diff options
Diffstat (limited to 'synapse')
| -rw-r--r-- | synapse/storage/databases/main/event_federation.py | 82 |
1 files changed, 53 insertions, 29 deletions
diff --git a/synapse/storage/databases/main/event_federation.py b/synapse/storage/databases/main/event_federation.py index 17f2fd4458..6b9a629edd 100644 --- a/synapse/storage/databases/main/event_federation.py +++ b/synapse/storage/databases/main/event_federation.py @@ -73,13 +73,30 @@ pdus_pruned_from_federation_queue = Counter( logger = logging.getLogger(__name__) -BACKFILL_EVENT_BACKOFF_UPPER_BOUND_SECONDS: int = int( - datetime.timedelta(days=7).total_seconds() -) -BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_SECONDS: int = int( - datetime.timedelta(hours=1).total_seconds() +# Parameters controlling exponential backoff between backfill failures. +# After the first failure to backfill, we wait 2 hours before trying again. If the +# second attempt fails, we wait 4 hours before trying again. If the third attempt fails, +# we wait 8 hours before trying again, ... and so on. +# +# Each successive backoff period is twice as long as the last. However we cap this +# period at a maximum of 2^8 = 256 hours: a little over 10 days. (This is the smallest +# power of 2 which yields a maximum backoff period of at least 7 days---which was the +# original maximum backoff period.) Even when we hit this cap, we will continue to +# make backfill attempts once every 10 days. +BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS = 8 +BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS = int( + datetime.timedelta(hours=1).total_seconds() * 1000 ) +# We need a cap on the power of 2 or else the backoff period +# 2^N * (milliseconds per hour) +# will overflow when calcuated within the database. We ensure overflow does not occur +# by checking that the largest backoff period fits in a 32-bit signed integer. +_LONGEST_BACKOFF_PERIOD_MILLISECONDS = ( + 2**BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS +) * BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS +assert 0 < _LONGEST_BACKOFF_PERIOD_MILLISECONDS <= ((2**31) - 1) + # All the info we need while iterating the DAG while backfilling @attr.s(frozen=True, slots=True, auto_attribs=True) @@ -767,7 +784,15 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas # persisted in our database yet (meaning we don't know their depth # specifically). So we need to look for the approximate depth from # the events connected to the current backwards extremeties. - sql = """ + + if isinstance(self.database_engine, PostgresEngine): + least_function = "LEAST" + elif isinstance(self.database_engine, Sqlite3Engine): + least_function = "MIN" + else: + raise RuntimeError("Unknown database engine") + + sql = f""" SELECT backward_extrem.event_id, event.depth FROM events AS event /** * Get the edge connections from the event_edges table @@ -825,7 +850,10 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas */ AND ( failed_backfill_attempt_info.event_id IS NULL - OR ? /* current_time */ >= failed_backfill_attempt_info.last_attempt_ts + /*least*/%s((1 << failed_backfill_attempt_info.num_attempts) * ? /* step */, ? /* upper bound */) + OR ? /* current_time */ >= failed_backfill_attempt_info.last_attempt_ts + ( + (1 << {least_function}(failed_backfill_attempt_info.num_attempts, ? /* max doubling steps */)) + * ? /* step */ + ) ) /** * Sort from highest (closest to the `current_depth`) to the lowest depth @@ -837,22 +865,15 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas LIMIT ? """ - if isinstance(self.database_engine, PostgresEngine): - least_function = "least" - elif isinstance(self.database_engine, Sqlite3Engine): - least_function = "min" - else: - raise RuntimeError("Unknown database engine") - txn.execute( - sql % (least_function,), + sql, ( room_id, False, current_depth, self._clock.time_msec(), - 1000 * BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_SECONDS, - 1000 * BACKFILL_EVENT_BACKOFF_UPPER_BOUND_SECONDS, + BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS, + BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS, limit, ), ) @@ -902,7 +923,14 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas def get_insertion_event_backward_extremities_in_room_txn( txn: LoggingTransaction, room_id: str ) -> List[Tuple[str, int]]: - sql = """ + if isinstance(self.database_engine, PostgresEngine): + least_function = "LEAST" + elif isinstance(self.database_engine, Sqlite3Engine): + least_function = "MIN" + else: + raise RuntimeError("Unknown database engine") + + sql = f""" SELECT insertion_event_extremity.event_id, event.depth /* We only want insertion events that are also marked as backwards extremities */ @@ -942,7 +970,10 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas */ AND ( failed_backfill_attempt_info.event_id IS NULL - OR ? /* current_time */ >= failed_backfill_attempt_info.last_attempt_ts + /*least*/%s((1 << failed_backfill_attempt_info.num_attempts) * ? /* step */, ? /* upper bound */) + OR ? /* current_time */ >= failed_backfill_attempt_info.last_attempt_ts + ( + (1 << {least_function}(failed_backfill_attempt_info.num_attempts, ? /* max doubling steps */)) + * ? /* step */ + ) ) /** * Sort from highest (closest to the `current_depth`) to the lowest depth @@ -954,21 +985,14 @@ class EventFederationWorkerStore(SignatureWorkerStore, EventsWorkerStore, SQLBas LIMIT ? """ - if isinstance(self.database_engine, PostgresEngine): - least_function = "least" - elif isinstance(self.database_engine, Sqlite3Engine): - least_function = "min" - else: - raise RuntimeError("Unknown database engine") - txn.execute( - sql % (least_function,), + sql, ( room_id, current_depth, self._clock.time_msec(), - 1000 * BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_SECONDS, - 1000 * BACKFILL_EVENT_BACKOFF_UPPER_BOUND_SECONDS, + BACKFILL_EVENT_EXPONENTIAL_BACKOFF_MAXIMUM_DOUBLING_STEPS, + BACKFILL_EVENT_EXPONENTIAL_BACKOFF_STEP_MILLISECONDS, limit, ), ) |