678 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			Python
		
	
	
			
		
		
	
	
			678 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			Python
		
	
	
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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#     http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from collections import namedtuple
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from typing import Dict, Iterable, List, Optional, Set
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from six import iteritems, itervalues
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import attr
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from frozendict import frozendict
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from prometheus_client import Histogram
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from twisted.internet import defer
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from synapse.api.constants import EventTypes
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from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, StateResolutionVersions
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from synapse.events import EventBase
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from synapse.events.snapshot import EventContext
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from synapse.logging.utils import log_function
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from synapse.state import v1, v2
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from synapse.storage.data_stores.main.events_worker import EventRedactBehaviour
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from synapse.types import StateMap
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from synapse.util.async_helpers import Linearizer
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from synapse.util.caches import get_cache_factor_for
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from synapse.util.caches.expiringcache import ExpiringCache
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from synapse.util.metrics import Measure, measure_func
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logger = logging.getLogger(__name__)
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# Metrics for number of state groups involved in a resolution.
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state_groups_histogram = Histogram(
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    "synapse_state_number_state_groups_in_resolution",
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    "Number of state groups used when performing a state resolution",
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    buckets=(1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"),
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)
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KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))
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SIZE_OF_CACHE = 100000 * get_cache_factor_for("state_cache")
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EVICTION_TIMEOUT_SECONDS = 60 * 60
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_NEXT_STATE_ID = 1
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POWER_KEY = (EventTypes.PowerLevels, "")
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def _gen_state_id():
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    global _NEXT_STATE_ID
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    s = "X%d" % (_NEXT_STATE_ID,)
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    _NEXT_STATE_ID += 1
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    return s
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class _StateCacheEntry(object):
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    __slots__ = ["state", "state_group", "state_id", "prev_group", "delta_ids"]
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    def __init__(self, state, state_group, prev_group=None, delta_ids=None):
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        # dict[(str, str), str] map  from (type, state_key) to event_id
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        self.state = frozendict(state)
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        # the ID of a state group if one and only one is involved.
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        # otherwise, None otherwise?
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        self.state_group = state_group
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        self.prev_group = prev_group
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        self.delta_ids = frozendict(delta_ids) if delta_ids is not None else None
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        # The `state_id` is a unique ID we generate that can be used as ID for
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        # this collection of state. Usually this would be the same as the
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        # state group, but on worker instances we can't generate a new state
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        # group each time we resolve state, so we generate a separate one that
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        # isn't persisted and is used solely for caches.
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        # `state_id` is either a state_group (and so an int) or a string. This
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        # ensures we don't accidentally persist a state_id as a stateg_group
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        if state_group:
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            self.state_id = state_group
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        else:
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            self.state_id = _gen_state_id()
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    def __len__(self):
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        return len(self.state)
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class StateHandler(object):
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    """Fetches bits of state from the stores, and does state resolution
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    where necessary
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    """
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    def __init__(self, hs):
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        self.clock = hs.get_clock()
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        self.store = hs.get_datastore()
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        self.state_store = hs.get_storage().state
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        self.hs = hs
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        self._state_resolution_handler = hs.get_state_resolution_handler()
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    @defer.inlineCallbacks
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    def get_current_state(
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        self, room_id, event_type=None, state_key="", latest_event_ids=None
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    ):
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        """ Retrieves the current state for the room. This is done by
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        calling `get_latest_events_in_room` to get the leading edges of the
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        event graph and then resolving any of the state conflicts.
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        This is equivalent to getting the state of an event that were to send
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        next before receiving any new events.
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        If `event_type` is specified, then the method returns only the one
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        event (or None) with that `event_type` and `state_key`.
