async def _calculate_state_delta(
self, room_id: str, current_state: StateMap[str]) -> DeltaState:
"""Calculate the new state deltas for a room.
Assumes that we are only persisting events for one room at a time.
"""
existing_state = await 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 current_state.items()
if ev_id != existing_state.get(key)
}
return DeltaState(to_delete=to_delete, to_insert=to_insert)
async def _persist_event_batch(
self,
events_and_contexts: List[Tuple[EventBase, EventContext]],
backfilled: bool = False,
) -> Dict[str, str]:
"""Callback for the _event_persist_queue
Calculates the change to current state and forward extremities, and
persists the given events and with those updates.
Returns:
A dictionary of event ID to event ID we didn't persist as we already
had another event persisted with the same TXN ID.
"""
replaced_events: Dict[str, str] = {}
if not events_and_contexts:
return replaced_events
# Check if any of the events have a transaction ID that has already been
# persisted, and if so we don't persist it again.
#
# We should have checked this a long time before we get here, but it's
# possible that different send event requests race in such a way that
# they both pass the earlier checks. Checking here isn't racey as we can
# have only one `_persist_events` per room being called at a time.
replaced_events = await self.main_store.get_already_persisted_events(
(event for event, _ in events_and_contexts))
if replaced_events:
events_and_contexts = [(e, ctx) for e, ctx in events_and_contexts
if e.event_id not in replaced_events]
if not events_and_contexts:
return replaced_events
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->set[event_ids] giving the new forward
# extremities in each room
new_forward_extremities: Dict[str, Set[str]] = {}
# 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: Dict[str, DeltaState] = {}
# Set of remote users which were in rooms the server has left. We
# should check if we still share any rooms and if not we mark their
# device lists as stale.
potentially_left_users: Set[str] = set()
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: Dict[str, List[Tuple[EventBase,
EventContext]]] = {}
for event, context in chunk:
events_by_room.setdefault(event.room_id, []).append(
(event, context))
for room_id, ev_ctx_rm in events_by_room.items():
latest_event_ids = set(
await self.main_store.get_latest_event_ids_in_room(
room_id))
new_latest_event_ids = await self._calculate_new_extremities(
room_id, ev_ctx_rm, 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_extremities[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.debug("Calculating state delta for room %s",
room_id)
with Measure(
self._clock,
"persist_events.get_new_state_after_events"):
res = await self._get_new_state_after_events(
room_id,
ev_ctx_rm,
latest_event_ids,
new_latest_event_ids,
)
current_state, delta_ids, new_latest_event_ids = res
# 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_extremities[
room_id] = new_latest_event_ids
# If either are not None then there has been a change,
# and we need to work out the delta (or use that
# given)
delta = None
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.
delta = DeltaState([], delta_ids)
elif current_state is not None:
with Measure(
self._clock,
"persist_events.calculate_state_delta"):
delta = await self._calculate_state_delta(
room_id, current_state)
if delta:
# If we have a change of state then lets check
# whether we're actually still a member of the room,
# or if our last user left. If we're no longer in
# the room then we delete the current state and
# extremities.
is_still_joined = await self._is_server_still_joined(
room_id,
ev_ctx_rm,
delta,
current_state,
potentially_left_users,
)
if not is_still_joined:
logger.info("Server no longer in room %s",
room_id)
latest_event_ids = set()
current_state = {}
delta.no_longer_in_room = True
state_delta_for_room[room_id] = delta
await self.persist_events_store._persist_events_and_state_updates(
chunk,
state_delta_for_room=state_delta_for_room,
new_forward_extremities=new_forward_extremities,
use_negative_stream_ordering=backfilled,
inhibit_local_membership_updates=backfilled,
)
await self._handle_potentially_left_users(potentially_left_users)
return replaced_events