# Copyright 2014-2016 OpenMarket Ltd # Copyright 2018 New Vector Ltd # # 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 heapq import logging from collections import ChainMap, defaultdict from typing import ( TYPE_CHECKING, Any, Awaitable, Callable, Collection, DefaultDict, Dict, FrozenSet, List, Mapping, Optional, Sequence, Set, Tuple, ) import attr from immutabledict import immutabledict from prometheus_client import Counter, Histogram from synapse.api.constants import EventTypes from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, StateResolutionVersions from synapse.events import EventBase from synapse.events.snapshot import ( EventContext, UnpersistedEventContext, UnpersistedEventContextBase, ) from synapse.logging.context import ContextResourceUsage from synapse.replication.http.state import ReplicationUpdateCurrentStateRestServlet from synapse.state import v1, v2 from synapse.storage.databases.main.events_worker import EventRedactBehaviour from synapse.types import StateMap from synapse.types.state import StateFilter from synapse.util.async_helpers import Linearizer from synapse.util.caches.expiringcache import ExpiringCache from synapse.util.metrics import Measure, measure_func if TYPE_CHECKING: from synapse.server import HomeServer from synapse.storage.controllers import StateStorageController from synapse.storage.databases.main import DataStore logger = logging.getLogger(__name__) metrics_logger = logging.getLogger("synapse.state.metrics") # Metrics for number of state groups involved in a resolution. state_groups_histogram = Histogram( "synapse_state_number_state_groups_in_resolution", "Number of state groups used when performing a state resolution", buckets=(1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"), ) EVICTION_TIMEOUT_SECONDS = 60 * 60 _NEXT_STATE_ID = 1 POWER_KEY = (EventTypes.PowerLevels, "") def _gen_state_id() -> str: global _NEXT_STATE_ID s = "X%d" % (_NEXT_STATE_ID,) _NEXT_STATE_ID += 1 return s class _StateCacheEntry: __slots__ = ["_state", "state_group", "prev_group", "delta_ids"] def __init__( self, state: Optional[StateMap[str]], state_group: Optional[int], prev_group: Optional[int] = None, delta_ids: Optional[StateMap[str]] = None, ): if state is None and state_group is None and prev_group is None: raise Exception("One of state, state_group or prev_group must be not None") if prev_group is not None and delta_ids is None: raise Exception("If prev_group is set so must delta_ids") # A map from (type, state_key) to event_id. # # This can be None if we have a `state_group` (as then we can fetch the # state from the DB.) self._state: Optional[StateMap[str]] = ( immutabledict(state) if state is not None else None ) # the ID of a state group if one and only one is involved. # otherwise, None otherwise? self.state_group = state_group self.prev_group = prev_group self.delta_ids: Optional[StateMap[str]] = ( immutabledict(delta_ids) if delta_ids is not None else None ) async def get_state( self, state_storage: "StateStorageController", state_filter: Optional["StateFilter"] = None, ) -> StateMap[str]: """Get the state map for this entry, either from the in-memory state or looking up the state group in the DB. """ if self._state is not None: return self._state if self.state_group is not None: return await state_storage.get_state_ids_for_group( self.state_group, state_filter ) assert self.prev_group is not None and self.delta_ids is not None prev_state = await state_storage.get_state_ids_for_group( self.prev_group, state_filter ) # ChainMap expects MutableMapping, but since we're using it immutably # its safe to give it immutable maps. return ChainMap(self.delta_ids, prev_state) # type: ignore[arg-type] def set_state_group(self, state_group: int) -> None: """Update the state group assigned to this state (e.g. after we've persisted it). Note: this will cause the cache entry to drop any stored state. """ self.state_group = state_group # We clear out the state as we know longer need to explicitly keep it in # the `state_cache` (as the store state group cache will do that). self._state = None def __len__(self) -> int: # The len should be used to estimate how large this cache entry is, for # cache eviction purposes. This is why it's fine to return 1 if we're # not storing any state. length = 0 if self._state: length += len(self._state) if self.delta_ids: length += len(self.delta_ids) return length or 1 # Make sure its