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        Returns:
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            map from (type, state_key) to event
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        """
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        if not latest_event_ids:
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            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
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        logger.debug("calling resolve_state_groups from get_current_state")
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        ret = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
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        state = ret.state
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        if event_type:
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            event_id = state.get((event_type, state_key))
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            event = None
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            if event_id:
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                event = yield self.store.get_event(event_id, allow_none=True)
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            return event
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        state_map = yield self.store.get_events(
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            list(state.values()), get_prev_content=False
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        )
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        state = {
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            key: state_map[e_id] for key, e_id in iteritems(state) if e_id in state_map
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        }
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        return state
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    @defer.inlineCallbacks
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    def get_current_state_ids(self, room_id, latest_event_ids=None):
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        """Get the current state, or the state at a set of events, for a room
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        Args:
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            room_id (str):
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            latest_event_ids (iterable[str]|None): if given, the forward
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                extremities to resolve. If None, we look them up from the
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                database (via a cache)
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        Returns:
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            Deferred[dict[(str, str), str)]]: the state dict, mapping from
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                (event_type, state_key) -> event_id
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        """
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        if not latest_event_ids:
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            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
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        logger.debug("calling resolve_state_groups from get_current_state_ids")
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        ret = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
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        state = ret.state
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        return state
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    @defer.inlineCallbacks
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    def get_current_users_in_room(self, room_id, latest_event_ids=None):
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        """
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        Get the users who are currently in a room.
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        Args:
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            room_id (str): The ID of the room.
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            latest_event_ids (List[str]|None): Precomputed list of latest
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                event IDs. Will be computed if None.
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        Returns:
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            Deferred[Dict[str,ProfileInfo]]: Dictionary of user IDs to their
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                profileinfo.
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        """
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        if not latest_event_ids:
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            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
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        logger.debug("calling resolve_state_groups from get_current_users_in_room")
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        entry = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
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        joined_users = yield self.store.get_joined_users_from_state(room_id, entry)
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        return joined_users
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    @defer.inlineCallbacks
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    def get_current_hosts_in_room(self, room_id):
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        event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
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        return (yield self.get_hosts_in_room_at_events(room_id, event_ids))
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    @defer.inlineCallbacks
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    def get_hosts_in_room_at_events(self, room_id, event_ids):
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        """Get the hosts that were in a room at the given event ids
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        Args:
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            room_id (str):
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            event_ids (list[str]):
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        Returns:
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            Deferred[list[str]]: the hosts in the room at the given events
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        """
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        entry = yield self.resolve_state_groups_for_events(room_id, event_ids)
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        joined_hosts = yield self.store.get_joined_hosts(room_id, entry)
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        return joined_hosts
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    @defer.inlineCallbacks
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    def compute_event_context(
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        self, event: EventBase, old_state: Optional[Iterable[EventBase]] = None
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    ):
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        """Build an EventContext structure for the event.
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        This works out what the current state should be for the event, and
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        generates a new state group if necessary.
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        Args:
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            event:
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            old_state: The state at the event if it can't be
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                calculated from existing events. This is normally only specified
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                when receiving an event from federation where we don't have the
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                prev events for, e.g. when backfilling.
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        Returns:
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            synapse.events.snapshot.EventContext:
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        """
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        if event.internal_metadata.is_outlier():
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            # If this is an outlier, then we know it shouldn't have any current
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            # state. Certainly store.get_current_state won't return any, and
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            # persisting the event won't store the state group.
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            # FIXME: why do we populate current_state_ids? I thought the point was
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            # that we weren't supposed to have any state for outliers?
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            if old_state:
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                prev_state_ids = {(s.type, s.state_key): s.event_id for s in old_state}
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                if event.is_state():
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                    current_state_ids = dict(prev_state_ids)
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                    key = (event.type, event.state_key)
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                    current_state_ids[key] = event.event_id
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                else:
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                    current_state_ids = prev_state_ids
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            else:
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                current_state_ids = {}
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                prev_state_ids = {}
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            # We don't store state for outliers, so we don't generate a state
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            # group for it.
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            context = EventContext.with_state(
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                state_group=None,
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                state_group_before_event=None,
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                current_state_ids=current_state_ids,
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                prev_state_ids=prev_state_ids,
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            )
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            return context
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        #
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        # first of all, figure out the state before the event
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        #
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        if old_state:
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            # if we're given the state before the event, then we use that
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            state_ids_before_event = {
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                (s.type, s.state_key): s.event_id for s in old_state
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            }
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            state_group_before_event = None
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            state_group_before_event_prev_group = None
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            deltas_to_state_group_before_event = None
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        else:
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            # otherwise, we'll need to resolve the state across the prev_events.
