Merge tag 'v0.33.3'

Features
--------

- Add support for the SNI extension to federation TLS connections. Thanks to @vojeroen! ([\#3439](https://github.com/matrix-org/synapse/issues/3439))
- Add /_media/r0/config ([\#3184](https://github.com/matrix-org/synapse/issues/3184))
- speed up /members API and add `at` and `membership` params as per MSC1227 ([\#3568](https://github.com/matrix-org/synapse/issues/3568))
- implement `summary` block in /sync response as per MSC688 ([\#3574](https://github.com/matrix-org/synapse/issues/3574))
- Add lazy-loading support to /messages as per MSC1227 ([\#3589](https://github.com/matrix-org/synapse/issues/3589))
- Add ability to limit number of monthly active users on the server ([\#3633](https://github.com/matrix-org/synapse/issues/3633))
- Support more federation endpoints on workers ([\#3653](https://github.com/matrix-org/synapse/issues/3653))
- Basic support for room versioning ([\#3654](https://github.com/matrix-org/synapse/issues/3654))
- Ability to disable client/server Synapse via conf toggle ([\#3655](https://github.com/matrix-org/synapse/issues/3655))
- Ability to whitelist specific threepids against monthly active user limiting ([\#3662](https://github.com/matrix-org/synapse/issues/3662))
- Add some metrics for the appservice and federation event sending loops ([\#3664](https://github.com/matrix-org/synapse/issues/3664))
- Where server is disabled, block ability for locked out users to read new messages ([\#3670](https://github.com/matrix-org/synapse/issues/3670))
- set admin uri via config, to be used in error messages where the user should contact the administrator ([\#3687](https://github.com/matrix-org/synapse/issues/3687))
- Synapse's presence functionality can now be disabled with the "use_presence" configuration option. ([\#3694](https://github.com/matrix-org/synapse/issues/3694))
- For resource limit blocked users, prevent writing into rooms ([\#3708](https://github.com/matrix-org/synapse/issues/3708))

Bugfixes
--------

- Fix occasional glitches in the synapse_event_persisted_position metric ([\#3658](https://github.com/matrix-org/synapse/issues/3658))
- Fix bug on deleting 3pid when using identity servers that don't support unbind API ([\#3661](https://github.com/matrix-org/synapse/issues/3661))
- Make the tests pass on Twisted < 18.7.0 ([\#3676](https://github.com/matrix-org/synapse/issues/3676))
- Don’t ship recaptcha_ajax.js, use it directly from Google ([\#3677](https://github.com/matrix-org/synapse/issues/3677))
- Fixes test_reap_monthly_active_users so it passes under postgres ([\#3681](https://github.com/matrix-org/synapse/issues/3681))
- Fix mau blocking calulation bug on login ([\#3689](https://github.com/matrix-org/synapse/issues/3689))
- Fix missing yield in synapse.storage.monthly_active_users.initialise_reserved_users ([\#3692](https://github.com/matrix-org/synapse/issues/3692))
- Improve HTTP request logging to include all requests ([\#3700](https://github.com/matrix-org/synapse/issues/3700))
- Avoid timing out requests while we are streaming back the response ([\#3701](https://github.com/matrix-org/synapse/issues/3701))
- Support more federation endpoints on workers ([\#3705](https://github.com/matrix-org/synapse/issues/3705), [\#3713](https://github.com/matrix-org/synapse/issues/3713))
- Fix "Starting db txn 'get_all_updated_receipts' from sentinel context" warning ([\#3710](https://github.com/matrix-org/synapse/issues/3710))
- Fix bug where `state_cache` cache factor ignored environment variables ([\#3719](https://github.com/matrix-org/synapse/issues/3719))
- Fix bug in v0.33.3rc1 which caused infinite loops and OOMs ([\#3723](https://github.com/matrix-org/synapse/issues/3723))
- Fix bug introduced in v0.33.3rc1 which made the ToS give a 500 error ([\#3732](https://github.com/matrix-org/synapse/issues/3732))

Deprecations and Removals
-------------------------

- The Shared-Secret registration method of the legacy v1/register REST endpoint has been removed. For a replacement, please see [the admin/register API documentation](https://github.com/matrix-org/synapse/blob/master/docs/admin_api/register_api.rst). ([\#3703](https://github.com/matrix-org/synapse/issues/3703))

Internal Changes
----------------

- The test suite now can run under PostgreSQL. ([\#3423](https://github.com/matrix-org/synapse/issues/3423))
- Refactor HTTP replication endpoints to reduce code duplication ([\#3632](https://github.com/matrix-org/synapse/issues/3632))
- Tests now correctly execute on Python 3. ([\#3647](https://github.com/matrix-org/synapse/issues/3647))
- Sytests can now be run inside a Docker container. ([\#3660](https://github.com/matrix-org/synapse/issues/3660))
- Port over enough to Python 3 to allow the sytests to start. ([\#3668](https://github.com/matrix-org/synapse/issues/3668))
- Update docker base image from alpine 3.7 to 3.8. ([\#3669](https://github.com/matrix-org/synapse/issues/3669))
- Rename synapse.util.async to synapse.util.async_helpers to mitigate async becoming a keyword on Python 3.7. ([\#3678](https://github.com/matrix-org/synapse/issues/3678))
- Synapse's tests are now formatted with the black autoformatter. ([\#3679](https://github.com/matrix-org/synapse/issues/3679))
- Implemented a new testing base class to reduce test boilerplate. ([\#3684](https://github.com/matrix-org/synapse/issues/3684))
- Rename MAU prometheus metrics ([\#3690](https://github.com/matrix-org/synapse/issues/3690))
- add new error type ResourceLimit ([\#3707](https://github.com/matrix-org/synapse/issues/3707))
- Logcontexts for replication command handlers ([\#3709](https://github.com/matrix-org/synapse/issues/3709))
- Update admin register API documentation to reference a real user ID. ([\#3712](https://github.com/matrix-org/synapse/issues/3712))

