Fix 'rejected_events_metadata' background update (matrix-org#9537)

erikjohnston · web-flow · commit a4fa044c0058 · 2021-03-03T16:04:24.000Z
Turns out matrix.org has an event that has duplicate auth events (which really isn't supposed to happen, but here we are). This caused the background update to fail due to `UniqueViolation`.
diff --git a/changelog.d/9537.bugfix b/changelog.d/9537.bugfix
@@ -0,0 +1 @@
+Fix rare edge case that caused a background update to fail if the server had rejected an event that had duplicate auth events.
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
@@ -696,7 +696,9 @@ def get_rejected_events(
                 )
 
             if not has_event_auth:
-                for auth_id in event.auth_event_ids():
+                # Old, dodgy, events may have duplicate auth events, which we
+                # need to deduplicate as we have a unique constraint.
+                for auth_id in set(event.auth_event_ids()):
                     auth_events.append(
                         {
                             "room_id": event.room_id,

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Fix rare edge case that caused a background update to fail if the server had rejected an event that had duplicate auth events.`
Original file line number	Diff line number	Diff line change
`@@ -696,7 +696,9 @@ def get_rejected_events(`
`696`	`696`	`)`
`697`	`697`
`698`	`698`	`if not has_event_auth:`
`699`		`- for auth_id in event.auth_event_ids():`
	`699`	`+ # Old, dodgy, events may have duplicate auth events, which we`
	`700`	`+ # need to deduplicate as we have a unique constraint.`
	`701`	`+ for auth_id in set(event.auth_event_ids()):`
`700`	`702`	`auth_events.append(`
`701`	`703`	`{`
`702`	`704`	`"room_id": event.room_id,`