not 0. class StateHandler: """Fetches bits of state from the stores, and does state resolution where necessary """ def __init__(self, hs: "HomeServer"): self.clock = hs.get_clock() self.store = hs.get_datastores().main self._state_storage_controller = hs.get_storage_controllers().state self.hs = hs self._state_resolution_handler = hs.get_state_resolution_handler() self._storage_controllers = hs.get_storage_controllers() self._events_shard_config = hs.config.worker.events_shard_config self._instance_name = hs.get_instance_name() self._update_current_state_client = ( ReplicationUpdateCurrentStateRestServlet.make_client(hs) ) async def compute_state_after_events( self, room_id: str, event_ids: Collection[str], state_filter: Optional[StateFilter] = None, await_full_state: bool = True, ) -> StateMap[str]: """Fetch the state after each of the given event IDs. Resolve them and return. This is typically used where `event_ids` is a collection of forward extremities in a room, intended to become the `prev_events` of a new event E. If so, the return value of this function represents the state before E. Args: room_id: the room_id containing the given events. event_ids: the events whose state should be fetched and resolved. await_full_state: if `True`, will block if we do not yet have complete state at these events and `state_filter` is not satisfied by partial state. Defaults to `True`. Returns: the state dict (a mapping from (event_type, state_key) -> event_id) which holds the resolution of the states after the given event IDs. """ logger.debug("calling resolve_state_groups from compute_state_after_events") if ( await_full_state and state_filter and not state_filter.must_await_full_state(self.hs.is_mine_id) ): await_full_state = False ret = await self.resolve_state_groups_for_events( room_id, event_ids, await_full_state ) return await ret.get_state(self._state_storage_controller, state_filter) async def get_current_user_ids_in_room( self, room_id: str, latest_event_ids: Collection[str] ) -> Set[str]: """ Get the users IDs who are currently in a room. Note: This is much slower than using the equivalent method `DataStore.get_users_in_room` or `DataStore.get_users_in_room_with_profiles`, so this should only be used when wanting the users at a particular point in the room. Args: room_id: The ID of the room. latest_event_ids: Precomputed list of latest event IDs. Will be computed if None. Returns: Set of user IDs in the room. """ assert latest_event_ids is not None logger.debug("calling resolve_state_groups from get_current_user_ids_in_room") entry = await self.resolve_state_groups_for_events(room_id, latest_event_ids) state = await entry.get_state(self._state_storage_controller, StateFilter.all()) return await self.store.get_joined_user_ids_from_state(room_id, state) async def get_hosts_in_room_at_events( self, room_id: str, event_ids: Collection[str] ) -> FrozenSet[str]: """Get the hosts that were in a room at the given event ids Args: room_id: event_ids: Returns: The hosts in the room at the given events """ entry = await self.resolve_state_groups_for_events(room_id, event_ids) state = await entry.get_state(self._state_storage_controller, StateFilter.all()) return await self.store.get_joined_hosts(room_id, state, entry) async def calculate_context_info( self, event: EventBase, state_ids_before_event: Optional[StateMap[str]] = None, partial_state: Optional[bool] = None, state_group_before_event: Optional[int] = None, ) -> UnpersistedEventContextBase: """ Calulates the contents of an unpersisted event context, other than the current state group (which is either provided or calculated when the event context is persisted) state_ids_before_event: The event ids of the full state before the event if it can't be calculated from existing events. This is normally only specified when receiving an event from federation where we don't have the prev events, e.g. when backfilling or when the event is being created for batch persisting. partial_state: `True` if `state_ids_before_event` is partial and omits non-critical membership events. `False` if `state_ids_before_event` is the full state. `None` when `state_ids_before_event` is not provided. In this case, the flag will be calculated based on `event`'s prev events. state_group_before_event: the current state group at the time of event, if known Returns: The event context. Raises: RuntimeError if `state_ids_before_event` is not