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Diffstat (limited to 'synapse/storage/persist_events.py')
| -rw-r--r-- | synapse/storage/persist_events.py | 644 |
1 files changed, 644 insertions, 0 deletions
diff --git a/synapse/storage/persist_events.py b/synapse/storage/persist_events.py new file mode 100644 index 0000000000..cd445be670 --- /dev/null +++ b/synapse/storage/persist_events.py @@ -0,0 +1,644 @@ +# -*- coding: utf-8 -*- +# Copyright 2014-2016 OpenMarket Ltd +# Copyright 2018-2019 New Vector Ltd +# Copyright 2019 The Matrix.org Foundation C.I.C. +# +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +import logging +from collections import deque, namedtuple + +from six import iteritems +from six.moves import range + +from prometheus_client import Counter, Histogram + +from twisted.internet import defer + +from synapse.api.constants import EventTypes +from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable +from synapse.metrics.background_process_metrics import run_as_background_process +from synapse.state import StateResolutionStore +from synapse.util.async_helpers import ObservableDeferred +from synapse.util.metrics import Measure + +logger = logging.getLogger(__name__) + +# The number of times we are recalculating the current state +state_delta_counter = Counter("synapse_storage_events_state_delta", "") + +# The number of times we are recalculating state when there is only a +# single forward extremity +state_delta_single_event_counter = Counter( + "synapse_storage_events_state_delta_single_event", "" +) + +# The number of times we are reculating state when we could have resonably +# calculated the delta when we calculated the state for an event we were +# persisting. +state_delta_reuse_delta_counter = Counter( + "synapse_storage_events_state_delta_reuse_delta", "" +) + +# The number of forward extremities for each new event. +forward_extremities_counter = Histogram( + "synapse_storage_events_forward_extremities_persisted", + "Number of forward extremities for each new event", + buckets=(1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"), +) + +# The number of stale forward extremities for each new event. Stale extremities +# are those that were in the previous set of extremities as well as the new. +stale_forward_extremities_counter = Histogram( + "synapse_storage_events_stale_forward_extremities_persisted", + "Number of unchanged forward extremities for each new event", + buckets=(0, 1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"), +) + + +class _EventPeristenceQueue(object): + """Queues up events so that they can be persisted in bulk with only one + concurrent transaction per room. + """ + + _EventPersistQueueItem = namedtuple( + "_EventPersistQueueItem", ("events_and_contexts", "backfilled", "deferred") + ) + + def __init__(self): + self._event_persist_queues = {} + self._currently_persisting_rooms = set() + + def add_to_queue(self, room_id, events_and_contexts, backfilled): + """Add events to the queue, with the given persist_event options. + + NB: due to the normal usage pattern of this method, it does *not* + follow the synapse logcontext rules, and leaves the logcontext in + place whether or not the returned deferred is ready. + + Args: + room_id (str): + events_and_contexts (list[(EventBase, EventContext)]): + backfilled (bool): + + Returns: + defer.Deferred: a deferred which will resolve once the events are + persisted. Runs its callbacks *without* a logcontext. + """ + queue = self._event_persist_queues.setdefault(room_id, deque()) + if queue: + # if the last item in the queue has the same `backfilled` setting, + # we can just add these new events to that item. + end_item = queue[-1] + if end_item.backfilled == backfilled: + end_item.events_and_contexts.extend(events_and_contexts) + return end_item.deferred.observe() + + deferred = ObservableDeferred(defer.Deferred(), consumeErrors=True) + + queue.append( + self._EventPersistQueueItem( + events_and_contexts=events_and_contexts, + backfilled=backfilled, + deferred=deferred, + ) + ) + + return deferred.observe() + + def handle_queue(self, room_id, per_item_callback): + """Attempts to handle the queue for a room if not already being handled. + + The given callback will be invoked with for each item in the queue, + of type _EventPersistQueueItem. The per_item_callback will continuously + be called with new items, unless the queue becomnes empty. The return + value of the function will be given to the deferreds waiting on the item, + exceptions will be passed to the deferreds as well. + + This function should therefore be called whenever anything is added + to the queue. + + If another callback is currently handling the queue then it will not be + invoked. + """ + + if room_id in self._currently_persisting_rooms: + return + + self._currently_persisting_rooms.add(room_id) + + @defer.inlineCallbacks + def handle_queue_loop(): + try: + queue = self._get_drainining_queue(room_id) + for item in queue: + try: + ret = yield per_item_callback(item) + except Exception: + with PreserveLoggingContext(): + item.deferred.errback() + else: + with PreserveLoggingContext(): + item.deferred.callback(ret) + finally: + queue = self._event_persist_queues.pop(room_id, None) + if queue: + self._event_persist_queues[room_id] = queue + self._currently_persisting_rooms.discard(room_id) + + # set handle_queue_loop off in the background + run_as_background_process("persist_events", handle_queue_loop) + + def _get_drainining_queue(self, room_id): + queue = self._event_persist_queues.setdefault(room_id, deque()) + + try: + while True: + yield queue.popleft() + except IndexError: + # Queue has been drained. + pass + + +class EventsPersistenceStore(object): + def __init__(self, hs): + # We ultimately want to split out the state store from the main store, + # so we use separate variables here even though they point to the same + # store for now. + self.main_store = hs.get_datastore() + self.state_store = hs.get_datastore() + + self._clock = hs.get_clock() + self.is_mine_id = hs.is_mine_id + self._event_persist_queue = _EventPeristenceQueue() + self._state_resolution_handler = hs.get_state_resolution_handler() + + @defer.inlineCallbacks + def persist_events(self, events_and_contexts, backfilled=False): + """ + Write events to the database + Args: + events_and_contexts: list of tuples of (event, context) + backfilled (bool): Whether the results are retrieved from federation + via backfill or not. Used to determine if they're "new" events + which might update the current state etc. + + Returns: + Deferred[int]: the stream ordering of the latest persisted event + """ + partitioned = {} + for event, ctx in events_and_contexts: + partitioned.setdefault(event.room_id, []).append((event, ctx)) + + deferreds = [] + for room_id, evs_ctxs in iteritems(partitioned): + d = self._event_persist_queue.add_to_queue( + room_id, evs_ctxs, backfilled=backfilled + ) + deferreds.append(d) + + for room_id in partitioned: + self._maybe_start_persisting(room_id) + + yield make_deferred_yieldable( + defer.gatherResults(deferreds, consumeErrors=True) + ) + + max_persisted_id = yield self.main_store.get_current_events_token() + + return max_persisted_id + + @defer.inlineCallbacks + def persist_event(self, event, context, backfilled=False): + """ + + Args: + event (EventBase): + context (EventContext): + backfilled (bool): + + Returns: + Deferred: resolves to (int, int): the stream ordering of ``event``, + and the stream ordering of the latest persisted event + """ + deferred = self._event_persist_queue.add_to_queue( + event.room_id, [(event, context)], backfilled=backfilled + ) + + self._maybe_start_persisting(event.room_id) + + yield make_deferred_yieldable(deferred) + + max_persisted_id = yield self.main_store.get_current_events_token() + return (event.internal_metadata.stream_ordering, max_persisted_id) + + def _maybe_start_persisting(self, room_id): + @defer.inlineCallbacks + def persisting_queue(item): + with Measure(self._clock, "persist_events"): + yield self._persist_events( + item.events_and_contexts, backfilled=item.backfilled + ) + + self._event_persist_queue.handle_queue(room_id, persisting_queue) + + @defer.inlineCallbacks + def _persist_events( + self, events_and_contexts, backfilled=False, delete_existing=False + ): + """Persist events to db + + Args: + events_and_contexts (list[(EventBase, EventContext)]): + backfilled (bool): + delete_existing (bool): + + Returns: + Deferred: resolves when the events have been persisted + """ + if not events_and_contexts: + return + + chunks = [ + events_and_contexts[x : x + 100] + for x in range(0, len(events_and_contexts), 100) + ] + + for chunk in chunks: + # We can't easily parallelize these since different chunks + # might contain the same event. :( + + # NB: Assumes that we are only persisting events for one room + # at a time. + + # map room_id->list[event_ids] giving the new forward + # extremities in each room + new_forward_extremeties = {} + + # map room_id->(type,state_key)->event_id tracking the full + # state in each room after adding these events. + # This is simply used to prefill the get_current_state_ids + # cache + current_state_for_room = {} + + # map room_id->(to_delete, to_insert) where to_delete is a list + # of type/state keys to remove from current state, and to_insert + # is a map (type,key)->event_id giving the state delta in each + # room + state_delta_for_room = {} + + if not backfilled: + with Measure(self._clock, "_calculate_state_and_extrem"): + # Work out the new "current state" for each room. + # We do this by working out what the new extremities are and then + # calculating the state from that. + events_by_room = {} + for event, context in chunk: + events_by_room.setdefault(event.room_id, []).append( + (event, context) + ) + + for room_id, ev_ctx_rm in iteritems(events_by_room): + latest_event_ids = yield self.main_store.get_latest_event_ids_in_room( + room_id + ) + new_latest_event_ids = yield self._calculate_new_extremities( + room_id, ev_ctx_rm, latest_event_ids + ) + + latest_event_ids = set(latest_event_ids) + if new_latest_event_ids == latest_event_ids: + # No change in extremities, so no change in state + continue + + # there should always be at least one forward extremity. + # (except during the initial persistence of the send_join + # results, in which case there will be no existing + # extremities, so we'll `continue` above and skip this bit.) + assert new_latest_event_ids, "No forward extremities left!" + + new_forward_extremeties[room_id] = new_latest_event_ids + + len_1 = ( + len(latest_event_ids) == 1 + and len(new_latest_event_ids) == 1 + ) + if len_1: + all_single_prev_not_state = all( + len(event.prev_event_ids()) == 1 + and not event.is_state() + for event, ctx in ev_ctx_rm + ) + # Don't bother calculating state if they're just + # a long chain of single ancestor non-state events. + if all_single_prev_not_state: + continue + + state_delta_counter.inc() + if len(new_latest_event_ids) == 1: + state_delta_single_event_counter.inc() + + # This is a fairly handwavey check to see if we could + # have guessed what the delta would have been when + # processing one of these events. + # What we're interested in is if the latest extremities + # were the same when we created the event as they are + # now. When this server creates a new event (as opposed + # to receiving it over federation) it will use the + # forward extremities as the prev_events, so we can + # guess this by looking at the prev_events and checking + # if they match the current forward extremities. + for ev, _ in ev_ctx_rm: + prev_event_ids = set(ev.prev_event_ids()) + if latest_event_ids == prev_event_ids: + state_delta_reuse_delta_counter.inc() + break + + logger.info("Calculating state delta for room %s", room_id) + with Measure( + self._clock, "persist_events.get_new_state_after_events" + ): + res = yield self._get_new_state_after_events( + room_id, + ev_ctx_rm, + latest_event_ids, + new_latest_event_ids, + ) + current_state, delta_ids = res + + # If either are not None then there has been a change, + # and we need to work out the delta (or use that + # given) + if delta_ids is not None: + # If there is a delta we know that we've + # only added or replaced state, never + # removed keys entirely. + state_delta_for_room[room_id] = ([], delta_ids) + elif current_state is not None: + with Measure( + self._clock, "persist_events.calculate_state_delta" + ): + delta = yield self._calculate_state_delta( + room_id, current_state + ) + state_delta_for_room[room_id] = delta + + # If we have the current_state then lets prefill + # the cache with it. + if current_state is not None: + current_state_for_room[room_id] = current_state + + yield self.main_store._persist_events( + chunk, + current_state_for_room=current_state_for_room, + state_delta_for_room=state_delta_for_room, + new_forward_extremeties=new_forward_extremeties, + backfilled=backfilled, + delete_existing=delete_existing, + ) + + @defer.inlineCallbacks + def _calculate_new_extremities(self, room_id, event_contexts, latest_event_ids): + """Calculates the new forward extremities for a room given events to + persist. + + Assumes that we are only persisting events for one room at a time. + """ + + # we're only interested in new events which aren't outliers and which aren't + # being rejected. + new_events = [ + event + for event, ctx in event_contexts + if not event.internal_metadata.is_outlier() + and not ctx.rejected + and not event.internal_metadata.is_soft_failed() + ] + + latest_event_ids = set(latest_event_ids) + + # start with the existing forward extremities + result = set(latest_event_ids) + + # add all the new events to the list + result.update(event.event_id for event in new_events) + + # Now remove all events which are prev_events of any of the new events + result.difference_update( + e_id for event in new_events for e_id in event.prev_event_ids() + ) + + # Remove any events which are prev_events of any existing events. + existing_prevs = yield self.main_store._get_events_which_are_prevs(result) + result.difference_update(existing_prevs) + + # Finally handle the case where the new events have soft-failed prev + # events. If they do we need to remove them and their prev events, + # otherwise we end up with dangling extremities. + existing_prevs = yield self.main_store._get_prevs_before_rejected( + e_id for event in new_events for e_id in event.prev_event_ids() + ) + result.difference_update(existing_prevs) + + # We only update metrics for events that change forward extremities + # (e.g. we ignore backfill/outliers/etc) + if result != latest_event_ids: + forward_extremities_counter.observe(len(result)) + stale = latest_event_ids & result + stale_forward_extremities_counter.observe(len(stale)) + + return result + + @defer.inlineCallbacks + def _get_new_state_after_events( + self, room_id, events_context, old_latest_event_ids, new_latest_event_ids + ): + """Calculate the current state dict after adding some new events to + a room + + Args: + room_id (str): + room to which the events are being added. Used for logging etc + + events_context (list[(EventBase, EventContext)]): + events and contexts which are being added to the room + + old_latest_event_ids (iterable[str]): + the old forward extremities for the room. + + new_latest_event_ids (iterable[str]): + the new forward extremities for the room. + + Returns: + Deferred[tuple[dict[(str,str), str]|None, dict[(str,str), str]|None]]: + Returns a tuple of two state maps, the first being the full new current + state and the second being the delta to the existing current state. + If both are None then there has been no change. + + If there has been a change then we only return the delta if its + already been calculated. Conversely if we do know the delta then + the new current state is only returned