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-rw-r--r--synapse/api/auth.py4
-rw-r--r--synapse/config/jwt_config.py2
-rw-r--r--synapse/config/logger.py2
-rw-r--r--synapse/config/registration.py2
-rw-r--r--synapse/config/room_directory.py2
-rw-r--r--synapse/config/tracer.py2
-rw-r--r--synapse/crypto/context_factory.py2
-rw-r--r--synapse/events/__init__.py2
-rw-r--r--synapse/events/utils.py2
-rw-r--r--synapse/groups/attestations.py2
-rw-r--r--synapse/groups/groups_server.py4
-rw-r--r--synapse/handlers/admin.py4
-rw-r--r--synapse/handlers/appservice.py52
-rw-r--r--synapse/handlers/auth.py6
-rw-r--r--synapse/handlers/cas_handler.py4
-rw-r--r--synapse/handlers/federation.py14
-rw-r--r--synapse/handlers/groups_local.py9
-rw-r--r--synapse/handlers/message.py2
-rw-r--r--synapse/handlers/oidc_handler.py10
-rw-r--r--synapse/handlers/presence.py4
-rw-r--r--synapse/handlers/profile.py9
-rw-r--r--synapse/handlers/room.py2
-rw-r--r--synapse/handlers/saml_handler.py4
-rw-r--r--synapse/handlers/search.py2
-rw-r--r--synapse/handlers/state_deltas.py2
-rw-r--r--synapse/handlers/sync.py4
-rw-r--r--synapse/handlers/typing.py2
-rw-r--r--synapse/handlers/user_directory.py2
-rw-r--r--synapse/http/federation/well_known_resolver.py2
-rw-r--r--synapse/http/matrixfederationclient.py6
-rw-r--r--synapse/http/request_metrics.py2
-rw-r--r--synapse/http/server.py6
-rw-r--r--synapse/http/servlet.py3
-rw-r--r--synapse/http/site.py20
-rw-r--r--synapse/logging/opentracing.py10
-rw-r--r--synapse/metrics/background_process_metrics.py14
-rw-r--r--synapse/notifier.py36
-rw-r--r--synapse/push/baserules.py2
-rw-r--r--synapse/push/bulk_push_rule_evaluator.py4
-rw-r--r--synapse/push/mailer.py41
-rw-r--r--synapse/push/pusherpool.py18
-rw-r--r--synapse/replication/tcp/redis.py4
-rw-r--r--synapse/rest/admin/devices.py2
-rw-r--r--synapse/rest/client/v1/events.py3
-rw-r--r--synapse/rest/client/v1/login.py3
-rw-r--r--synapse/rest/client/v1/logout.py6
-rw-r--r--synapse/rest/client/v1/presence.py3
-rw-r--r--synapse/rest/client/v1/profile.py6
-rw-r--r--synapse/rest/client/v1/push_rule.py3
-rw-r--r--synapse/rest/client/v1/pusher.py9
-rw-r--r--synapse/rest/client/v1/room.py17
-rw-r--r--synapse/rest/client/v1/voip.py3
-rw-r--r--synapse/rest/client/v2_alpha/account.py3
-rw-r--r--synapse/rest/client/v2_alpha/auth.py3
-rw-r--r--synapse/rest/client/v2_alpha/register.py3
-rw-r--r--synapse/server_notices/consent_server_notices.py2
-rw-r--r--synapse/state/__init__.py2
-rw-r--r--synapse/state/v1.py2
-rw-r--r--synapse/state/v2.py2
-rw-r--r--synapse/static/client/login/js/login.js2
-rw-r--r--synapse/storage/databases/main/__init__.py1
-rw-r--r--synapse/storage/databases/main/registration.py156
62 files changed, 284 insertions, 273 deletions
diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index bff87fabde..526cb58c5f 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -184,9 +184,7 @@ class Auth:
         """
         try:
             ip_addr = self.hs.get_ip_from_request(request)
-            user_agent = request.requestHeaders.getRawHeaders(
-                b"User-Agent", default=[b""]
-            )[0].decode("ascii", "surrogateescape")
+            user_agent = request.get_user_agent("")
 
             access_token = self.get_access_token_from_request(request)
 
diff --git a/synapse/config/jwt_config.py b/synapse/config/jwt_config.py
index 3252ad9e7f..f30330abb6 100644
--- a/synapse/config/jwt_config.py
+++ b/synapse/config/jwt_config.py
@@ -63,7 +63,7 @@ class JWTConfig(Config):
         # and issued at ("iat") claims are validated if present.
         #
         # Note that this is a non-standard login type and client support is
-        # expected to be non-existant.
+        # expected to be non-existent.
         #
         # See https://github.com/matrix-org/synapse/blob/master/docs/jwt.md.
         #
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index 13d6f6a3ea..6b7be28aee 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -105,7 +105,7 @@ root:
     # then write them to a file.
     #
     # Replace "buffer" with "console" to log to stderr instead. (Note that you'll
-    # also need to update the configuation for the `twisted` logger above, in
+    # also need to update the configuration for the `twisted` logger above, in
     # this case.)
     #
     handlers: [buffer]
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index d7e3690a32..b0a77a2e43 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -143,7 +143,7 @@ class RegistrationConfig(Config):
             RoomCreationPreset.TRUSTED_PRIVATE_CHAT,
         }
 
-        # Pull the creater/inviter from the configuration, this gets used to
+        # Pull the creator/inviter from the configuration, this gets used to
         # send invites for invite-only rooms.
         mxid_localpart = config.get("auto_join_mxid_localpart")
         self.auto_join_user_id = None
diff --git a/synapse/config/room_directory.py b/synapse/config/room_directory.py
index 6de1f9d103..92e1b67528 100644
--- a/synapse/config/room_directory.py
+++ b/synapse/config/room_directory.py
@@ -99,7 +99,7 @@ class RoomDirectoryConfig(Config):
         #
         # Options for the rules include:
         #
-        #   user_id: Matches agaisnt the creator of the alias
+        #   user_id: Matches against the creator of the alias
         #   room_id: Matches against the room ID being published
         #   alias: Matches against any current local or canonical aliases
         #            associated with the room
diff --git a/synapse/config/tracer.py b/synapse/config/tracer.py
index 8be1346113..0c1a854f09 100644
--- a/synapse/config/tracer.py
+++ b/synapse/config/tracer.py
@@ -67,7 +67,7 @@ class TracerConfig(Config):
             # This is a list of regexes which are matched against the server_name of the
             # homeserver.
             #
-            # By defult, it is empty, so no servers are matched.
+            # By default, it is empty, so no servers are matched.
             #
             #homeserver_whitelist:
             #  - ".*"
diff --git a/synapse/crypto/context_factory.py b/synapse/crypto/context_factory.py
index 79668a402e..57fd426e87 100644
--- a/synapse/crypto/context_factory.py
+++ b/synapse/crypto/context_factory.py
@@ -149,7 +149,7 @@ class FederationPolicyForHTTPS:
         return SSLClientConnectionCreator(host, ssl_context, should_verify)
 
     def creatorForNetloc(self, hostname, port):
-        """Implements the IPolicyForHTTPS interace so that this can be passed
+        """Implements the IPolicyForHTTPS interface so that this can be passed
         directly to agents.
         """
         return self.get_options(hostname)
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 65df62107f..e203206865 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -59,7 +59,7 @@ class DictProperty:
             #
             # To exclude the KeyError from the traceback, we explicitly
             # 'raise from e1.__context__' (which is better than 'raise from None',
-            # becuase that would omit any *earlier* exceptions).
+            # because that would omit any *earlier* exceptions).
             #
             raise AttributeError(
                 "'%s' has no '%s' property" % (type(instance), self.key)
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 355cbe05f1..14f7f1156f 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -180,7 +180,7 @@ def only_fields(dictionary, fields):
     in 'fields'.
 