10 files changed, 681 insertions, 271 deletions

diff --git a/synapse/replication/http/__init__.py b/synapse/replication/http/__init__.py
index 589ee94c66..19f214281e 100644
--- a/synapse/replication/http/__init__.py
+++ b/synapse/replication/http/__init__.py
@@ -14,7 +14,7 @@
 # limitations under the License.
 
 from synapse.http.server import JsonResource
-from synapse.replication.http import membership, send_event
+from synapse.replication.http import federation, membership, send_event
 
 REPLICATION_PREFIX = "/_synapse/replication"
 
@@ -27,3 +27,4 @@ class ReplicationRestResource(JsonResource):
     def register_servlets(self, hs):
         send_event.register_servlets(hs, self)
         membership.register_servlets(hs, self)
+        federation.register_servlets(hs, self)
diff --git a/synapse/replication/http/_base.py b/synapse/replication/http/_base.py
new file mode 100644
index 0000000000..5e5376cf58
--- /dev/null
+++ b/synapse/replication/http/_base.py
@@ -0,0 +1,215 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# 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 abc
+import logging
+import re
+
+from six.moves import urllib
+
+from twisted.internet import defer
+
+from synapse.api.errors import CodeMessageException, HttpResponseException
+from synapse.util.caches.response_cache import ResponseCache
+from synapse.util.stringutils import random_string
+
+logger = logging.getLogger(__name__)
+
+
+class ReplicationEndpoint(object):
+    """Helper base class for defining new replication HTTP endpoints.
+
+    This creates an endpoint under `/_synapse/replication/:NAME/:PATH_ARGS..`
+    (with an `/:txn_id` prefix for cached requests.), where NAME is a name,
+    PATH_ARGS are a tuple of parameters to be encoded in the URL.
+
+    For example, if `NAME` is "send_event" and `PATH_ARGS` is `("event_id",)`,
+    with `CACHE` set to true then this generates an endpoint:
+
+        /_synapse/replication/send_event/:event_id/:txn_id
+
+    For POST/PUT requests the payload is serialized to json and sent as the
+    body, while for GET requests the payload is added as query parameters. See
+    `_serialize_payload` for details.
+
+    Incoming requests are handled by overriding `_handle_request`. Servers
+    must call `register` to register the path with the HTTP server.
+
+    Requests can be sent by calling the client returned by `make_client`.
+
+    Attributes:
+        NAME (str): A name for the endpoint, added to the path as well as used
+            in logging and metrics.
+        PATH_ARGS (tuple[str]): A list of parameters to be added to the path.
+            Adding parameters to the path (rather than payload) can make it
+            easier to follow along in the log files.
+        METHOD (str): The method of the HTTP request, defaults to POST. Can be
+            one of POST, PUT or GET. If GET then the payload is sent as query
+            parameters rather than a JSON body.
+        CACHE (bool): Whether server should cache the result of the request/
+            If true then transparently adds a txn_id to all requests, and
+            `_handle_request` must return a Deferred.
+        RETRY_ON_TIMEOUT(bool): Whether or not to retry the request when a 504
+            is received.
+    """
+
+    __metaclass__ = abc.ABCMeta
+
+    NAME = abc.abstractproperty()
+    PATH_ARGS = abc.abstractproperty()
+
+    METHOD = "POST"
+    CACHE = True
+    RETRY_ON_TIMEOUT = True
+
+    def __init__(self, hs):
+        if self.CACHE:
+            self.response_cache = ResponseCache(
+                hs, "repl." + self.NAME,
+                timeout_ms=30 * 60 * 1000,
+            )
+
+        assert self.METHOD in ("PUT", "POST", "GET")
+
+    @abc.abstractmethod
+    def _serialize_payload(**kwargs):
+        """Static method that is called when creating a request.
+
+        Concrete implementations should have explicit parameters (rather than
+        kwargs) so that an appropriate exception is raised if the client is
+        called with unexpected parameters. All PATH_ARGS must appear in
+        argument list.
+
+        Returns:
+            Deferred[dict]|dict: If POST/PUT request then dictionary must be
+            JSON serialisable, otherwise must be appropriate for adding as
+            query args.
+        """
+        return {}
+
+    @abc.abstractmethod
+    def _handle_request(self, request, **kwargs):
+        """Handle incoming request.
+
+        This is called with the request object and PATH_ARGS.
+
+        Returns:
+            Deferred[dict]: A JSON serialisable dict to be used as response
+            body of request.
+        """
+        pass
+
+    @classmethod
+    def make_client(cls, hs):
+        """Create a client that makes requests.
+
+        Returns a callable that accepts the same parameters as `_serialize_payload`.
+        """
+        clock = hs.get_clock()
+        host = hs.config.worker_replication_host
+        port = hs.config.worker_replication_http_port
+
+        client = hs.get_simple_http_client()
+
+        @defer.inlineCallbacks
+        def send_request(**kwargs):
+            data = yield cls._serialize_payload(**kwargs)
+
+            url_args = [urllib.parse.quote(kwargs[name]) for name in cls.PATH_ARGS]
+
+            if cls.CACHE:
+                txn_id = random_string(10)
+                url_args.append(txn_id)
+
