Safe async event cache (#13308)

Fix race conditions in the async cache invalidation logic, by separating
the async & local invalidation calls and ensuring any async call i
executed first.

Signed off by Nick @ Beeper (@Fizzadar).

1 files changed, 3 insertions, 3 deletions

diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index fa2266ba20..156e1bd5ab 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -1293,7 +1293,7 @@ class PersistEventsStore:
         depth_updates: Dict[str, int] = {}
         for event, context in events_and_contexts:
             # Remove the any existing cache entries for the event_ids
-            txn.call_after(self.store._invalidate_get_event_cache, event.event_id)
+            self.store.invalidate_get_event_cache_after_txn(txn, event.event_id)
             # Then update the `stream_ordering` position to mark the latest
             # event as the front of the room. This should not be done for
             # backfilled events because backfilled events have negative
@@ -1675,7 +1675,7 @@ class PersistEventsStore:
                     (cache_entry.event.event_id,), cache_entry
                 )
 
-        txn.call_after(prefill)
+        txn.async_call_after(prefill)
 
     def _store_redaction(self, txn: LoggingTransaction, event: EventBase) -> None:
         """Invalidate the caches for the redacted event.
@@ -1684,7 +1684,7 @@ class PersistEventsStore:
         _invalidate_caches_for_event.
         """
         assert event.redacts is not None
-        txn.call_after(self.store._invalidate_get_event_cache, event.redacts)
+        self.store.invalidate_get_event_cache_after_txn(txn, event.redacts)
         txn.call_after(self.store.get_relations_for_event.invalidate, (event.redacts,))
         txn.call_after(self.store.get_applicable_edit.invalidate, (event.redacts,))