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            logger.debug("calling resolve_state_groups from compute_event_context")
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            entry = yield self.resolve_state_groups_for_events(
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                event.room_id, event.prev_event_ids()
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            )
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            state_ids_before_event = entry.state
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            state_group_before_event = entry.state_group
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            state_group_before_event_prev_group = entry.prev_group
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            deltas_to_state_group_before_event = entry.delta_ids
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        #
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        # make sure that we have a state group at that point. If it's not a state event,
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        # that will be the state group for the new event. If it *is* a state event,
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        # it might get rejected (in which case we'll need to persist it with the
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        # previous state group)
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        #
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        if not state_group_before_event:
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            state_group_before_event = yield self.state_store.store_state_group(
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                event.event_id,
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                event.room_id,
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                prev_group=state_group_before_event_prev_group,
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                delta_ids=deltas_to_state_group_before_event,
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                current_state_ids=state_ids_before_event,
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            )
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            # XXX: can we update the state cache entry for the new state group? or
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            # could we set a flag on resolve_state_groups_for_events to tell it to
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            # always make a state group?
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        #
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        # now if it's not a state event, we're done
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        #
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        if not event.is_state():
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            return EventContext.with_state(
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                state_group_before_event=state_group_before_event,
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                state_group=state_group_before_event,
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                current_state_ids=state_ids_before_event,
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                prev_state_ids=state_ids_before_event,
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                prev_group=state_group_before_event_prev_group,
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                delta_ids=deltas_to_state_group_before_event,
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            )
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        #
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        # otherwise, we'll need to create a new state group for after the event
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        #
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        key = (event.type, event.state_key)
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        if key in state_ids_before_event:
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            replaces = state_ids_before_event[key]
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            if replaces != event.event_id:
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                event.unsigned["replaces_state"] = replaces
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        state_ids_after_event = dict(state_ids_before_event)
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        state_ids_after_event[key] = event.event_id
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        delta_ids = {key: event.event_id}
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        state_group_after_event = yield self.state_store.store_state_group(
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            event.event_id,
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            event.room_id,
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            prev_group=state_group_before_event,
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            delta_ids=delta_ids,
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            current_state_ids=state_ids_after_event,
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        )
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        return EventContext.with_state(
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            state_group=state_group_after_event,
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            state_group_before_event=state_group_before_event,
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            current_state_ids=state_ids_after_event,
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            prev_state_ids=state_ids_before_event,
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            prev_group=state_group_before_event,
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            delta_ids=delta_ids,
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        )
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    @measure_func()
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    @defer.inlineCallbacks
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    def resolve_state_groups_for_events(self, room_id, event_ids):
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        """ Given a list of event_ids this method fetches the state at each
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        event, resolves conflicts between them and returns them.
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        Args:
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            room_id (str)
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            event_ids (list[str])
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            explicit_room_version (str|None): If set uses the the given room
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                version to choose the resolution algorithm. If None, then
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                checks the database for room version.
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        Returns:
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            Deferred[_StateCacheEntry]: resolved state
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        """
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        logger.debug("resolve_state_groups event_ids %s", event_ids)
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        # map from state group id to the state in that state group (where
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        # 'state' is a map from state key to event id)
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        # dict[int, dict[(str, str), str]]
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        state_groups_ids = yield self.state_store.get_state_groups_ids(
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            room_id, event_ids
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        )
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        if len(state_groups_ids) == 0:
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            return _StateCacheEntry(state={}, state_group=None)
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        elif len(state_groups_ids) == 1:
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            name, state_list = list(state_groups_ids.items()).pop()
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            prev_group, delta_ids = yield self.state_store.get_state_group_delta(name)
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            return _StateCacheEntry(
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                state=state_list,
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                state_group=name,
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                prev_group=prev_group,
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                delta_ids=delta_ids,
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            )
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        room_version = yield self.store.get_room_version_id(room_id)
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        result = yield self._state_resolution_handler.resolve_state_groups(
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            room_id,
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            room_version,
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            state_groups_ids,
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            None,
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            state_res_store=StateResolutionStore(self.store),
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        )
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        return result
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    @defer.inlineCallbacks
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    def resolve_events(self, room_version, state_sets, event):
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        logger.info(
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            "Resolving state for %s with %d groups", event.room_id, len(state_sets)
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        )
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        state_set_ids = [
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            {(ev.type, ev.state_key): ev.event_id for ev in st} for st in state_sets
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        ]
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        state_map = {ev.event_id: ev for st in state_sets for ev in st}
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        with Measure(self.clock, "state._resolve_events"):
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            new_state = yield resolve_events_with_store(
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                event.room_id,
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                room_version,
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                state_set_ids,
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						|
                event_map=state_map,
 | 
						|
                state_res_store=StateResolutionStore(self.store),
 | 
						|
            )
 | 
						|
 | 
						|
        new_state = {key: state_map[ev_id] for key, ev_id in iteritems(new_state)}
 | 
						|
 | 
						|
        return new_state
 | 
						|
 | 
						|
 | 
						|
class StateResolutionHandler(object):
 | 
						|
    """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):
 | 
						|
        self.clock = hs.get_clock()
