diff options
Diffstat (limited to 'synapse/storage/databases')
| -rw-r--r-- | synapse/storage/databases/main/events_worker.py | 154 |
1 files changed, 112 insertions, 42 deletions
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py index c6bf316d5b..c6bcfe1c32 100644 --- a/synapse/storage/databases/main/events_worker.py +++ b/synapse/storage/databases/main/events_worker.py @@ -72,7 +72,7 @@ from synapse.util.metrics import Measure logger = logging.getLogger(__name__) -# These values are used in the `enqueus_event` and `_do_fetch` methods to +# These values are used in the `enqueue_event` and `_fetch_loop` methods to # control how we batch/bulk fetch events from the database. # The values are plucked out of thing air to make initial sync run faster # on jki.re @@ -602,7 +602,7 @@ class EventsWorkerStore(SQLBaseStore): # already due to `_get_events_from_db`). fetching_deferred: ObservableDeferred[ Dict[str, _EventCacheEntry] - ] = ObservableDeferred(defer.Deferred()) + ] = ObservableDeferred(defer.Deferred(), consumeErrors=True) for event_id in missing_events_ids: self._current_event_fetches[event_id] = fetching_deferred @@ -736,35 +736,118 @@ class EventsWorkerStore(SQLBaseStore): for e in state_to_include.values() ] - def _do_fetch(self, conn: Connection) -> None: + def _maybe_start_fetch_thread(self) -> None: + """Starts an event fetch thread if we are not yet at the maximum number.""" + with self._event_fetch_lock: + if ( + self._event_fetch_list + and self._event_fetch_ongoing < EVENT_QUEUE_THREADS + ): + self._event_fetch_ongoing += 1 + event_fetch_ongoing_gauge.set(self._event_fetch_ongoing) + # `_event_fetch_ongoing` is decremented in `_fetch_thread`. + should_start = True + else: + should_start = False + + if should_start: + run_as_background_process("fetch_events", self._fetch_thread) + + async def _fetch_thread(self) -> None: + """Services requests for events from `_event_fetch_list`.""" + exc = None + try: + await self.db_pool.runWithConnection(self._fetch_loop) + except BaseException as e: + exc = e + raise + finally: + should_restart = False + event_fetches_to_fail = [] + with self._event_fetch_lock: + self._event_fetch_ongoing -= 1 + event_fetch_ongoing_gauge.set(self._event_fetch_ongoing) + + # There may still be work remaining in `_event_fetch_list` if we + # failed, or it was added in between us deciding to exit and + # decrementing `_event_fetch_ongoing`. + if self._event_fetch_list: + if exc is None: + # We decided to exit, but then some more work was added + # before `_event_fetch_ongoing` was decremented. + # If a new event fetch thread was not started, we should + # restart ourselves since the remaining event fetch threads + # may take a while to get around to the new work. + # + # Unfortunately it is not possible to tell whether a new + # event fetch thread was started, so we restart + # unconditionally. If we are unlucky, we will end up with + # an idle fetch thread, but it will time out after + # `EVENT_QUEUE_ITERATIONS * EVENT_QUEUE_TIMEOUT_S` seconds + # in any case. + # + # Note that multiple fetch threads may run down this path at + # the same time. + should_restart = True + elif isinstance(exc, Exception): + if self._event_fetch_ongoing == 0: + # We were the last remaining fetcher and failed. + # Fail any outstanding fetches since no one else will + # handle them. + event_fetches_to_fail = self._event_fetch_list + self._event_fetch_list = [] + else: + # We weren't the last remaining fetcher, so another + # fetcher will pick up the work. This will either happen + # after their existing work, however long that takes, + # or after at most `EVENT_QUEUE_TIMEOUT_S` seconds if + # they are idle. + pass + else: + # The exception is a `SystemExit`, `KeyboardInterrupt` or + # `GeneratorExit`. Don't try to do anything clever here. + pass + + if should_restart: + # We exited cleanly but noticed more work. + self._maybe_start_fetch_thread() + + if event_fetches_to_fail: + # We were the last remaining fetcher and failed. + # Fail any outstanding fetches since no one else will handle them. + assert exc is not None + with PreserveLoggingContext(): + for _, deferred in event_fetches_to_fail: + deferred.errback(exc) + + def _fetch_loop(self, conn: Connection) -> None: """Takes a database connection and waits for requests for events from the _event_fetch_list queue. """ - try: - i = 0 - while True: - with self._event_fetch_lock: - event_list = self._event_fetch_list - self._event_fetch_list = [] - - if not event_list: - single_threaded = self.database_engine.single_threaded - if ( - not self.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING - or single_threaded - or i > EVENT_QUEUE_ITERATIONS - ): - break - else: - self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S) - i += 1 - continue - i = 0 + i = 0 + while True: + with self._event_fetch_lock: + event_list = self._event_fetch_list + self._event_fetch_list = [] + + if not event_list: + # There are no requests waiting. If we haven't yet reached the + # maximum iteration limit, wait for some more requests to turn up. + # Otherwise, bail out. + single_threaded = self.database_engine.single_threaded + if ( + not self.USE_DEDICATED_DB_THREADS_FOR_EVENT_FETCHING + or single_threaded + or i > EVENT_QUEUE_ITERATIONS + ): + return + + self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S) + i += 1 + continue + i = 0 - self._fetch_event_list(conn, event_list) - finally: - self._event_fetch_ongoing -= 1 - event_fetch_ongoing_gauge.set(self._event_fetch_ongoing) + self._fetch_event_list(conn, event_list) def _fetch_event_list( self, conn: Connection, event_list: List[Tuple[List[str], defer.Deferred]] @@ -806,9 +889,7 @@ class EventsWorkerStore(SQLBaseStore): # We only want to resolve deferreds from the main thread def fire(evs, exc): for _, d in evs: - if not d.called: - with PreserveLoggingContext(): - d.errback(exc) + d.errback(exc) with PreserveLoggingContext(): self.hs.get_reactor().callFromThread(fire, event_list, e) @@ -983,20 +1064,9 @@ class EventsWorkerStore(SQLBaseStore): events_d = defer.Deferred() with self._event_fetch_lock: self._event_fetch_list.append((events, events_d)) - self._event_fetch_lock.notify() - if self._event_fetch_ongoing < EVENT_QUEUE_THREADS: - self._event_fetch_ongoing += 1 - event_fetch_ongoing_gauge.set(self._event_fetch_ongoing) - should_start = True - else: - should_start = False - - if should_start: - run_as_background_process( - "fetch_events", self.db_pool.runWithConnection, self._do_fetch - ) + self._maybe_start_fetch_thread() logger.debug("Loading %d events: %s", len(events), events) with PreserveLoggingContext(): |