MatrixSynapse/synapse/storage/controllers/persist_events.py

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# 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
from typing import (
TYPE_CHECKING,
Any,
Awaitable,
Callable,
ClassVar,
Collection,
Deque,
Dict,
Generator,
Generic,
Iterable,
List,
Optional,
Set,
Tuple,
TypeVar,
Union,
)
import attr
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 import opentracing
from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.storage.controllers.state import StateStorageController
from synapse.storage.databases import Databases
from synapse.storage.databases.main.events import DeltaState
from synapse.storage.databases.main.events_worker import EventRedactBehaviour
from synapse.storage.state import StateFilter
from synapse.types import (
PersistedEventPosition,
RoomStreamToken,
StateMap,
get_domain_from_id,
)
from synapse.util.async_helpers import ObservableDeferred, yieldable_gather_results
from synapse.util.metrics import Measure
if TYPE_CHECKING:
from synapse.server import HomeServer
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"),
)
state_resolutions_during_persistence = Counter(
"synapse_storage_events_state_resolutions_during_persistence",
"Number of times we had to do state res to calculate new current state",
)
potential_times_prune_extremities = Counter(
"synapse_storage_events_potential_times_prune_extremities",
"Number of times we might be able to prune extremities",
)
times_pruned_extremities = Counter(
"synapse_storage_events_times_pruned_extremities",
"Number of times we were actually be able to prune extremities",
)
@attr.s(auto_attribs=True, slots=True)
class _PersistEventsTask:
"""A batch of events to persist."""
name: ClassVar[str] = "persist_event_batch" # used for opentracing
events_and_contexts: List[Tuple[EventBase, EventContext]]
backfilled: bool
def try_merge(self, task: "_EventPersistQueueTask") -> bool:
"""Batches events with the same backfilled option together."""
if (
not isinstance(task, _PersistEventsTask)
or self.backfilled != task.backfilled
):
return False
self.events_and_contexts.extend(task.events_and_contexts)
return True
@attr.s(auto_attribs=True, slots=True)
class _UpdateCurrentStateTask:
"""A room whose current state needs recalculating."""
name: ClassVar[str] = "update_current_state" # used for opentracing
def try_merge(self, task: "_EventPersistQueueTask") -> bool:
"""Deduplicates consecutive recalculations of current state."""
return isinstance(task, _UpdateCurrentStateTask)
_EventPersistQueueTask = Union[_PersistEventsTask, _UpdateCurrentStateTask]
@attr.s(auto_attribs=True, slots=True)
class _EventPersistQueueItem:
task: _EventPersistQueueTask
deferred: ObservableDeferred
parent_opentracing_span_contexts: List = attr.ib(factory=list)
"""A list of opentracing spans waiting for this batch"""
opentracing_span_context: Any = None
"""The opentracing span under which the persistence actually happened"""
_PersistResult = TypeVar("_PersistResult")
class _EventPeristenceQueue(Generic[_PersistResult]):
"""Queues up tasks so that they can be processed with only one concurrent
transaction per room.
Tasks can be bulk persistence of events or recalculation of a room's current state.
"""
def __init__(
self,
per_item_callback: Callable[
[str, _EventPersistQueueTask],
Awaitable[_PersistResult],
],
):
"""Create a new event persistence queue
The per_item_callback will be called for each item added via add_to_queue,
and its result will be returned via the Deferreds returned from add_to_queue.
"""
self._event_persist_queues: Dict[str, Deque[_EventPersistQueueItem]] = {}
self._currently_persisting_rooms: Set[str] = set()
self._per_item_callback = per_item_callback
async def add_to_queue(
self,
room_id: str,
task: _EventPersistQueueTask,
) -> _PersistResult:
"""Add a task to the queue.
If we are not already processing tasks in this room, starts off a background
process to to so, calling the per_item_callback for each item.
Args:
room_id (str):
task (_EventPersistQueueTask): A _PersistEventsTask or
_UpdateCurrentStateTask to process.
Returns:
the result returned by the `_per_item_callback` passed to
`__init__`.
