         Returns:
-            THe new stream ID.
+            The new stream ID.
         """
 
         async with self._device_list_id_gen.get_next() as stream_id:
@@ -1134,19 +1134,14 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             raise StoreError(500, "Problem storing device.")
 
     async def delete_device(self, user_id: str, device_id: str) -> None:
-        """Delete a device.
+        """Delete a device and its device_inbox.
 
         Args:
             user_id: The ID of the user which owns the device
             device_id: The ID of the device to delete
         """
-        await self.db_pool.simple_delete_one(
-            table="devices",
-            keyvalues={"user_id": user_id, "device_id": device_id, "hidden": False},
-            desc="delete_device",
-        )
 
-        self.device_id_exists_cache.invalidate((user_id, device_id))
+        await self.delete_devices(user_id, [device_id])
 
     async def delete_devices(self, user_id: str, device_ids: List[str]) -> None:
         """Deletes several devices.
@@ -1155,13 +1150,25 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             user_id: The ID of the user which owns the devices
             device_ids: The IDs of the devices to delete
         """
-        await self.db_pool.simple_delete_many(
-            table="devices",
-            column="device_id",
-            iterable=device_ids,
-            keyvalues={"user_id": user_id, "hidden": False},
-            desc="delete_devices",
-        )
+
+        def _delete_devices_txn(txn: LoggingTransaction) -> None:
+            self.db_pool.simple_delete_many_txn(
+                txn,
+                table="devices",
+                column="device_id",
+                values=device_ids,
+                keyvalues={"user_id": user_id, "hidden": False},
+            )
+
+            self.db_pool.simple_delete_many_txn(
+                txn,
+                table="device_inbox",
+                column="device_id",
+                values=device_ids,
+                keyvalues={"user_id": user_id},
+            )
+
+        await self.db_pool.runInteraction("delete_devices", _delete_devices_txn)
         for device_id in device_ids:
             self.device_id_exists_cache.invalidate((user_id, device_id))
 
@@ -1315,7 +1322,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
 
     async def add_device_change_to_streams(
         self, user_id: str, device_ids: Collection[str], hosts: List[str]
-    ):
+    ) -> int:
         """Persist that a user's devices have been updated, and which hosts
         (if any) should be poked.
         """
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 8d9086ecf0..596275c23c 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -24,6 +24,7 @@ from typing import (
     Iterable,
     List,
     Optional,
+    Sequence,
     Set,
     Tuple,
 )
@@ -494,7 +495,7 @@ class PersistEventsStore:
         event_chain_id_gen: SequenceGenerator,
         event_to_room_id: Dict[str, str],
         event_to_types: Dict[str, Tuple[str, str]],
-        event_to_auth_chain: Dict[str, List[str]],
+        event_to_auth_chain: Dict[str, Sequence[str]],
     ) -> None:
         """Calculate the chain cover index for the given events.
 
@@ -786,7 +787,7 @@ class PersistEventsStore:
         event_chain_id_gen: SequenceGenerator,
         event_to_room_id: Dict[str, str],
         event_to_types: Dict[str, Tuple[str, str]],
-        event_to_auth_chain: Dict[str, List[str]],
+        event_to_auth_chain: Dict[str, Sequence[str]],
         events_to_calc_chain_id_for: Set[str],
         chain_map: Dict[str, Tuple[int, int]],
     ) -> Dict[str, Tuple[int, int]]:
@@ -1794,7 +1795,7 @@ class PersistEventsStore:
         )
 
         # Insert an edge for every prev_event connection
-        for prev_event_id in event.prev_events:
+        for prev_event_id in event.prev_event_ids():
             self.db_pool.simple_insert_txn(
                 txn,
                 table="insertion_event_edges",
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index ae37901be9..c6bf316d5b 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -28,6 +28,7 @@ from typing import (
 
 import attr
 from constantly import NamedConstant, Names
+from prometheus_client import Gauge
 from typing_extensions import Literal
 
 from twisted.internet import defer
@@ -81,6 +82,12 @@ EVENT_QUEUE_ITERATIONS = 3  # No. times we block waiting for requests for events
 EVENT_QUEUE_TIMEOUT_S = 0.1  # Timeout when waiting for requests for events
 
 
+event_fetch_ongoing_gauge = Gauge(
+    "synapse_event_fetch_ongoing",
+    "The number of event fetchers that are running",
+)
+
+
 @attr.s(slots=True, auto_attribs=True)
 class _EventCacheEntry:
     event: EventBase
@@ -222,6 +229,7 @@ class EventsWorkerStore(SQLBaseStore):
         self._event_fetch_lock = threading.Condition()
         self._event_fetch_list = []
         self._event_fetch_ongoing = 0
+        event_fetch_ongoing_gauge.set(self._event_fetch_ongoing)
 
         # We define this sequence here so that it can be referenced from both
         # the DataStore and PersistEventStore.
@@ -732,28 +740,31 @@ class EventsWorkerStore(SQLBaseStore):
         """Takes a database connection and waits for requests for events from
         the _event_fetch_list queue.
         """
-        i = 0
-        while True:
-            with self._event_fetch_lock:
-                event_list = self._event_fetch_list
-                self._event_fetch_list = []
-
-                if not event_list:
-                    single_threaded = self.database_engine.single_threaded
-                    if (
-                        not self.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING
-                        or single_threaded
-                        or i > EVENT_QUEUE_ITERATIONS
-                    ):
-                        self._event_fetch_ongoing -= 1
-                        return
-                    else:
-                        self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S)
-                        i += 1
-                        continue
-                i = 0
-
-            self._fetch_event_list(conn, event_list)
+        try:
+            i = 0
+            while True:
+                with self._event_fetch_lock:
+                    event_list = self._event_fetch_list
+                    self._event_fetch_list = []
+
+                    if not event_list:
+                        single_threaded = self.database_engine.single_threaded
+                        if (
+                            not self.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING
+                            or single_threaded
+                            or i > EVENT_QUEUE_ITERATIONS
+                        ):
+                            break
+                        else:
+                            self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S)
+                            i += 1
+                            continue
+                    i = 0
+
+                self._fetch_event_list(conn, event_list)
+        finally:
+            self._event_fetch_ongoing -= 1
+            event_fetch_ongoing_gauge.set(self._event_fetch_ongoing)
 
     def _fetch_event_list(
         self, conn: Connection, event_list: List[Tuple[List[str], defer.Deferred]]
@@ -977,6 +988,7 @@ class EventsWorkerStore(SQLBaseStore):
 
             if self._event_fetch_ongoing < EVENT_QUEUE_THREADS:
                 self._event_fetch_ongoing += 1
+                event_fetch_ongoing_gauge.set(self._event_fetch_ongoing)
                 should_start = True
             else:
                 should_start = False
diff --git a/synapse/storage/databases/main/group_server.py b/synapse/storage/databases/main/group_server.py
index e70d3649ff..bb621df0dd 100644
--- a/synapse/storage/databases/main/group_server.py
+++ b/synapse/storage/databases/main/group_server.py
@@ -13,15 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
 
 from typing_extensions import TypedDict
 
 from synapse.api.errors import SynapseError
 from synapse.storage._base import SQLBaseStore, db_to_json
+from synapse.storage.database import DatabasePool
+from synapse.storage.types import Connection
 from synapse.types import JsonDict
 from synapse.util import json_encoder
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 # The category ID for the "default" category. We don't store as null in the
 # database to avoid the fun of null != null
 _DEFAULT_CATEGORY_ID = ""
@@ -35,6 +40,16 @@ class _RoomInGroup(TypedDict):
 
 
 class GroupServerWorkerStore(SQLBaseStore):
+    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
+        database.updates.register_background_index_update(
+            update_name="local_group_updates_index",
+            index_name="local_group_updates_stream_id_index",
+            table="local_group_updates",
+            columns=("stream_id",),
+            unique=True,
+        )
+        super().__init__(database, db_conn, hs)
+
     async def get_group(self, group_id: str) -> Optional[Dict[str, Any]]:
         return await self.db_pool.simple_select_one(
             table="groups",
diff --git a/synapse/storage/databases/main/lock.py b/synapse/storage/databases/main/lock.py
index 3d1dff660b..3d0df0cbd4 100644
--- a/synapse/storage/databases/main/lock.py
+++ b/synapse/storage/databases/main/lock.py
@@ -14,6 +14,7 @@
 import logging
 from types import TracebackType
 from typing import TYPE_CHECKING, Dict, Optional, Tuple, Type
+from weakref import WeakValueDictionary
 
 from twisted.internet.interfaces import IReactorCore
 
@@ -61,7 +62,7 @@ class LockStore(SQLBaseStore):
 
         # A map from `(lock_name, lock_key)` to the token of any locks that we
         # think we currently hold.
-        self._live_tokens: Dict[Tuple[str, str], str] = {}
+        self._live_tokens: Dict[Tuple[str, str], Lock] = WeakValueDictionary()
 
         # When we shut down we want to remove the locks. Technically this can
         # lead to a race, as we may drop the lock while we are still processing.
@@ -80,10 +81,10 @@ class LockStore(SQLBaseStore):
 
         # We need to take a copy of the tokens dict as dropping the locks will
         # cause the dictionary to change.
-        tokens = dict(self._live_tokens)
+        locks = dict(self._live_tokens)
 
-        for (lock_name, lock_key), token in tokens.items():
-            await self._drop_lock(lock_name, lock_key, token)
+        for lock in locks.values():
+            await lock.release()
 
         logger.info("Dropped locks due to shutdown")
 
@@ -93,6 +94,11 @@ class LockStore(SQLBaseStore):
         used (otherwise the lock will leak).
         """
 
+        # Check if this process has taken out a lock and if it's still valid.
+        lock = self._live_tokens.get((lock_name, lock_key))
+        if lock and await lock.is_still_valid():
+            return None
+
         now = self._clock.time_msec()
         token = random_string(6)
 
@@ -100,7 +106,9 @@ class LockStore(SQLBaseStore):
 
             def _try_acquire_lock_txn(txn: LoggingTransaction) -> bool:
                 # We take out the lock if either a) there is no row for the lock
-                # already or b) the existing row has timed out.
+                # already, b) the existing row has timed out, or c) the row is
+                # for this instance (which means the process got killed and
+                # restarted)
                 sql = """
                     INSERT INTO worker_locks (lock_name, lock_key, instance_name, token, last_renewed_ts)
                     VALUES (?, ?, ?, ?, ?)
@@ -112,6 +120,7 @@ class LockStore(SQLBaseStore):
                             last_renewed_ts = EXCLUDED.last_renewed_ts
                         WHERE
                             worker_locks.last_renewed_ts < ?
+                            OR worker_locks.instance_name = EXCLUDED.instance_name
                 """
                 txn.execute(
                     sql,
@@ -148,11 +157,11 @@ class LockStore(SQLBaseStore):
                     WHERE
                         lock_name = ?
                         AND lock_key = ?
-                        AND last_renewed_ts < ?
+                        AND (last_renewed_ts < ? OR instance_name = ?)
                 """
                 txn.execute(
                     sql,
-                    (lock_name, lock_key, now - _LOCK_TIMEOUT_MS),
+                    (lock_name, lock_key, now - _LOCK_TIMEOUT_MS, self._instance_name),
                 )
 
                 inserted = self.db_pool.simple_upsert_txn_emulated(
@@ -179,9 +188,7 @@ class LockStore(SQLBaseStore):
             if not did_lock:
                 return None
 
-        self._live_tokens[(lock_name, lock_key)] = token
-
-        return Lock(
+        lock = Lock(
             self._reactor,
             self._clock,
             self,
@@ -190,6 +197,10 @@ class LockStore(SQLBaseStore):
             token=token,
         )
 
+        self._live_tokens[(lock_name, lock_key)] = lock
+
+        return lock
+
     async def _is_lock_still_valid(
         self, lock_name: str, lock_key: str, token: str
     ) -> bool:
diff --git a/synapse/storage/databases/main/presence.py b/synapse/storage/databases/main/presence.py
index 12cf6995eb..cc0eebdb46 100644
--- a/synapse/storage/databases/main/presence.py
+++ b/synapse/storage/databases/main/presence.py
@@ -92,7 +92,7 @@ class PresenceStore(PresenceBackgroundUpdateStore):
             prefilled_cache=presence_cache_prefill,
         )
 