 | 
						|
 | 
						|
        # dict of set of event_ids -> _StateCacheEntry.
 | 
						|
        self._state_cache = None
 | 
						|
        self.resolve_linearizer = Linearizer(name="state_resolve_lock")
 | 
						|
 | 
						|
        self._state_cache = ExpiringCache(
 | 
						|
            cache_name="state_cache",
 | 
						|
            clock=self.clock,
 | 
						|
            max_len=SIZE_OF_CACHE,
 | 
						|
            expiry_ms=EVICTION_TIMEOUT_SECONDS * 1000,
 | 
						|
            iterable=True,
 | 
						|
            reset_expiry_on_get=True,
 | 
						|
        )
 | 
						|
 | 
						|
    @defer.inlineCallbacks
 | 
						|
    @log_function
 | 
						|
    def resolve_state_groups(
 | 
						|
        self, room_id, room_version, state_groups_ids, event_map, state_res_store
 | 
						|
    ):
 | 
						|
        """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 (str): room we are resolving for (used for logging and sanity checks)
 | 
						|
            room_version (str): version of the room
 | 
						|
            state_groups_ids (dict[int, dict[(str, str), str]]):
 | 
						|
                 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(dict[str,FrozenEvent]|None):
 | 
						|
                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 fof 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 (StateResolutionStore)
 | 
						|
 | 
						|
        Returns:
 | 
						|
            Deferred[_StateCacheEntry]: resolved state
 | 
						|
        """
 | 
						|
        logger.debug("resolve_state_groups state_groups %s", state_groups_ids.keys())
 | 
						|
 | 
						|
        group_names = frozenset(state_groups_ids.keys())
 | 
						|
 | 
						|
        with (yield self.resolve_linearizer.queue(group_names)):
 | 
						|
            if self._state_cache is not None:
 | 
						|
                cache = self._state_cache.get(group_names, None)
 | 
						|
                if cache:
 | 
						|
                    return cache
 | 
						|
 | 
						|
            logger.info(
 | 
						|
                "Resolving state for %s with %d groups", room_id, len(state_groups_ids)
 | 
						|
            )
 | 
						|
 | 
						|
            state_groups_histogram.observe(len(state_groups_ids))