"""
queue = self._event_persist_queues.setdefault(room_id, deque())
if queue and queue[-1].task.try_merge(task):
# the new task has been merged into the last task in the queue
end_item = queue[-1]
else:
deferred: ObservableDeferred[_PersistResult] = ObservableDeferred(
defer.Deferred(), consumeErrors=True
)
end_item = _EventPersistQueueItem(
task=task,
deferred=deferred,
)
queue.append(end_item)
# also add our active opentracing span to the item so that we get a link back
span = opentracing.active_span()
if span:
end_item.parent_opentracing_span_contexts.append(span.context)
# start a processor for the queue, if there isn't one already
self._handle_queue(room_id)
# wait for the queue item to complete
res = await make_deferred_yieldable(end_item.deferred.observe())
# add another opentracing span which links to the persist trace.
with opentracing.start_active_span_follows_from(
f"{task.name}_complete", (end_item.opentracing_span_context,)
):
pass
return res
def _handle_queue(self, room_id: str) -> None:
"""Attempts to handle the queue for a room if not already being handled.
The queue's 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 becomes 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() -> None:
try:
queue = self._get_drainining_queue(room_id)
for item in queue:
try:
with opentracing.start_active_span_follows_from(
item.task.name,
item.parent_opentracing_span_contexts,
inherit_force_tracing=True,
) as scope:
if scope:
item.opentracing_span_context = scope.span.context
ret = await self._per_item_callback(room_id, item.task)
except Exception:
with PreserveLoggingContext():
item.deferred.errback()
else:
with PreserveLoggingContext():
item.deferred.callback(ret)
finally:
remaining_queue = self._event_persist_queues.pop(room_id, None)
if remaining_queue:
self._event_persist_queues[room_id] = remaining_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: str
) -> Generator[_EventPersistQueueItem, None, None]:
queue = self._event_persist_queues.setdefault(room_id, deque())
try:
while True:
yield queue.popleft()
except IndexError:
# Queue has been drained.
pass
2022-05-31 14:17:50 +02:00
class EventsPersistenceStorageController:
2019-10-30 14:33:38 +01:00
"""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: "HomeServer",
stores: Databases,
state_controller: StateStorageController,
):
# 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.
2019-10-23 17:14:16 +02:00
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._process_event_persist_queue_task
)
self._state_resolution_handler = hs.get_state_resolution_handler()
self._state_controller = state_controller
async def _process_event_persist_queue_task(
self,
room_id: str,
task: _EventPersistQueueTask,
) -> Dict[str, str]:
"""Callback for the _event_persist_queue
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.
"""
if isinstance(task, _PersistEventsTask):
return await self._persist_event_batch(room_id, task)
elif isinstance(task, _UpdateCurrentStateTask):
await self._update_current_state(room_id, task)
return {}
else:
raise AssertionError(
f"Found an unexpected task type in event persistence queue: {task}"
)
@opentracing.trace
async def persist_events(
self,
events_and_contexts: Iterable[Tuple[EventBase, EventContext]],
backfilled: bool = False,
) -> Tuple[List[EventBase], 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:
List of events persisted, the current position room stream position.
The list of events persisted may not be the same as those passed in
if they were deduplicated due to an event already existing that
matched the transaction ID; the existing event is returned in such
a case.