     If there are no event fields specified then all fields are included.
-    The entries may include '.' charaters to indicate sub-fields.
+    The entries may include '.' characters to indicate sub-fields.
     So ['content.body'] will include the 'body' field of the 'content' object.
     A literal '.' character in a field name may be escaped using a '\'.
 
diff --git a/synapse/groups/attestations.py b/synapse/groups/attestations.py
index a86b3debc5..41cf07cc88 100644
--- a/synapse/groups/attestations.py
+++ b/synapse/groups/attestations.py
@@ -22,7 +22,7 @@ attestations have a validity period so need to be periodically renewed.
 If a user leaves (or gets kicked out of) a group, either side can still use
 their attestation to "prove" their membership, until the attestation expires.
 Therefore attestations shouldn't be relied on to prove membership in important
-cases, but can for less important situtations, e.g. showing a users membership
+cases, but can for less important situations, e.g. showing a users membership
 of groups on their profile, showing flairs, etc.
 
 An attestation is a signed blob of json that looks like:
diff --git a/synapse/groups/groups_server.py b/synapse/groups/groups_server.py
index e5f85b472d..0d042cbfac 100644
--- a/synapse/groups/groups_server.py
+++ b/synapse/groups/groups_server.py
@@ -113,7 +113,7 @@ class GroupsServerWorkerHandler:
             entry = await self.room_list_handler.generate_room_entry(
                 room_id, len(joined_users), with_alias=False, allow_private=True
             )
-            entry = dict(entry)  # so we don't change whats cached
+            entry = dict(entry)  # so we don't change what's cached
             entry.pop("room_id", None)
 
             room_entry["profile"] = entry
@@ -550,7 +550,7 @@ class GroupsServerHandler(GroupsServerWorkerHandler):
                 group_id, room_id, is_public=is_public
             )
         else:
-            raise SynapseError(400, "Uknown config option")
+            raise SynapseError(400, "Unknown config option")
 
         return {}
 
diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index 1ce2091b46..a703944543 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -88,7 +88,7 @@ class AdminHandler(BaseHandler):
 
         # We only try and fetch events for rooms the user has been in. If
         # they've been e.g. invited to a room without joining then we handle
-        # those seperately.
+        # those separately.
         rooms_user_has_been_in = await self.store.get_rooms_user_has_been_in(user_id)
 
         for index, room in enumerate(rooms):
@@ -226,7 +226,7 @@ class ExfiltrationWriter:
         """
 
     def finished(self):
-        """Called when all data has succesfully been exported and written.
+        """Called when all data has successfully been exported and written.
 
         This functions return value is passed to the caller of
         `export_user_data`.
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 64dea23fc5..3ed29a2c16 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 import logging
-from typing import Dict, List, Optional
+from typing import Dict, List, Optional, Union
 
 from prometheus_client import Counter
 
@@ -30,7 +30,10 @@ from synapse.metrics import (
     event_processing_loop_counter,
     event_processing_loop_room_count,
 )
-from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.metrics.background_process_metrics import (
+    run_as_background_process,
+    wrap_as_background_process,
+)
 from synapse.types import Collection, JsonDict, RoomStreamToken, UserID
 from synapse.util.metrics import Measure
 
@@ -53,7 +56,7 @@ class ApplicationServicesHandler:
         self.current_max = 0
         self.is_processing = False
 
-    async def notify_interested_services(self, max_token: RoomStreamToken):
+    def notify_interested_services(self, max_token: RoomStreamToken):
         """Notifies (pushes) all application services interested in this event.
 
         Pushing is done asynchronously, so this method won't block for any
@@ -72,6 +75,12 @@ class ApplicationServicesHandler:
         if self.is_processing:
             return
 
+        # We only start a new background process if necessary rather than
+        # optimistically (to cut down on overhead).
+        self._notify_interested_services(max_token)
+
+    @wrap_as_background_process("notify_interested_services")
+    async def _notify_interested_services(self, max_token: RoomStreamToken):
         with Measure(self.clock, "notify_interested_services"):
             self.is_processing = True
             try:
@@ -166,8 +175,11 @@ class ApplicationServicesHandler:
             finally:
                 self.is_processing = False
 
-    async def notify_interested_services_ephemeral(
-        self, stream_key: str, new_token: Optional[int], users: Collection[UserID] = [],
+    def notify_interested_services_ephemeral(
+        self,
+        stream_key: str,
+        new_token: Optional[int],
+        users: Collection[Union[str, UserID]] = [],
     ):
         """This is called by the notifier in the background
         when a ephemeral event handled by the homeserver.
@@ -183,13 +195,34 @@ class ApplicationServicesHandler:
             new_token: The latest stream token
             users: The user(s) involved with the event.
         """
+        if not self.notify_appservices:
+            return
+
+        if stream_key not in ("typing_key", "receipt_key", "presence_key"):
+            return
+
         services = [
             service
             for service in self.store.get_app_services()
             if service.supports_ephemeral
         ]
-        if not services or not self.notify_appservices:
+        if not services:
             return
+
+        # We only start a new background process if necessary rather than
+        # optimistically (to cut down on overhead).
+        self._notify_interested_services_ephemeral(
+            services, stream_key, new_token, users
+        )
+
+    @wrap_as_background_process("notify_interested_services_ephemeral")
+    async def _notify_interested_services_ephemeral(
+        self,
+        services: List[ApplicationService],
+        stream_key: str,
+        new_token: Optional[int],
+        users: Collection[Union[str, UserID]],
+    ):
         logger.info("Checking interested services for %s" % (stream_key))
         with Measure(self.clock, "notify_interested_services_ephemeral"):
             for service in services:
@@ -237,14 +270,17 @@ class ApplicationServicesHandler:
         return receipts
 
     async def _handle_presence(
-        self, service: ApplicationService, users: Collection[UserID]
-    ) -> List[JsonDict]:
+        self, service: ApplicationService, users: Collection[Union[str, UserID]]
+    ):
         events = []  # type: List[JsonDict]
         presence_source = self.event_sources.sources["presence"]
         from_key = await self.store.get_type_stream_id_for_appservice(
             service, "presence"
         )
         for user in users:
+            if isinstance(user, str):
+                user = UserID.from_string(user)
+
             interested = await service.is_interested_in_presence(user, self.store)
             if not interested:
                 continue
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 8619fbb982..dd14ab69d7 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -470,9 +470,7 @@ class AuthHandler(BaseHandler):
             # authentication flow.
             await self.store.set_ui_auth_clientdict(sid, clientdict)
 
-        user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
-            0
-        ].decode("ascii", "surrogateescape")
+        user_agent = request.get_user_agent("")
 
         await self.store.add_user_agent_ip_to_ui_auth_session(
             session.session_id, user_agent, clientip
@@ -692,7 +690,7 @@ class AuthHandler(BaseHandler):
         Creates a new access token for the user with the given user ID.
 
         The user is assumed to have been authenticated by some other
-        machanism (e.g. CAS), and the user_id converted to the canonical case.
+        mechanism (e.g. CAS), and the user_id converted to the canonical case.
 
         The device will be recorded in the table if it is not there already.
 
diff --git a/synapse/handlers/cas_handler.py b/synapse/handlers/cas_handler.py
index a4cc4b9a5a..048a3b3c0b 100644
--- a/synapse/handlers/cas_handler.py
+++ b/synapse/handlers/cas_handler.py
@@ -212,9 +212,7 @@ class CasHandler:
         else:
             if not registered_user_id:
                 # Pull out the user-agent and IP from the request.
-                user_agent = request.requestHeaders.getRawHeaders(
-                    b"User-Agent", default=[b""]
-                )[0].decode("ascii", "surrogateescape")
+                user_agent = request.get_user_agent("")
                 ip_address = self.hs.get_ip_from_request(request)
 
                 registered_user_id = await self._registration_handler.register_user(
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index fde8f00531..c386957706 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -112,7 +112,7 @@ class FederationHandler(BaseHandler):
     """Handles events that originated from federation.
         Responsible for:
         a) handling received Pdus before handing them on as Events to the rest
-        of the homeserver (including auth and state conflict resoultion)
+        of the homeserver (including auth and state conflict resolutions)
         b) converting events that were produced by local clients that may need
         to be sent to remote homeservers.
         c) doing the necessary dances to invite remote users and join remote
@@ -477,7 +477,7 @@ class FederationHandler(BaseHandler):
         # ----
         #
         # Update richvdh 2018/09/18: There are a number of problems with timing this
-        # request out agressively on the client side:
+        # request out aggressively on the client side:
         #
         # - it plays badly with the server-side rate-limiter, which starts tarpitting you
         #   if you send too many requests at once, so you end up with the server carefully
@@ -495,13 +495,13 @@ class FederationHandler(BaseHandler):
         #   we'll end up back here for the *next* PDU in the list, which exacerbates the
         #   problem.
         #
-        # - the agressive 10s timeout was introduced to deal with incoming federation
+        # - the aggressive 10s timeout was introduced to deal with incoming federation
         #   requests taking 8 hours to process. It's not entirely clear why that was going
         #   on; certainly there were other issues causing traffic storms which are now
         #   resolved, and I think in any case we may be more sensible about our locking
         #   now. We're *certainly* more sensible about our logging.
         #
-        # All that said: Let's try increasing the timout to 60s and see what happens.
+        # All that said: Let's try increasing the timeout to 60s and see what happens.
 
