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

Limit concurrent event sends for a room

synapse/handlers/message.py

@@ -454,7 +454,6 @@ class EventCreationHandler(object):
         """
         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:
@@ -557,6 +556,13 @@ class EventCreationHandler(object):
 
         See self.create_event and self.send_nonmember_event.
         """
+
+        # 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,

synapse/rest/client/v1/room.py

@@ -165,17 +165,12 @@ class RoomStateEventRestServlet(ClientV1RestServlet):
                 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}