Handle race between persisting an event and un-partial stating a room (#13100) Whenever we want to persist an event, we first compute an event context, which includes the state at the event and a flag indicating whether the state is partial. After a lot of processing, we finally try to store the event in the database, which can fail for partial state events when the containing room has been un-partial stated in the meantime. We detect the race as a foreign key constraint failure in the data store layer and turn it into a special `PartialStateConflictError` exception, which makes its way up to the method in which we computed the event context. To make things difficult, the exception needs to cross a replication request: `/fed_send_events` for events coming over federation and `/send_event` for events from clients. We transport the `PartialStateConflictError` as a `409 Conflict` over replication and turn `409`s back into `PartialStateConflictError`s on the worker making the request. All client events go through `EventCreationHandler.handle_new_client_event`, which is called in *a lot* of places. Instead of trying to update all the code which creates client events, we turn the `PartialStateConflictError` into a `429 Too Many Requests` in `EventCreationHandler.handle_new_client_event` and hope that clients take it as a hint to retry their request. On the federation event side, there are 7 places which compute event contexts. 4 of them use outlier event contexts: `FederationEventHandler._auth_and_persist_outliers_inner`, `FederationHandler.do_knock`, `FederationHandler.on_invite_request` and `FederationHandler.do_remotely_reject_invite`. These events won't have the partial state flag, so we do not need to do anything for then. The remaining 3 paths which create events are `FederationEventHandler.process_remote_join`, `FederationEventHandler.on_send_membership_event` and `FederationEventHandler._process_received_pdu`. We can't experience the race in `process_remote_join`, unless we're handling an additional join into a partial state room, which currently blocks, so we make no attempt to handle it correctly. `on_send_membership_event` is only called by `FederationServer._on_send_membership_event`, so we catch the `PartialStateConflictError` there and retry just once. `_process_received_pdu` is called by `on_receive_pdu` for incoming events and `_process_pulled_event` for backfill. The latter should never try to persist partial state events, so we ignore it. We catch the `PartialStateConflictError` in `on_receive_pdu` and retry just once. Refering to the graph of code paths in https://github.com/matrix-org/synapse/issues/12988#issuecomment-1156857648 may make the above make more sense. Signed-off-by: Sean Quah <seanq@matrix.org>
2022-07-05 17:12:52 +02:00
Raises:
PartialStateConflictError: if attempting to persist a partial state event in
a room that has been un-partial stated.
"""
partitioned: Dict[str, List[Tuple[EventBase, EventContext]]] = {}
for event, ctx in events_and_contexts:
partitioned.setdefault(event.room_id, []).append((event, ctx))
async def enqueue(
item: Tuple[str, List[Tuple[EventBase, EventContext]]]
) -> Dict[str, str]:
room_id, evs_ctxs = item
return await self._event_persist_queue.add_to_queue(
room_id,
_PersistEventsTask(events_and_contexts=evs_ctxs, backfilled=backfilled),
)
ret_vals = await yieldable_gather_results(enqueue, partitioned.items())
# Each call to add_to_queue returns a map from event ID to existing event ID if
# the event was deduplicated. (The dict may also include other entries if
# the event was persisted in a batch with other events).
#
# Since we use `yieldable_gather_results` we need to merge the returned list
# of dicts into one.
replaced_events: Dict[str, str] = {}
for d in ret_vals:
replaced_events.update(d)
events = []
for event, _ in events_and_contexts:
existing_event_id = replaced_events.get(event.event_id)
if existing_event_id:
events.append(await self.main_store.get_event(existing_event_id))
else:
events.append(event)
return (
events,
self.main_store.get_room_max_token(),
)
@opentracing.trace
async def persist_event(
self, event: EventBase, context: EventContext, backfilled: bool = False
) -> Tuple[EventBase, PersistedEventPosition, RoomStreamToken]:
"""
Returns:
The event, stream ordering of `event`, and the stream ordering of the
latest persisted event. The returned event may not match the given
event if it was deduplicated due to an existing event matching the
transaction ID.