-    async def update_presence(self, presence_states):
+    async def update_presence(self, presence_states) -> Tuple[int, int]:
         assert self._can_persist_presence
 
         stream_ordering_manager = self._presence_id_gen.get_next_mult(
diff --git a/synapse/storage/databases/main/profile.py b/synapse/storage/databases/main/profile.py
index ba7075caa5..dd8e27e226 100644
--- a/synapse/storage/databases/main/profile.py
+++ b/synapse/storage/databases/main/profile.py
@@ -91,7 +91,7 @@ class ProfileWorkerStore(SQLBaseStore):
         )
 
     async def update_remote_profile_cache(
-        self, user_id: str, displayname: str, avatar_url: str
+        self, user_id: str, displayname: Optional[str], avatar_url: Optional[str]
     ) -> int:
         return await self.db_pool.simple_update(
             table="remote_profile_cache",
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 40760fbd1b..53576ad52f 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -13,13 +13,14 @@
 # limitations under the License.
 
 import logging
-from typing import Optional, Tuple
+from typing import List, Optional, Tuple, Union
 
 import attr
 
 from synapse.api.constants import RelationTypes
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
+from synapse.storage.database import LoggingTransaction
 from synapse.storage.databases.main.stream import generate_pagination_where_clause
 from synapse.storage.relations import (
     AggregationPaginationToken,
@@ -63,7 +64,7 @@ class RelationsWorkerStore(SQLBaseStore):
         """
 
         where_clause = ["relates_to_id = ?"]
-        where_args = [event_id]
+        where_args: List[Union[str, int]] = [event_id]
 
         if relation_type is not None:
             where_clause.append("relation_type = ?")
@@ -80,8 +81,8 @@ class RelationsWorkerStore(SQLBaseStore):
         pagination_clause = generate_pagination_where_clause(
             direction=direction,
             column_names=("topological_ordering", "stream_ordering"),
-            from_token=attr.astuple(from_token) if from_token else None,
-            to_token=attr.astuple(to_token) if to_token else None,
+            from_token=attr.astuple(from_token) if from_token else None,  # type: ignore[arg-type]
+            to_token=attr.astuple(to_token) if to_token else None,  # type: ignore[arg-type]
             engine=self.database_engine,
         )
 
@@ -106,7 +107,9 @@ class RelationsWorkerStore(SQLBaseStore):
             order,
         )
 
-        def _get_recent_references_for_event_txn(txn):
+        def _get_recent_references_for_event_txn(
+            txn: LoggingTransaction,
+        ) -> PaginationChunk:
             txn.execute(sql, where_args + [limit + 1])
 
             last_topo_id = None
@@ -160,7 +163,7 @@ class RelationsWorkerStore(SQLBaseStore):
         """
 
         where_clause = ["relates_to_id = ?", "relation_type = ?"]
-        where_args = [event_id, RelationTypes.ANNOTATION]
+        where_args: List[Union[str, int]] = [event_id, RelationTypes.ANNOTATION]
 
         if event_type:
             where_clause.append("type = ?")
@@ -169,8 +172,8 @@ class RelationsWorkerStore(SQLBaseStore):
         having_clause = generate_pagination_where_clause(
             direction=direction,
             column_names=("COUNT(*)", "MAX(stream_ordering)"),
-            from_token=attr.astuple(from_token) if from_token else None,
-            to_token=attr.astuple(to_token) if to_token else None,
+            from_token=attr.astuple(from_token) if from_token else None,  # type: ignore[arg-type]
+            to_token=attr.astuple(to_token) if to_token else None,  # type: ignore[arg-type]
             engine=self.database_engine,
         )
 
@@ -199,7 +202,9 @@ class RelationsWorkerStore(SQLBaseStore):
             having_clause=having_clause,
         )
 
-        def _get_aggregation_groups_for_event_txn(txn):
+        def _get_aggregation_groups_for_event_txn(
+            txn: LoggingTransaction,
+        ) -> PaginationChunk:
             txn.execute(sql, where_args + [limit + 1])
 
             next_batch = None
@@ -254,11 +259,12 @@ class RelationsWorkerStore(SQLBaseStore):
             LIMIT 1
         """
 
-        def _get_applicable_edit_txn(txn):
+        def _get_applicable_edit_txn(txn: LoggingTransaction) -> Optional[str]:
             txn.execute(sql, (event_id, RelationTypes.REPLACE))
             row = txn.fetchone()
             if row:
                 return row[0]
+            return None
 
         edit_id = await self.db_pool.runInteraction(
             "get_applicable_edit", _get_applicable_edit_txn
@@ -267,7 +273,7 @@ class RelationsWorkerStore(SQLBaseStore):
         if not edit_id:
             return None
 
-        return await self.get_event(edit_id, allow_none=True)
+        return await self.get_event(edit_id, allow_none=True)  # type: ignore[attr-defined]
 
     @cached()
     async def get_thread_summary(
@@ -283,7 +289,9 @@ class RelationsWorkerStore(SQLBaseStore):
             The number of items in the thread and the most recent response, if any.
         """
 
-        def _get_thread_summary_txn(txn) -> Tuple[int, Optional[str]]:
+        def _get_thread_summary_txn(
+            txn: LoggingTransaction,
+        ) -> Tuple[int, Optional[str]]:
             # Fetch the count of threaded events and the latest event ID.
             # TODO Should this only allow m.room.message events.
             sql = """
@@ -312,7 +320,7 @@ class RelationsWorkerStore(SQLBaseStore):
                     AND relation_type = ?
             """
             txn.execute(sql, (event_id, RelationTypes.THREAD))
-            count = txn.fetchone()[0]
+            count = txn.fetchone()[0]  # type: ignore[index]
 
             return count, latest_event_id
 
@@ -322,7 +330,7 @@ class RelationsWorkerStore(SQLBaseStore):
 
         latest_event = None
         if latest_event_id:
-            latest_event = await self.get_event(latest_event_id, allow_none=True)
+            latest_event = await self.get_event(latest_event_id, allow_none=True)  # type: ignore[attr-defined]
 
         return count, latest_event
 
@@ -354,7 +362,7 @@ class RelationsWorkerStore(SQLBaseStore):
             LIMIT 1;
         """
 
-        def _get_if_user_has_annotated_event(txn):
+        def _get_if_user_has_annotated_event(txn: LoggingTransaction) -> bool:
             txn.execute(
                 sql,
                 (
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index f879bbe7c7..cefc77fa0f 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -412,22 +412,33 @@ class RoomWorkerStore(SQLBaseStore):
             limit: maximum amount of rooms to retrieve
             order_by: the sort order of the returned list
             reverse_order: whether to reverse the room list
-            search_term: a string to filter room names by
+            search_term: a string to filter room names,
+                canonical alias and room ids by.
+                Room ID must match exactly. Canonical alias must match a substring of the local part.
         Returns:
             A list of room dicts and an integer representing the total number of
             rooms that exist given this query
         """
         # Filter room names by a string
         where_statement = ""
+        search_pattern = []
         if search_term:
-            where_statement = "WHERE LOWER(state.name) LIKE ?"
+            where_statement = """
+                WHERE LOWER(state.name) LIKE ?
+                OR LOWER(state.canonical_alias) LIKE ?
+                OR state.room_id = ?
+            """
 
             # Our postgres db driver converts ? -> %s in SQL strings as that's the
             # placeholder for postgres.
             # HOWEVER, if you put a % into your SQL then everything goes wibbly.
             # To get around this, we're going to surround search_term with %'s
             # before giving it to the database in python instead
-            search_term = "%" + search_term.lower() + "%"
+            search_pattern = [
+                "%" + search_term.lower() + "%",
+                "#%" + search_term.lower() + "%:%",
+                search_term,
+            ]
 
         # Set ordering
         if RoomSortOrder(order_by) == RoomSortOrder.SIZE:
@@ -519,12 +530,9 @@ class RoomWorkerStore(SQLBaseStore):
         )
 
         def _get_rooms_paginate_txn(txn):
-            # Execute the data query
-            sql_values = (limit, start)
-            if search_term:
-                # Add the search term into the WHERE clause
-                sql_values = (search_term,) + sql_values
-            txn.execute(info_sql, sql_values)
+            # Add the search term into the WHERE clause
+            # and execute the data query
+            txn.execute(info_sql, search_pattern + [limit, start])
 
             # Refactor room query data into a structured dictionary
             rooms = []
@@ -551,8 +559,7 @@ class RoomWorkerStore(SQLBaseStore):
             # Execute the count query
 
             # Add the search term into the WHERE clause if present
-            sql_values = (search_term,) if search_term else ()
-            txn.execute(count_sql, sql_values)
+            txn.execute(count_sql, search_pattern)
 
             room_count = txn.fetchone()
             return rooms, room_count[0]
diff --git a/synapse/storage/databases/main/room_batch.py b/synapse/storage/databases/main/room_batch.py
index dcbce8fdcf..97b2618437 100644
--- a/synapse/storage/databases/main/room_batch.py
+++ b/synapse/storage/databases/main/room_batch.py
@@ -18,7 +18,7 @@ from synapse.storage._base import SQLBaseStore
 
 
 class RoomBatchStore(SQLBaseStore):
-    async def get_insertion_event_by_batch_id(
+    async def get_insertion_event_id_by_batch_id(
         self, room_id: str, batch_id: str
     ) -> Optional[str]:
         """Retrieve a insertion event ID.
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 4b288bb2e7..033a9831d6 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -570,7 +570,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
     async def get_joined_users_from_context(
         self, event: EventBase, context: EventContext
-    ):
+    ) -> Dict[str, ProfileInfo]:
         state_group = context.state_group
         if not state_group:
             # If state_group is None it means it has yet to be assigned a
@@ -584,7 +584,9 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             event.room_id, state_group, current_state_ids, event=event, context=context
         )
 
-    async def get_joined_users_from_state(self, room_id, state_entry):
+    async def get_joined_users_from_state(
+        self, room_id, state_entry
+    ) -> Dict[str, ProfileInfo]:
         state_group = state_entry.state_group
         if not state_group:
             # If state_group is None it means it has yet to be assigned a
@@ -607,7 +609,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         cache_context,
         event=None,
         context=None,
-    ):
+    ) -> Dict[str, ProfileInfo]:
         # We don't use `state_group`, it's there so that we can cache based
         # on it. However, it's important that it's never None, since two current_states
         # with a state_group of None are likely to be different.
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index 1629d2a53c..e45adfcb55 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -131,17 +131,9 @@ def prepare_database(
                     "config==None in prepare_database, but database is not empty"
                 )
 
-            # if it's a worker app, refuse to upgrade the database, to avoid multiple
-            # workers doing it at once.
-            if (
-                config.worker.worker_app is not None
-                and version_info.current_version != SCHEMA_VERSION
-            ):
-                raise UpgradeDatabaseException(
-                    OUTDATED_SCHEMA_ON_WORKER_ERROR
-                    % (SCHEMA_VERSION, version_info.current_version)
-                )
-
+            # This should be run on all processes, master or worker. The master will
+            # apply the deltas, while workers will check if any outstanding deltas
+            # exist and raise an PrepareDatabaseException if they do.
             _upgrade_existing_database(
                 cur,
                 version_info,
@@ -149,6 +141,7 @@ def prepare_database(
                 config,
                 databases=databases,
             )
+
         else:
             logger.info("%r: Initialising new database", databases)
 