         try:
             missing_events = await self.federation_client.get_missing_events(
@@ -1120,7 +1120,7 @@ class FederationHandler(BaseHandler):
                     logger.info(str(e))
                     continue
                 except RequestSendFailed as e:
-                    logger.info("Falied to get backfill from %s because %s", dom, e)
+                    logger.info("Failed to get backfill from %s because %s", dom, e)
                     continue
                 except FederationDeniedError as e:
                     logger.info(e)
@@ -1545,7 +1545,7 @@ class FederationHandler(BaseHandler):
         #
         # The reasons we have the destination server rather than the origin
         # server send it are slightly mysterious: the origin server should have
-        # all the neccessary state once it gets the response to the send_join,
+        # all the necessary state once it gets the response to the send_join,
         # so it could send the event itself if it wanted to. It may be that
         # doing it this way reduces failure modes, or avoids certain attacks
         # where a new server selectively tells a subset of the federation that
@@ -1649,7 +1649,7 @@ class FederationHandler(BaseHandler):
         event.internal_metadata.outlier = True
         event.internal_metadata.out_of_band_membership = True
 
-        # Try the host that we succesfully called /make_leave/ on first for
+        # Try the host that we successfully called /make_leave/ on first for
         # the /send_leave/ request.
         host_list = list(target_hosts)
         try:
diff --git a/synapse/handlers/groups_local.py b/synapse/handlers/groups_local.py
index 9684e60fc8..abd8d2af44 100644
--- a/synapse/handlers/groups_local.py
+++ b/synapse/handlers/groups_local.py
@@ -17,7 +17,7 @@
 import logging
 
 from synapse.api.errors import HttpResponseException, RequestSendFailed, SynapseError
-from synapse.types import get_domain_from_id
+from synapse.types import GroupID, get_domain_from_id
 
 logger = logging.getLogger(__name__)
 
@@ -28,6 +28,9 @@ def _create_rerouter(func_name):
     """
 
     async def f(self, group_id, *args, **kwargs):
+        if not GroupID.is_valid(group_id):
+            raise SynapseError(400, "%s was not legal group ID" % (group_id,))
+
         if self.is_mine_id(group_id):
             return await getattr(self.groups_server_handler, func_name)(
                 group_id, *args, **kwargs
@@ -346,7 +349,7 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
                 server_name=get_domain_from_id(group_id),
             )
 
-        # TODO: Check that the group is public and we're being added publically
+        # TODO: Check that the group is public and we're being added publicly
         is_publicised = content.get("publicise", False)
 
         token = await self.store.register_user_group_membership(
@@ -391,7 +394,7 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
                 server_name=get_domain_from_id(group_id),
             )
 
-        # TODO: Check that the group is public and we're being added publically
+        # TODO: Check that the group is public and we're being added publicly
         is_publicised = content.get("publicise", False)
 
         token = await self.store.register_user_group_membership(
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index d6855c60ea..f1b4d35182 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -657,7 +657,7 @@ class EventCreationHandler:
             context: The event context.
 
         Returns:
-            The previous verion of the event is returned, if it is found in the
+            The previous version of the event is returned, if it is found in the
             event context. Otherwise, None is returned.
         """
         prev_state_ids = await context.get_prev_state_ids()
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index 05ac86e697..331d4e7e96 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -217,7 +217,7 @@ class OidcHandler:
 
         This is based on the requested scopes: if the scopes include
         ``openid``, the provider should give use an ID token containing the
-        user informations. If not, we should fetch them using the
+        user information. If not, we should fetch them using the
         ``access_token`` with the ``userinfo_endpoint``.
         """
 
@@ -426,7 +426,7 @@ class OidcHandler:
         return resp
 
     async def _fetch_userinfo(self, token: Token) -> UserInfo:
-        """Fetch user informations from the ``userinfo_endpoint``.
+        """Fetch user information from the ``userinfo_endpoint``.
 
         Args:
             token: the token given by the ``token_endpoint``.
@@ -695,9 +695,7 @@ class OidcHandler:
                 return
 
         # Pull out the user-agent and IP from the request.
-        user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
-            0
-        ].decode("ascii", "surrogateescape")
+        user_agent = request.get_user_agent("")
         ip_address = self.hs.get_ip_from_request(request)
 
         # Call the mapper to register/login the user
@@ -756,7 +754,7 @@ class OidcHandler:
                 Defaults to an hour.
 
         Returns:
-            A signed macaroon token with the session informations.
+            A signed macaroon token with the session information.
         """
         macaroon = pymacaroons.Macaroon(
             location=self._server_name, identifier="key", key=self._macaroon_secret_key,
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index 1000ac95ff..49a00eed9c 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -802,7 +802,7 @@ class PresenceHandler(BasePresenceHandler):
             between the requested tokens due to the limit.
 
             The token returned can be used in a subsequent call to this
-            function to get further updatees.
+            function to get further updates.
 
             The updates are a list of 2-tuples of stream ID and the row data
         """
@@ -977,7 +977,7 @@ def should_notify(old_state, new_state):
             new_state.last_active_ts - old_state.last_active_ts
             > LAST_ACTIVE_GRANULARITY
         ):
-            # Only notify about last active bumps if we're not currently acive
+            # Only notify about last active bumps if we're not currently active
             if not new_state.currently_active:
                 notify_reason_counter.labels("last_active_change_online").inc()
                 return True
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index 92700b589c..3875e53c08 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -98,11 +98,18 @@ class ProfileHandler(BaseHandler):
             except RequestSendFailed as e:
                 raise SynapseError(502, "Failed to fetch profile") from e
             except HttpResponseException as e:
+                if e.code < 500 and e.code != 404:
+                    # Other codes are not allowed in c2s API
+                    logger.info(
+                        "Server replied with wrong response: %s %s", e.code, e.msg
+                    )
+
+                    raise SynapseError(502, "Failed to fetch profile")
                 raise e.to_synapse_error()
 
     async def get_profile_from_cache(self, user_id: str) -> JsonDict:
         """Get the profile information from our local cache. If the user is
-        ours then the profile information will always be corect. Otherwise,
+        ours then the profile information will always be correct. Otherwise,
         it may be out of date/missing.
         """
         target_user = UserID.from_string(user_id)
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index ec300d8877..c5b1f1f1e1 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1268,7 +1268,7 @@ class RoomShutdownHandler:
             )
 
             # We now wait for the create room to come back in via replication so
-            # that we can assume that all the joins/invites have propogated before
+            # that we can assume that all the joins/invites have propagated before
             # we try and auto join below.
             await self._replication.wait_for_stream_position(
                 self.hs.config.worker.events_shard_config.get_instance(new_room_id),
diff --git a/synapse/handlers/saml_handler.py b/synapse/handlers/saml_handler.py
index 285c481a96..fd6c5e9ea8 100644
--- a/synapse/handlers/saml_handler.py
+++ b/synapse/handlers/saml_handler.py
@@ -216,9 +216,7 @@ class SamlHandler:
                 return
 
         # Pull out the user-agent and IP from the request.
-        user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
-            0
-        ].decode("ascii", "surrogateescape")
+        user_agent = request.get_user_agent("")
         ip_address = self.hs.get_ip_from_request(request)
 
         # Call the mapper to register/login the user
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index e9402e6e2e..66f1bbcfc4 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -139,7 +139,7 @@ class SearchHandler(BaseHandler):
             # Filter to apply to results
             filter_dict = room_cat.get("filter", {})
 
-            # What to order results by (impacts whether pagination can be doen)
+            # What to order results by (impacts whether pagination can be done)
             order_by = room_cat.get("order_by", "rank")
 