Handle race between persisting an event and un-partial stating a room (#13100) Whenever we want to persist an event, we first compute an event context, which includes the state at the event and a flag indicating whether the state is partial. After a lot of processing, we finally try to store the event in the database, which can fail for partial state events when the containing room has been un-partial stated in the meantime. We detect the race as a foreign key constraint failure in the data store layer and turn it into a special `PartialStateConflictError` exception, which makes its way up to the method in which we computed the event context. To make things difficult, the exception needs to cross a replication request: `/fed_send_events` for events coming over federation and `/send_event` for events from clients. We transport the `PartialStateConflictError` as a `409 Conflict` over replication and turn `409`s back into `PartialStateConflictError`s on the worker making the request. All client events go through `EventCreationHandler.handle_new_client_event`, which is called in *a lot* of places. Instead of trying to update all the code which creates client events, we turn the `PartialStateConflictError` into a `429 Too Many Requests` in `EventCreationHandler.handle_new_client_event` and hope that clients take it as a hint to retry their request. On the federation event side, there are 7 places which compute event contexts. 4 of them use outlier event contexts: `FederationEventHandler._auth_and_persist_outliers_inner`, `FederationHandler.do_knock`, `FederationHandler.on_invite_request` and `FederationHandler.do_remotely_reject_invite`. These events won't have the partial state flag, so we do not need to do anything for then. The remaining 3 paths which create events are `FederationEventHandler.process_remote_join`, `FederationEventHandler.on_send_membership_event` and `FederationEventHandler._process_received_pdu`. We can't experience the race in `process_remote_join`, unless we're handling an additional join into a partial state room, which currently blocks, so we make no attempt to handle it correctly. `on_send_membership_event` is only called by `FederationServer._on_send_membership_event`, so we catch the `PartialStateConflictError` there and retry just once. `_process_received_pdu` is called by `on_receive_pdu` for incoming events and `_process_pulled_event` for backfill. The latter should never try to persist partial state events, so we ignore it. We catch the `PartialStateConflictError` in `on_receive_pdu` and retry just once. Refering to the graph of code paths in https://github.com/matrix-org/synapse/issues/12988#issuecomment-1156857648 may make the above make more sense. Signed-off-by: Sean Quah <seanq@matrix.org>
2022-07-05 17:12:52 +02:00
Raises:
PartialStateConflictError: if attempting to persist a partial state event in
a room that has been un-partial stated.
"""
# add_to_queue returns a map from event ID to existing event ID if the
# event was deduplicated. (The dict may also include other entries if
# the event was persisted in a batch with other events.)
replaced_events = await self._event_persist_queue.add_to_queue(
event.room_id,
_PersistEventsTask(
events_and_contexts=[(event, context)], backfilled=backfilled
),
)
replaced_event = replaced_events.get(event.event_id)
if replaced_event:
event = await self.main_store.get_event(replaced_event)
event_stream_id = event.internal_metadata.stream_ordering
# stream ordering should have been assigned by now
assert event_stream_id
pos = PersistedEventPosition(self._instance_name, event_stream_id)
return event, pos, self.main_store.get_room_max_token()
async def update_current_state(self, room_id: str) -> None:
"""Recalculate the current state for a room, and persist it"""
await self._event_persist_queue.add_to_queue(
room_id,
_UpdateCurrentStateTask(),
)
async def _update_current_state(
self, room_id: str, _task: _UpdateCurrentStateTask
) -> None:
"""Callback for the _event_persist_queue
Recalculates the current state for a room, and persists it.
"""
state = await self._calculate_current_state(room_id)
delta = await self._calculate_state_delta(room_id, state)
await self.persist_events_store.update_current_state(room_id, delta)
async def _calculate_current_state(self, room_id: str) -> StateMap[str]:
"""Calculate the current state of a room, based on the forward extremities
Args:
room_id: room for which to calculate current state
Returns:
map from (type, state_key) to event id for the current state in the room
"""
latest_event_ids = await self.main_store.get_latest_event_ids_in_room(room_id)
state_groups = set(
(
await self.main_store._get_state_group_for_events(latest_event_ids)
).values()
)
state_maps_by_state_group = await self.state_store._get_state_for_groups(
state_groups
)
if len(state_groups) == 1:
# If there is only one state group, then we know what the current
# state is.
return state_maps_by_state_group[state_groups.pop()]
# Ok, we need to defer to the state handler to resolve our state sets.
logger.debug("calling resolve_state_groups from preserve_events")
# Avoid a circular import.
from synapse.state import StateResolutionStore
room_version = await self.main_store.get_room_version_id(room_id)
res = await self._state_resolution_handler.resolve_state_groups(
room_id,
room_version,
state_maps_by_state_group,
event_map=None,
state_res_store=StateResolutionStore(self.main_store),
)
return await res.get_state(self._state_controller, StateFilter.all())
async def _persist_event_batch(
self, _room_id: str, task: _PersistEventsTask
) -> Dict[str, str]:
"""Callback for the _event_persist_queue
Calculates the change to current state and forward extremities, and
2019-10-30 14:33:38 +01:00
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.
