diff --git a/synapse/handlers/pagination.py b/synapse/handlers/pagination.py
index 6fd7afa280..365c9cabcb 100644
--- a/synapse/handlers/pagination.py
+++ b/synapse/handlers/pagination.py
@@ -507,15 +507,17 @@ class PaginationHandler:
# Initially fetch the events from the database. With any luck, we can return
# these without blocking on backfill (handled below).
- events, next_key = (
- await self.store.paginate_room_events_by_topological_ordering(
- room_id=room_id,
- from_key=from_token.room_key,
- to_key=to_room_key,
- direction=pagin_config.direction,
- limit=pagin_config.limit,
- event_filter=event_filter,
- )
+ (
+ events,
+ next_key,
+ limited,
+ ) = await self.store.paginate_room_events_by_topological_ordering(
+ room_id=room_id,
+ from_key=from_token.room_key,
+ to_key=to_room_key,
+ direction=pagin_config.direction,
+ limit=pagin_config.limit,
+ event_filter=event_filter,
)
if pagin_config.direction == Direction.BACKWARDS:
@@ -575,25 +577,31 @@ class PaginationHandler:
or missing_too_many_events
or not_enough_events_to_fill_response
):
- did_backfill = await self.hs.get_federation_handler().maybe_backfill(
+ # Historical Note: There used to be a check here for if backfill was
+ # successful or not
+ await self.hs.get_federation_handler().maybe_backfill(
room_id,
curr_topo,
limit=pagin_config.limit,
)
- # If we did backfill something, refetch the events from the database to
- # catch anything new that might have been added since we last fetched.
- if did_backfill:
- events, next_key = (
- await self.store.paginate_room_events_by_topological_ordering(
- room_id=room_id,
- from_key=from_token.room_key,
- to_key=to_room_key,
- direction=pagin_config.direction,
- limit=pagin_config.limit,
- event_filter=event_filter,
- )
- )
+ # Regardless if we backfilled or not, another worker or even a
+ # simultaneous request may have backfilled for us while we were held
+ # behind the linearizer. This should not have too much additional
+ # database load as it will only be triggered if a backfill *might* have
+ # been needed
+ (
+ events,
+ next_key,
+ limited,
+ ) = await self.store.paginate_room_events_by_topological_ordering(
+ room_id=room_id,
+ from_key=from_token.room_key,
+ to_key=to_room_key,
+ direction=pagin_config.direction,
+ limit=pagin_config.limit,
+ event_filter=event_filter,
+ )
else:
# Otherwise, we can backfill in the background for eventual
# consistency's sake but we don't need to block the client waiting
@@ -608,6 +616,15 @@ class PaginationHandler:
next_token = from_token.copy_and_replace(StreamKeyType.ROOM, next_key)
+ # We might have hit some internal filtering first, for example rejected
+ # events. Ensure we return a pagination token then.
+ if not events and limited:
+ return {
+ "chunk": [],
+ "start": await from_token.to_string(self.store),
+ "end": await next_token.to_string(self.store),
+ }
+
# if no events are returned from pagination, that implies
# we have reached the end of the available events.
# In that case we do not return end, to tell the client
|