             # Return the current state of the rooms?
diff --git a/synapse/handlers/state_deltas.py b/synapse/handlers/state_deltas.py
index 7a4ae0727a..fb4f70e8e2 100644
--- a/synapse/handlers/state_deltas.py
+++ b/synapse/handlers/state_deltas.py
@@ -32,7 +32,7 @@ class StateDeltasHandler:
         Returns:
             None if the field in the events either both match `public_value`
             or if neither do, i.e. there has been no change.
-            True if it didnt match `public_value` but now does
+            True if it didn't match `public_value` but now does
             False if it did match `public_value` but now doesn't
         """
         prev_event = None
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index b527724bc4..32e53c2d25 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -754,7 +754,7 @@ class SyncHandler:
         """
         # TODO(mjark) Check if the state events were received by the server
         # after the previous sync, since we need to include those state
-        # updates even if they occured logically before the previous event.
+        # updates even if they occurred logically before the previous event.
         # TODO(mjark) Check for new redactions in the state events.
 
         with Measure(self.clock, "compute_state_delta"):
@@ -1882,7 +1882,7 @@ class SyncHandler:
         # members (as the client otherwise doesn't have enough info to form
         # the name itself).
         if sync_config.filter_collection.lazy_load_members() and (
-            # we recalulate the summary:
+            # we recalculate the summary:
             #   if there are membership changes in the timeline, or
             #   if membership has changed during a gappy sync, or
             #   if this is an initial sync.
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index d3692842e3..8758066c74 100644
--- a/synapse/handlers/typing.py
+++ b/synapse/handlers/typing.py
@@ -371,7 +371,7 @@ class TypingWriterHandler(FollowerTypingHandler):
             between the requested tokens due to the limit.
 
             The token returned can be used in a subsequent call to this
-            function to get further updatees.
+            function to get further updates.
 
             The updates are a list of 2-tuples of stream ID and the row data
         """
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index 79393c8829..afbebfc200 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -31,7 +31,7 @@ class UserDirectoryHandler(StateDeltasHandler):
     N.B.: ASSUMES IT IS THE ONLY THING THAT MODIFIES THE USER DIRECTORY
 
     The user directory is filled with users who this server can see are joined to a
-    world_readable or publically joinable room. We keep a database table up to date
+    world_readable or publicly joinable room. We keep a database table up to date
     by streaming changes of the current state and recalculating whether users should
     be in the directory or not when necessary.
     """
diff --git a/synapse/http/federation/well_known_resolver.py b/synapse/http/federation/well_known_resolver.py
index a306faa267..1cc666fbf6 100644
--- a/synapse/http/federation/well_known_resolver.py
+++ b/synapse/http/federation/well_known_resolver.py
@@ -172,7 +172,7 @@ class WellKnownResolver:
         had_valid_well_known = self._had_valid_well_known_cache.get(server_name, False)
 
         # We do this in two steps to differentiate between possibly transient
-        # errors (e.g. can't connect to host, 503 response) and more permenant
+        # errors (e.g. can't connect to host, 503 response) and more permanent
         # errors (such as getting a 404 response).
         response, body = await self._make_well_known_request(
             server_name, retry=had_valid_well_known
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index c23a4d7c0c..04766ca965 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -587,7 +587,7 @@ class MatrixFederationHttpClient:
         """
         Builds the Authorization headers for a federation request
         Args:
-            destination (bytes|None): The desination homeserver of the request.
+            destination (bytes|None): The destination homeserver of the request.
                 May be None if the destination is an identity server, in which case
                 destination_is must be non-None.
             method (bytes): The HTTP method of the request
@@ -640,7 +640,7 @@ class MatrixFederationHttpClient:
         backoff_on_404=False,
         try_trailing_slash_on_400=False,
     ):
-        """ Sends the specifed json data using PUT
+        """ Sends the specified json data using PUT
 
         Args:
             destination (str): The remote server to send the HTTP request
@@ -729,7 +729,7 @@ class MatrixFederationHttpClient:
         ignore_backoff=False,
         args={},
     ):
-        """ Sends the specifed json data using POST
+        """ Sends the specified json data using POST
 
         Args:
             destination (str): The remote server to send the HTTP request
diff --git a/synapse/http/request_metrics.py b/synapse/http/request_metrics.py
index cd94e789e8..7c5defec82 100644
--- a/synapse/http/request_metrics.py
+++ b/synapse/http/request_metrics.py
@@ -109,7 +109,7 @@ in_flight_requests_db_sched_duration = Counter(
 # The set of all in flight requests, set[RequestMetrics]
 _in_flight_requests = set()
 
-# Protects the _in_flight_requests set from concurrent accesss
+# Protects the _in_flight_requests set from concurrent access
 _in_flight_requests_lock = threading.Lock()
 
 
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 00b98af3d4..65dbd339ac 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -182,7 +182,7 @@ class HttpServer:
         """ Register a callback that gets fired if we receive a http request
         with the given method for a path that matches the given regex.
 
-        If the regex contains groups these gets passed to the calback via
+        If the regex contains groups these gets passed to the callback via
         an unpacked tuple.
 
         Args:
@@ -241,7 +241,7 @@ class _AsyncResource(resource.Resource, metaclass=abc.ABCMeta):
 
     async def _async_render(self, request: Request):
         """Delegates to `_async_render_<METHOD>` methods, or returns a 400 if
-        no appropriate method exists. Can be overriden in sub classes for
+        no appropriate method exists. Can be overridden in sub classes for
         different routing.
         """
         # Treat HEAD requests as GET requests.
@@ -386,7 +386,7 @@ class JsonResource(DirectServeJsonResource):
     async def _async_render(self, request):
         callback, servlet_classname, group_dict = self._get_handler_for_request(request)
 
-        # Make sure we have an appopriate name for this handler in prometheus
+        # Make sure we have an appropriate name for this handler in prometheus
         # (rather than the default of JsonResource).
         request.request_metrics.name = servlet_classname
 
diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index fd90ba7828..b361b7cbaf 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -272,7 +272,6 @@ class RestServlet:
       on_PUT
       on_POST
       on_DELETE
-      on_OPTIONS
 
     Automatically handles turning CodeMessageExceptions thrown by these methods
     into the appropriate HTTP response.
@@ -283,7 +282,7 @@ class RestServlet:
         if hasattr(self, "PATTERNS"):
             patterns = self.PATTERNS
 
-            for method in ("GET", "PUT", "POST", "OPTIONS", "DELETE"):
+            for method in ("GET", "PUT", "POST", "DELETE"):
                 if hasattr(self, "on_%s" % (method,)):
                     servlet_classname = self.__class__.__name__
                     method_handler = getattr(self, "on_%s" % (method,))
diff --git a/synapse/http/site.py b/synapse/http/site.py
index 6e79b47828..ddb1770b09 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -109,8 +109,14 @@ class SynapseRequest(Request):
             method = self.method.decode("ascii")
         return method
 
-    def get_user_agent(self):
-        return self.requestHeaders.getRawHeaders(b"User-Agent", [None])[-1]
+    def get_user_agent(self, default: str) -> str:
+        """Return the last User-Agent header, or the given default.
+        """
+        user_agent = self.requestHeaders.getRawHeaders(b"User-Agent", [None])[-1]
+        if user_agent is None:
+            return default
+
+        return user_agent.decode("ascii", "replace")
 
     def render(self, resrc):
         # this is called once a Resource has been found to serve the request; in our
@@ -161,7 +167,9 @@ class SynapseRequest(Request):
             yield
         except Exception:
             # this should already have been caught, and sent back to the client as a 500.
-            logger.exception("Asynchronous messge handler raised an uncaught exception")
+            logger.exception(
+                "Asynchronous message handler raised an uncaught exception"
+            )
         finally:
             # the request handler has finished its work and either sent the whole response
             # back, or handed over responsibility to a Producer.
@@ -274,11 +282,7 @@ class SynapseRequest(Request):
         # with maximum recursion trying to log errors about
         # the charset problem.
         # c.f. https://github.com/matrix-org/synapse/issues/3471
-        user_agent = self.get_user_agent()
-        if user_agent is not None:
-            user_agent = user_agent.decode("utf-8", "replace")
-        else:
-            user_agent = "-"
+        user_agent = self.get_user_agent("-")
 
         code = str(self.code)
         if not self.finished:
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index e58850faff..ab586c318c 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -317,7 +317,7 @@ def ensure_active_span(message, ret=None):
 