Handle race between persisting an event and un-partial stating a room (#13100) Whenever we want to persist an event, we first compute an event context, which includes the state at the event and a flag indicating whether the state is partial. After a lot of processing, we finally try to store the event in the database, which can fail for partial state events when the containing room has been un-partial stated in the meantime. We detect the race as a foreign key constraint failure in the data store layer and turn it into a special `PartialStateConflictError` exception, which makes its way up to the method in which we computed the event context. To make things difficult, the exception needs to cross a replication request: `/fed_send_events` for events coming over federation and `/send_event` for events from clients. We transport the `PartialStateConflictError` as a `409 Conflict` over replication and turn `409`s back into `PartialStateConflictError`s on the worker making the request. All client events go through `EventCreationHandler.handle_new_client_event`, which is called in *a lot* of places. Instead of trying to update all the code which creates client events, we turn the `PartialStateConflictError` into a `429 Too Many Requests` in `EventCreationHandler.handle_new_client_event` and hope that clients take it as a hint to retry their request. On the federation event side, there are 7 places which compute event contexts. 4 of them use outlier event contexts: `FederationEventHandler._auth_and_persist_outliers_inner`, `FederationHandler.do_knock`, `FederationHandler.on_invite_request` and `FederationHandler.do_remotely_reject_invite`. These events won't have the partial state flag, so we do not need to do anything for then. The remaining 3 paths which create events are `FederationEventHandler.process_remote_join`, `FederationEventHandler.on_send_membership_event` and `FederationEventHandler._process_received_pdu`. We can't experience the race in `process_remote_join`, unless we're handling an additional join into a partial state room, which currently blocks, so we make no attempt to handle it correctly. `on_send_membership_event` is only called by `FederationServer._on_send_membership_event`, so we catch the `PartialStateConflictError` there and retry just once. `_process_received_pdu` is called by `on_receive_pdu` for incoming events and `_process_pulled_event` for backfill. The latter should never try to persist partial state events, so we ignore it. We catch the `PartialStateConflictError` in `on_receive_pdu` and retry just once. Refering to the graph of code paths in https://github.com/matrix-org/synapse/issues/12988#issuecomment-1156857648 may make the above make more sense. Signed-off-by: Sean Quah <seanq@matrix.org>
2022-07-05 17:12:52 +02:00
Raises:
PartialStateConflictError: if attempting to persist a partial state event in
a room that has been un-partial stated.
"""
events_and_contexts = task.events_and_contexts
backfilled = task.backfilled
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
async def _calculate_new_extremities(
self,
room_id: str,
event_contexts: List[Tuple[EventBase, EventContext]],
latest_event_ids: Collection[str],
) -> Set[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: Collection[
str
] = await self.persist_events_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 = 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: Set[str],
new_latest_event_ids: Set[str],
) -> Tuple[Optional[StateMap[str]], Optional[StateMap[str]], Set[str]]:
"""Calculate the current state dict after adding some new events to
a room
Args:
room_id:
room to which the events are being added. Used for logging etc
events_context:
events and contexts which are being added to the room
old_latest_event_ids:
the old forward extremities for the room.
new_latest_event_ids :
the new forward extremities for the room.
Returns:
Returns a tuple of two state maps and a set of new forward
extremities.
The first state map is the full new current state and the second
is the delta to the existing current state. If both are None then
there has been no change. Either or neither can be None if there
has been a change.
The function may prune some old entries from the set of new
forward extremities if it's safe to do so.
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 (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.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, new_latest_event_ids
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.
return None, delta_ids, new_latest_event_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.
state_groups_map = await self.state_store._get_state_for_groups(
new_state_groups
)
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, new_latest_event_ids
# 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),
)
state_resolutions_during_persistence.inc()
# If the returned state matches the state group of one of the new
# forward extremities then we check if we are able to prune some state
# extremities.
if res.state_group and res.state_group in new_state_groups:
new_latest_event_ids = await self._prune_extremities(
room_id,
new_latest_event_ids,
res.state_group,
event_id_to_state_group,
events_context,
)
full_state = await res.get_state(self._state_controller)
return full_state, None, new_latest_event_ids
async def _prune_extremities(
self,
room_id: str,
new_latest_event_ids: Set[str],
resolved_state_group: int,
event_id_to_state_group: Dict[str, int],
events_context: List[Tuple[EventBase, EventContext]],
) -> Set[str]:
"""See if we can prune any of the extremities after calculating the
resolved state.