+            if cls.METHOD == "POST":
+                request_func = client.post_json_get_json
+            elif cls.METHOD == "PUT":
+                request_func = client.put_json
+            elif cls.METHOD == "GET":
+                request_func = client.get_json
+            else:
+                # We have already asserted in the constructor that a
+                # compatible was picked, but lets be paranoid.
+                raise Exception(
+                    "Unknown METHOD on %s replication endpoint" % (cls.NAME,)
+                )
+
+            uri = "http://%s:%s/_synapse/replication/%s/%s" % (
+                host, port, cls.NAME, "/".join(url_args)
+            )
+
+            try:
+                # We keep retrying the same request for timeouts. This is so that we
+                # have a good idea that the request has either succeeded or failed on
+                # the master, and so whether we should clean up or not.
+                while True:
+                    try:
+                        result = yield request_func(uri, data)
+                        break
+                    except CodeMessageException as e:
+                        if e.code != 504 or not cls.RETRY_ON_TIMEOUT:
+                            raise
+
+                    logger.warn("%s request timed out", cls.NAME)
+
+                    # If we timed out we probably don't need to worry about backing
+                    # off too much, but lets just wait a little anyway.
+                    yield clock.sleep(1)
+            except HttpResponseException as e:
+                # We convert to SynapseError as we know that it was a SynapseError
+                # on the master process that we should send to the client. (And
+                # importantly, not stack traces everywhere)
+                raise e.to_synapse_error()
+
+            defer.returnValue(result)
+
+        return send_request
+
+    def register(self, http_server):
+        """Called by the server to register this as a handler to the
+        appropriate path.
+        """
+
+        url_args = list(self.PATH_ARGS)
+        handler = self._handle_request
+        method = self.METHOD
+
+        if self.CACHE:
+            handler = self._cached_handler
+            url_args.append("txn_id")
+
+        args = "/".join("(?P<%s>[^/]+)" % (arg,) for arg in url_args)
+        pattern = re.compile("^/_synapse/replication/%s/%s$" % (
+            self.NAME,
+            args
+        ))
+
+        http_server.register_paths(method, [pattern], handler)
+
+    def _cached_handler(self, request, txn_id, **kwargs):
+        """Called on new incoming requests when caching is enabled. Checks
+        if there is a cached response for the request and returns that,
+        otherwise calls `_handle_request` and caches its response.
+        """
+        # We just use the txn_id here, but we probably also want to use the
+        # other PATH_ARGS as well.
+
+        assert self.CACHE
+
+        return self.response_cache.wrap(
+            txn_id,
+            self._handle_request,
+            request, **kwargs
+        )
diff --git a/synapse/replication/http/federation.py b/synapse/replication/http/federation.py
new file mode 100644
index 0000000000..64a79da162
--- /dev/null
+++ b/synapse/replication/http/federation.py
@@ -0,0 +1,259 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# 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 twisted.internet import defer
+
+from synapse.events import FrozenEvent
+from synapse.events.snapshot import EventContext
+from synapse.http.servlet import parse_json_object_from_request
+from synapse.replication.http._base import ReplicationEndpoint
+from synapse.util.metrics import Measure
+
+logger = logging.getLogger(__name__)
+
+
+class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
+    """Handles events newly received from federation, including persisting and
+    notifying.
+
+    The API looks like:
+
+        POST /_synapse/replication/fed_send_events/:txn_id
+
+        {
+            "events": [{
+                "event": { .. serialized event .. },
+                "internal_metadata": { .. serialized internal_metadata .. },
+                "rejected_reason": ..,   // The event.rejected_reason field
+                "context": { .. serialized event context .. },
+            }],
+            "backfilled": false
+    """
+
+    NAME = "fed_send_events"
+    PATH_ARGS = ()
+
+    def __init__(self, hs):
+        super(ReplicationFederationSendEventsRestServlet, self).__init__(hs)
+
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self.federation_handler = hs.get_handlers().federation_handler
+
+    @staticmethod
+    @defer.inlineCallbacks
+    def _serialize_payload(store, event_and_contexts, backfilled):
+        """
+        Args:
+            store
+            event_and_contexts (list[tuple[FrozenEvent, EventContext]])
+            backfilled (bool): Whether or not the events are the result of
+                backfilling
+        """
+        event_payloads = []
+        for event, context in event_and_contexts:
+            serialized_context = yield context.serialize(event, store)
+
+            event_payloads.append({
+                "event": event.get_pdu_json(),
+                "internal_metadata": event.internal_metadata.get_dict(),
+                "rejected_reason": event.rejected_reason,