 
 @contextlib.contextmanager
-def _noop_context_manager(*args, **kwargs):
+def noop_context_manager(*args, **kwargs):
     """Does exactly what it says on the tin"""
     yield
 
@@ -413,7 +413,7 @@ def start_active_span(
     """
 
     if opentracing is None:
-        return _noop_context_manager()
+        return noop_context_manager()
 
     return opentracing.tracer.start_active_span(
         operation_name,
@@ -428,7 +428,7 @@ def start_active_span(
 
 def start_active_span_follows_from(operation_name, contexts):
     if opentracing is None:
-        return _noop_context_manager()
+        return noop_context_manager()
 
     references = [opentracing.follows_from(context) for context in contexts]
     scope = start_active_span(operation_name, references=references)
@@ -459,7 +459,7 @@ def start_active_span_from_request(
     # Also, twisted uses byte arrays while opentracing expects strings.
 
     if opentracing is None:
-        return _noop_context_manager()
+        return noop_context_manager()
 
     header_dict = {
         k.decode(): v[0].decode() for k, v in request.requestHeaders.getAllRawHeaders()
@@ -497,7 +497,7 @@ def start_active_span_from_edu(
     """
 
     if opentracing is None:
-        return _noop_context_manager()
+        return noop_context_manager()
 
     carrier = json_decoder.decode(edu_content.get("context", "{}")).get(
         "opentracing", {}
diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index ea5f1c7b62..658f6ecd72 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -24,7 +24,7 @@ from prometheus_client.core import REGISTRY, Counter, Gauge
 from twisted.internet import defer
 
 from synapse.logging.context import LoggingContext, PreserveLoggingContext
-from synapse.logging.opentracing import start_active_span
+from synapse.logging.opentracing import noop_context_manager, start_active_span
 
 if TYPE_CHECKING:
     import resource
@@ -167,7 +167,7 @@ class _BackgroundProcess:
         )
 
 
-def run_as_background_process(desc: str, func, *args, **kwargs):
+def run_as_background_process(desc: str, func, *args, bg_start_span=True, **kwargs):
     """Run the given function in its own logcontext, with resource metrics
 
     This should be used to wrap processes which are fired off to run in the
@@ -181,6 +181,9 @@ def run_as_background_process(desc: str, func, *args, **kwargs):
     Args:
         desc: a description for this background process type
         func: a function, which may return a Deferred or a coroutine
+        bg_start_span: Whether to start an opentracing span. Defaults to True.
+            Should only be disabled for processes that will not log to or tag
+            a span.
         args: positional args for func
         kwargs: keyword args for func
 
@@ -199,7 +202,10 @@ def run_as_background_process(desc: str, func, *args, **kwargs):
         with BackgroundProcessLoggingContext(desc) as context:
             context.request = "%s-%i" % (desc, count)
             try:
-                with start_active_span(desc, tags={"request_id": context.request}):
+                ctx = noop_context_manager()
+                if bg_start_span:
+                    ctx = start_active_span(desc, tags={"request_id": context.request})
+                with ctx:
                     result = func(*args, **kwargs)
 
                     if inspect.isawaitable(result):
@@ -266,7 +272,7 @@ class BackgroundProcessLoggingContext(LoggingContext):
 
         super().__exit__(type, value, traceback)
 
-        # The background process has finished. We explictly remove and manually
+        # The background process has finished. We explicitly remove and manually
         # update the metrics here so that if nothing is scraping metrics the set
         # doesn't infinitely grow.
         with _bg_metrics_lock:
diff --git a/synapse/notifier.py b/synapse/notifier.py
index 2e993411b9..eb56b26f21 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -40,7 +40,6 @@ from synapse.handlers.presence import format_user_presence_state
 from synapse.logging.context import PreserveLoggingContext
 from synapse.logging.utils import log_function
 from synapse.metrics import LaterGauge
-from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.streams.config import PaginationConfig
 from synapse.types import (
     Collection,
@@ -310,44 +309,37 @@ class Notifier:
         """
 
         # poke any interested application service.
-        run_as_background_process(
-            "_notify_app_services", self._notify_app_services, max_room_stream_token
-        )
-
-        run_as_background_process(
-            "_notify_pusher_pool", self._notify_pusher_pool, max_room_stream_token
-        )
+        self._notify_app_services(max_room_stream_token)
+        self._notify_pusher_pool(max_room_stream_token)
 
         if self.federation_sender:
             self.federation_sender.notify_new_events(max_room_stream_token)
 
-    async def _notify_app_services(self, max_room_stream_token: RoomStreamToken):
+    def _notify_app_services(self, max_room_stream_token: RoomStreamToken):
         try:
-            await self.appservice_handler.notify_interested_services(
-                max_room_stream_token
-            )
+            self.appservice_handler.notify_interested_services(max_room_stream_token)
         except Exception:
             logger.exception("Error notifying application services of event")
 
-    async def _notify_app_services_ephemeral(
+    def _notify_app_services_ephemeral(
         self,
         stream_key: str,
         new_token: Union[int, RoomStreamToken],
-        users: Collection[UserID] = [],
+        users: Collection[Union[str, UserID]] = [],
     ):
         try:
             stream_token = None
             if isinstance(new_token, int):
                 stream_token = new_token
-            await self.appservice_handler.notify_interested_services_ephemeral(
+            self.appservice_handler.notify_interested_services_ephemeral(
                 stream_key, stream_token, users
             )
         except Exception:
             logger.exception("Error notifying application services of event")
 
-    async def _notify_pusher_pool(self, max_room_stream_token: RoomStreamToken):
+    def _notify_pusher_pool(self, max_room_stream_token: RoomStreamToken):
         try:
-            await self._pusher_pool.on_new_notifications(max_room_stream_token)
+            self._pusher_pool.on_new_notifications(max_room_stream_token)
         except Exception:
             logger.exception("Error pusher pool of event")
 
@@ -384,16 +376,12 @@ class Notifier:
                 self.notify_replication()
 
                 # Notify appservices
-                run_as_background_process(
-                    "_notify_app_services_ephemeral",
-                    self._notify_app_services_ephemeral,
-                    stream_key,
-                    new_token,
-                    users,
+                self._notify_app_services_ephemeral(
+                    stream_key, new_token, users,
                 )
 
     def on_new_replication_data(self) -> None:
-        """Used to inform replication listeners that something has happend
+        """Used to inform replication listeners that something has happened
         without waking up any of the normal user event streams"""
         self.notify_replication()
 
diff --git a/synapse/push/baserules.py b/synapse/push/baserules.py
index 8047873ff1..2858b61fb1 100644
--- a/synapse/push/baserules.py
+++ b/synapse/push/baserules.py
@@ -37,7 +37,7 @@ def list_with_base_rules(rawrules, use_new_defaults=False):
     modified_base_rules = {r["rule_id"]: r for r in rawrules if r["priority_class"] < 0}
 
     # Remove the modified base rules from the list, They'll be added back
-    # in the default postions in the list.
+    # in the default positions in the list.
     rawrules = [r for r in rawrules if r["priority_class"] >= 0]
 
     # shove the server default rules for each kind onto the end of each
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index a701defcdd..d9b5478b53 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -390,12 +390,12 @@ class RulesForRoom:
                     continue
 
                 # If a user has left a room we remove their push rule. If they
-                # joined then we readd it later in _update_rules_with_member_event_ids
+                # joined then we re-add it later in _update_rules_with_member_event_ids
                 ret_rules_by_user.pop(user_id, None)
                 missing_member_event_ids[user_id] = event_id
 
             if missing_member_event_ids:
-                # If we have some memebr events we haven't seen, look them up
+                # If we have some member events we haven't seen, look them up
                 # and fetch push rules for them if appropriate.
                 logger.debug("Found new member events %r", missing_member_event_ids)
                 await self._update_rules_with_member_event_ids(
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index 155791b754..38195c8eea 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -24,7 +24,7 @@ from typing import Iterable, List, TypeVar
 import bleach
 import jinja2
 