@@ -357,6 +350,18 @@ def _upgrade_existing_database(
 
     is_worker = config and config.worker.worker_app is not None
 
+    # If the schema version needs to be updated, and we are on a worker, we immediately
+    # know to bail out as workers cannot update the database schema. Only one process
+    # must update the database at the time, therefore we delegate this task to the master.
+    if is_worker and current_schema_state.current_version < SCHEMA_VERSION:
+        # If the DB is on an older version than we expect then we refuse
+        # to start the worker (as the main process needs to run first to
+        # update the schema).
+        raise UpgradeDatabaseException(
+            OUTDATED_SCHEMA_ON_WORKER_ERROR
+            % (SCHEMA_VERSION, current_schema_state.current_version)
+        )
+
     if (
         current_schema_state.compat_version is not None
         and current_schema_state.compat_version > SCHEMA_VERSION
diff --git a/synapse/storage/schema/main/delta/65/03remove_hidden_devices_from_device_inbox.sql b/synapse/storage/schema/main/delta/65/03remove_hidden_devices_from_device_inbox.sql
new file mode 100644
index 0000000000..7b3592dcf0
--- /dev/null
+++ b/synapse/storage/schema/main/delta/65/03remove_hidden_devices_from_device_inbox.sql
@@ -0,0 +1,22 @@
+/* Copyright 2021 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+-- Remove messages from the device_inbox table which were orphaned
+-- because a device was hidden using Synapse earlier than 1.47.0.
+-- This runs as background task, but may take a bit to finish.
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (6503, 'remove_hidden_devices_from_device_inbox', '{}');
diff --git a/synapse/storage/schema/main/delta/65/04_local_group_updates.sql b/synapse/storage/schema/main/delta/65/04_local_group_updates.sql
new file mode 100644
index 0000000000..a178abfe12
--- /dev/null
+++ b/synapse/storage/schema/main/delta/65/04_local_group_updates.sql
@@ -0,0 +1,18 @@
+/* Copyright 2021 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Check index on `local_group_updates.stream_id`.
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (6504, 'local_group_updates_index', '{}');
diff --git a/synapse/storage/schema/main/delta/65/06remove_deleted_devices_from_device_inbox.sql b/synapse/storage/schema/main/delta/65/06remove_deleted_devices_from_device_inbox.sql
new file mode 100644
index 0000000000..82f6408b36
--- /dev/null
+++ b/synapse/storage/schema/main/delta/65/06remove_deleted_devices_from_device_inbox.sql
@@ -0,0 +1,34 @@
+/* Copyright 2021 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+-- Remove messages from the device_inbox table which were orphaned
+-- when a device was deleted using Synapse earlier than 1.47.0.
+-- This runs as background task, but may take a bit to finish.
+
+-- Remove any existing instances of this job running. It's OK to stop and restart this job,
+-- as it's just deleting entries from a table - no progress will be lost.
+--
+-- This is necessary due a similar migration running the job accidentally
+-- being included in schema version 64 during v1.47.0rc1,rc2. If a
+-- homeserver had updated from Synapse <=v1.45.0 (schema version <=64),
+-- then they would have started running this background update already.
+-- If that update was still running, then simply inserting it again would
+-- cause an SQL failure. So we effectively do an "upsert" here instead.
+
+DELETE FROM background_updates WHERE update_name = 'remove_deleted_devices_from_device_inbox';
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (6506, 'remove_deleted_devices_from_device_inbox', '{}');
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 5df80ea8e7..96efc5f3e3 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -22,11 +22,11 @@ from typing import (
     Any,
     Awaitable,
     Callable,
+    Collection,
     Dict,
     Generic,
     Hashable,
     Iterable,
-    List,
     Optional,
     Set,
     TypeVar,
@@ -76,12 +76,17 @@ class ObservableDeferred(Generic[_T]):
     def __init__(self, deferred: "defer.Deferred[_T]", consumeErrors: bool = False):
         object.__setattr__(self, "_deferred", deferred)
         object.__setattr__(self, "_result", None)
-        object.__setattr__(self, "_observers", set())
+        object.__setattr__(self, "_observers", [])
 
         def callback(r):
             object.__setattr__(self, "_result", (True, r))
-            while self._observers:
-                observer = self._observers.pop()
+
+            # once we have set _result, no more entries will be added to _observers,
+            # so it's safe to replace it with the empty tuple.
+            observers = self._observers
+            object.__setattr__(self, "_observers", ())
+
+            for observer in observers:
                 try:
                     observer.callback(r)
                 except Exception as e:
@@ -95,12 +100,16 @@ class ObservableDeferred(Generic[_T]):
 
         def errback(f):
             object.__setattr__(self, "_result", (False, f))
-            while self._observers:
+
+            # once we have set _result, no more entries will be added to _observers,
+            # so it's safe to replace it with the empty tuple.
+            observers = self._observers
+            object.__setattr__(self, "_observers", ())
+
+            for observer in observers:
                 # This is a little bit of magic to correctly propagate stack
                 # traces when we `await` on one of the observer deferreds.
                 f.value.__failure__ = f
-
-                observer = self._observers.pop()
                 try:
                     observer.errback(f)
                 except Exception as e:
@@ -127,20 +136,13 @@ class ObservableDeferred(Generic[_T]):
         """
         if not self._result:
             d: "defer.Deferred[_T]" = defer.Deferred()
-
-            def remove(r):
-                self._observers.discard(d)
-                return r
-
-            d.addBoth(remove)
-
-            self._observers.add(d)
+            self._observers.append(d)
             return d
         else:
             success, res = self._result
             return defer.succeed(res) if success else defer.fail(res)
 
-    def observers(self) -> "List[defer.Deferred[_T]]":
+    def observers(self) -> "Collection[defer.Deferred[_T]]":
         return self._observers
 
     def has_called(self) -> bool:
diff --git a/sytest-blacklist b/sytest-blacklist
index 65bf1774e3..57e603a4a6 100644
--- a/sytest-blacklist
+++ b/sytest-blacklist
@@ -32,3 +32,6 @@ We can't peek into rooms with invited history_visibility
 We can't peek into rooms with joined history_visibility
 Local users can peek by room alias
 Peeked rooms only turn up in the sync for the device who peeked them
+
+# Validation needs to be added to Synapse: #10554
+Rejects invalid device keys
diff --git a/tests/crypto/test_keyring.py b/tests/crypto/test_keyring.py
index 745c295d3b..cbecc1c20f 100644
--- a/tests/crypto/test_keyring.py
+++ b/tests/crypto/test_keyring.py
@@ -197,6 +197,18 @@ class KeyringTestCase(unittest.HomeserverTestCase):
         # self.assertFalse(d.called)
         self.get_success(d)
 
+    def test_verify_for_server_locally(self):
+        """Ensure that locally signed JSON can be verified without fetching keys
+        over federation
+        """
+        kr = keyring.Keyring(self.hs)
+        json1 = {}
+        signedjson.sign.sign_json(json1, self.hs.hostname, self.hs.signing_key)
+
+        # Test that verify_json_for_server succeeds on a object signed by ourselves
+        d = kr.verify_json_for_server(self.hs.hostname, json1, 0)
+        self.get_success(d)
+
     def test_verify_json_for_server_with_null_valid_until_ms(self):
         """Tests that we correctly handle key requests for keys we've stored
         with a null `ts_valid_until_ms`
diff --git a/tests/handlers/test_admin.py b/tests/handlers/test_admin.py
index 59de1142b1..abf2a0fe0d 100644
--- a/tests/handlers/test_admin.py
+++ b/tests/handlers/test_admin.py
@@ -17,8 +17,9 @@ from unittest.mock import Mock
 
 import synapse.rest.admin
 import synapse.storage
-from synapse.api.constants import EventTypes
-from synapse.rest.client import login, room
+from synapse.api.constants import EventTypes, JoinRules
+from synapse.api.room_versions import RoomVersions
+from synapse.rest.client import knock, login, room
 
 from tests import unittest
 
@@ -28,6 +29,7 @@ class ExfiltrateData(unittest.HomeserverTestCase):
         synapse.rest.admin.register_servlets_for_client_rest_resource,
         login.register_servlets,
         room.register_servlets,
+        knock.register_servlets,
     ]
 
     def prepare(self, reactor, clock, hs):
@@ -201,3 +203,32 @@ class ExfiltrateData(unittest.HomeserverTestCase):
         self.assertEqual(args[0], room_id)
         self.assertEqual(args[1].content["membership"], "invite")
         self.assertTrue(args[2])  # Assert there is at least one bit of state
+
+    def test_knock(self):
+        """Tests that knock get handled correctly."""
+        # create a knockable v7 room
+        room_id = self.helper.create_room_as(
+            self.user1, room_version=RoomVersions.V7.identifier, tok=self.token1
+        )
+        self.helper.send_state(
+            room_id,
+            EventTypes.JoinRules,
+            {"join_rule": JoinRules.KNOCK},
+            tok=self.token1,
+        )
+
+        self.helper.send(room_id, body="Hello!", tok=self.token1)
+        self.helper.knock(room_id, self.user2, tok=self.token2)
+
+        writer = Mock()
+
+        self.get_success(self.admin_handler.export_user_data(self.user2, writer))
+
+        writer.write_events.assert_not_called()
+        writer.write_state.assert_not_called()
+        writer.write_knock.assert_called_once()
+
+        args = writer.write_knock.call_args[0]
+        self.assertEqual(args[0], room_id)
+        self.assertEqual(args[1].content["membership"], "knock")
+        self.assertTrue(args[2])  # Assert there is at least one bit of state
diff --git a/tests/handlers/test_appservice.py b/tests/handlers/test_appservice.py
index 43998020b2..1f6a924452 100644
--- a/tests/handlers/test_appservice.py
+++ b/tests/handlers/test_appservice.py
@@ -40,6 +40,7 @@ class AppServiceHandlerTestCase(unittest.TestCase):
         hs.get_application_service_scheduler.return_value = self.mock_scheduler
         hs.get_clock.return_value = MockClock()
         self.handler = ApplicationServicesHandler(hs)
+        self.event_source = hs.get_event_sources()
 
     def test_notify_interested_services(self):
         interested_service = self._mkservice(is_interested=True)
@@ -252,6 +253,56 @@ class AppServiceHandlerTestCase(unittest.TestCase):
             },
         )
 
+    def test_notify_interested_services_ephemeral(self):
+        """
+        Test sending ephemeral events to the appservice handler are scheduled
+        to be pushed out to interested appservices, and that the stream ID is
+        updated accordingly.
+        """
+        interested_service = self._mkservice(is_interested=True)
+        services = [interested_service]
+
+        self.mock_store.get_app_services.return_value = services
+        self.mock_store.get_type_stream_id_for_appservice.return_value = make_awaitable(
+            579
+        )
+
+        event = Mock(event_id="event_1")
+        self.event_source.sources.receipt.get_new_events_as.return_value = (
+            make_awaitable(([event], None))
+        )
+
+        self.handler.notify_interested_services_ephemeral("receipt_key", 580)
+        self.mock_scheduler.submit_ephemeral_events_for_as.assert_called_once_with(
+            interested_service, [event]
+        )
+        self.mock_store.set_type_stream_id_for_appservice.assert_called_once_with(
+            interested_service,
+            "read_receipt",
+            580,
+        )
+
+    def test_notify_interested_services_ephemeral_out_of_order(self):
+        """
+        Test sending out of order ephemeral events to the appservice handler
+        are ignored.
+        """
+        interested_service = self._mkservice(is_interested=True)
+        services = [interested_service]
+
+        self.mock_store.get_app_services.return_value = services
+        self.mock_store.get_type_stream_id_for_appservice.return_value = make_awaitable(
+            580
+        )
+
+        event = Mock(event_id="event_1")
+        self.event_source.sources.receipt.get_new_events_as.return_value = (
+            make_awaitable(([event], None))
+        )
+
+        self.handler.notify_interested_services_ephemeral("receipt_key", 579)
+        self.mock_scheduler.submit_ephemeral_events_for_as.assert_not_called()
+
     def _mkservice(self, is_interested, protocols=None):
         service = Mock()
         service.is_interested.return_value = make_awaitable(is_interested)
diff --git a/tests/handlers/test_device.py b/tests/handlers/test_device.py
index 3ac48e5e95..43031e07ea 100644
--- a/tests/handlers/test_device.py
+++ b/tests/handlers/test_device.py
@@ -160,6 +160,37 @@ class DeviceTestCase(unittest.HomeserverTestCase):
         # we'd like to check the access token was invalidated, but that's a
         # bit of a PITA.
 