+                "context": serialized_context,
+            })
+
+        payload = {
+            "events": event_payloads,
+            "backfilled": backfilled,
+        }
+
+        defer.returnValue(payload)
+
+    @defer.inlineCallbacks
+    def _handle_request(self, request):
+        with Measure(self.clock, "repl_fed_send_events_parse"):
+            content = parse_json_object_from_request(request)
+
+            backfilled = content["backfilled"]
+
+            event_payloads = content["events"]
+
+            event_and_contexts = []
+            for event_payload in event_payloads:
+                event_dict = event_payload["event"]
+                internal_metadata = event_payload["internal_metadata"]
+                rejected_reason = event_payload["rejected_reason"]
+                event = FrozenEvent(event_dict, internal_metadata, rejected_reason)
+
+                context = yield EventContext.deserialize(
+                    self.store, event_payload["context"],
+                )
+
+                event_and_contexts.append((event, context))
+
+        logger.info(
+            "Got %d events from federation",
+            len(event_and_contexts),
+        )
+
+        yield self.federation_handler.persist_events_and_notify(
+            event_and_contexts, backfilled,
+        )
+
+        defer.returnValue((200, {}))
+
+
+class ReplicationFederationSendEduRestServlet(ReplicationEndpoint):
+    """Handles EDUs newly received from federation, including persisting and
+    notifying.
+
+    Request format:
+
+        POST /_synapse/replication/fed_send_edu/:edu_type/:txn_id
+
+        {
+            "origin": ...,
+            "content: { ... }
+        }
+    """
+
+    NAME = "fed_send_edu"
+    PATH_ARGS = ("edu_type",)
+
+    def __init__(self, hs):
+        super(ReplicationFederationSendEduRestServlet, self).__init__(hs)
+
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self.registry = hs.get_federation_registry()
+
+    @staticmethod
+    def _serialize_payload(edu_type, origin, content):
+        return {
+            "origin": origin,
+            "content": content,
+        }
+
+    @defer.inlineCallbacks
+    def _handle_request(self, request, edu_type):
+        with Measure(self.clock, "repl_fed_send_edu_parse"):
+            content = parse_json_object_from_request(request)
+
+            origin = content["origin"]
+            edu_content = content["content"]
+
+        logger.info(
+            "Got %r edu from %s",
+            edu_type, origin,
+        )
+
+        result = yield self.registry.on_edu(edu_type, origin, edu_content)
+
+        defer.returnValue((200, result))
+
+
+class ReplicationGetQueryRestServlet(ReplicationEndpoint):
+    """Handle responding to queries from federation.
+
+    Request format:
+
+        POST /_synapse/replication/fed_query/:query_type
+
+        {
+            "args": { ... }
+        }
+    """
+
+    NAME = "fed_query"
+    PATH_ARGS = ("query_type",)
+
+    # This is a query, so let's not bother caching
+    CACHE = False
+
+    def __init__(self, hs):
+        super(ReplicationGetQueryRestServlet, self).__init__(hs)
+
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self.registry = hs.get_federation_registry()
+
+    @staticmethod
+    def _serialize_payload(query_type, args):
+        """
+        Args:
+            query_type (str)
+            args (dict): The arguments received for the given query type
+        """
+        return {
+            "args": args,
+        }
+
+    @defer.inlineCallbacks
+    def _handle_request(self, request, query_type):
+        with Measure(self.clock, "repl_fed_query_parse"):
+            content = parse_json_object_from_request(request)
+
+            args = content["args"]
+
+        logger.info(
+            "Got %r query",
+            query_type,
+        )
+
+        result = yield self.registry.on_query(query_type, args)
+
+        defer.returnValue((200, result))
+
+
+class ReplicationCleanRoomRestServlet(ReplicationEndpoint):
+    """Called to clean up any data in DB for a given room, ready for the
+    server to join the room.
+
+    Request format:
+
+        POST /_synapse/replication/fed_query/:fed_cleanup_room/:txn_id
+
+        {}
+    """
+
+    NAME = "fed_cleanup_room"
+    PATH_ARGS = ("room_id",)
+
+    def __init__(self, hs):
+        super(ReplicationCleanRoomRestServlet, self).__init__(hs)
+
+        self.store = hs.get_datastore()
+
+    @staticmethod
+    def _serialize_payload(room_id, args):
+        """
+        Args:
+            room_id (str)
+        """
+        return {}
+
+    @defer.inlineCallbacks
+    def _handle_request(self, request, room_id):
+        yield self.store.clean_room_for_join(room_id)
+
+        defer.returnValue((200, {}))
+
+
+def register_servlets(hs, http_server):
+    ReplicationFederationSendEventsRestServlet(hs).register(http_server)
+    ReplicationFederationSendEduRestServlet(hs).register(http_server)
+    ReplicationGetQueryRestServlet(hs).register(http_server)
+    ReplicationCleanRoomRestServlet(hs).register(http_server)
diff --git a/synapse/replication/http/membership.py b/synapse/replication/http/membership.py
index 7a3cfb159c..e58bebf12a 100644
--- a/synapse/replication/http/membership.py
+++ b/synapse/replication/http/membership.py
@@ -14,182 +14,63 @@
 # limitations under the License.
 
