diff --git a/synapse/storage/persist_events.py b/synapse/storage/persist_events.py
new file mode 100644
index 0000000000..cf66225574
--- /dev/null
+++ b/synapse/storage/persist_events.py
@@ -0,0 +1,652 @@
+# -*- 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.storage.data_stores import DataStores
+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 EventsPersistenceStorage(object):
+ """High level interface for handling persisting newly received events.
+
+ Takes care of batching up events by room, and calculating the necessary
+ current state and forward extremity changes.
+ """
+
+ def __init__(self, hs, stores: DataStores):
+ # 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 = stores.main
+ self.state_store = stores.main
+
+ 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
+ ):
+ """Calculates the change to current state and forward extremities, and
+ persists the given events and with those updates.
+
+ 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_and_state_updates(
+ 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
|