+    def test_delete_device_and_device_inbox(self):
+        self._record_users()
+
+        # add an device_inbox
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "device_inbox",
+                {
+                    "user_id": user1,
+                    "device_id": "abc",
+                    "stream_id": 1,
+                    "message_json": "{}",
+                },
+            )
+        )
+
+        # delete the device
+        self.get_success(self.handler.delete_device(user1, "abc"))
+
+        # check that the device_inbox was deleted
+        res = self.get_success(
+            self.store.db_pool.simple_select_one(
+                table="device_inbox",
+                keyvalues={"user_id": user1, "device_id": "abc"},
+                retcols=("user_id", "device_id"),
+                allow_none=True,
+                desc="get_device_id_from_device_inbox",
+            )
+        )
+        self.assertIsNone(res)
+
     def test_update_device(self):
         self._record_users()
 
diff --git a/tests/handlers/test_e2e_keys.py b/tests/handlers/test_e2e_keys.py
index 39e7b1ab25..0c3b86fda9 100644
--- a/tests/handlers/test_e2e_keys.py
+++ b/tests/handlers/test_e2e_keys.py
@@ -17,6 +17,8 @@ from unittest import mock
 
 from signedjson import key as key, sign as sign
 
+from twisted.internet import defer
+
 from synapse.api.constants import RoomEncryptionAlgorithms
 from synapse.api.errors import Codes, SynapseError
 
@@ -630,3 +632,152 @@ class E2eKeysHandlerTestCase(unittest.HomeserverTestCase):
             ],
             other_master_key["signatures"][local_user]["ed25519:" + usersigning_pubkey],
         )
+
+    def test_query_devices_remote_no_sync(self):
+        """Tests that querying keys for a remote user that we don't share a room
+        with returns the cross signing keys correctly.
+        """
+
+        remote_user_id = "@test:other"
+        local_user_id = "@test:test"
+
+        remote_master_key = "85T7JXPFBAySB/jwby4S3lBPTqY3+Zg53nYuGmu1ggY"
+        remote_self_signing_key = "QeIiFEjluPBtI7WQdG365QKZcFs9kqmHir6RBD0//nQ"
+
+        self.hs.get_federation_client().query_client_keys = mock.Mock(
+            return_value=defer.succeed(
+                {
+                    "device_keys": {remote_user_id: {}},
+                    "master_keys": {
+                        remote_user_id: {
+                            "user_id": remote_user_id,
+                            "usage": ["master"],
+                            "keys": {"ed25519:" + remote_master_key: remote_master_key},
+                        },
+                    },
+                    "self_signing_keys": {
+                        remote_user_id: {
+                            "user_id": remote_user_id,
+                            "usage": ["self_signing"],
+                            "keys": {
+                                "ed25519:"
+                                + remote_self_signing_key: remote_self_signing_key
+                            },
+                        }
+                    },
+                }
+            )
+        )
+
+        e2e_handler = self.hs.get_e2e_keys_handler()
+
+        query_result = self.get_success(
+            e2e_handler.query_devices(
+                {
+                    "device_keys": {remote_user_id: []},
+                },
+                timeout=10,
+                from_user_id=local_user_id,
+                from_device_id="some_device_id",
+            )
+        )
+
+        self.assertEqual(query_result["failures"], {})
+        self.assertEqual(
+            query_result["master_keys"],
+            {
+                remote_user_id: {
+                    "user_id": remote_user_id,
+                    "usage": ["master"],
+                    "keys": {"ed25519:" + remote_master_key: remote_master_key},
+                },
+            },
+        )
+        self.assertEqual(
+            query_result["self_signing_keys"],
+            {
+                remote_user_id: {
+                    "user_id": remote_user_id,
+                    "usage": ["self_signing"],
+                    "keys": {
+                        "ed25519:" + remote_self_signing_key: remote_self_signing_key
+                    },
+                }
+            },
+        )
+
+    def test_query_devices_remote_sync(self):
+        """Tests that querying keys for a remote user that we share a room with,
+        but haven't yet fetched the keys for, returns the cross signing keys
+        correctly.
+        """
+
+        remote_user_id = "@test:other"
+        local_user_id = "@test:test"
+
+        self.store.get_rooms_for_user = mock.Mock(
+            return_value=defer.succeed({"some_room_id"})
+        )
+
+        remote_master_key = "85T7JXPFBAySB/jwby4S3lBPTqY3+Zg53nYuGmu1ggY"
+        remote_self_signing_key = "QeIiFEjluPBtI7WQdG365QKZcFs9kqmHir6RBD0//nQ"
+
+        self.hs.get_federation_client().query_user_devices = mock.Mock(
+            return_value=defer.succeed(
+                {
+                    "user_id": remote_user_id,
+                    "stream_id": 1,
+                    "devices": [],
+                    "master_key": {
+                        "user_id": remote_user_id,
+                        "usage": ["master"],
+                        "keys": {"ed25519:" + remote_master_key: remote_master_key},
+                    },
+                    "self_signing_key": {
+                        "user_id": remote_user_id,
+                        "usage": ["self_signing"],
+                        "keys": {
+                            "ed25519:"
+                            + remote_self_signing_key: remote_self_signing_key
+                        },
+                    },
+                }
+            )
+        )
+
+        e2e_handler = self.hs.get_e2e_keys_handler()
+
+        query_result = self.get_success(
+            e2e_handler.query_devices(
+                {
+                    "device_keys": {remote_user_id: []},
+                },
+                timeout=10,
+                from_user_id=local_user_id,
+                from_device_id="some_device_id",
+            )
+        )
+
+        self.assertEqual(query_result["failures"], {})
+        self.assertEqual(
+            query_result["master_keys"],
+            {
+                remote_user_id: {
+                    "user_id": remote_user_id,
+                    "usage": ["master"],
+                    "keys": {"ed25519:" + remote_master_key: remote_master_key},
+                }
+            },
+        )
+        self.assertEqual(
+            query_result["self_signing_keys"],
+            {
+                remote_user_id: {
+                    "user_id": remote_user_id,
+                    "usage": ["self_signing"],
+                    "keys": {
+                        "ed25519:" + remote_self_signing_key: remote_self_signing_key
+                    },
+                }
+            },
+        )
diff --git a/tests/module_api/test_api.py b/tests/module_api/test_api.py
index e915dd5c7c..d16cd141a7 100644
--- a/tests/module_api/test_api.py
+++ b/tests/module_api/test_api.py
@@ -15,12 +15,12 @@ from unittest.mock import Mock
 
 from twisted.internet import defer
 
-from synapse.api.constants import EduTypes
+from synapse.api.constants import EduTypes, EventTypes
 from synapse.events import EventBase
 from synapse.federation.units import Transaction
 from synapse.handlers.presence import UserPresenceState
 from synapse.rest import admin
-from synapse.rest.client import login, presence, room
+from synapse.rest.client import login, presence, profile, room
 from synapse.types import create_requester
 
 from tests.events.test_presence_router import send_presence_update, sync_presence
@@ -37,6 +37,7 @@ class ModuleApiTestCase(HomeserverTestCase):
         login.register_servlets,
         room.register_servlets,
         presence.register_servlets,
+        profile.register_servlets,
     ]
 
     def prepare(self, reactor, clock, homeserver):
@@ -115,7 +116,6 @@ class ModuleApiTestCase(HomeserverTestCase):
 
         # Insert a second ip, agent at a later date. We should be able to retrieve it.
         last_seen_2 = last_seen_1 + 10000
-        print("%s => %s" % (last_seen_1, last_seen_2))
         self.get_success(
             self.store.insert_client_ip(
                 user_id, "access_token", "ip_2", "user_agent_2", "device_2", last_seen_2
@@ -385,6 +385,152 @@ class ModuleApiTestCase(HomeserverTestCase):
 
         self.assertTrue(found_update)
 
+    def test_update_membership(self):
+        """Tests that the module API can update the membership of a user in a room."""
+        peter = self.register_user("peter", "hackme")
+        lesley = self.register_user("lesley", "hackme")
+        tok = self.login("peter", "hackme")
+        lesley_tok = self.login("lesley", "hackme")
+
+        # Make peter create a public room.
+        room_id = self.helper.create_room_as(
+            room_creator=peter, is_public=True, tok=tok
+        )
+
+        # Set a profile for lesley.
+        channel = self.make_request(
+            method="PUT",
+            path="/_matrix/client/r0/profile/%s/displayname" % lesley,
+            content={"displayname": "Lesley May"},
+            access_token=lesley_tok,
+        )
+
+        self.assertEqual(channel.code, 200, channel.result)
+
+        channel = self.make_request(
+            method="PUT",
+            path="/_matrix/client/r0/profile/%s/avatar_url" % lesley,
+            content={"avatar_url": "some_url"},
+            access_token=lesley_tok,
+        )
+
+        self.assertEqual(channel.code, 200, channel.result)
+
+        # Make Peter invite Lesley to the room.
+        self.get_success(
+            defer.ensureDeferred(
+                self.module_api.update_room_membership(peter, lesley, room_id, "invite")
+            )
+        )
+
+        res = self.helper.get_state(
+            room_id=room_id,
+            event_type="m.room.member",
+            state_key=lesley,
+            tok=tok,
+        )
+
+        # Check the membership is correct.
+        self.assertEqual(res["membership"], "invite")
+
+        # Also check that the profile was correctly filled out, and that it's not
+        # Peter's.
+        self.assertEqual(res["displayname"], "Lesley May")
+        self.assertEqual(res["avatar_url"], "some_url")
+
+        # Make lesley join it.
+        self.get_success(
+            defer.ensureDeferred(
+                self.module_api.update_room_membership(lesley, lesley, room_id, "join")
+            )
+        )
+
+        # Check that the membership of lesley in the room is "join".
+        res = self.helper.get_state(
+            room_id=room_id,
+            event_type="m.room.member",
+            state_key=lesley,
+            tok=tok,
+        )
+
+        self.assertEqual(res["membership"], "join")
+
+        # Also check that the profile was correctly filled out.
+        self.assertEqual(res["displayname"], "Lesley May")
+        self.assertEqual(res["avatar_url"], "some_url")
+
+        # Make peter kick lesley from the room.
+        self.get_success(
+            defer.ensureDeferred(
+                self.module_api.update_room_membership(peter, lesley, room_id, "leave")
+            )
+        )
+
+        # Check that the membership of lesley in the room is "leave".
+        res = self.helper.get_state(
+            room_id=room_id,
+            event_type="m.room.member",
+            state_key=lesley,
+            tok=tok,
+        )
+
+        self.assertEqual(res["membership"], "leave")
+
+        # Try to send a membership update from a non-local user and check that it fails.
+        d = defer.ensureDeferred(
+            self.module_api.update_room_membership(
+                "@nicolas:otherserver.com",
+                lesley,
+                room_id,
+                "invite",
+            )
+        )
+
+        self.get_failure(d, RuntimeError)
+
+        # Check that inviting a user that doesn't have a profile falls back to using a
+        # default (localpart + no avatar) profile.
+        simone = "@simone:" + self.hs.config.server.server_name
+        self.get_success(
+            defer.ensureDeferred(
+                self.module_api.update_room_membership(peter, simone, room_id, "invite")
+            )
+        )
+
+        res = self.helper.get_state(
+            room_id=room_id,
+            event_type="m.room.member",
+            state_key=simone,
+            tok=tok,
+        )
+
+        self.assertEqual(res["membership"], "invite")
+        self.assertEqual(res["displayname"], "simone")
+        self.assertIsNone(res["avatar_url"])
+
+    def test_get_room_state(self):
+        """Tests that a module can retrieve the state of a room through the module API."""
+        user_id = self.register_user("peter", "hackme")
+        tok = self.login("peter", "hackme")
+
+        # Create a room and send some custom state in it.
+        room_id = self.helper.create_room_as(tok=tok)
+        self.helper.send_state(room_id, "org.matrix.test", {}, tok=tok)
+
+        # Check that the module API can successfully fetch state for the room.
+        state = self.get_success(
+            defer.ensureDeferred(self.module_api.get_room_state(room_id))
+        )
+
+        # Check that a few standard events are in the returned state.
+        self.assertIn((EventTypes.Create, ""), state)
+        self.assertIn((EventTypes.Member, user_id), state)
+
+        # Check that our custom state event is in the returned state.
+        self.assertEqual(state[("org.matrix.test", "")].sender, user_id)
+        self.assertEqual(state[("org.matrix.test", "")].state_key, "")
+        self.assertEqual(state[("org.matrix.test", "")].content, {})
+
 
