Limit the number of events that can be created on a given room concurretnly

synapse/handlers/message.py

@@ -24,7 +24,7 @@ from synapse.push.action_generator import ActionGenerator
 from synapse.types import (
     UserID, RoomAlias, RoomStreamToken, get_domain_from_id
 )
-from synapse.util.async import run_on_reactor, ReadWriteLock
+from synapse.util.async import run_on_reactor, ReadWriteLock, Limiter
 from synapse.util.logcontext import preserve_fn
 from synapse.util.metrics import measure_func
 from synapse.visibility import filter_events_for_client
@@ -50,6 +50,8 @@ class MessageHandler(BaseHandler):
 
         self.pagination_lock = ReadWriteLock()
 
+        self.limiter = Limiter(max_count=5)
+
     @defer.inlineCallbacks
     def purge_history(self, room_id, event_id):
         event = yield self.store.get_event(event_id)
@@ -191,6 +193,7 @@ class MessageHandler(BaseHandler):
         """
         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:
@@ -221,6 +224,7 @@ class MessageHandler(BaseHandler):
                 builder=builder,
                 prev_event_ids=prev_event_ids,
             )
+
         defer.returnValue((event, context))
 
     @defer.inlineCallbacks