 import logging
-import re
 
 from twisted.internet import defer
 
-from synapse.api.errors import HttpResponseException
-from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.servlet import parse_json_object_from_request
+from synapse.replication.http._base import ReplicationEndpoint
 from synapse.types import Requester, UserID
 from synapse.util.distributor import user_joined_room, user_left_room
 
 logger = logging.getLogger(__name__)
 
 
-@defer.inlineCallbacks
-def remote_join(client, host, port, requester, remote_room_hosts,
-                room_id, user_id, content):
-    """Ask the master to do a remote join for the given user to the given room
+class ReplicationRemoteJoinRestServlet(ReplicationEndpoint):
+    """Does a remote join for the given user to the given room
 
-    Args:
-        client (SimpleHttpClient)
-        host (str): host of master
-        port (int): port on master listening for HTTP replication
-        requester (Requester)
-        remote_room_hosts (list[str]): Servers to try and join via
-        room_id (str)
-        user_id (str)
-        content (dict): The event content to use for the join event
+    Request format:
 
-    Returns:
-        Deferred
-    """
-    uri = "http://%s:%s/_synapse/replication/remote_join" % (host, port)
-
-    payload = {
-        "requester": requester.serialize(),
-        "remote_room_hosts": remote_room_hosts,
-        "room_id": room_id,
-        "user_id": user_id,
-        "content": content,
-    }
-
-    try:
-        result = yield client.post_json_get_json(uri, payload)
-    except HttpResponseException as e:
-        # We convert to SynapseError as we know that it was a SynapseError
-        # on the master process that we should send to the client. (And
-        # importantly, not stack traces everywhere)
-        raise e.to_synapse_error()
-    defer.returnValue(result)
-
-
-@defer.inlineCallbacks
-def remote_reject_invite(client, host, port, requester, remote_room_hosts,
-                         room_id, user_id):
-    """Ask master to reject the invite for the user and room.
-
-    Args:
-        client (SimpleHttpClient)
-        host (str): host of master
-        port (int): port on master listening for HTTP replication
-        requester (Requester)
-        remote_room_hosts (list[str]): Servers to try and reject via
-        room_id (str)
-        user_id (str)
-
-    Returns:
-        Deferred
-    """
-    uri = "http://%s:%s/_synapse/replication/remote_reject_invite" % (host, port)
-
-    payload = {
-        "requester": requester.serialize(),
-        "remote_room_hosts": remote_room_hosts,
-        "room_id": room_id,
-        "user_id": user_id,
-    }
-
-    try:
-        result = yield client.post_json_get_json(uri, payload)
-    except HttpResponseException as e:
-        # We convert to SynapseError as we know that it was a SynapseError
-        # on the master process that we should send to the client. (And
-        # importantly, not stack traces everywhere)
-        raise e.to_synapse_error()
-    defer.returnValue(result)
-
-
-@defer.inlineCallbacks
-def get_or_register_3pid_guest(client, host, port, requester,
-                               medium, address, inviter_user_id):
-    """Ask the master to get/create a guest account for given 3PID.
-
-    Args:
-        client (SimpleHttpClient)
-        host (str): host of master
-        port (int): port on master listening for HTTP replication
-        requester (Requester)
-        medium (str)
-        address (str)
-        inviter_user_id (str): The user ID who is trying to invite the
-            3PID
-
-    Returns:
-        Deferred[(str, str)]: A 2-tuple of `(user_id, access_token)` of the
-        3PID guest account.
-    """
+        POST /_synapse/replication/remote_join/:room_id/:user_id
 
-    uri = "http://%s:%s/_synapse/replication/get_or_register_3pid_guest" % (host, port)
-
-    payload = {
-        "requester": requester.serialize(),
-        "medium": medium,
-        "address": address,
-        "inviter_user_id": inviter_user_id,
-    }
-
-    try:
-        result = yield client.post_json_get_json(uri, payload)
-    except HttpResponseException as e:
-        # We convert to SynapseError as we know that it was a SynapseError
-        # on the master process that we should send to the client. (And
-        # importantly, not stack traces everywhere)
-        raise e.to_synapse_error()
-    defer.returnValue(result)
-
-
-@defer.inlineCallbacks
-def notify_user_membership_change(client, host, port, user_id, room_id, change):
-    """Notify master that a user has joined or left the room
-
-    Args:
-        client (SimpleHttpClient)
-        host (str): host of master
-        port (int): port on master listening for HTTP replication.
-        user_id (str)
-        room_id (str)
-        change (str): Either "join" or "left"
-
-    Returns:
-        Deferred
+        {
+            "requester": ...,
+            "remote_room_hosts": [...],
+            "content": { ... }
+        }
     """
-    assert change in ("joined", "left")
-
-    uri = "http://%s:%s/_synapse/replication/user_%s_room" % (host, port, change)
-
-    payload = {
-        "user_id": user_id,
-        "room_id": room_id,
-    }
-
-    try:
-        result = yield client.post_json_get_json(uri, payload)
-    except HttpResponseException as e:
-        # We convert to SynapseError as we know that it was a SynapseError
-        # on the master process that we should send to the client. (And
-        # importantly, not stack traces everywhere)
-        raise e.to_synapse_error()
-    defer.returnValue(result)
-
 
-class ReplicationRemoteJoinRestServlet(RestServlet):
-    PATTERNS = [re.compile("^/_synapse/replication/remote_join$")]
+    NAME = "remote_join"
+    PATH_ARGS = ("room_id", "user_id",)
 
     def __init__(self, hs):
-        super(ReplicationRemoteJoinRestServlet, self).__init__()
+        super(ReplicationRemoteJoinRestServlet, self).__init__(hs)
 
         self.federation_handler = hs.get_handlers().federation_handler
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
 
+    @staticmethod
+    def _serialize_payload(requester, room_id, user_id, remote_room_hosts,
+                           content):
+        """
+        Args:
+            requester(Requester)
+            room_id (str)
+            user_id (str)
+            remote_room_hosts (list[str]): Servers to try and join via
+            content(dict): The event content to use for the join event
+        """
+        return {
+            "requester": requester.serialize(),
+            "remote_room_hosts": remote_room_hosts,
+            "content": content,
+        }
+
     @defer.inlineCallbacks
-    def on_POST(self, request):
+    def _handle_request(self, request, room_id, user_id):
         content = parse_json_object_from_request(request)
 
         remote_room_hosts = content["remote_room_hosts"]
-        room_id = content["room_id"]
-        user_id = content["user_id"]
         event_content = content["content"]
 
         requester = Requester.deserialize(self.store, content["requester"])
@@ -212,23 +93,48 @@ class ReplicationRemoteJoinRestServlet(RestServlet):
         defer.returnValue((200, {}))
 
 
-class ReplicationRemoteRejectInviteRestServlet(RestServlet):
-    PATTERNS = [re.compile("^/_synapse/replication/remote_reject_invite$")]
+class ReplicationRemoteRejectInviteRestServlet(ReplicationEndpoint):
+    """Rejects the invite for the user and room.
+
+    Request format:
+
+        POST /_synapse/replication/remote_reject_invite/:room_id/:user_id
+
+        {
+            "requester": ...,
+            "remote_room_hosts": [...],
+        }
+    """
+
+    NAME = "remote_reject_invite"
+    PATH_ARGS = ("room_id", "user_id",)
 
     def __init__(self, hs):
-        super(ReplicationRemoteRejectInviteRestServlet, self).__init__()
+        super(ReplicationRemoteRejectInviteRestServlet, self).__init__(hs)
 
         self.federation_handler = hs.get_handlers().federation_handler
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
 