 class ModuleApiWorkerTestCase(BaseMultiWorkerStreamTestCase):
     """For testing ModuleApi functionality in a multi-worker setup"""
diff --git a/tests/push/test_email.py b/tests/push/test_email.py
index fa8018e5a7..90f800e564 100644
--- a/tests/push/test_email.py
+++ b/tests/push/test_email.py
@@ -65,7 +65,7 @@ class EmailPusherTests(HomeserverTestCase):
             "notif_from": "test@example.com",
             "riot_base_url": None,
         }
-        config["public_baseurl"] = "aaa"
+        config["public_baseurl"] = "http://aaa"
         config["start_pushers"] = True
 
         hs = self.setup_test_homeserver(config=config)
diff --git a/tests/rest/admin/test_background_updates.py b/tests/rest/admin/test_background_updates.py
new file mode 100644
index 0000000000..78c48db552
--- /dev/null
+++ b/tests/rest/admin/test_background_updates.py
@@ -0,0 +1,218 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import synapse.rest.admin
+from synapse.rest.client import login
+from synapse.server import HomeServer
+
+from tests import unittest
+
+
+class BackgroundUpdatesTestCase(unittest.HomeserverTestCase):
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs: HomeServer):
+        self.store = hs.get_datastore()
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+    def _register_bg_update(self):
+        "Adds a bg update but doesn't start it"
+
+        async def _fake_update(progress, batch_size) -> int:
+            await self.clock.sleep(0.2)
+            return batch_size
+
+        self.store.db_pool.updates.register_background_update_handler(
+            "test_update",
+            _fake_update,
+        )
+
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                table="background_updates",
+                values={
+                    "update_name": "test_update",
+                    "progress_json": "{}",
+                },
+            )
+        )
+
+    def test_status_empty(self):
+        """Test the status API works."""
+
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/status",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        # Background updates should be enabled, but none should be running.
+        self.assertDictEqual(
+            channel.json_body, {"current_updates": {}, "enabled": True}
+        )
+
+    def test_status_bg_update(self):
+        """Test the status API works with a background update."""
+
+        # Create a new background update
+
+        self._register_bg_update()
+
+        self.store.db_pool.updates.start_doing_background_updates()
+        self.reactor.pump([1.0, 1.0])
+
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/status",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        # Background updates should be enabled, and one should be running.
+        self.assertDictEqual(
+            channel.json_body,
+            {
+                "current_updates": {
+                    "master": {
+                        "name": "test_update",
+                        "average_items_per_ms": 0.1,
+                        "total_duration_ms": 1000.0,
+                        "total_item_count": 100,
+                    }
+                },
+                "enabled": True,
+            },
+        )
+
+    def test_enabled(self):
+        """Test the enabled API works."""
+
+        # Create a new background update
+
+        self._register_bg_update()
+        self.store.db_pool.updates.start_doing_background_updates()
+
+        # Test that GET works and returns enabled is True.
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/enabled",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertDictEqual(channel.json_body, {"enabled": True})
+
+        # Disable the BG updates
+        channel = self.make_request(
+            "POST",
+            "/_synapse/admin/v1/background_updates/enabled",
+            content={"enabled": False},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertDictEqual(channel.json_body, {"enabled": False})
+
+        # Advance a bit and get the current status, note this will finish the in
+        # flight background update so we call it the status API twice and check
+        # there was no change.
+        self.reactor.pump([1.0, 1.0])
+
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/status",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertDictEqual(
+            channel.json_body,
+            {
+                "current_updates": {
+                    "master": {
+                        "name": "test_update",
+                        "average_items_per_ms": 0.1,
+                        "total_duration_ms": 1000.0,
+                        "total_item_count": 100,
+                    }
+                },
+                "enabled": False,
+            },
+        )
+
+        # Run the reactor for a bit so the BG updates would have a chance to run
+        # if they were to.
+        self.reactor.pump([1.0, 1.0])
+
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/status",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        # There should be no change from the previous /status response.
+        self.assertDictEqual(
+            channel.json_body,
+            {
+                "current_updates": {
+                    "master": {
+                        "name": "test_update",
+                        "average_items_per_ms": 0.1,
+                        "total_duration_ms": 1000.0,
+                        "total_item_count": 100,
+                    }
+                },
+                "enabled": False,
+            },
+        )
+
+        # Re-enable the background updates.
+
+        channel = self.make_request(
+            "POST",
+            "/_synapse/admin/v1/background_updates/enabled",
+            content={"enabled": True},
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        self.assertDictEqual(channel.json_body, {"enabled": True})
+
+        self.reactor.pump([1.0, 1.0])
+
+        channel = self.make_request(
+            "GET",
+            "/_synapse/admin/v1/background_updates/status",
+            access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        # Background updates should be enabled and making progress.
+        self.assertDictEqual(
+            channel.json_body,
+            {
+                "current_updates": {
+                    "master": {
+                        "name": "test_update",
+                        "average_items_per_ms": 0.1,
+                        "total_duration_ms": 2000.0,
+                        "total_item_count": 200,
+                    }
+                },
+                "enabled": True,
+            },
+        )
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index 0fa55e03b4..46116644ce 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -17,8 +17,6 @@ import urllib.parse
 from typing import List, Optional
 from unittest.mock import Mock
 
-from parameterized import parameterized_class
-
 import synapse.rest.admin
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import Codes
@@ -29,13 +27,6 @@ from tests import unittest
 """Tests admin REST events for /rooms paths."""
 
 
-@parameterized_class(
-    ("method", "url_template"),
-    [
-        ("POST", "/_synapse/admin/v1/rooms/%s/delete"),
-        ("DELETE", "/_synapse/admin/v1/rooms/%s"),
-    ],
-)
 class DeleteRoomTestCase(unittest.HomeserverTestCase):
     servlets = [
         synapse.rest.admin.register_servlets,
@@ -67,7 +58,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         self.room_id = self.helper.create_room_as(
             self.other_user, tok=self.other_user_tok
         )
-        self.url = self.url_template % self.room_id
+        self.url = "/_synapse/admin/v1/rooms/%s" % self.room_id
 
     def test_requester_is_no_admin(self):
         """
@@ -75,7 +66,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         """
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             json.dumps({}),
             access_token=self.other_user_tok,
@@ -88,10 +79,10 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         """
         Check that unknown rooms/server return error 404.
         """
-        url = self.url_template % "!unknown:test"
+        url = "/_synapse/admin/v1/rooms/%s" % "!unknown:test"
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             url,
             json.dumps({}),
             access_token=self.admin_user_tok,
@@ -104,10 +95,10 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         """
         Check that invalid room names, return an error 400.
         """
-        url = self.url_template % "invalidroom"
+        url = "/_synapse/admin/v1/rooms/%s" % "invalidroom"
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             url,
             json.dumps({}),
             access_token=self.admin_user_tok,
@@ -126,7 +117,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"new_room_user_id": "@unknown:test"})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -145,7 +136,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"new_room_user_id": "@not:exist.bla"})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -164,7 +155,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"block": "NotBool"})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -180,7 +171,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"purge": "NotBool"})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -206,7 +197,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"block": True, "purge": True})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url.encode("ascii"),
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -239,7 +230,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         body = json.dumps({"block": False, "purge": True})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url.encode("ascii"),
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -270,10 +261,10 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
         # Assert one user in room
         self._is_member(room_id=self.room_id, user_id=self.other_user)
 
-        body = json.dumps({"block": False, "purge": False})
+        body = json.dumps({"block": True, "purge": False})
 
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url.encode("ascii"),
             content=body.encode(encoding="utf_8"),
             access_token=self.admin_user_tok,
@@ -287,7 +278,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
 
         with self.assertRaises(AssertionError):
             self._is_purged(self.room_id)
-        self._is_blocked(self.room_id, expect=False)
+        self._is_blocked(self.room_id, expect=True)
         self._has_no_members(self.room_id)
 
     def test_shutdown_room_consent(self):
@@ -319,7 +310,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
 
         # Test that the admin can still send shutdown
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             json.dumps({"new_room_user_id": self.admin_user}),
             access_token=self.admin_user_tok,
@@ -365,7 +356,7 @@ class DeleteRoomTestCase(unittest.HomeserverTestCase):
 
         # Test that the admin can still send shutdown
         channel = self.make_request(
-            self.method,
+            "DELETE",
             self.url,
             json.dumps({"new_room_user_id": self.admin_user}),
             access_token=self.admin_user_tok,
@@ -689,36 +680,6 @@ class RoomTestCase(unittest.HomeserverTestCase):
         reversing the order, etc.
         """
 
-        def _set_canonical_alias(room_id: str, test_alias: str, admin_user_tok: str):
-            # Create a new alias to this room
-            url = "/_matrix/client/r0/directory/room/%s" % (
-                urllib.parse.quote(test_alias),
-            )
-            channel = self.make_request(
-                "PUT",
-                url.encode("ascii"),
-                {"room_id": room_id},
-                access_token=admin_user_tok,
-            )
-            self.assertEqual(
-                200, int(channel.result["code"]), msg=channel.result["body"]
-            )
-
-            # Set this new alias as the canonical alias for this room
-            self.helper.send_state(
-                room_id,
-                "m.room.aliases",
-                {"aliases": [test_alias]},
-                tok=admin_user_tok,
-                state_key="test",
-            )
-            self.helper.send_state(
-                room_id,
-                "m.room.canonical_alias",
-                {"alias": test_alias},
-                tok=admin_user_tok,
-            )
-
         def _order_test(
             order_type: str,
             expected_room_list: List[str],
@@ -790,9 +751,9 @@ class RoomTestCase(unittest.HomeserverTestCase):
         )
 
         # Set room canonical room aliases
-        _set_canonical_alias(room_id_1, "#A_alias:test", self.admin_user_tok)
-        _set_canonical_alias(room_id_2, "#B_alias:test", self.admin_user_tok)
-        _set_canonical_alias(room_id_3, "#C_alias:test", self.admin_user_tok)
+        self._set_canonical_alias(room_id_1, "#A_alias:test", self.admin_user_tok)
+        self._set_canonical_alias(room_id_2, "#B_alias:test", self.admin_user_tok)
+        self._set_canonical_alias(room_id_3, "#C_alias:test", self.admin_user_tok)
 
         # Set room member size in the reverse order. room 1 -> 1 member, 2 -> 2, 3 -> 3
         user_1 = self.register_user("bob1", "pass")
@@ -859,7 +820,7 @@ class RoomTestCase(unittest.HomeserverTestCase):
         room_id_2 = self.helper.create_room_as(self.admin_user, tok=self.admin_user_tok)
 
         room_name_1 = "something"
-        room_name_2 = "else"
+        room_name_2 = "LoremIpsum"
 
         # Set the name for each room
         self.helper.send_state(
@@ -875,6 +836,8 @@ class RoomTestCase(unittest.HomeserverTestCase):
             tok=self.admin_user_tok,
         )
 
+        self._set_canonical_alias(room_id_1, "#Room_Alias1:test", self.admin_user_tok)
+
         def _search_test(
             expected_room_id: Optional[str],
             search_term: str,
@@ -923,24 +886,36 @@ class RoomTestCase(unittest.HomeserverTestCase):
                 r = rooms[0]
                 self.assertEqual(expected_room_id, r["room_id"])
 
-        # Perform search tests
+        # Test searching by room name
         _search_test(room_id_1, "something")
         _search_test(room_id_1, "thing")
 
-        _search_test(room_id_2, "else")
-        _search_test(room_id_2, "se")
+        _search_test(room_id_2, "LoremIpsum")
+        _search_test(room_id_2, "lorem")
 
         # Test case insensitive
         _search_test(room_id_1, "SOMETHING")
         _search_test(room_id_1, "THING")
 
-        _search_test(room_id_2, "ELSE")
-        _search_test(room_id_2, "SE")
+        _search_test(room_id_2, "LOREMIPSUM")
+        _search_test(room_id_2, "LOREM")
 
         _search_test(None, "foo")
         _search_test(None, "bar")
         _search_test(None, "", expected_http_code=400)
 
+        # Test that the whole room id returns the room
+        _search_test(room_id_1, room_id_1)
+        # Test that the search by room_id is case sensitive
+        _search_test(None, room_id_1.lower())
+        # Test search part of local part of room id do not match
+        _search_test(None, room_id_1[1:10])
+
+        # Test that whole room alias return no result, because of domain
+        _search_test(None, "#Room_Alias1:test")
+        # Test search local part of alias
+        _search_test(room_id_1, "alias1")
+
     def test_search_term_non_ascii(self):
         """Test that searching for a room with non-ASCII characters works correctly"""
 
@@ -1123,6 +1098,32 @@ class RoomTestCase(unittest.HomeserverTestCase):
         # the create_room already does the right thing, so no need to verify that we got
         # the state events it created.
 