provided and one or more prev events are missing or outliers. """ assert not event.internal_metadata.is_outlier() # # first of all, figure out the state before the event, unless we # already have it. # if state_ids_before_event: # if we're given the state before the event, then we use that state_group_before_event_prev_group = None deltas_to_state_group_before_event = None # the partial_state flag must be provided assert partial_state is not None else: # otherwise, we'll need to resolve the state across the prev_events. # partial_state should not be set explicitly in this case: # we work it out dynamically assert partial_state is None # if any of the prev-events have partial state, so do we. # (This is slightly racy - the prev-events might get fixed up before we use # their states - but I don't think that really matters; it just means we # might redundantly recalculate the state for this event later.) prev_event_ids = event.prev_event_ids() incomplete_prev_events = await self.store.get_partial_state_events( prev_event_ids ) partial_state = any(incomplete_prev_events.values()) if partial_state: logger.debug( "New/incoming event %s refers to prev_events %s with partial state", event.event_id, [k for (k, v) in incomplete_prev_events.items() if v], ) logger.debug("calling resolve_state_groups from compute_event_context") # we've already taken into account partial state, so no need to wait for # complete state here. entry = await self.resolve_state_groups_for_events( event.room_id, event.prev_event_ids(), await_full_state=False, ) state_group_before_event_prev_group = entry.prev_group deltas_to_state_group_before_event = entry.delta_ids state_ids_before_event = None # We make sure that we have a state group assigned to the state. if entry.state_group is None: # store_state_group requires us to have either a previous state group # (with deltas) or the complete state map. So, if we don't have a # previous state group, load the complete state map now. if state_group_before_event_prev_group is None: state_ids_before_event = await entry.get_state( self._state_storage_controller, StateFilter.all() ) state_group_before_event = ( await self._state_storage_controller.store_state_group( event.event_id, event.room_id, prev_group=state_group_before_event_prev_group, delta_ids=deltas_to_state_group_before_event, current_state_ids=state_ids_before_event, ) ) entry.set_state_group(state_group_before_event) else: state_group_before_event = entry.state_group # # now if it's not a state event, we're done # if not event.is_state(): return UnpersistedEventContext( storage=self._storage_controllers, state_group_before_event=state_group_before_event, state_group_after_event=state_group_before_event, state_delta_due_to_event={}, prev_group_for_state_group_before_event=state_group_before_event_prev_group, delta_ids_to_state_group_before_event=deltas_to_state_group_before_event, partial_state=partial_state, state_map_before_event=state_ids_before_event, ) # # otherwise, we'll need to set up creating a new state group for after the event # key = (event.type, event.state_key) if state_ids_before_event is not None: replaces = state_ids_before_event.get(key) else: replaces_state_map = await entry.get_state( self._state_storage_controller, StateFilter.from_types([key]) ) replaces = replaces_state_map.get(key) if replaces and replaces != event.event_id: event.unsigned["replaces_state"] = replaces delta_ids = {key: event.event_id} return UnpersistedEventContext( storage=self._storage_controllers, state_group_before_event=state_group_before_event, state_group_after_event=None, state_delta_due_to_event=delta_ids, prev_group_for_state_group_before_event=state_group_before_event_prev_group, delta_ids_to_state_group_before_event=deltas_to_state_group_before_event, partial_state=partial_state, state_map_before_event=state_ids_before_event, ) async def compute_event_context( self, event: EventBase, state_ids_before_event: Optional[StateMap[str]] = None, partial_state: Optional[bool] = None, ) -> EventContext: """Build an EventContext structure for a non-outlier event. (for an outlier, call EventContext.for_outlier directly) This works out what the current state should be for the event, and generates a new state group if necessary. Args: event: state_ids_before_event: The event ids of the state before the event if it can't be calculated from existing events. This is normally only specified