-from synapse.api.constants import EventTypes
+from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import StoreError
 from synapse.config.emailconfig import EmailSubjectConfig
 from synapse.logging.context import make_deferred_yieldable
@@ -317,9 +317,14 @@ class Mailer:
     async def get_room_vars(
         self, room_id, user_id, notifs, notif_events, room_state_ids
     ):
-        my_member_event_id = room_state_ids[("m.room.member", user_id)]
-        my_member_event = await self.store.get_event(my_member_event_id)
-        is_invite = my_member_event.content["membership"] == "invite"
+        # Check if one of the notifs is an invite event for the user.
+        is_invite = False
+        for n in notifs:
+            ev = notif_events[n["event_id"]]
+            if ev.type == EventTypes.Member and ev.state_key == user_id:
+                if ev.content.get("membership") == Membership.INVITE:
+                    is_invite = True
+                    break
 
         room_name = await calculate_room_name(self.store, room_state_ids, user_id)
 
@@ -461,16 +466,26 @@ class Mailer:
                 self.store, room_state_ids[room_id], user_id, fallback_to_members=False
             )
 
-            my_member_event_id = room_state_ids[room_id][("m.room.member", user_id)]
-            my_member_event = await self.store.get_event(my_member_event_id)
-            if my_member_event.content["membership"] == "invite":
-                inviter_member_event_id = room_state_ids[room_id][
-                    ("m.room.member", my_member_event.sender)
-                ]
-                inviter_member_event = await self.store.get_event(
-                    inviter_member_event_id
+            # See if one of the notifs is an invite event for the user
+            invite_event = None
+            for n in notifs_by_room[room_id]:
+                ev = notif_events[n["event_id"]]
+                if ev.type == EventTypes.Member and ev.state_key == user_id:
+                    if ev.content.get("membership") == Membership.INVITE:
+                        invite_event = ev
+                        break
+
+            if invite_event:
+                inviter_member_event_id = room_state_ids[room_id].get(
+                    ("m.room.member", invite_event.sender)
                 )
-                inviter_name = name_from_member_event(inviter_member_event)
+                inviter_name = invite_event.sender
+                if inviter_member_event_id:
+                    inviter_member_event = await self.store.get_event(
+                        inviter_member_event_id, allow_none=True
+                    )
+                    if inviter_member_event:
+                        inviter_name = name_from_member_event(inviter_member_event)
 
                 if room_name is None:
                     return self.email_subjects.invite_from_person % {
diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py
index 0080c68ce2..f325964983 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -19,7 +19,10 @@ from typing import TYPE_CHECKING, Dict, Union
 
 from prometheus_client import Gauge
 
-from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.metrics.background_process_metrics import (
+    run_as_background_process,
+    wrap_as_background_process,
+)
 from synapse.push import PusherConfigException
 from synapse.push.emailpusher import EmailPusher
 from synapse.push.httppusher import HttpPusher
@@ -187,7 +190,7 @@ class PusherPool:
                 )
                 await self.remove_pusher(p["app_id"], p["pushkey"], p["user_name"])
 
-    async def on_new_notifications(self, max_token: RoomStreamToken):
+    def on_new_notifications(self, max_token: RoomStreamToken):
         if not self.pushers:
             # nothing to do here.
             return
@@ -201,6 +204,17 @@ class PusherPool:
             # Nothing to do
             return
 
+        # We only start a new background process if necessary rather than
+        # optimistically (to cut down on overhead).
+        self._on_new_notifications(max_token)
+
+    @wrap_as_background_process("on_new_notifications")
+    async def _on_new_notifications(self, max_token: RoomStreamToken):
+        # We just use the minimum stream ordering and ignore the vector clock
+        # component. This is safe to do as long as we *always* ignore the vector
+        # clock components.
+        max_stream_id = max_token.stream
+
         prev_stream_id = self._last_room_stream_id_seen
         self._last_room_stream_id_seen = max_stream_id
 
diff --git a/synapse/replication/tcp/redis.py b/synapse/replication/tcp/redis.py
index de19705c1f..bc6ba709a7 100644
--- a/synapse/replication/tcp/redis.py
+++ b/synapse/replication/tcp/redis.py
@@ -166,7 +166,9 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
         Args:
             cmd (Command)
         """
-        run_as_background_process("send-cmd", self._async_send_command, cmd)
+        run_as_background_process(
+            "send-cmd", self._async_send_command, cmd, bg_start_span=False
+        )
 
     async def _async_send_command(self, cmd: Command):
         """Encode a replication command and send it over our outbound connection"""
diff --git a/synapse/rest/admin/devices.py b/synapse/rest/admin/devices.py
index a163863322..ffd3aa38f7 100644
--- a/synapse/rest/admin/devices.py
+++ b/synapse/rest/admin/devices.py
@@ -119,7 +119,7 @@ class DevicesRestServlet(RestServlet):
             raise NotFoundError("Unknown user")
 
         devices = await self.device_handler.get_devices_by_user(target_user.to_string())
-        return 200, {"devices": devices}
+        return 200, {"devices": devices, "total": len(devices)}
 
 
 class DeleteDevicesRestServlet(RestServlet):
diff --git a/synapse/rest/client/v1/events.py b/synapse/rest/client/v1/events.py
index 1ecb77aa26..6de4078290 100644
--- a/synapse/rest/client/v1/events.py
+++ b/synapse/rest/client/v1/events.py
@@ -67,9 +67,6 @@ class EventStreamRestServlet(RestServlet):
 
         return 200, chunk
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
 
 class EventRestServlet(RestServlet):
     PATTERNS = client_patterns("/events/(?P<event_id>[^/]*)$", v1=True)
diff --git a/synapse/rest/client/v1/login.py b/synapse/rest/client/v1/login.py
index b82a4e978a..94452fcbf5 100644
--- a/synapse/rest/client/v1/login.py
+++ b/synapse/rest/client/v1/login.py
@@ -114,9 +114,6 @@ class LoginRestServlet(RestServlet):
 
         return 200, {"flows": flows}
 
-    def on_OPTIONS(self, request: SynapseRequest):
-        return 200, {}
-
     async def on_POST(self, request: SynapseRequest):
         self._address_ratelimiter.ratelimit(request.getClientIP())
 
diff --git a/synapse/rest/client/v1/logout.py b/synapse/rest/client/v1/logout.py
index f792b50cdc..ad8cea49c6 100644
--- a/synapse/rest/client/v1/logout.py
+++ b/synapse/rest/client/v1/logout.py
@@ -30,9 +30,6 @@ class LogoutRestServlet(RestServlet):
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
     async def on_POST(self, request):
         requester = await self.auth.get_user_by_req(request, allow_expired=True)
 
@@ -58,9 +55,6 @@ class LogoutAllRestServlet(RestServlet):
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
     async def on_POST(self, request):
         requester = await self.auth.get_user_by_req(request, allow_expired=True)
         user_id = requester.user.to_string()
diff --git a/synapse/rest/client/v1/presence.py b/synapse/rest/client/v1/presence.py
index 79d8e3057f..23a529f8e3 100644
--- a/synapse/rest/client/v1/presence.py
+++ b/synapse/rest/client/v1/presence.py
@@ -86,9 +86,6 @@ class PresenceStatusRestServlet(RestServlet):
 
         return 200, {}
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
 
 def register_servlets(hs, http_server):
     PresenceStatusRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v1/profile.py b/synapse/rest/client/v1/profile.py
index e7fcd2b1ff..85a66458c5 100644
--- a/synapse/rest/client/v1/profile.py
+++ b/synapse/rest/client/v1/profile.py
@@ -67,9 +67,6 @@ class ProfileDisplaynameRestServlet(RestServlet):
 
         return 200, {}
 
-    def on_OPTIONS(self, request, user_id):
-        return 200, {}
-
 
 class ProfileAvatarURLRestServlet(RestServlet):
     PATTERNS = client_patterns("/profile/(?P<user_id>[^/]*)/avatar_url", v1=True)
@@ -118,9 +115,6 @@ class ProfileAvatarURLRestServlet(RestServlet):
 
         return 200, {}
 
-    def on_OPTIONS(self, request, user_id):
-        return 200, {}
-
 
 class ProfileRestServlet(RestServlet):
     PATTERNS = client_patterns("/profile/(?P<user_id>[^/]*)", v1=True)
diff --git a/synapse/rest/client/v1/push_rule.py b/synapse/rest/client/v1/push_rule.py
index f9eecb7cf5..241e535917 100644
--- a/synapse/rest/client/v1/push_rule.py
+++ b/synapse/rest/client/v1/push_rule.py
@@ -155,9 +155,6 @@ class PushRuleRestServlet(RestServlet):
         else:
             raise UnrecognizedRequestError()
 