+    def _set_canonical_alias(self, room_id: str, test_alias: str, admin_user_tok: str):
+        # Create a new alias to this room
+        url = "/_matrix/client/r0/directory/room/%s" % (urllib.parse.quote(test_alias),)
+        channel = self.make_request(
+            "PUT",
+            url.encode("ascii"),
+            {"room_id": room_id},
+            access_token=admin_user_tok,
+        )
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+
+        # Set this new alias as the canonical alias for this room
+        self.helper.send_state(
+            room_id,
+            "m.room.aliases",
+            {"aliases": [test_alias]},
+            tok=admin_user_tok,
+            state_key="test",
+        )
+        self.helper.send_state(
+            room_id,
+            "m.room.canonical_alias",
+            {"alias": test_alias},
+            tok=admin_user_tok,
+        )
+
 
 class JoinAliasRoomTestCase(unittest.HomeserverTestCase):
 
diff --git a/tests/rest/client/test_consent.py b/tests/rest/client/test_consent.py
index 84d092ca82..fcdc565814 100644
--- a/tests/rest/client/test_consent.py
+++ b/tests/rest/client/test_consent.py
@@ -35,7 +35,6 @@ class ConsentResourceTestCase(unittest.HomeserverTestCase):
     def make_homeserver(self, reactor, clock):
 
         config = self.default_config()
-        config["public_baseurl"] = "aaaa"
         config["form_secret"] = "123abc"
 
         # Make some temporary templates...
diff --git a/tests/rest/client/test_register.py b/tests/rest/client/test_register.py
index 66dcfc9f88..6e7c0f11df 100644
--- a/tests/rest/client/test_register.py
+++ b/tests/rest/client/test_register.py
@@ -891,7 +891,6 @@ class AccountValidityRenewalByEmailTestCase(unittest.HomeserverTestCase):
             "smtp_pass": None,
             "notif_from": "test@example.com",
         }
-        config["public_baseurl"] = "aaa"
 
         self.hs = self.setup_test_homeserver(config=config)
 
diff --git a/tests/rest/client/test_sync.py b/tests/rest/client/test_sync.py
index 95be369d4b..c427686376 100644
--- a/tests/rest/client/test_sync.py
+++ b/tests/rest/client/test_sync.py
@@ -14,6 +14,8 @@
 # limitations under the License.
 import json
 
+from parameterized import parameterized
+
 import synapse.rest.admin
 from synapse.api.constants import (
     EventContentFields,
@@ -417,7 +419,30 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Test that the first user can't see the other user's hidden read receipt
         self.assertEqual(self._get_read_receipt(), None)
 
-    def test_read_receipt_with_empty_body(self):
+    @parameterized.expand(
+        [
+            # Old Element version, expected to send an empty body
+            (
+                "agent1",
+                "Element/1.2.2 (Linux; U; Android 9; MatrixAndroidSDK_X 0.0.1)",
+                200,
+            ),
+            # Old SchildiChat version, expected to send an empty body
+            ("agent2", "SchildiChat/1.2.1 (Android 10)", 200),
+            # Expected 400: Denies empty body starting at version 1.3+
+            ("agent3", "Element/1.3.6 (Android 10)", 400),
+            ("agent4", "SchildiChat/1.3.6 (Android 11)", 400),
+            # Contains "Riot": Receipts with empty bodies expected
+            ("agent5", "Element (Riot.im) (Android 9)", 200),
+            # Expected 400: Does not contain "Android"
+            ("agent6", "Element/1.2.1", 400),
+            # Expected 400: Different format, missing "/" after Element; existing build that should allow empty bodies, but minimal ongoing usage
+            ("agent7", "Element dbg/1.1.8-dev (Android)", 400),
+        ]
+    )
+    def test_read_receipt_with_empty_body(
+        self, name, user_agent: str, expected_status_code: int
+    ):
         # Send a message as the first user
         res = self.helper.send(self.room_id, body="hello", tok=self.tok)
 
@@ -426,8 +451,9 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
             "POST",
             "/rooms/%s/receipt/m.read/%s" % (self.room_id, res["event_id"]),
             access_token=self.tok2,
+            custom_headers=[("User-Agent", user_agent)],
         )
-        self.assertEqual(channel.code, 200)
+        self.assertEqual(channel.code, expected_status_code)
 
     def _get_read_receipt(self):
         """Syncs and returns the read receipt."""
diff --git a/tests/rest/client/test_third_party_rules.py b/tests/rest/client/test_third_party_rules.py
index 531f09c48b..4e71b6ec12 100644
--- a/tests/rest/client/test_third_party_rules.py
+++ b/tests/rest/client/test_third_party_rules.py
@@ -15,7 +15,7 @@ import threading
 from typing import TYPE_CHECKING, Dict, Optional, Tuple
 from unittest.mock import Mock
 
-from synapse.api.constants import EventTypes
+from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
@@ -25,6 +25,7 @@ from synapse.types import JsonDict, Requester, StateMap
 from synapse.util.frozenutils import unfreeze
 
 from tests import unittest
+from tests.test_utils import make_awaitable
 
 if TYPE_CHECKING:
     from synapse.module_api import ModuleApi
@@ -74,7 +75,7 @@ class LegacyChangeEvents(LegacyThirdPartyRulesTestModule):
         return d
 
 
-class ThirdPartyRulesTestCase(unittest.HomeserverTestCase):
+class ThirdPartyRulesTestCase(unittest.FederatingHomeserverTestCase):
     servlets = [
         admin.register_servlets,
         login.register_servlets,
@@ -86,11 +87,29 @@ class ThirdPartyRulesTestCase(unittest.HomeserverTestCase):
 
         load_legacy_third_party_event_rules(hs)
 
+        # We're not going to be properly signing events as our remote homeserver is fake,
+        # therefore disable event signature checks.
+        # Note that these checks are not relevant to this test case.
+
+        # Have this homeserver auto-approve all event signature checking.
+        async def approve_all_signature_checking(_, pdu):
+            return pdu
+
+        hs.get_federation_server()._check_sigs_and_hash = approve_all_signature_checking
+
+        # Have this homeserver skip event auth checks. This is necessary due to
+        # event auth checks ensuring that events were signed by the sender's homeserver.
+        async def _check_event_auth(origin, event, context, *args, **kwargs):
+            return context
+
+        hs.get_federation_event_handler()._check_event_auth = _check_event_auth
+
         return hs
 
     def prepare(self, reactor, clock, homeserver):
-        # Create a user and room to play with during the tests
+        # Create some users and a room to play with during the tests
         self.user_id = self.register_user("kermit", "monkey")
+        self.invitee = self.register_user("invitee", "hackme")
         self.tok = self.login("kermit", "monkey")
 
         # Some tests might prevent room creation on purpose.
@@ -197,19 +216,9 @@ class ThirdPartyRulesTestCase(unittest.HomeserverTestCase):
             {"x": "x"},
             access_token=self.tok,
         )
-        # check_event_allowed has some error handling, so it shouldn't 500 just because a
-        # module did something bad.
-        self.assertEqual(channel.code, 200, channel.result)
-        event_id = channel.json_body["event_id"]
-
-        channel = self.make_request(
-            "GET",
-            "/_matrix/client/r0/rooms/%s/event/%s" % (self.room_id, event_id),
-            access_token=self.tok,
-        )
-        self.assertEqual(channel.code, 200, channel.result)
-        ev = channel.json_body
-        self.assertEqual(ev["content"]["x"], "x")
+        # Because check_event_allowed raises an exception, it leads to a
+        # 500 Internal Server Error
+        self.assertEqual(channel.code, 500, channel.result)
 
     def test_modify_event(self):
         """The module can return a modified version of the event"""
@@ -424,6 +433,74 @@ class ThirdPartyRulesTestCase(unittest.HomeserverTestCase):
             self.assertEqual(channel.code, 200)
             self.assertEqual(channel.json_body["i"], i)
 
+    def test_on_new_event(self):
+        """Test that the on_new_event callback is called on new events"""
+        on_new_event = Mock(make_awaitable(None))
+        self.hs.get_third_party_event_rules()._on_new_event_callbacks.append(
+            on_new_event
+        )
+
+        # Send a message event to the room and check that the callback is called.
+        self.helper.send(room_id=self.room_id, tok=self.tok)
+        self.assertEqual(on_new_event.call_count, 1)
+
+        # Check that the callback is also called on membership updates.
+        self.helper.invite(
+            room=self.room_id,
+            src=self.user_id,
+            targ=self.invitee,
+            tok=self.tok,
+        )
+
+        self.assertEqual(on_new_event.call_count, 2)
+
+        args, _ = on_new_event.call_args
+
+        self.assertEqual(args[0].membership, Membership.INVITE)
+        self.assertEqual(args[0].state_key, self.invitee)
+
+        # Check that the invitee's membership is correct in the state that's passed down
+        # to the callback.
+        self.assertEqual(
+            args[1][(EventTypes.Member, self.invitee)].membership,
+            Membership.INVITE,
+        )
+
+        # Send an event over federation and check that the callback is also called.
+        self._send_event_over_federation()
+        self.assertEqual(on_new_event.call_count, 3)
+
+    def _send_event_over_federation(self) -> None:
+        """Send a dummy event over federation and check that the request succeeds."""
+        body = {
+            "origin": self.hs.config.server.server_name,
+            "origin_server_ts": self.clock.time_msec(),
+            "pdus": [
+                {
+                    "sender": self.user_id,
+                    "type": EventTypes.Message,
+                    "state_key": "",
+                    "content": {"body": "hello world", "msgtype": "m.text"},
+                    "room_id": self.room_id,
+                    "depth": 0,
+                    "origin_server_ts": self.clock.time_msec(),
+                    "prev_events": [],
+                    "auth_events": [],
+                    "signatures": {},
+                    "unsigned": {},
+                }
+            ],
+        }
+
+        channel = self.make_request(
+            method="PUT",
+            path="/_matrix/federation/v1/send/1",
+            content=body,
+            federation_auth_origin=self.hs.config.server.server_name.encode("utf8"),
+        )
+
+        self.assertEqual(channel.code, 200, channel.result)
+
     def _update_power_levels(self, event_default: int = 0):
         """Updates the room's power levels.
 
diff --git a/tests/rest/client/utils.py b/tests/rest/client/utils.py
index 71fa87ce92..ec0979850b 100644
--- a/tests/rest/client/utils.py
+++ b/tests/rest/client/utils.py
@@ -120,6 +120,35 @@ class RestHelper:
             expect_code=expect_code,
         )
 
