1 files changed, 54 insertions, 0 deletions
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py
index 6b9a629edd..309a4ba664 100644
--- a/synapse/storage/databases/main/event_federation.py
+++ b/synapse/storage/databases/main/event_federation.py
@@ -1501,6 +1501,12 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
             event_id: The event that failed to be fetched or processed
             cause: The error message or reason that we failed to pull the event
         """
+        logger.debug(
+            "record_event_failed_pull_attempt room_id=%s, event_id=%s, cause=%s",
+            room_id,
+            event_id,
+            cause,
+        )
         await self.db_pool.runInteraction(
             "record_event_failed_pull_attempt",
             self._record_event_failed_pull_attempt_upsert_txn,
@@ -1530,6 +1536,54 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas
 
         txn.execute(sql, (room_id, event_id, 1, self._clock.time_msec(), cause))
 
+    @trace
+    async def get_event_ids_to_not_pull_from_backoff(
+        self,
+        room_id: str,
+        event_ids: Collection[str],
+    ) -> List[str]:
+        """
+        Filter down the events to ones that we've failed to pull before recently. Uses
+        exponential backoff.
+
+        Args:
+            room_id: The room that the events belong to
+            event_ids: A list of events to filter down
+
+        Returns:
+            List of event_ids that should not be attempted to be pulled
+        """
+        event_failed_pull_attempts = await self.db_pool.simple_select_many_batch(
+            table="event_failed_pull_attempts",
+            column="event_id",
+            iterable=event_ids,
+            keyvalues={},
+            retcols=(
+                "event_id",
+                "last_attempt_ts",
+                "num_attempts",
+            ),
+            desc="get_event_ids_to_not_pull_from_backoff",
+        )
+
+        current_time = self._clock.time_msec()
+        return [
+            event_failed_pull_attempt["event_id"]
+            for event_failed_pull_attempt in event_failed_pull_attempts
+            # Exponential back-off (up to the upper bound) so we don't try to
+            # pull the same event over and over. ex. 2hr, 4hr, 8hr, 16hr, etc.
+            if current_time
+            < event_failed_pull_attempt["last_attempt_ts"]
+            + (
+                2
+                ** min(
+                    event_failed_pull_attempt["num_attempts"],
+                    BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS,
+                )
+            )
+            * BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS
+        ]
+
     async def get_missing_events(
         self,
         room_id: str,