-    def on_OPTIONS(self, request, path):
-        return 200, {}
-
     def notify_user(self, user_id):
         stream_id = self.store.get_max_push_rules_stream_id()
         self.notifier.on_new_event("push_rules_key", stream_id, users=[user_id])
diff --git a/synapse/rest/client/v1/pusher.py b/synapse/rest/client/v1/pusher.py
index 28dabf1c7a..8fe83f321a 100644
--- a/synapse/rest/client/v1/pusher.py
+++ b/synapse/rest/client/v1/pusher.py
@@ -60,9 +60,6 @@ class PushersRestServlet(RestServlet):
 
         return 200, {"pushers": filtered_pushers}
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
 
 class PushersSetRestServlet(RestServlet):
     PATTERNS = client_patterns("/pushers/set$", v1=True)
@@ -140,9 +137,6 @@ class PushersSetRestServlet(RestServlet):
 
         return 200, {}
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
 
 class PushersRemoveRestServlet(RestServlet):
     """
@@ -182,9 +176,6 @@ class PushersRemoveRestServlet(RestServlet):
         )
         return None
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
 
 def register_servlets(hs, http_server):
     PushersRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 00b4397082..25d3cc6148 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -72,20 +72,6 @@ class RoomCreateRestServlet(TransactionRestServlet):
     def register(self, http_server):
         PATTERNS = "/createRoom"
         register_txn_path(self, PATTERNS, http_server)
-        # define CORS for all of /rooms in RoomCreateRestServlet for simplicity
-        http_server.register_paths(
-            "OPTIONS",
-            client_patterns("/rooms(?:/.*)?$", v1=True),
-            self.on_OPTIONS,
-            self.__class__.__name__,
-        )
-        # define CORS for /createRoom[/txnid]
-        http_server.register_paths(
-            "OPTIONS",
-            client_patterns("/createRoom(?:/.*)?$", v1=True),
-            self.on_OPTIONS,
-            self.__class__.__name__,
-        )
 
     def on_PUT(self, request, txn_id):
         set_tag("txn_id", txn_id)
@@ -104,9 +90,6 @@ class RoomCreateRestServlet(TransactionRestServlet):
         user_supplied_config = parse_json_object_from_request(request)
         return user_supplied_config
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
 
 # TODO: Needs unit testing for generic events
 class RoomStateEventRestServlet(TransactionRestServlet):
diff --git a/synapse/rest/client/v1/voip.py b/synapse/rest/client/v1/voip.py
index b8d491ca5c..d07ca2c47c 100644
--- a/synapse/rest/client/v1/voip.py
+++ b/synapse/rest/client/v1/voip.py
@@ -69,9 +69,6 @@ class VoipRestServlet(RestServlet):
             },
         )
 
-    def on_OPTIONS(self, request):
-        return 200, {}
-
 
 def register_servlets(hs, http_server):
     VoipRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index e857cff176..51effc4d8e 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -268,9 +268,6 @@ class PasswordRestServlet(RestServlet):
 
         return 200, {}
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
 
 class DeactivateAccountRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/deactivate$")
diff --git a/synapse/rest/client/v2_alpha/auth.py b/synapse/rest/client/v2_alpha/auth.py
index 5fbfae5991..fab077747f 100644
--- a/synapse/rest/client/v2_alpha/auth.py
+++ b/synapse/rest/client/v2_alpha/auth.py
@@ -176,9 +176,6 @@ class AuthRestServlet(RestServlet):
         respond_with_html(request, 200, html)
         return None
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
 
 def register_servlets(hs, http_server):
     AuthRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index 395b6a82a9..8f2c8cd991 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -642,9 +642,6 @@ class RegisterRestServlet(RestServlet):
 
         return 200, return_dict
 
-    def on_OPTIONS(self, _):
-        return 200, {}
-
     async def _do_appservice_registration(self, username, as_token, body):
         user_id = await self.registration_handler.appservice_register(
             username, as_token
diff --git a/synapse/server_notices/consent_server_notices.py b/synapse/server_notices/consent_server_notices.py
index 3673e7f47e..9137c4edb1 100644
--- a/synapse/server_notices/consent_server_notices.py
+++ b/synapse/server_notices/consent_server_notices.py
@@ -104,7 +104,7 @@ class ConsentServerNotices:
 
 
 def copy_with_str_subst(x: Any, substitutions: Any) -> Any:
-    """Deep-copy a structure, carrying out string substitions on any strings
+    """Deep-copy a structure, carrying out string substitutions on any strings
 
     Args:
         x (object): structure to be copied
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 5b0900aa3c..1fa3b280b4 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -547,7 +547,7 @@ class StateResolutionHandler:
             event_map:
                 a dict from event_id to event, for any events that we happen to
                 have in flight (eg, those currently being persisted). This will be
-                used as a starting point fof finding the state we need; any missing
+                used as a starting point for finding the state we need; any missing
                 events will be requested via state_res_store.
 
                 If None, all events will be fetched via state_res_store.
diff --git a/synapse/state/v1.py b/synapse/state/v1.py
index a493279cbd..85edae053d 100644
--- a/synapse/state/v1.py
+++ b/synapse/state/v1.py
@@ -56,7 +56,7 @@ async def resolve_events_with_store(
         event_map:
             a dict from event_id to event, for any events that we happen to
             have in flight (eg, those currently being persisted). This will be
-            used as a starting point fof finding the state we need; any missing
+            used as a starting point for finding the state we need; any missing
             events will be requested via state_map_factory.
 
             If None, all events will be fetched via state_map_factory.
diff --git a/synapse/state/v2.py b/synapse/state/v2.py
index edf94e7ad6..f57df0d728 100644
--- a/synapse/state/v2.py
+++ b/synapse/state/v2.py
@@ -69,7 +69,7 @@ async def resolve_events_with_store(
         event_map:
             a dict from event_id to event, for any events that we happen to
             have in flight (eg, those currently being persisted). This will be
-            used as a starting point fof finding the state we need; any missing
+            used as a starting point for finding the state we need; any missing
             events will be requested via state_res_store.
 
             If None, all events will be fetched via state_res_store.
diff --git a/synapse/static/client/login/js/login.js b/synapse/static/client/login/js/login.js
index 3678670ec7..744800ec77 100644
--- a/synapse/static/client/login/js/login.js
+++ b/synapse/static/client/login/js/login.js
@@ -182,7 +182,7 @@ matrixLogin.passwordLogin = function() {
 };
 
 /*
- * The onLogin function gets called after a succesful login.
+ * The onLogin function gets called after a successful login.
  *
  * It is expected that implementations override this to be notified when the
  * login is complete. The response to the login call is provided as the single
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index 9b16f45f3e..43660ec4fb 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -146,7 +146,6 @@ class DataStore(
             db_conn, "e2e_cross_signing_keys", "stream_id"
         )
 
-        self._access_tokens_id_gen = IdGenerator(db_conn, "access_tokens", "id")
         self._event_reports_id_gen = IdGenerator(db_conn, "event_reports", "id")
         self._push_rule_id_gen = IdGenerator(db_conn, "push_rules", "id")
         self._push_rules_enable_id_gen = IdGenerator(db_conn, "push_rules_enable", "id")
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 4c843b7679..b0329e17ec 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -16,29 +16,33 @@
 # limitations under the License.
 import logging
 import re
-from typing import Any, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
 
 from synapse.api.constants import UserTypes
 from synapse.api.errors import Codes, StoreError, SynapseError, ThreepidValidationError
 from synapse.metrics.background_process_metrics import wrap_as_background_process
-from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import DatabasePool
-from synapse.storage.types import Cursor
+from synapse.storage.databases.main.cache import CacheInvalidationWorkerStore
+from synapse.storage.databases.main.stats import StatsStore
+from synapse.storage.types import Connection, Cursor
+from synapse.storage.util.id_generators import IdGenerator
 from synapse.storage.util.sequence import build_sequence_generator
 from synapse.types import UserID
 from synapse.util.caches.descriptors import cached
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 THIRTY_MINUTES_IN_MS = 30 * 60 * 1000
 
 logger = logging.getLogger(__name__)
 
