Make `handle_new_client_event` throws `PartialStateConflictError` (#14665)

Then adapts calling code to retry when needed so it doesn't 500
to clients.

Signed-off-by: Mathieu Velten <mathieuv@matrix.org>
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/synapse/handlers/room_batch.py b/synapse/handlers/room_batch.py

index 411a6fb22f..c73d2adaad 100644
--- a/synapse/handlers/room_batch.py
+++ b/synapse/handlers/room_batch.py
@@ -375,6 +375,8 @@ class RoomBatchHandler:
         # Events are sorted by (topological_ordering, stream_ordering)
         # where topological_ordering is just depth.
         for (event, context) in reversed(events_to_persist):
+            # This call can't raise `PartialStateConflictError` since we forbid
+            # use of the historical batch API during partial state
             await self.event_creation_handler.handle_new_client_event(
                 await self.create_requester_for_user_id_from_app_service(
                     event.sender, app_service_requester.app_service