+    def knock(self, room=None, user=None, reason=None, expect_code=200, tok=None):
+        temp_id = self.auth_user_id
+        self.auth_user_id = user
+        path = "/knock/%s" % room
+        if tok:
+            path = path + "?access_token=%s" % tok
+
+        data = {}
+        if reason:
+            data["reason"] = reason
+
+        channel = make_request(
+            self.hs.get_reactor(),
+            self.site,
+            "POST",
+            path,
+            json.dumps(data).encode("utf8"),
+        )
+
+        assert (
+            int(channel.result["code"]) == expect_code
+        ), "Expected: %d, got: %d, resp: %r" % (
+            expect_code,
+            int(channel.result["code"]),
+            channel.result["body"],
+        )
+
+        self.auth_user_id = temp_id
+
     def leave(self, room=None, user=None, expect_code=200, tok=None):
         self.change_membership(
             room=room,
diff --git a/tests/rest/media/v1/test_media_storage.py b/tests/rest/media/v1/test_media_storage.py
index 4ae00755c9..4cf1ed5ddf 100644
--- a/tests/rest/media/v1/test_media_storage.py
+++ b/tests/rest/media/v1/test_media_storage.py
@@ -248,7 +248,7 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         self.media_id = "example.com/12345"
 
-    def _req(self, content_disposition):
+    def _req(self, content_disposition, include_content_type=True):
 
         channel = make_request(
             self.reactor,
@@ -271,8 +271,11 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         headers = {
             b"Content-Length": [b"%d" % (len(self.test_image.data))],
-            b"Content-Type": [self.test_image.content_type],
         }
+
+        if include_content_type:
+            headers[b"Content-Type"] = [self.test_image.content_type]
+
         if content_disposition:
             headers[b"Content-Disposition"] = [content_disposition]
 
@@ -285,6 +288,17 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         return channel
 
+    def test_handle_missing_content_type(self):
+        channel = self._req(
+            b"inline; filename=out" + self.test_image.extension,
+            include_content_type=False,
+        )
+        headers = channel.headers
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            headers.getRawHeaders(b"Content-Type"), [b"application/octet-stream"]
+        )
+
     def test_disposition_filename_ascii(self):
         """
         If the filename is filename=<ascii> then Synapse will decode it as an
diff --git a/tests/rest/test_well_known.py b/tests/rest/test_well_known.py
index b2c0279ba0..118aa93a32 100644
--- a/tests/rest/test_well_known.py
+++ b/tests/rest/test_well_known.py
@@ -11,17 +11,19 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from twisted.web.resource import Resource
 
-
-from synapse.rest.well_known import WellKnownResource
+from synapse.rest.well_known import well_known_resource
 
 from tests import unittest
 
 
 class WellKnownTests(unittest.HomeserverTestCase):
     def create_test_resource(self):
-        # replace the JsonResource with a WellKnownResource
-        return WellKnownResource(self.hs)
+        # replace the JsonResource with a Resource wrapping the WellKnownResource
+        res = Resource()
+        res.putChild(b".well-known", well_known_resource(self.hs))
+        return res
 
     @unittest.override_config(
         {
@@ -29,7 +31,7 @@ class WellKnownTests(unittest.HomeserverTestCase):
             "default_identity_server": "https://testis",
         }
     )
-    def test_well_known(self):
+    def test_client_well_known(self):
         channel = self.make_request(
             "GET", "/.well-known/matrix/client", shorthand=False
         )
@@ -48,9 +50,27 @@ class WellKnownTests(unittest.HomeserverTestCase):
             "public_baseurl": None,
         }
     )
-    def test_well_known_no_public_baseurl(self):
+    def test_client_well_known_no_public_baseurl(self):
         channel = self.make_request(
             "GET", "/.well-known/matrix/client", shorthand=False
         )
 
         self.assertEqual(channel.code, 404)
+
+    @unittest.override_config({"serve_server_wellknown": True})
+    def test_server_well_known(self):
+        channel = self.make_request(
+            "GET", "/.well-known/matrix/server", shorthand=False
+        )
+
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            channel.json_body,
+            {"m.server": "test:443"},
+        )
+
+    def test_server_well_known_disabled(self):
+        channel = self.make_request(
+            "GET", "/.well-known/matrix/server", shorthand=False
+        )
+        self.assertEqual(channel.code, 404)
diff --git a/tests/storage/databases/main/test_deviceinbox.py b/tests/storage/databases/main/test_deviceinbox.py
new file mode 100644
index 0000000000..4b67bd15b7
--- /dev/null
+++ b/tests/storage/databases/main/test_deviceinbox.py
@@ -0,0 +1,164 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the 'License');
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an 'AS IS' BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.rest import admin
+from synapse.rest.client import devices
+
+from tests.unittest import HomeserverTestCase
+
+
+class DeviceInboxBackgroundUpdateStoreTestCase(HomeserverTestCase):
+
+    servlets = [
+        admin.register_servlets,
+        devices.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.store = hs.get_datastore()
+        self.user_id = self.register_user("foo", "pass")
+
+    def test_background_remove_deleted_devices_from_device_inbox(self):
+        """Test that the background task to delete old device_inboxes works properly."""
+
+        # create a valid device
+        self.get_success(
+            self.store.store_device(self.user_id, "cur_device", "display_name")
+        )
+
+        # Add device_inbox to devices
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "device_inbox",
+                {
+                    "user_id": self.user_id,
+                    "device_id": "cur_device",
+                    "stream_id": 1,
+                    "message_json": "{}",
+                },
+            )
+        )
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "device_inbox",
+                {
+                    "user_id": self.user_id,
+                    "device_id": "old_device",
+                    "stream_id": 2,
+                    "message_json": "{}",
+                },
+            )
+        )
+
+        # Insert and run the background update.
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "remove_deleted_devices_from_device_inbox",
+                    "progress_json": "{}",
+                },
+            )
+        )
+
+        # ... and tell the DataStore that it hasn't finished all updates yet
+        self.store.db_pool.updates._all_done = False
+
+        self.wait_for_background_updates()
+
+        # Make sure the background task deleted old device_inbox
+        res = self.get_success(
+            self.store.db_pool.simple_select_onecol(
+                table="device_inbox",
+                keyvalues={},
+                retcol="device_id",
+                desc="get_device_id_from_device_inbox",
+            )
+        )
+        self.assertEqual(1, len(res))
+        self.assertEqual(res[0], "cur_device")
+
+    def test_background_remove_hidden_devices_from_device_inbox(self):
+        """Test that the background task to delete hidden devices
+        from device_inboxes works properly."""
+
+        # create a valid device
+        self.get_success(
+            self.store.store_device(self.user_id, "cur_device", "display_name")
+        )
+
+        # create a hidden device
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "devices",
+                values={
+                    "user_id": self.user_id,
+                    "device_id": "hidden_device",
+                    "display_name": "hidden_display_name",
+                    "hidden": True,
+                },
+            )
+        )
+
+        # Add device_inbox to devices
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "device_inbox",
+                {
+                    "user_id": self.user_id,
+                    "device_id": "cur_device",
+                    "stream_id": 1,
+                    "message_json": "{}",
+                },
+            )
+        )
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "device_inbox",
+                {
+                    "user_id": self.user_id,
+                    "device_id": "hidden_device",
+                    "stream_id": 2,
+                    "message_json": "{}",
+                },
+            )
+        )
+
+        # Insert and run the background update.
+        self.get_success(
+            self.store.db_pool.simple_insert(
+                "background_updates",
+                {
+                    "update_name": "remove_hidden_devices_from_device_inbox",
+                    "progress_json": "{}",
+                },
+            )
+        )
+
+        # ... and tell the DataStore that it hasn't finished all updates yet
+        self.store.db_pool.updates._all_done = False
+
+        self.wait_for_background_updates()
+
+        # Make sure the background task deleted hidden devices from device_inbox
+        res = self.get_success(
+            self.store.db_pool.simple_select_onecol(
+                table="device_inbox",
+                keyvalues={},
+                retcol="device_id",
+                desc="get_device_id_from_device_inbox",
+            )
+        )
+        self.assertEqual(1, len(res))
+        self.assertEqual(res[0], "cur_device")
diff --git a/tests/storage/test_client_ips.py b/tests/storage/test_client_ips.py
index 0e4013ebea..c8ac67e35b 100644
--- a/tests/storage/test_client_ips.py
+++ b/tests/storage/test_client_ips.py
@@ -20,6 +20,7 @@ from parameterized import parameterized
 import synapse.rest.admin
 from synapse.http.site import XForwardedForRequest
 from synapse.rest.client import login
+from synapse.storage.databases.main.client_ips import LAST_SEEN_GRANULARITY
 from synapse.types import UserID
 
 from tests import unittest
@@ -171,6 +172,27 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
         if after_persisting:
             # Trigger the storage loop
             self.reactor.advance(10)
+        else:
+            # Check that the new IP and user agent has not been stored yet
+            db_result = self.get_success(
+                self.store.db_pool.simple_select_list(
+                    table="devices",
+                    keyvalues={},
+                    retcols=("user_id", "ip", "user_agent", "device_id", "last_seen"),
+                ),
+            )
+            self.assertEqual(
+                db_result,
+                [
+                    {
+                        "user_id": user_id,
+                        "device_id": device_id,
+                        "ip": None,
+                        "user_agent": None,
+                        "last_seen": None,
+                    },
+                ],
+            )
 
         result = self.get_success(
             self.store.get_last_client_ip_by_device(user_id, device_id)
@@ -189,6 +211,104 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
             },
         )
 
+    def test_get_last_client_ip_by_device_combined_data(self):
+        """Test that `get_last_client_ip_by_device` combines persisted and unpersisted
+        data together correctly
+        """
+        self.reactor.advance(12345678)
+
+        user_id = "@user:id"
+        device_id_1 = "MY_DEVICE_1"
+        device_id_2 = "MY_DEVICE_2"
+
+        # Insert user IPs
+        self.get_success(
+            self.store.store_device(
+                user_id,
+                device_id_1,
+                "display name",
+            )
+        )
+        self.get_success(
+            self.store.store_device(
+                user_id,
+                device_id_2,
+                "display name",
+            )
+        )
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token_1", "ip_1", "user_agent_1", device_id_1
+            )
+        )
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token_2", "ip_2", "user_agent_2", device_id_2
+            )
+        )
+
+        # Trigger the storage loop and wait for the rate limiting period to be over
+        self.reactor.advance(10 + LAST_SEEN_GRANULARITY / 1000)
+
+        # Update the user agent for the second device, without running the storage loop
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token_2", "ip_2", "user_agent_3", device_id_2
+            )
+        )
+
+        # Check that the new IP and user agent has not been stored yet
+        db_result = self.get_success(
+            self.store.db_pool.simple_select_list(
+                table="devices",
+                keyvalues={},
+                retcols=("user_id", "ip", "user_agent", "device_id", "last_seen"),
+            ),
+        )
+        self.assertCountEqual(
+            db_result,
+            [
+                {
+                    "user_id": user_id,
+                    "device_id": device_id_1,
+                    "ip": "ip_1",
+                    "user_agent": "user_agent_1",
+                    "last_seen": 12345678000,
+                },
+                {
+                    "user_id": user_id,
+                    "device_id": device_id_2,
+                    "ip": "ip_2",
+                    "user_agent": "user_agent_2",
+                    "last_seen": 12345678000,
+                },
+            ],
+        )
+
+        # Check that data from the database and memory are combined together correctly
+        result = self.get_success(
+            self.store.get_last_client_ip_by_device(user_id, None)
+        )
+        self.assertEqual(
+            result,
+            {
+                (user_id, device_id_1): {
+                    "user_id": user_id,
+                    "device_id": device_id_1,
+                    "ip": "ip_1",
+                    "user_agent": "user_agent_1",
+                    "last_seen": 12345678000,
+                },
+                (user_id, device_id_2): {
+                    "user_id": user_id,
+                    "device_id": device_id_2,
+                    "ip": "ip_2",
+                    "user_agent": "user_agent_3",
+                    "last_seen": 12345688000 + LAST_SEEN_GRANULARITY,
+                },
+            },
+        )
+
     @parameterized.expand([(False,), (True,)])
     def test_get_user_ip_and_agents(self, after_persisting: bool):
         """Test `get_user_ip_and_agents` for persisted and unpersisted data"""
@@ -207,6 +327,16 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
         if after_persisting:
             # Trigger the storage loop
             self.reactor.advance(10)
+        else:
+            # Check that the new IP and user agent has not been stored yet
+            db_result = self.get_success(
+                self.store.db_pool.simple_select_list(
+                    table="user_ips",
+                    keyvalues={},
+                    retcols=("access_token", "ip", "user_agent", "last_seen"),
+                ),
+            )
+            self.assertEqual(db_result, [])
 
         self.assertEqual(
             self.get_success(self.store.get_user_ip_and_agents(user)),
@@ -220,6 +350,82 @@ class ClientIpStoreTestCase(unittest.HomeserverTestCase):
             ],
         )
 