+    @staticmethod
+    def _serialize_payload(requester, room_id, user_id, remote_room_hosts):
+        """
+        Args:
+            requester(Requester)
+            room_id (str)
+            user_id (str)
+            remote_room_hosts (list[str]): Servers to try and reject via
+        """
+        return {
+            "requester": requester.serialize(),
+            "remote_room_hosts": remote_room_hosts,
+        }
+
     @defer.inlineCallbacks
-    def on_POST(self, request):
+    def _handle_request(self, request, room_id, user_id):
         content = parse_json_object_from_request(request)
 
         remote_room_hosts = content["remote_room_hosts"]
-        room_id = content["room_id"]
-        user_id = content["user_id"]
 
         requester = Requester.deserialize(self.store, content["requester"])
 
@@ -264,18 +170,50 @@ class ReplicationRemoteRejectInviteRestServlet(RestServlet):
         defer.returnValue((200, ret))
 
 
-class ReplicationRegister3PIDGuestRestServlet(RestServlet):
-    PATTERNS = [re.compile("^/_synapse/replication/get_or_register_3pid_guest$")]
+class ReplicationRegister3PIDGuestRestServlet(ReplicationEndpoint):
+    """Gets/creates a guest account for given 3PID.
+
+    Request format:
+
+        POST /_synapse/replication/get_or_register_3pid_guest/
+
+        {
+            "requester": ...,
+            "medium": ...,
+            "address": ...,
+            "inviter_user_id": ...
+        }
+    """
+
+    NAME = "get_or_register_3pid_guest"
+    PATH_ARGS = ()
 
     def __init__(self, hs):
-        super(ReplicationRegister3PIDGuestRestServlet, self).__init__()
+        super(ReplicationRegister3PIDGuestRestServlet, self).__init__(hs)
 
         self.registeration_handler = hs.get_handlers().registration_handler
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
 
+    @staticmethod
+    def _serialize_payload(requester, medium, address, inviter_user_id):
+        """
+        Args:
+            requester(Requester)
+            medium (str)
+            address (str)
+            inviter_user_id (str): The user ID who is trying to invite the
+                3PID
+        """
+        return {
+            "requester": requester.serialize(),
+            "medium": medium,
+            "address": address,
+            "inviter_user_id": inviter_user_id,
+        }
+
     @defer.inlineCallbacks
-    def on_POST(self, request):
+    def _handle_request(self, request):
         content = parse_json_object_from_request(request)
 
         medium = content["medium"]
@@ -296,23 +234,41 @@ class ReplicationRegister3PIDGuestRestServlet(RestServlet):
         defer.returnValue((200, ret))
 
 
-class ReplicationUserJoinedLeftRoomRestServlet(RestServlet):
-    PATTERNS = [re.compile("^/_synapse/replication/user_(?P<change>joined|left)_room$")]
+class ReplicationUserJoinedLeftRoomRestServlet(ReplicationEndpoint):
+    """Notifies that a user has joined or left the room
+
+    Request format:
+
+        POST /_synapse/replication/membership_change/:room_id/:user_id/:change
+
+        {}
+    """
+
+    NAME = "membership_change"
+    PATH_ARGS = ("room_id", "user_id", "change")
+    CACHE = False  # No point caching as should return instantly.
 
     def __init__(self, hs):
-        super(ReplicationUserJoinedLeftRoomRestServlet, self).__init__()
+        super(ReplicationUserJoinedLeftRoomRestServlet, self).__init__(hs)
 
         self.registeration_handler = hs.get_handlers().registration_handler
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
         self.distributor = hs.get_distributor()
 
-    def on_POST(self, request, change):
-        content = parse_json_object_from_request(request)
+    @staticmethod
+    def _serialize_payload(room_id, user_id, change):
+        """
+        Args:
+            room_id (str)
+            user_id (str)
+            change (str): Either "joined" or "left"
+        """
+        assert change in ("joined", "left",)
 
-        user_id = content["user_id"]
-        room_id = content["room_id"]
+        return {}
 
+    def _handle_request(self, request, room_id, user_id, change):
         logger.info("user membership change: %s in %s", user_id, room_id)
 
         user = UserID.from_string(user_id)
diff --git a/synapse/replication/http/send_event.py b/synapse/replication/http/send_event.py
index d3509dc288..5b52c91650 100644
--- a/synapse/replication/http/send_event.py
+++ b/synapse/replication/http/send_event.py
@@ -14,86 +14,26 @@
 # limitations under the License.
 
 import logging
-import re
 
 from twisted.internet import defer
 
-from synapse.api.errors import CodeMessageException, HttpResponseException
 from synapse.events import FrozenEvent
 from synapse.events.snapshot import EventContext
-from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.servlet import parse_json_object_from_request
+from synapse.replication.http._base import ReplicationEndpoint
 from synapse.types import Requester, UserID
-from synapse.util.caches.response_cache import ResponseCache
 from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
 