if we've already calculated + it. + """ + # map from state_group to ((type, key) -> event_id) state map + state_groups_map = {} + + # Map from (prev state group, new state group) -> delta state dict + state_group_deltas = {} + + for ev, ctx in events_context: + if ctx.state_group is None: + # This should only happen for outlier events. + if not ev.internal_metadata.is_outlier(): + raise Exception( + "Context for new event %s has no state " + "group" % (ev.event_id,) + ) + continue + + if ctx.state_group in state_groups_map: + continue + + # We're only interested in pulling out state that has already + # been cached in the context. We'll pull stuff out of the DB later + # if necessary. + current_state_ids = ctx.get_cached_current_state_ids() + if current_state_ids is not None: + state_groups_map[ctx.state_group] = current_state_ids + + if ctx.prev_group: + state_group_deltas[(ctx.prev_group, ctx.state_group)] = ctx.delta_ids + + # We need to map the event_ids to their state groups. First, let's + # check if the event is one we're persisting, in which case we can + # pull the state group from its context. + # Otherwise we need to pull the state group from the database. + + # Set of events we need to fetch groups for. (We know none of the old + # extremities are going to be in events_context). + missing_event_ids = set(old_latest_event_ids) + + event_id_to_state_group = {} + for event_id in new_latest_event_ids: + # First search in the list of new events we're adding. + for ev, ctx in events_context: + if event_id == ev.event_id and ctx.state_group is not None: + event_id_to_state_group[event_id] = ctx.state_group + break + else: + # If we couldn't find it, then we'll need to pull + # the state from the database + missing_event_ids.add(event_id) + + if missing_event_ids: + # Now pull out the state groups for any missing events from DB + event_to_groups = yield self.state_store._get_state_group_for_events( + missing_event_ids + ) + event_id_to_state_group.update(event_to_groups) + + # State groups of old_latest_event_ids + old_state_groups = set( + event_id_to_state_group[evid] for evid in old_latest_event_ids + ) + + # State groups of new_latest_event_ids + new_state_groups = set( + event_id_to_state_group[evid] for evid in new_latest_event_ids + ) + + # If they old and new groups are the same then we don't need to do + # anything. + if old_state_groups == new_state_groups: + return None, None + + if len(new_state_groups) == 1 and len(old_state_groups) == 1: + # If we're going from one state group to another, lets check if + # we have a delta for that transition. If we do then we can just + # return that. + + new_state_group = next(iter(new_state_groups)) + old_state_group = next(iter(old_state_groups)) + + delta_ids = state_group_deltas.get((old_state_group, new_state_group), None) + if delta_ids is not None: + # We have a delta from the existing to new current state, + # so lets just return that. If we happen to already have + # the current state in memory then lets also return that, + # but it doesn't matter if we don't. + new_state = state_groups_map.get(new_state_group) + return new_state, delta_ids + + # Now that we have calculated new_state_groups we need to get + # their state IDs so we can resolve to a single state set. + missing_state = new_state_groups - set(state_groups_map) + if missing_state: + group_to_state = yield self.state_store._get_state_for_groups(missing_state) + state_groups_map.update(group_to_state) + + if len(new_state_groups) == 1: + # If there is only one state group, then we know what the current + # state is. + return state_groups_map[new_state_groups.pop()], None + + # Ok, we need to defer to the state handler to resolve our state sets. + + state_groups = {sg: state_groups_map[sg] for sg in new_state_groups} + + events_map = {ev.event_id: ev for ev, _ in events_context} + + # We need to get the room version, which is in the create event. + # Normally that'd be in the database, but its also possible that we're + # currently trying to persist it. + room_version = None + for ev, _ in events_context: + if ev.type == EventTypes.Create and ev.state_key == "": + room_version = ev.content.get("room_version", "1") + break + + if not room_version: + room_version = yield self.main_store.get_room_version(room_id) + + logger.debug("calling resolve_state_groups from preserve_events") + res = yield self._state_resolution_handler.resolve_state_groups( + room_id, + room_version, + state_groups, + events_map, + state_res_store=StateResolutionStore(self.main_store), + ) + + return res.state, None + + @defer.inlineCallbacks + def _calculate_state_delta(self, room_id, current_state): + """Calculate the new state deltas for a room. + + Assumes that we are only persisting events for one room at a time. + + Returns: + tuple[list, dict] (to_delete, to_insert): where to_delete are the + type/state_keys to remove from current_state_events and `to_insert` + are the updates to current_state_events. + """ + existing_state = yield self.main_store.get_current_state_ids(room_id) + + to_delete = [key for key in existing_state if key not in current_state] + + to_insert = { + key: ev_id + for key, ev_id in iteritems(current_state) + if ev_id != existing_state.get(key) + } + + return to_delete, to_insert |