Merge pull request #3079 from matrix-org/erikj/limit_concurrent_sends

Limit concurrent event sends for a room

synapse/handlers/message.py

@@ -454,40 +454,39 @@ def create_event(self, requester, event_dict, token_id=None, txn_id=None,
         """
         builder = self.event_builder_factory.new(event_dict)
 
-        with (yield self.limiter.queue(builder.room_id)):
-            self.validator.validate_new(builder)
-
-            if builder.type == EventTypes.Member:
-                membership = builder.content.get("membership", None)
-                target = UserID.from_string(builder.state_key)
-
-                if membership in {Membership.JOIN, Membership.INVITE}:
-                    # If event doesn't include a display name, add one.
-                    profile = self.profile_handler
-                    content = builder.content
-
-                    try:
-                        if "displayname" not in content:
-                            content["displayname"] = yield profile.get_displayname(target)
-                        if "avatar_url" not in content:
-                            content["avatar_url"] = yield profile.get_avatar_url(target)
-                    except Exception as e:
-                        logger.info(
-                            "Failed to get profile information for %r: %s",
-                            target, e
-                        )
+        self.validator.validate_new(builder)
+
+        if builder.type == EventTypes.Member:
+            membership = builder.content.get("membership", None)
+            target = UserID.from_string(builder.state_key)
+
+            if membership in {Membership.JOIN, Membership.INVITE}:
+                # If event doesn't include a display name, add one.
+                profile = self.profile_handler
+                content = builder.content
+
+                try:
+                    if "displayname" not in content:
+                        content["displayname"] = yield profile.get_displayname(target)
+                    if "avatar_url" not in content:
+                        content["avatar_url"] = yield profile.get_avatar_url(target)
+                except Exception as e:
+                    logger.info(
+                        "Failed to get profile information for %r: %s",
+                        target, e
+                    )
 
-            if token_id is not None:
-                builder.internal_metadata.token_id = token_id
+        if token_id is not None:
+            builder.internal_metadata.token_id = token_id
 
-            if txn_id is not None:
-                builder.internal_metadata.txn_id = txn_id
+        if txn_id is not None:
+            builder.internal_metadata.txn_id = txn_id
 
-            event, context = yield self.create_new_client_event(
-                builder=builder,
-                requester=requester,
-                prev_event_ids=prev_event_ids,
-            )
+        event, context = yield self.create_new_client_event(
+            builder=builder,
+            requester=requester,
+            prev_event_ids=prev_event_ids,
+        )
 
         defer.returnValue((event, context))
 
@@ -557,27 +556,34 @@ def create_and_send_nonmember_event(
 
         See self.create_event and self.send_nonmember_event.
         """
-        event, context = yield self.create_event(
-            requester,
-            event_dict,
-            token_id=requester.access_token_id,
-            txn_id=txn_id
-        )
 
-        spam_error = self.spam_checker.check_event_for_spam(event)
-        if spam_error:
-            if not isinstance(spam_error, basestring):
-                spam_error = "Spam is not permitted here"
-            raise SynapseError(
-                403, spam_error, Codes.FORBIDDEN
+        # We limit the number of concurrent event sends in a room so that we
+        # don't fork the DAG too much. If we don't limit then we can end up in
+        # a situation where event persistence can't keep up, causing
+        # extremities to pile up, which in turn leads to state resolution
+        # taking longer.
+        with (yield self.limiter.queue(event_dict["room_id"])):
+            event, context = yield self.create_event(
+                requester,
+                event_dict,
+                token_id=requester.access_token_id,
+                txn_id=txn_id
             )
 
-        yield self.send_nonmember_event(
-            requester,
-            event,
-            context,
-            ratelimit=ratelimit,
-        )
+            spam_error = self.spam_checker.check_event_for_spam(event)
+            if spam_error:
+                if not isinstance(spam_error, basestring):
+                    spam_error = "Spam is not permitted here"
+                raise SynapseError(
+                    403, spam_error, Codes.FORBIDDEN
+                )
+
+            yield self.send_nonmember_event(
+                requester,
+                event,
+                context,
+                ratelimit=ratelimit,
+            )
         defer.returnValue(event)
 
     @measure_func("create_new_client_event")

synapse/rest/client/v1/room.py

@@ -165,17 +165,12 @@ def on_PUT(self, request, room_id, event_type, state_key, txn_id=None):
                 content=content,
             )
         else:
-            event, context = yield self.event_creation_hander.create_event(
+            event = yield self.event_creation_hander.create_and_send_nonmember_event(
                 requester,
                 event_dict,
-                token_id=requester.access_token_id,
                 txn_id=txn_id,
             )
 
-            yield self.event_creation_hander.send_nonmember_event(
-                requester, event, context,
-            )
-
         ret = {}
         if event:
             ret = {"event_id": event.event_id}