 | 
						|
 | 
						|
            # start by assuming we won't have any conflicted state, and build up the new
 | 
						|
            # state map by iterating through the state groups. If we discover a conflict,
 | 
						|
            # we give up and instead use `resolve_events_with_store`.
 | 
						|
            #
 | 
						|
            # XXX: is this actually worthwhile, or should we just let
 | 
						|
            # resolve_events_with_store do it?
 | 
						|
            new_state = {}
 | 
						|
            conflicted_state = False
 | 
						|
            for st in itervalues(state_groups_ids):
 | 
						|
                for key, e_id in iteritems(st):
 | 
						|
                    if key in new_state:
 | 
						|
                        conflicted_state = True
 | 
						|
                        break
 | 
						|
                    new_state[key] = e_id
 | 
						|
                if conflicted_state:
 | 
						|
                    break
 | 
						|
 | 
						|
            if conflicted_state:
 | 
						|
                logger.info("Resolving conflicted state for %r", room_id)
 | 
						|
                with Measure(self.clock, "state._resolve_events"):
 | 
						|
                    new_state = yield resolve_events_with_store(
 | 
						|
                        room_id,
 | 
						|
                        room_version,
 | 
						|
                        list(itervalues(state_groups_ids)),
 | 
						|
                        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)
 | 
						|
 | 
						|
            if self._state_cache is not None:
 | 
						|
                self._state_cache[group_names] = cache
 | 
						|
 | 
						|
            return cache
 | 
						|
 | 
						|
 | 
						|
def _make_state_cache_entry(new_state, state_groups_ids):
 | 
						|
    """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 (dict[(str, str), str]): resolved state map (mapping from
 | 
						|
           (type, state_key) to event_id)
 | 
						|
 | 
						|
        state_groups_ids (dict[int, dict[(str, str), str]]):
 | 
						|
                 map from state group id to the state in that state group
 | 
						|
                (where 'state' is a map from state key to event id)
 | 
						|
 | 
						|
    Returns:
 | 
						|
        _StateCacheEntry
 | 
						|
    """
 | 
						|
    # 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(itervalues(new_state))
 | 
						|
    for sg, state in iteritems(state_groups_ids):
 | 
						|
        if len(new_state_event_ids) != len(state):
 | 
						|
            continue
 | 
						|
 | 
						|
        old_state_event_ids = set(itervalues(state))
 | 
						|
        if new_state_event_ids == old_state_event_ids:
 | 
						|
            # got an exact match.
 | 
						|
            return _StateCacheEntry(state=new_state, 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 = None
 | 
						|
 | 
						|
    for old_group, old_state in iteritems(state_groups_ids):
 | 
						|
        n_delta_ids = {k: v for k, v in iteritems(new_state) 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
 | 
						|
 | 
						|
    return _StateCacheEntry(
 | 
						|
        state=new_state, state_group=None, prev_group=prev_group, delta_ids=delta_ids
 | 
						|
    )
 | 
						|
 | 
						|
 | 
						|
def resolve_events_with_store(
 | 
						|
    room_id: str,
 | 
						|
    room_version: str,
 | 
						|
    state_sets: List[StateMap[str]],
 | 
						|
    event_map: Optional[Dict[str, EventBase]],
 | 
						|
    state_res_store: "StateResolutionStore",
 | 
						|
):
 | 
						|
    """
 | 
						|
    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 fof 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:
 | 
						|
        Deferred[dict[(str, str), str]]:
 | 
						|
            a map from (type, state_key) to event_id.
 | 
						|
    """
 | 
						|
    v = KNOWN_ROOM_VERSIONS[room_version]
 | 
						|
    if v.state_res == StateResolutionVersions.V1:
 | 
						|
        return v1.resolve_events_with_store(
 | 
						|
            room_id, state_sets, event_map, state_res_store.get_events
 | 
						|
        )
 | 
						|
    else:
 | 
						|
        return v2.resolve_events_with_store(
 | 
						|
            room_id, room_version, state_sets, event_map, state_res_store
 | 
						|
        )
 | 
						|
 | 
						|
 | 
						|
@attr.s
 | 
						|
class StateResolutionStore(object):
 | 
						|
    """Interface that allows state resolution algorithms to access the database
 | 
						|
    in well defined way.
 | 
						|
 | 
						|
    Args:
 | 
						|
        store (DataStore)
 | 
						|
    """
 | 
						|
 | 
						|
    store = attr.ib()
 | 
						|
 | 
						|
    def get_events(self, event_ids, allow_rejected=False):
 | 
						|
        """Get events from the database
 | 
						|
 | 
						|
        Args:
 | 
						|
            event_ids (list): The event_ids of the events to fetch
 | 
						|
            allow_rejected (bool): If True return rejected events.
 | 
						|
 | 
						|
        Returns:
 | 
						|
            Deferred[dict[str, FrozenEvent]]: 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, state_sets: List[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:
 | 
						|
            Deferred[Set[str]]: Set of event IDs.
 | 
						|
        """
 | 
						|
 | 
						|
        return self.store.get_auth_chain_difference(state_sets)
 |