diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index f382961099..4300e8dd40 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -44,6 +44,7 @@ from synapse.api.errors import (
AuthError,
Codes,
FederationError,
+ FederationPullAttemptBackoffError,
HttpResponseException,
RequestSendFailed,
SynapseError,
@@ -567,6 +568,9 @@ class FederationEventHandler:
event: partial-state event to be de-partial-stated
Raises:
+ FederationPullAttemptBackoffError if we are are deliberately not attempting
+ to pull the given event over federation because we've already done so
+ recently and are backing off.
FederationError if we fail to request state from the remote server.
"""
logger.info("Updating state for %s", event.event_id)
@@ -901,6 +905,18 @@ class FederationEventHandler:
context,
backfilled=backfilled,
)
+ except FederationPullAttemptBackoffError as exc:
+ # Log a warning about why we failed to process the event (the error message
+ # for `FederationPullAttemptBackoffError` is pretty good)
+ logger.warning("_process_pulled_event: %s", exc)
+ # We do not record a failed pull attempt when we backoff fetching a missing
+ # `prev_event` because not being able to fetch the `prev_events` just means
+ # we won't be able to de-outlier the pulled event. But we can still use an
+ # `outlier` in the state/auth chain for another event. So we shouldn't stop
+ # a downstream event from trying to pull it.
+ #
+ # This avoids a cascade of backoff for all events in the DAG downstream from
+ # one event backoff upstream.
except FederationError as e:
await self._store.record_event_failed_pull_attempt(
event.room_id, event_id, str(e)
@@ -947,6 +963,9 @@ class FederationEventHandler:
The event context.
Raises:
+ FederationPullAttemptBackoffError if we are are deliberately not attempting
+ to pull the given event over federation because we've already done so
+ recently and are backing off.
FederationError if we fail to get the state from the remote server after any
missing `prev_event`s.
"""
@@ -957,6 +976,18 @@ class FederationEventHandler:
seen = await self._store.have_events_in_timeline(prevs)
missing_prevs = prevs - seen
+ # If we've already recently attempted to pull this missing event, don't
+ # try it again so soon. Since we have to fetch all of the prev_events, we can
+ # bail early here if we find any to ignore.
+ prevs_to_ignore = await self._store.get_event_ids_to_not_pull_from_backoff(
+ room_id, missing_prevs
+ )
+ if len(prevs_to_ignore) > 0:
+ raise FederationPullAttemptBackoffError(
+ event_ids=prevs_to_ignore,
+ message=f"While computing context for event={event_id}, not attempting to pull missing prev_event={prevs_to_ignore[0]} because we already tried to pull recently (backing off).",
+ )
+
if not missing_prevs:
return await self._state_handler.compute_event_context(event)
|