 
-class RegistrationWorkerStore(SQLBaseStore):
-    def __init__(self, database: DatabasePool, db_conn, hs):
+class RegistrationWorkerStore(CacheInvalidationWorkerStore):
+    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
         super().__init__(database, db_conn, hs)
 
         self.config = hs.config
-        self.clock = hs.get_clock()
 
         # Note: we don't check this sequence for consistency as we'd have to
         # call `find_max_generated_user_id_localpart` each time, which is
@@ -55,7 +59,7 @@ class RegistrationWorkerStore(SQLBaseStore):
 
         # Create a background job for culling expired 3PID validity tokens
         if hs.config.run_background_tasks:
-            self.clock.looping_call(
+            self._clock.looping_call(
                 self.cull_expired_threepid_validation_tokens, THIRTY_MINUTES_IN_MS
             )
 
@@ -92,7 +96,7 @@ class RegistrationWorkerStore(SQLBaseStore):
         if not info:
             return False
 
-        now = self.clock.time_msec()
+        now = self._clock.time_msec()
         trial_duration_ms = self.config.mau_trial_days * 24 * 60 * 60 * 1000
         is_trial = (now - info["creation_ts"] * 1000) < trial_duration_ms
         return is_trial
@@ -257,7 +261,7 @@ class RegistrationWorkerStore(SQLBaseStore):
         return await self.db_pool.runInteraction(
             "get_users_expiring_soon",
             select_users_txn,
-            self.clock.time_msec(),
+            self._clock.time_msec(),
             self.config.account_validity.renew_at,
         )
 
@@ -328,13 +332,17 @@ class RegistrationWorkerStore(SQLBaseStore):
         await self.db_pool.runInteraction("set_server_admin", set_server_admin_txn)
 
     def _query_for_auth(self, txn, token):
-        sql = (
-            "SELECT users.name, users.is_guest, users.shadow_banned, access_tokens.id as token_id,"
-            " access_tokens.device_id, access_tokens.valid_until_ms"
-            " FROM users"
-            " INNER JOIN access_tokens on users.name = access_tokens.user_id"
-            " WHERE token = ?"
-        )
+        sql = """
+            SELECT users.name,
+                users.is_guest,
+                users.shadow_banned,
+                access_tokens.id as token_id,
+                access_tokens.device_id,
+                access_tokens.valid_until_ms
+            FROM users
+            INNER JOIN access_tokens on users.name = access_tokens.user_id
+            WHERE token = ?
+        """
 
         txn.execute(sql, (token,))
         rows = self.db_pool.cursor_to_dict(txn)
@@ -803,7 +811,7 @@ class RegistrationWorkerStore(SQLBaseStore):
         await self.db_pool.runInteraction(
             "cull_expired_threepid_validation_tokens",
             cull_expired_threepid_validation_tokens_txn,
-            self.clock.time_msec(),
+            self._clock.time_msec(),
         )
 
     @wrap_as_background_process("account_validity_set_expiration_dates")
@@ -890,10 +898,10 @@ class RegistrationWorkerStore(SQLBaseStore):
 
 
 class RegistrationBackgroundUpdateStore(RegistrationWorkerStore):
-    def __init__(self, database: DatabasePool, db_conn, hs):
+    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
         super().__init__(database, db_conn, hs)
 
-        self.clock = hs.get_clock()
+        self._clock = hs.get_clock()
         self.config = hs.config
 
         self.db_pool.updates.register_background_index_update(
@@ -1016,13 +1024,56 @@ class RegistrationBackgroundUpdateStore(RegistrationWorkerStore):
 
         return 1
 
+    async def set_user_deactivated_status(
+        self, user_id: str, deactivated: bool
+    ) -> None:
+        """Set the `deactivated` property for the provided user to the provided value.
+
+        Args:
+            user_id: The ID of the user to set the status for.
+            deactivated: The value to set for `deactivated`.
+        """
+
+        await self.db_pool.runInteraction(
+            "set_user_deactivated_status",
+            self.set_user_deactivated_status_txn,
+            user_id,
+            deactivated,
+        )
+
+    def set_user_deactivated_status_txn(self, txn, user_id: str, deactivated: bool):
+        self.db_pool.simple_update_one_txn(
+            txn=txn,
+            table="users",
+            keyvalues={"name": user_id},
+            updatevalues={"deactivated": 1 if deactivated else 0},
+        )
+        self._invalidate_cache_and_stream(
+            txn, self.get_user_deactivated_status, (user_id,)
+        )
+        txn.call_after(self.is_guest.invalidate, (user_id,))
+
+    @cached()
+    async def is_guest(self, user_id: str) -> bool:
+        res = await self.db_pool.simple_select_one_onecol(
+            table="users",
+            keyvalues={"name": user_id},
+            retcol="is_guest",
+            allow_none=True,
+            desc="is_guest",
+        )
+
+        return res if res else False
+
 
-class RegistrationStore(RegistrationBackgroundUpdateStore):
-    def __init__(self, database: DatabasePool, db_conn, hs):
+class RegistrationStore(StatsStore, RegistrationBackgroundUpdateStore):
+    def __init__(self, database: DatabasePool, db_conn: Connection, hs: "HomeServer"):
         super().__init__(database, db_conn, hs)
 
         self._ignore_unknown_session_error = hs.config.request_token_inhibit_3pid_errors
 
+        self._access_tokens_id_gen = IdGenerator(db_conn, "access_tokens", "id")
+
     async def add_access_token_to_user(
         self,
         user_id: str,
@@ -1138,19 +1189,19 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
     def _register_user(
         self,
         txn,
-        user_id,
-        password_hash,
-        was_guest,
-        make_guest,
-        appservice_id,
-        create_profile_with_displayname,
-        admin,
-        user_type,
-        shadow_banned,
+        user_id: str,
+        password_hash: Optional[str],
+        was_guest: bool,
+        make_guest: bool,
+        appservice_id: Optional[str],
+        create_profile_with_displayname: Optional[str],
+        admin: bool,
+        user_type: Optional[str],
+        shadow_banned: bool,
     ):
         user_id_obj = UserID.from_string(user_id)
 
-        now = int(self.clock.time())
+        now = int(self._clock.time())
 
         try:
             if was_guest:
@@ -1374,18 +1425,6 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
 
         await self.db_pool.runInteraction("delete_access_token", f)
 
-    @cached()
-    async def is_guest(self, user_id: str) -> bool:
-        res = await self.db_pool.simple_select_one_onecol(
-            table="users",
-            keyvalues={"name": user_id},
-            retcol="is_guest",
-            allow_none=True,
-            desc="is_guest",
-        )
-
-        return res if res else False
-
     async def add_user_pending_deactivation(self, user_id: str) -> None:
         """
         Adds a user to the table of users who need to be parted from all the rooms they're
@@ -1479,7 +1518,7 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
                 txn,
                 table="threepid_validation_session",
                 keyvalues={"session_id": session_id},
-                updatevalues={"validated_at": self.clock.time_msec()},
+                updatevalues={"validated_at": self._clock.time_msec()},
             )
 
             return next_link
@@ -1547,35 +1586,6 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
             start_or_continue_validation_session_txn,
         )
 
-    async def set_user_deactivated_status(
-        self, user_id: str, deactivated: bool
-    ) -> None:
-        """Set the `deactivated` property for the provided user to the provided value.
-
-        Args:
-            user_id: The ID of the user to set the status for.
-            deactivated: The value to set for `deactivated`.
-        """
-
-        await self.db_pool.runInteraction(
-            "set_user_deactivated_status",
-            self.set_user_deactivated_status_txn,
-            user_id,
-            deactivated,
-        )
-
-    def set_user_deactivated_status_txn(self, txn, user_id, deactivated):
-        self.db_pool.simple_update_one_txn(
-            txn=txn,
-            table="users",
-            keyvalues={"name": user_id},
-            updatevalues={"deactivated": 1 if deactivated else 0},
-        )
-        self._invalidate_cache_and_stream(
-            txn, self.get_user_deactivated_status, (user_id,)
-        )
-        txn.call_after(self.is_guest.invalidate, (user_id,))
-
 
 def find_max_generated_user_id_localpart(cur: Cursor) -> int:
     """