Correctly figure out which rooms we've sent down

synapse/handlers/sync.py

@@ -284,18 +284,29 @@ class SyncHandler(BaseHandler):
         room_pagination_config = {
             "l": pagination_limit,
             "o": 0,
-            "t": now_token,
+            "t": now_token.to_string(),
         }
 
         room_to_last_ts = yield self._get_room_timestamps_at_token(
-            room_ids=[e.room_id for e in room_list if e.membership == Membership.JOIN],
+            room_ids=[
+                e.room_id for e in room_list if e.membership == Membership.JOIN
+            ],
             token=now_token,
         )
 
-        joined_rooms_list = frozenset([
-            room_id for room_id, _f in
-            sorted(room_to_last_ts.items(), key=lambda item: -item[1])
-        ][:pagination_limit])
+        if room_to_last_ts:
+            sorted_list = sorted(
+                room_to_last_ts.items(),
+                key=lambda item: -item[1]
+            )[:pagination_limit]
+
+            _, bottom_ts = sorted_list[-1]
+            room_pagination_config["ts"] = bottom_ts
+
+            joined_rooms_list = frozenset(room_id for room_id, _f in sorted_list)
+        else:
+            room_pagination_config = {}
+            joined_rooms_list = frozenset()
 
         @defer.inlineCallbacks
         def _generate_room_entry(event):
@@ -500,6 +511,18 @@ class SyncHandler(BaseHandler):
             account_data_by_room, full_state=True, leave_token=leave_token,
         )
 
+    @defer.inlineCallbacks
+    def _get_rooms_that_need_full_state(self, room_ids, since_token, pa_ts):
+        start_ts = yield self._get_room_timestamps_at_token(room_ids, since_token)
+
+        missing_list = frozenset(
+            room_id for room_id, ts in
+            sorted(start_ts.items(), key=lambda item: -item[1])
+            if ts < pa_ts
+        )
+
+        defer.returnValue(missing_list)
+
     @defer.inlineCallbacks
     def incremental_sync_with_gap(self, sync_config, batch_token):
         """ Get the incremental delta needed to bring the client up to
@@ -508,6 +531,7 @@ class SyncHandler(BaseHandler):
             A Deferred SyncResult.
         """
         since_token = batch_token.stream_token
+        room_pagination_config = batch_token.pagination_config
 
         now_token = yield self.event_sources.get_current_token()
 
@@ -638,18 +662,30 @@ class SyncHandler(BaseHandler):
             limit=timeline_limit + 1,
         )
 
+        p_room_token = room_pagination_config.get("t", None)
+        if p_room_token:
+            needing_full_state = yield self._get_rooms_that_need_full_state(
+                joined_room_ids,
+                since_token,
+                room_pagination_config.get("ts", 0),
+            )
+        else:
+            needing_full_state = set()
+
         joined = []
         # We loop through all room ids, even if there are no new events, in case
         # there are non room events taht we need to notify about.
         for room_id in joined_room_ids:
             room_entry = room_to_events.get(room_id, None)
 
+            need_full_state = room_id in needing_full_state
+
             if room_entry:
                 events, start_key = room_entry
 
                 prev_batch_token = now_token.copy_and_replace("room_key", start_key)
 
-                newly_joined_room = room_id in newly_joined_rooms
+                newly_joined_room = (room_id in newly_joined_rooms) or need_full_state
                 full_state = newly_joined_room
 
                 batch = yield self.load_filtered_recents(
@@ -659,6 +695,9 @@ class SyncHandler(BaseHandler):
                     newly_joined_room=newly_joined_room,
                 )
             else:
+                if need_full_state:
+                    continue
+
                 batch = TimelineBatch(
                     events=[],
                     prev_batch=since_token,