+    def test_get_user_ip_and_agents_combined_data(self):
+        """Test that `get_user_ip_and_agents` combines persisted and unpersisted data
+        together correctly
+        """
+        self.reactor.advance(12345678)
+
+        user_id = "@user:id"
+        user = UserID.from_string(user_id)
+
+        # Insert user IPs
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token", "ip_1", "user_agent_1", "MY_DEVICE_1"
+            )
+        )
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token", "ip_2", "user_agent_2", "MY_DEVICE_2"
+            )
+        )
+
+        # Trigger the storage loop and wait for the rate limiting period to be over
+        self.reactor.advance(10 + LAST_SEEN_GRANULARITY / 1000)
+
+        # Update the user agent for the second device, without running the storage loop
+        self.get_success(
+            self.store.insert_client_ip(
+                user_id, "access_token", "ip_2", "user_agent_3", "MY_DEVICE_2"
+            )
+        )
+
+        # Check that the new IP and user agent has not been stored yet
+        db_result = self.get_success(
+            self.store.db_pool.simple_select_list(
+                table="user_ips",
+                keyvalues={},
+                retcols=("access_token", "ip", "user_agent", "last_seen"),
+            ),
+        )
+        self.assertEqual(
+            db_result,
+            [
+                {
+                    "access_token": "access_token",
+                    "ip": "ip_1",
+                    "user_agent": "user_agent_1",
+                    "last_seen": 12345678000,
+                },
+                {
+                    "access_token": "access_token",
+                    "ip": "ip_2",
+                    "user_agent": "user_agent_2",
+                    "last_seen": 12345678000,
+                },
+            ],
+        )
+
+        # Check that data from the database and memory are combined together correctly
+        self.assertCountEqual(
+            self.get_success(self.store.get_user_ip_and_agents(user)),
+            [
+                {
+                    "access_token": "access_token",
+                    "ip": "ip_1",
+                    "user_agent": "user_agent_1",
+                    "last_seen": 12345678000,
+                },
+                {
+                    "access_token": "access_token",
+                    "ip": "ip_2",
+                    "user_agent": "user_agent_3",
+                    "last_seen": 12345688000 + LAST_SEEN_GRANULARITY,
+                },
+            ],
+        )
+
     @override_config({"limit_usage_by_mau": False, "max_mau_value": 50})
     def test_disabled_monthly_active_user(self):
         user_id = "@user:server"
diff --git a/tests/storage/test_rollback_worker.py b/tests/storage/test_rollback_worker.py
new file mode 100644
index 0000000000..0ce0892165
--- /dev/null
+++ b/tests/storage/test_rollback_worker.py
@@ -0,0 +1,119 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from typing import List
+from unittest import mock
+
+from synapse.app.generic_worker import GenericWorkerServer
+from synapse.storage.database import LoggingDatabaseConnection
+from synapse.storage.prepare_database import PrepareDatabaseException, prepare_database
+from synapse.storage.schema import SCHEMA_VERSION
+
+from tests.unittest import HomeserverTestCase
+
+
+def fake_listdir(filepath: str) -> List[str]:
+    """
+    A fake implementation of os.listdir which we can use to mock out the filesystem.
+
+    Args:
+        filepath: The directory to list files for.
+
+    Returns:
+        A list of files and folders in the directory.
+    """
+    if filepath.endswith("full_schemas"):
+        return [SCHEMA_VERSION]
+
+    return ["99_add_unicorn_to_database.sql"]
+
+
+class WorkerSchemaTests(HomeserverTestCase):
+    def make_homeserver(self, reactor, clock):
+        hs = self.setup_test_homeserver(
+            federation_http_client=None, homeserver_to_use=GenericWorkerServer
+        )
+        return hs
+
+    def default_config(self):
+        conf = super().default_config()
+
+        # Mark this as a worker app.
+        conf["worker_app"] = "yes"
+
+        return conf
+
+    def test_rolling_back(self):
+        """Test that workers can start if the DB is a newer schema version"""
+
+        db_pool = self.hs.get_datastore().db_pool
+        db_conn = LoggingDatabaseConnection(
+            db_pool._db_pool.connect(),
+            db_pool.engine,
+            "tests",
+        )
+
+        cur = db_conn.cursor()
+        cur.execute("UPDATE schema_version SET version = ?", (SCHEMA_VERSION + 1,))
+
+        db_conn.commit()
+
+        prepare_database(db_conn, db_pool.engine, self.hs.config)
+
+    def test_not_upgraded_old_schema_version(self):
+        """Test that workers don't start if the DB has an older schema version"""
+        db_pool = self.hs.get_datastore().db_pool
+        db_conn = LoggingDatabaseConnection(
+            db_pool._db_pool.connect(),
+            db_pool.engine,
+            "tests",
+        )
+
+        cur = db_conn.cursor()
+        cur.execute("UPDATE schema_version SET version = ?", (SCHEMA_VERSION - 1,))
+
+        db_conn.commit()
+
+        with self.assertRaises(PrepareDatabaseException):
+            prepare_database(db_conn, db_pool.engine, self.hs.config)
+
+    def test_not_upgraded_current_schema_version_with_outstanding_deltas(self):
+        """
+        Test that workers don't start if the DB is on the current schema version,
+        but there are still outstanding delta migrations to run.
+        """
+        db_pool = self.hs.get_datastore().db_pool
+        db_conn = LoggingDatabaseConnection(
+            db_pool._db_pool.connect(),
+            db_pool.engine,
+            "tests",
+        )
+
+        # Set the schema version of the database to the current version
+        cur = db_conn.cursor()
+        cur.execute("UPDATE schema_version SET version = ?", (SCHEMA_VERSION,))
+
+        db_conn.commit()
+
+        # Path `os.listdir` here to make synapse think that there is a migration
+        # file ready to be run.
+        # Note that we can't patch this function for the whole method, else Synapse
+        # will try to find the file when building the database initially.
+        with mock.patch("os.listdir", mock.Mock(side_effect=fake_listdir)):
+            with self.assertRaises(PrepareDatabaseException):
+                # Synapse should think that there is an outstanding migration file due to
+                # patching 'os.listdir' in the function decorator.
+                #
+                # We expect Synapse to raise an exception to indicate the master process
+                # needs to apply this migration file.
+                prepare_database(db_conn, db_pool.engine, self.hs.config)
diff --git a/tests/util/caches/test_deferred_cache.py b/tests/util/caches/test_deferred_cache.py
index 54a88a8325..c613ce3f10 100644
--- a/tests/util/caches/test_deferred_cache.py
+++ b/tests/util/caches/test_deferred_cache.py
@@ -47,9 +47,7 @@ class DeferredCacheTestCase(TestCase):
             self.assertTrue(set_d.called)
             return r
 
-        # TODO: Actually ObservableDeferred *doesn't* run its tests in order on py3.8.
-        #   maybe we should fix that?
-        # get_d.addCallback(check1)
+        get_d.addCallback(check1)
 
         # now fire off all the deferreds
         origin_d.callback(99)
diff --git a/tests/util/caches/test_descriptors.py b/tests/util/caches/test_descriptors.py
index 39947a166b..ced3efd93f 100644
--- a/tests/util/caches/test_descriptors.py
+++ b/tests/util/caches/test_descriptors.py
@@ -17,6 +17,7 @@ from typing import Set
 from unittest import mock
 
 from twisted.internet import defer, reactor
+from twisted.internet.defer import Deferred
 
 from synapse.api.errors import SynapseError
 from synapse.logging.context import (
@@ -703,6 +704,48 @@ class CachedListDescriptorTestCase(unittest.TestCase):
             obj.mock.assert_called_once_with((40,), 2)
             self.assertEqual(r, {10: "fish", 40: "gravy"})
 
+    def test_concurrent_lookups(self):
+        """All concurrent lookups should get the same result"""
+
+        class Cls:
+            def __init__(self):
+                self.mock = mock.Mock()
+
+            @descriptors.cached()
+            def fn(self, arg1):
+                pass
+
+            @descriptors.cachedList("fn", "args1")
+            def list_fn(self, args1) -> "Deferred[dict]":
+                return self.mock(args1)
+
+        obj = Cls()
+        deferred_result = Deferred()
+        obj.mock.return_value = deferred_result
+
+        # start off several concurrent lookups of the same key
+        d1 = obj.list_fn([10])
+        d2 = obj.list_fn([10])
+        d3 = obj.list_fn([10])
+
+        # the mock should have been called exactly once
+        obj.mock.assert_called_once_with((10,))
+        obj.mock.reset_mock()
+
+        # ... and none of the calls should yet be complete
+        self.assertFalse(d1.called)
+        self.assertFalse(d2.called)
+        self.assertFalse(d3.called)
+
+        # complete the lookup. @cachedList functions need to complete with a map
+        # of input->result
+        deferred_result.callback({10: "peas"})
+
+        # ... which should give the right result to all the callers
+        self.assertEqual(self.successResultOf(d1), {10: "peas"})
+        self.assertEqual(self.successResultOf(d2), {10: "peas"})
+        self.assertEqual(self.successResultOf(d3), {10: "peas"})
+
     @defer.inlineCallbacks
     def test_invalidate(self):
         """Make sure that invalidation callbacks are called."""
diff --git a/tests/util/test_async_utils.py b/tests/util/test_async_helpers.py
index 069f875962..ab89cab812 100644
--- a/tests/util/test_async_utils.py
+++ b/tests/util/test_async_helpers.py
@@ -21,11 +21,78 @@ from synapse.logging.context import (
     PreserveLoggingContext,
     current_context,
 )
-from synapse.util.async_helpers import timeout_deferred
+from synapse.util.async_helpers import ObservableDeferred, timeout_deferred
 
 from tests.unittest import TestCase
 
 
+class ObservableDeferredTest(TestCase):
+    def test_succeed(self):
+        origin_d = Deferred()
+        observable = ObservableDeferred(origin_d)
+
+        observer1 = observable.observe()
+        observer2 = observable.observe()
+
+        self.assertFalse(observer1.called)
+        self.assertFalse(observer2.called)
+
+        # check the first observer is called first
+        def check_called_first(res):
+            self.assertFalse(observer2.called)
+            return res
+
+        observer1.addBoth(check_called_first)
+
+        # store the results
+        results = [None, None]
+
+        def check_val(res, idx):
+            results[idx] = res
+            return res
+
+        observer1.addCallback(check_val, 0)
+        observer2.addCallback(check_val, 1)
+
+        origin_d.callback(123)
+        self.assertEqual(results[0], 123, "observer 1 callback result")
+        self.assertEqual(results[1], 123, "observer 2 callback result")
+
+    def test_failure(self):
+        origin_d = Deferred()
+        observable = ObservableDeferred(origin_d, consumeErrors=True)
+
+        observer1 = observable.observe()
+        observer2 = observable.observe()
+
+        self.assertFalse(observer1.called)
+        self.assertFalse(observer2.called)
+
+        # check the first observer is called first
+        def check_called_first(res):
+            self.assertFalse(observer2.called)
+            return res
+
+        observer1.addBoth(check_called_first)
+
+        # store the results
+        results = [None, None]
+
+        def check_val(res, idx):
+            results[idx] = res
+            return None
+
+        observer1.addErrback(check_val, 0)
+        observer2.addErrback(check_val, 1)
+
+        try:
+            raise Exception("gah!")
+        except Exception as e:
+            origin_d.errback(e)
+        self.assertEqual(str(results[0].value), "gah!", "observer 1 errback result")
+        self.assertEqual(str(results[1].value), "gah!", "observer 2 errback result")
+
+
 class TimeoutDeferredTest(TestCase):
     def setUp(self):
         self.clock = Clock()