when receiving an event from federation where we don't have the prev events, e.g. when backfilling. partial_state: `True` if `state_ids_before_event` is partial and omits non-critical membership events. `False` if `state_ids_before_event` is the full state. `None` when `state_ids_before_event` is not provided. In this case, the flag will be calculated based on `event`'s prev events. entry: A state cache entry for the resolved state across the prev events. We may have already calculated this, so if it's available pass it in Returns: The event context. Raises: RuntimeError if `state_ids_before_event` is not provided and one or more prev events are missing or outliers. """ unpersisted_context = await self.calculate_context_info( event=event, state_ids_before_event=state_ids_before_event, partial_state=partial_state, ) return await unpersisted_context.persist(event) @measure_func() async def resolve_state_groups_for_events( self, room_id: str, event_ids: Collection[str], await_full_state: bool = True ) -> _StateCacheEntry: """Given a list of event_ids this method fetches the state at each event, resolves conflicts between them and returns them. Args: room_id event_ids await_full_state: if true, will block if we do not yet have complete state at these events. Returns: The resolved state Raises: RuntimeError if we don't have a state group for one or more of the events (ie. they are outliers or unknown) """ logger.debug("resolve_state_groups event_ids %s", event_ids) state_groups = await self._state_storage_controller.get_state_group_for_events( event_ids, await_full_state=await_full_state ) state_group_ids = state_groups.values() # check if each event has same state group id, if so there's no state to resolve state_group_ids_set = set(state_group_ids) if len(state_group_ids_set) == 1: (state_group_id,) = state_group_ids_set ( prev_group, delta_ids, ) = await self._state_storage_controller.get_state_group_delta( state_group_id ) return _StateCacheEntry( state=None, state_group=state_group_id, prev_group=prev_group, delta_ids=delta_ids, ) elif len(state_group_ids_set) == 0: return _StateCacheEntry(state={}, state_group=None) room_version = await self.store.get_room_version_id(room_id) state_to_resolve = await self._state_storage_controller.get_state_for_groups( state_group_ids_set ) result = await self._state_resolution_handler.resolve_state_groups( room_id, room_version, state_to_resolve, None, state_res_store=StateResolutionStore(self.store), ) return result async def update_current_state(self, room_id: str) -> None: """Recalculates the current state for a room, and persists it. Raises: SynapseError(502): if all attempts to connect to the event persister worker fail """ writer_instance = self._events_shard_config.get_instance(room_id) if writer_instance != self._instance_name: await self._update_current_state_client( instance_name=writer_instance, room_id=room_id, ) return assert self._storage_controllers.persistence is not None await self._storage_controllers.persistence.update_current_state(room_id) @attr.s(slots=True, auto_attribs=True) class _StateResMetrics: """Keeps track of some usage metrics about state res.""" # System and User CPU time, in seconds cpu_time: float = 0.0 # time spent on database transactions (excluding scheduling time). This roughly # corresponds to the amount of work done on the db server, excluding event fetches. db_time: float = 0.0 # number of events fetched from the db. db_events: int = 0 _biggest_room_by_cpu_counter = Counter( "synapse_state_res_cpu_for_biggest_room_seconds", "CPU time spent performing state resolution for the single most expensive " "room for state resolution", ) _biggest_room_by_db_counter = Counter( "synapse_state_res_db_for_biggest_room_seconds", "Database time spent performing state resolution for the single most " "expensive room for state resolution", ) _cpu_times = Histogram( "synapse_state_res_cpu_for_all_rooms_seconds", "CPU time (utime+stime) spent computing a single state resolution", ) _db_times = Histogram( "synapse_state_res_db_for_all_rooms_seconds", "Database time spent computing a single state resolution", ) class StateResolutionHandler: """Responsible for doing state conflict resolution. Note that the storage layer depends on this handler, so all functions must be storage-independent. """ def __init__(self, hs: "HomeServer"): self.clock = hs.get_clock() self.resolve_linearizer = Linearizer(name="state_resolve_lock") # dict of set of event_ids -> _StateCacheEntry. self._state_cache: ExpiringCache[ FrozenSet[int], _StateCacheEntry ] = ExpiringCache( cache_name="state_cache", clock=self.clock, max_len=100000, expiry_ms=EVICTION_TIMEOUT_SECONDS * 1000, iterable=True, reset_expiry_on_get=True, ) # # stuff for tracking time spent on state-res by room # # tracks the amount of work done on state res per room self._state_res_metrics: DefaultDict[str, _StateResMetrics] = defaultdict( _StateResMetrics ) self.clock.looping_call(self._report_metrics, 120 * 1000) async def resolve_state_groups( self, room_id: str, room_version: str, state_groups_ids: Mapping[int, StateMap[str]], event_map: Optional[Dict[str, EventBase]], state_res_store: "StateResolutionStore", ) -> _StateCacheEntry: """Resolves conflicts between a set of state groups Always generates a new state group (unless we hit the cache), so should not be called for a single state group Args: room_id: room we are resolving for (used for logging and sanity checks) room_version: version of the room state_groups_ids: A map from state group id to the state in that state group (where 'state' is a map from state key to event id) event_map: a dict from event_id to event, for any events that we happen to have in flight (eg, those currently being persisted). This will be used as a starting point for finding the state we need; any missing events will be requested via state_res_store. If None, all events will be fetched via state_res_store. state_res_store Returns: The resolved state """ group_names = frozenset(state_groups_ids.keys()) async with self.resolve_linearizer.queue(group_names): cache = self._state_cache.get(group_names, None) if cache: return cache logger.info( "Resolving state for %s with groups %s", room_id, list(group_names), ) state_groups_histogram.observe(len(state_groups_ids)) new_state = await self.resolve_events_with_store( room_id, room_version, list(state_groups_ids.values()), event_map=event_map, state_res_store=state_res_store, ) # if the new state matches any of the input state groups, we can # use that state group again. Otherwise we will generate a state_id # which will be used as a cache key for future resolutions, but # not get persisted. with Measure(self.clock, "state.create_group_ids"): cache = _make_state_cache_entry(new_state, state_groups_ids) self._state_cache[group_names] = cache return cache async def resolve_events_with_store( self, room_id: str, room_version: str, state_sets: Sequence[StateMap[str]], event_map: Optional[Dict[str, EventBase]], state_res_store: "StateResolutionStore", ) -> StateMap[str]: """ Args: room_id: the room we are working in room_version: Version of the room state_sets: List of dicts of (type, state_key) -> event_id, which are the different state groups to resolve. event_map: a dict from event_id to event, for any events that we happen to have in flight (eg, those currently being persisted). This will be used as a starting point for finding the state we need; any missing events will be requested via state_map_factory. If None, all events will be fetched via state_res_store. state_res_store: a place to fetch events from Returns: a map from (type, state_key) to event_id. """ try: with Measure(self.clock, "state._resolve_events") as m: room_version_obj = KNOWN_ROOM_VERSIONS[room_version] if room_version_obj.state_res == StateResolutionVersions.V1: return await v1.resolve_events_with_store( room_id, room_version_obj, state_sets, event_map, state_res_store.get_events, ) else: return await v2.resolve_events_with_store( self.clock, room_id, room_version_obj, state_sets, event_map, state_res_store, ) finally: self._record_state_res_metrics(room_id, m.get_resource_usage()) def _record_state_res_metrics( self, room_id: str, rusage: ContextResourceUsage ) -> None: room_metrics = self._state_res_metrics[room_id] room_metrics.cpu_time += rusage.ru_utime + rusage.ru_stime room_metrics.db_time += rusage.db_txn_duration_sec room_metrics.db_events += rusage.evt_db_fetch_count _cpu_times.observe(rusage.ru_utime + rusage.ru_stime) _db_times.observe(rusage.db_txn_duration_sec) def _report_metrics(self) -> None: if not self._state_res_metrics: # no state res has happened since the last iteration: don't bother logging. return self._report_biggest( lambda i: i.cpu_time, "CPU time", _biggest_room_by_cpu_counter, ) self._report_biggest( lambda i: i.db_time, "DB