 
-@defer.inlineCallbacks
-def send_event_to_master(clock, store, client, host, port, requester, event, context,
-                         ratelimit, extra_users):
-    """Send event to be handled on the master
-
-    Args:
-        clock (synapse.util.Clock)
-        store (DataStore)
-        client (SimpleHttpClient)
-        host (str): host of master
-        port (int): port on master listening for HTTP replication
-        requester (Requester)
-        event (FrozenEvent)
-        context (EventContext)
-        ratelimit (bool)
-        extra_users (list(UserID)): Any extra users to notify about event
-    """
-    uri = "http://%s:%s/_synapse/replication/send_event/%s" % (
-        host, port, event.event_id,
-    )
-
-    serialized_context = yield context.serialize(event, store)
-
-    payload = {
-        "event": event.get_pdu_json(),
-        "internal_metadata": event.internal_metadata.get_dict(),
-        "rejected_reason": event.rejected_reason,
-        "context": serialized_context,
-        "requester": requester.serialize(),
-        "ratelimit": ratelimit,
-        "extra_users": [u.to_string() for u in extra_users],
-    }
-
-    try:
-        # We keep retrying the same request for timeouts. This is so that we
-        # have a good idea that the request has either succeeded or failed on
-        # the master, and so whether we should clean up or not.
-        while True:
-            try:
-                result = yield client.put_json(uri, payload)
-                break
-            except CodeMessageException as e:
-                if e.code != 504:
-                    raise
-
-            logger.warn("send_event request timed out")
-
-            # If we timed out we probably don't need to worry about backing
-            # off too much, but lets just wait a little anyway.
-            yield clock.sleep(1)
-    except HttpResponseException as e:
-        # We convert to SynapseError as we know that it was a SynapseError
-        # on the master process that we should send to the client. (And
-        # importantly, not stack traces everywhere)
-        raise e.to_synapse_error()
-    defer.returnValue(result)
-
-
-class ReplicationSendEventRestServlet(RestServlet):
+class ReplicationSendEventRestServlet(ReplicationEndpoint):
     """Handles events newly created on workers, including persisting and
     notifying.
 
     The API looks like:
 
-        POST /_synapse/replication/send_event/:event_id
+        POST /_synapse/replication/send_event/:event_id/:txn_id
 
         {
             "event": { .. serialized event .. },
@@ -105,27 +45,47 @@ class ReplicationSendEventRestServlet(RestServlet):
             "extra_users": [],
         }
     """
-    PATTERNS = [re.compile("^/_synapse/replication/send_event/(?P<event_id>[^/]+)$")]
+    NAME = "send_event"
+    PATH_ARGS = ("event_id",)
 
     def __init__(self, hs):
-        super(ReplicationSendEventRestServlet, self).__init__()
+        super(ReplicationSendEventRestServlet, self).__init__(hs)
 
         self.event_creation_handler = hs.get_event_creation_handler()
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
 
-        # The responses are tiny, so we may as well cache them for a while
-        self.response_cache = ResponseCache(hs, "send_event", timeout_ms=30 * 60 * 1000)
+    @staticmethod
+    @defer.inlineCallbacks
+    def _serialize_payload(event_id, store, event, context, requester,
+                           ratelimit, extra_users):
+        """
+        Args:
+            event_id (str)
+            store (DataStore)
+            requester (Requester)
+            event (FrozenEvent)
+            context (EventContext)
+            ratelimit (bool)
+            extra_users (list(UserID)): Any extra users to notify about event
+        """
+
+        serialized_context = yield context.serialize(event, store)
+
+        payload = {
+            "event": event.get_pdu_json(),
+            "internal_metadata": event.internal_metadata.get_dict(),
+            "rejected_reason": event.rejected_reason,
+            "context": serialized_context,
+            "requester": requester.serialize(),
+            "ratelimit": ratelimit,
+            "extra_users": [u.to_string() for u in extra_users],
+        }
 
-    def on_PUT(self, request, event_id):
-        return self.response_cache.wrap(
-            event_id,
-            self._handle_request,
-            request
-        )
+        defer.returnValue(payload)
 
     @defer.inlineCallbacks
-    def _handle_request(self, request):
+    def _handle_request(self, request, event_id):
         with Measure(self.clock, "repl_send_event_parse"):
             content = parse_json_object_from_request(request)
 
diff --git a/synapse/replication/slave/storage/events.py b/synapse/replication/slave/storage/events.py
index bdb5eee4af..4830c68f35 100644
--- a/synapse/replication/slave/storage/events.py
+++ b/synapse/replication/slave/storage/events.py
@@ -44,8 +44,8 @@ class SlavedEventStore(EventFederationWorkerStore,
                        RoomMemberWorkerStore,
                        EventPushActionsWorkerStore,
                        StreamWorkerStore,
-                       EventsWorkerStore,
                        StateGroupWorkerStore,
+                       EventsWorkerStore,
                        SignatureWorkerStore,
                        UserErasureWorkerStore,
                        BaseSlavedStore):
diff --git a/synapse/replication/slave/storage/transactions.py b/synapse/replication/slave/storage/transactions.py
index 9c9a5eadd9..3527beb3c9 100644
--- a/synapse/replication/slave/storage/transactions.py
+++ b/synapse/replication/slave/storage/transactions.py
@@ -13,19 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.storage import DataStore
 from synapse.storage.transactions import TransactionStore
 
 from ._base import BaseSlavedStore
 
 
-class TransactionStore(BaseSlavedStore):
-    get_destination_retry_timings = TransactionStore.__dict__[
-        "get_destination_retry_timings"
-    ]
-    _get_destination_retry_timings = DataStore._get_destination_retry_timings.__func__
-    set_destination_retry_timings = DataStore.set_destination_retry_timings.__func__
-    _set_destination_retry_timings = DataStore._set_destination_retry_timings.__func__
-
-    prep_send_transaction = DataStore.prep_send_transaction.__func__
-    delivered_txn = DataStore.delivered_txn.__func__
+class SlavedTransactionStore(TransactionStore, BaseSlavedStore):
+    pass
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 970e94313e..cbe9645817 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -107,7 +107,7 @@ class ReplicationClientHandler(object):
         Can be overriden in subclasses to handle more.
         """
         logger.info("Received rdata %s -> %s", stream_name, token)
-        self.store.process_replication_rows(stream_name, token, rows)
+        return self.store.process_replication_rows(stream_name, token, rows)
 
     def on_position(self, stream_name, token):
         """Called when we get new position data. By default this just pokes
@@ -115,7 +115,7 @@ class ReplicationClientHandler(object):
 
