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forked-synapse/synapse/storage/persist_events.py
Erik Johnston ea70f1c362
Various clean ups to room stream tokens. (#8423)
2020-09-29 21:48:33 +01:00

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# -*- 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 itertools
import logging
from collections import deque, namedtuple
from typing import Dict, Iterable, List, Optional, Set, Tuple
from prometheus_client import Counter, Histogram
from twisted.internet import defer
from synapse.api.constants import EventTypes, Membership
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.storage.databases import Databases
from synapse.storage.databases.main.events import DeltaState
from synapse.types import Collection, PersistedEventPosition, RoomStreamToken, StateMap
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:
"""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)
async def handle_queue_loop():
try:
queue = self._get_drainining_queue(room_id)
for item in queue:
try:
ret = await 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:
"""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: Databases):
# 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.state
assert stores.persist_events
self.persist_events_store = stores.persist_events
self._clock = hs.get_clock()
self._instance_name = hs.get_instance_name()
self.is_mine_id = hs.is_mine_id
self._event_persist_queue = _EventPeristenceQueue()
self._state_resolution_handler = hs.get_state_resolution_handler()
async def persist_events(
self,
events_and_contexts: Iterable[Tuple[EventBase, EventContext]],
backfilled: bool = False,
) -> RoomStreamToken:
"""
Write events to the database
Args:
events_and_contexts: list of tuples of (event, context)
backfilled: 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:
the stream ordering of the latest persisted event
"""
partitioned = {} # type: Dict[str, List[Tuple[EventBase, EventContext]]]
for event, ctx in events_and_contexts:
partitioned.setdefault(event.room_id, []).append((event, ctx))
deferreds = []
for room_id, evs_ctxs in partitioned.items():
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)
await make_deferred_yieldable(
defer.gatherResults(deferreds, consumeErrors=True)
)
return self.main_store.get_room_max_token()
async def persist_event(
self, event: EventBase, context: EventContext, backfilled: bool = False
) -> Tuple[PersistedEventPosition, RoomStreamToken]:
"""
Returns:
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)
await make_deferred_yieldable(deferred)
event_stream_id = event.internal_metadata.stream_ordering
pos = PersistedEventPosition(self._instance_name, event_stream_id)
return pos, self.main_store.get_room_max_token()
def _maybe_start_persisting(self, room_id: str):
async def persisting_queue(item):
with Measure(self._clock, "persist_events"):
await self._persist_events(
item.events_and_contexts, backfilled=item.backfilled
)
self._event_persist_queue.handle_queue(room_id, persisting_queue)
async def _persist_events(
self,
events_and_contexts: List[Tuple[EventBase, EventContext]],
backfilled: bool = False,
):
"""Calculates the change to current state and forward extremities, and
persists the given events and with those updates.
"""
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 = {}
# 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() # type: Set[str]
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 = (
{}
) # type: 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 = 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
)
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.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 = res
# 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 = []
current_state = {}
delta.no_longer_in_room = True
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
await self.persist_events_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,
)
await self._handle_potentially_left_users(potentially_left_users)
async def _calculate_new_extremities(
self,
room_id: str,
event_contexts: List[Tuple[EventBase, EventContext]],
latest_event_ids: Collection[str],
):
"""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 = await self.persist_events_store._get_events_which_are_prevs(
result
) # type: Collection[str]
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 = await self.persist_events_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
async def _get_new_state_after_events(
self,
room_id: str,
events_context: List[Tuple[EventBase, EventContext]],
old_latest_event_ids: Iterable[str],
new_latest_event_ids: Iterable[str],
) -> Tuple[Optional[StateMap[str]], Optional[StateMap[str]]]:
"""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:
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 = await self.main_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 = {
event_id_to_state_group[evid] for evid in old_latest_event_ids
}
# State groups of new_latest_event_ids
new_state_groups = {
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 = await 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 = await self.main_store.get_room_version_id(room_id)
logger.debug("calling resolve_state_groups from preserve_events")
# Avoid a circular import.
from synapse.state import StateResolutionStore
res = await 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
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 _is_server_still_joined(
self,
room_id: str,
ev_ctx_rm: List[Tuple[EventBase, EventContext]],
delta: DeltaState,
current_state: Optional[StateMap[str]],
potentially_left_users: Set[str],
) -> bool:
"""Check if the server will still be joined after the given events have
been persised.
Args:
room_id
ev_ctx_rm
delta: The delta of current state between what is in the database
and what the new current state will be.
current_state: The new current state if it already been calculated,
otherwise None.
potentially_left_users: If the server has left the room, then joined
remote users will be added to this set to indicate that the
server may no longer be sharing a room with them.
"""
if not any(
self.is_mine_id(state_key)
for typ, state_key in itertools.chain(delta.to_delete, delta.to_insert)
if typ == EventTypes.Member
):
# There have been no changes to membership of our users, so nothing
# has changed and we assume we're still in the room.
return True
# Check if any of the given events are a local join that appear in the
# current state
events_to_check = [] # Event IDs that aren't an event we're persisting
for (typ, state_key), event_id in delta.to_insert.items():
if typ != EventTypes.Member or not self.is_mine_id(state_key):
continue
for event, _ in ev_ctx_rm:
if event_id == event.event_id:
if event.membership == Membership.JOIN:
return True
# The event is not in `ev_ctx_rm`, so we need to pull it out of
# the DB.
events_to_check.append(event_id)
# Check if any of the changes that we don't have events for are joins.
if events_to_check:
rows = await self.main_store.get_membership_from_event_ids(events_to_check)
is_still_joined = any(row["membership"] == Membership.JOIN for row in rows)
if is_still_joined:
return True
# None of the new state events are local joins, so we check the database
# to see if there are any other local users in the room. We ignore users
# whose state has changed as we've already their new state above.
users_to_ignore = [
state_key
for typ, state_key in itertools.chain(delta.to_insert, delta.to_delete)
if typ == EventTypes.Member and self.is_mine_id(state_key)
]
if await self.main_store.is_local_host_in_room_ignoring_users(
room_id, users_to_ignore
):
return True
# The server will leave the room, so we go and find out which remote
# users will still be joined when we leave.
if current_state is None:
current_state = await self.main_store.get_current_state_ids(room_id)
current_state = dict(current_state)
for key in delta.to_delete:
current_state.pop(key, None)
current_state.update(delta.to_insert)
remote_event_ids = [
event_id
for (typ, state_key,), event_id in current_state.items()
if typ == EventTypes.Member and not self.is_mine_id(state_key)
]
rows = await self.main_store.get_membership_from_event_ids(remote_event_ids)
potentially_left_users.update(
row["user_id"] for row in rows if row["membership"] == Membership.JOIN
)
return False
async def _handle_potentially_left_users(self, user_ids: Set[str]):
"""Given a set of remote users check if the server still shares a room with
them. If not then mark those users' device cache as stale.
"""
if not user_ids:
return
joined_users = await self.main_store.get_users_server_still_shares_room_with(
user_ids
)
left_users = user_ids - joined_users
for user_id in left_users:
await self.main_store.mark_remote_user_device_list_as_unsubscribed(user_id)
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