Wait for streams to catch up when processing HTTP replication. (#14820)

This should hopefully mitigate a class of races where data gets out of
sync due a HTTP replication request racing with the replication streams.

1 files changed, 4 insertions, 0 deletions

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

index 6df000faaf..904a721483 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -2259,6 +2259,10 @@ class FederationEventHandler:
                 event_and_contexts, backfilled=backfilled
             )
 
+            # After persistence we always need to notify replication there may
+            # be new data.
+            self._notifier.notify_replication()
+
             if self._ephemeral_messages_enabled:
                 for event in events:
                     # If there's an expiry timestamp on the event, schedule its expiry.