         Can be overriden in subclasses to handle more.
         """
-        self.store.process_replication_rows(stream_name, token, [])
+        return self.store.process_replication_rows(stream_name, token, [])
 
     def on_sync(self, data):
         """When we received a SYNC we wake up any deferreds that were waiting
diff --git a/synapse/replication/tcp/commands.py b/synapse/replication/tcp/commands.py
index f3908df642..327556f6a1 100644
--- a/synapse/replication/tcp/commands.py
+++ b/synapse/replication/tcp/commands.py
@@ -59,6 +59,12 @@ class Command(object):
         """
         return self.data
 
+    def get_logcontext_id(self):
+        """Get a suitable string for the logcontext when processing this command"""
+
+        # by default, we just use the command name.
+        return self.NAME
+
 
 class ServerCommand(Command):
     """Sent by the server on new connection and includes the server_name.
@@ -116,6 +122,9 @@ class RdataCommand(Command):
             _json_encoder.encode(self.row),
         ))
 
+    def get_logcontext_id(self):
+        return "RDATA-" + self.stream_name
+
 
 class PositionCommand(Command):
     """Sent by the client to tell the client the stream postition without
@@ -190,6 +199,9 @@ class ReplicateCommand(Command):
     def to_line(self):
         return " ".join((self.stream_name, str(self.token),))
 
+    def get_logcontext_id(self):
+        return "REPLICATE-" + self.stream_name
+
 
 class UserSyncCommand(Command):
     """Sent by the client to inform the server that a user has started or
diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py
index dec5ac0913..74e892c104 100644
--- a/synapse/replication/tcp/protocol.py
+++ b/synapse/replication/tcp/protocol.py
@@ -63,6 +63,8 @@ from twisted.protocols.basic import LineOnlyReceiver
 from twisted.python.failure import Failure
 
 from synapse.metrics import LaterGauge
+from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.util.logcontext import make_deferred_yieldable, run_in_background
 from synapse.util.stringutils import random_string
 
 from .commands import (
@@ -222,7 +224,11 @@ class BaseReplicationStreamProtocol(LineOnlyReceiver):
 
         # Now lets try and call on_<CMD_NAME> function
         try:
-            getattr(self, "on_%s" % (cmd_name,))(cmd)
+            run_as_background_process(
+                "replication-" + cmd.get_logcontext_id(),
+                getattr(self, "on_%s" % (cmd_name,)),
+                cmd,
+            )
         except Exception:
             logger.exception("[%s] Failed to handle line: %r", self.id(), line)
 
@@ -387,7 +393,7 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
         self.name = cmd.data
 
     def on_USER_SYNC(self, cmd):
-        self.streamer.on_user_sync(
+        return self.streamer.on_user_sync(
             self.conn_id, cmd.user_id, cmd.is_syncing, cmd.last_sync_ms,
         )
 
@@ -397,22 +403,33 @@ class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol):
 
         if stream_name == "ALL":
             # Subscribe to all streams we're publishing to.
-            for stream in iterkeys(self.streamer.streams_by_name):
-                self.subscribe_to_stream(stream, token)
+            deferreds = [
+                run_in_background(
+                    self.subscribe_to_stream,
+                    stream, token,
+                )
+                for stream in iterkeys(self.streamer.streams_by_name)
+            ]
+
+            return make_deferred_yieldable(
+                defer.gatherResults(deferreds, consumeErrors=True)
+            )
         else:
-            self.subscribe_to_stream(stream_name, token)
+            return self.subscribe_to_stream(stream_name, token)
 
     def on_FEDERATION_ACK(self, cmd):
-        self.streamer.federation_ack(cmd.token)
+        return self.streamer.federation_ack(cmd.token)
 
     def on_REMOVE_PUSHER(self, cmd):
-        self.streamer.on_remove_pusher(cmd.app_id, cmd.push_key, cmd.user_id)
+        return self.streamer.on_remove_pusher(
+            cmd.app_id, cmd.push_key, cmd.user_id,
+        )
 
     def on_INVALIDATE_CACHE(self, cmd):
-        self.streamer.on_invalidate_cache(cmd.cache_func, cmd.keys)
+        return self.streamer.on_invalidate_cache(cmd.cache_func, cmd.keys)
 
     def on_USER_IP(self, cmd):
-        self.streamer.on_user_ip(
+        return self.streamer.on_user_ip(
             cmd.user_id, cmd.access_token, cmd.ip, cmd.user_agent, cmd.device_id,
             cmd.last_seen,
         )
@@ -542,14 +559,13 @@ class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol):
             # Check if this is the last of a batch of updates
             rows = self.pending_batches.pop(stream_name, [])
             rows.append(row)
-
-            self.handler.on_rdata(stream_name, cmd.token, rows)
+            return self.handler.on_rdata(stream_name, cmd.token, rows)
 
     def on_POSITION(self, cmd):
-        self.handler.on_position(cmd.stream_name, cmd.token)
+        return self.handler.on_position(cmd.stream_name, cmd.token)
 
     def on_SYNC(self, cmd):
-        self.handler.on_sync(cmd.data)
+        return self.handler.on_sync(cmd.data)
 
     def replicate(self, stream_name, token):
         """Send the subscription request to the server