time", _biggest_room_by_db_counter, ) self._state_res_metrics.clear() def _report_biggest( self, extract_key: Callable[[_StateResMetrics], Any], metric_name: str, prometheus_counter_metric: Counter, ) -> None: """Report metrics on the biggest rooms for state res Args: extract_key: a callable which, given a _StateResMetrics, extracts a single metric to sort by. metric_name: the name of the metric we have extracted, for the log line prometheus_counter_metric: a prometheus metric recording the sum of the the extracted metric """ n_to_log = 10 if not metrics_logger.isEnabledFor(logging.DEBUG): # only need the most expensive if we don't have debug logging, which # allows nlargest() to degrade to max() n_to_log = 1 items = self._state_res_metrics.items() # log the N biggest rooms biggest: List[Tuple[str, _StateResMetrics]] = heapq.nlargest( n_to_log, items, key=lambda i: extract_key(i[1]) ) metrics_logger.debug( "%i biggest rooms for state-res by %s: %s", len(biggest), metric_name, ["%s (%gs)" % (r, extract_key(m)) for (r, m) in biggest], ) # report info on the single biggest to prometheus _, biggest_metrics = biggest[0] prometheus_counter_metric.inc(extract_key(biggest_metrics)) def _make_state_cache_entry( new_state: StateMap[str], state_groups_ids: Mapping[int, StateMap[str]] ) -> _StateCacheEntry: """Given a resolved state, and a set of input state groups, pick one to base a new state group on (if any), and return an appropriately-constructed _StateCacheEntry. Args: new_state: resolved state map (mapping from (type, state_key) to event_id) state_groups_ids: map from state group id to the state in that state group (where 'state' is a map from state key to event id) Returns: The cache entry. """ # if the new state matches any of the input state groups, we can # use that state group again. Otherwise we will generate a state_id # which will be used as a cache key for future resolutions, but # not get persisted. # first look for exact matches new_state_event_ids = set(new_state.values()) for sg, state in state_groups_ids.items(): if len(new_state_event_ids) != len(state): continue old_state_event_ids = set(state.values()) if new_state_event_ids == old_state_event_ids: # got an exact match. return _StateCacheEntry(state=None, state_group=sg) # TODO: We want to create a state group for this set of events, to # increase cache hits, but we need to make sure that it doesn't # end up as a prev_group without being added to the database # failing that, look for the closest match. prev_group = None delta_ids: Optional[StateMap[str]] = None for old_group, old_state in state_groups_ids.items(): if old_state.keys() - new_state.keys(): # Currently we don't support deltas that remove keys from the state # map, so we have to ignore this group as a candidate to base the # new group on. continue n_delta_ids = {k: v for k, v in new_state.items() if old_state.get(k) != v} if not delta_ids or len(n_delta_ids) < len(delta_ids): prev_group = old_group delta_ids = n_delta_ids if prev_group is not None: # If we have a prev group and deltas then we can drop the new state from # the cache (to reduce memory usage). return _StateCacheEntry( state=None, state_group=None, prev_group=prev_group, delta_ids=delta_ids ) else: return _StateCacheEntry(state=new_state, state_group=None) @attr.s(slots=True, auto_attribs=True) class StateResolutionStore: """Interface that allows state resolution algorithms to access the database in well defined way. """ store: "DataStore" def get_events( self, event_ids: Collection[str], allow_rejected: bool = False ) -> Awaitable[Dict[str, EventBase]]: """Get events from the database Args: event_ids: The event_ids of the events to fetch allow_rejected: If True return rejected events. Returns: An awaitable which resolves to a dict from event_id to event. """ return self.store.get_events( event_ids, redact_behaviour=EventRedactBehaviour.as_is, get_prev_content=False, allow_rejected=allow_rejected, ) def get_auth_chain_difference( self, room_id: str, state_sets: List[Set[str]] ) -> Awaitable[Set[str]]: """Given sets of state events figure out the auth chain difference (as per state res v2 algorithm). This equivalent to fetching the full auth chain for each set of state and returning the events that don't appear in each and every auth chain. Returns: An awaitable that resolves to a set of event IDs. """ return self.store.get_auth_chain_difference(room_id, state_sets)