Only send events that originate on this server.

Or events that are sent via the federation "send_join" API.

This should match the behaviour from before v0.18.5 and #1635 landed.

synapse/events/__init__.py

@@ -36,6 +36,15 @@ class _EventInternalMetadata(object):
     def is_invite_from_remote(self):
         return getattr(self, "invite_from_remote", False)
 
+    def get_send_on_behalf_of(self):
+        """Whether this server should send the event on behalf of another server.
+        This is used by the federation "send_join" API to forward the initial join
+        event for a server in the room.
+
+        returns a str with the name of the server this event is sent on behalf of.
+        """
+        return getattr(self, "get_send_on_behalf_of", None)
+
 
 def _event_dict_property(key):
     def getter(self):

synapse/federation/transaction_queue.py

@@ -61,6 +61,7 @@ class TransactionQueue(object):
         self.transport_layer = hs.get_federation_transport_client()
 
         self.clock = hs.get_clock()
+        self.is_mine_id = hs.is_mine_id
 
         # Is a mapping from destinations -> deferreds. Used to keep track
         # of which destinations have transactions in flight and when they are
@@ -152,6 +153,12 @@ class TransactionQueue(object):
                     break
 
                 for event in events:
+                    # Only send events for this server.
+                    send_on_behalf_of = event.internal_metadata.get_send_on_behalf_of()
+                    is_mine = self.is_mine_id(event.event_id)
+                    if not is_mine and send_on_behalf_of is None:
+                        continue
+
                     # Get the state from before the event.
                     # We need to make sure that this is the state from before
                     # the event and not from after it.
@@ -167,6 +174,11 @@ class TransactionQueue(object):
                     destinations = set(
                         get_domain_from_id(user_id) for user_id in users_in_room
                     )
+                    if send_on_behalf_of is not None:
+                        # If we are sending the event on behalf of another server
+                        # then it already has the event and there is no reason to
+                        # send the event to it.
+                        destinations.discard(send_on_behalf_of)
 
                     logger.debug("Sending %s to %r", event, destinations)
 

synapse/handlers/federation.py

@@ -790,6 +790,10 @@ class FederationHandler(BaseHandler):
         )
 
         event.internal_metadata.outlier = False
+        # Send this event on behalf of the origin server since they may not
+        # have an up to data view of the state of the room at this event so
+        # will not know which servers to send the event to.
+        event.internal_metadata.send_on_behalf_of = origin
 
         context, event_stream_id, max_stream_id = yield self._handle_new_event(
             origin, event