Correctly handle receiving 'missing' Pdus from federation, rather than just discarding them.

synapse/handlers/federation.py

@@ -100,17 +100,11 @@ class FederationHandler(BaseHandler):
                 is_new_state = yield self.state_handler.handle_new_state(
                     pdu
                 )
-                if not is_new_state:
-                    return
             else:
                 is_new_state = False
         # TODO: Implement something in federation that allows us to
         # respond to PDU.
 
-        if hasattr(event, "state_key") and not is_new_state:
-            logger.debug("Ignoring old state: %s", event.event_id)
-            return
-
         target_is_mine = False
         if hasattr(event, "target_host"):
             target_is_mine = event.target_host == self.hs.hostname
@@ -141,7 +135,11 @@ class FederationHandler(BaseHandler):
 
         else:
             with (yield self.room_lock.lock(event.room_id)):
-                yield self.store.persist_event(event, backfilled)
+                yield self.store.persist_event(
+                    event,
+                    backfilled,
+                    is_new_state=is_new_state
+                )
 
             room = yield self.store.get_room(event.room_id)
 

synapse/storage/__init__.py

@@ -68,7 +68,8 @@ class DataStore(RoomMemberStore, RoomStore,
 
     @defer.inlineCallbacks
     @log_function
-    def persist_event(self, event=None, backfilled=False, pdu=None):
+    def persist_event(self, event=None, backfilled=False, pdu=None,
+                      is_new_state=True):
         stream_ordering = None
         if backfilled:
             if not self.min_token_deferred.called:
@@ -83,6 +84,7 @@ class DataStore(RoomMemberStore, RoomStore,
                 event=event,
                 backfilled=backfilled,
                 stream_ordering=stream_ordering,
+                is_new_state=is_new_state,
             )
         except _RollbackButIsFineException as e:
             pass
@@ -109,12 +111,14 @@ class DataStore(RoomMemberStore, RoomStore,
         defer.returnValue(event)
 
     def _persist_pdu_event_txn(self, txn, pdu=None, event=None,
-                               backfilled=False, stream_ordering=None):
+                               backfilled=False, stream_ordering=None,
+                               is_new_state=True):
         if pdu is not None:
             self._persist_event_pdu_txn(txn, pdu)
         if event is not None:
             return self._persist_event_txn(
-                txn, event, backfilled, stream_ordering
+                txn, event, backfilled, stream_ordering,
+                is_new_state=is_new_state,
             )
 
     def _persist_event_pdu_txn(self, txn, pdu):
@@ -141,7 +145,8 @@ class DataStore(RoomMemberStore, RoomStore,
         self._update_min_depth_for_context_txn(txn, pdu.context, pdu.depth)
 
     @log_function
-    def _persist_event_txn(self, txn, event, backfilled, stream_ordering=None):
+    def _persist_event_txn(self, txn, event, backfilled, stream_ordering=None,
+                           is_new_state=True):
         if event.type == RoomMemberEvent.TYPE:
             self._store_room_member_txn(txn, event)
         elif event.type == FeedbackEvent.TYPE:
@@ -195,7 +200,7 @@ class DataStore(RoomMemberStore, RoomStore,
             )
             raise _RollbackButIsFineException("_persist_event")
 
-        if not backfilled and hasattr(event, "state_key"):
+        if is_new_state and hasattr(event, "state_key"):
             vals = {
                 "event_id": event.event_id,
                 "room_id": event.room_id,

tests/handlers/test_federation.py

@@ -74,7 +74,9 @@ class FederationTestCase(unittest.TestCase):
 
         yield self.handlers.federation_handler.on_receive_pdu(pdu, False)
 
-        self.datastore.persist_event.assert_called_once_with(ANY, False)
+        self.datastore.persist_event.assert_called_once_with(
+            ANY, False, is_new_state=False
+        )
         self.notifier.on_new_room_event.assert_called_once_with(ANY)
 
     @defer.inlineCallbacks