"""
potential_times_prune_extremities.inc()
# We keep all the extremities that have the same state group, and
# see if we can drop the others.
new_new_extrems = {
e
for e in new_latest_event_ids
if event_id_to_state_group[e] == resolved_state_group
}
dropped_extrems = set(new_latest_event_ids) - new_new_extrems
logger.debug("Might drop extremities: %s", dropped_extrems)
# We only drop events from the extremities list if:
# 1. we're not currently persisting them;
# 2. they're not our own events (or are dummy events); and
# 3. they're either:
# 1. over N hours old and more than N events ago (we use depth to
# calculate); or
# 2. we are persisting an event from the same domain and more than
# M events ago.
#
# The idea is that we don't want to drop events that are "legitimate"
# extremities (that we would want to include as prev events), only
# "stuck" extremities that are e.g. due to a gap in the graph.
#
# Note that we either drop all of them or none of them. If we only drop
# some of the events we don't know if state res would come to the same
# conclusion.
for ev, _ in events_context:
if ev.event_id in dropped_extrems:
logger.debug(
"Not dropping extremities: %s is being persisted", ev.event_id
)
return new_latest_event_ids
dropped_events = await self.main_store.get_events(
dropped_extrems,
allow_rejected=True,
redact_behaviour=EventRedactBehaviour.as_is,
)
new_senders = {get_domain_from_id(e.sender) for e, _ in events_context}
one_day_ago = self._clock.time_msec() - 24 * 60 * 60 * 1000
current_depth = max(e.depth for e, _ in events_context)
for event in dropped_events.values():
# If the event is a local dummy event then we should check it
# doesn't reference any local events, as we want to reference those
# if we send any new events.
#
# Note we do this recursively to handle the case where a dummy event
# references a dummy event that only references remote events.
#
# Ideally we'd figure out a way of still being able to drop old
# dummy events that reference local events, but this is good enough
# as a first cut.
events_to_check: Collection[EventBase] = [event]
while events_to_check:
new_events: Set[str] = set()
for event_to_check in events_to_check:
if self.is_mine_id(event_to_check.sender):
if event_to_check.type != EventTypes.Dummy:
logger.debug("Not dropping own event")
return new_latest_event_ids
new_events.update(event_to_check.prev_event_ids())
prev_events = await self.main_store.get_events(
new_events,
allow_rejected=True,
redact_behaviour=EventRedactBehaviour.as_is,
)
events_to_check = prev_events.values()
if (
event.origin_server_ts < one_day_ago
and event.depth < current_depth - 100
):
continue
# We can be less conservative about dropping extremities from the
# same domain, though we do want to wait a little bit (otherwise
# we'll immediately remove all extremities from a given server).
if (
get_domain_from_id(event.sender) in new_senders
and event.depth < current_depth - 20
):
continue
logger.debug(
"Not dropping as too new and not in new_senders: %s",
new_senders,
)
return new_latest_event_ids
times_pruned_extremities.inc()
logger.info(
"Pruning forward extremities in room %s: from %s -> %s",
room_id,
new_latest_event_ids,
new_new_extrems,
)
return new_new_extrems
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_partial_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:
members = await self.main_store.get_membership_from_event_ids(
events_to_check
)
is_still_joined = any(
member and member.membership == Membership.JOIN
for member in members.values()
)
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_partial_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)
]
members = await self.main_store.get_membership_from_event_ids(remote_event_ids)
potentially_left_users.update(
member.user_id
for member in members.values()
if member and member.membership == Membership.JOIN
)
return False
async def _handle_potentially_left_users(self, user_ids: Set[str]) -> None:
"""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)