mirror of
https://github.com/element-hq/synapse.git
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385 lines
12 KiB
Python
385 lines
12 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014, 2015 OpenMarket 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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from twisted.internet import defer
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from synapse.util.logutils import log_function
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from synapse.util.async import run_on_reactor
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from synapse.util.expiringcache import ExpiringCache
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from synapse.api.constants import EventTypes
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from synapse.api.errors import AuthError
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from synapse.api.auth import AuthEventTypes
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from synapse.events.snapshot import EventContext
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from collections import namedtuple
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import logging
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import hashlib
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logger = logging.getLogger(__name__)
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def _get_state_key_from_event(event):
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return event.state_key
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KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))
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SIZE_OF_CACHE = 1000
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EVICTION_TIMEOUT_SECONDS = 20
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class _StateCacheEntry(object):
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def __init__(self, state, state_group, ts):
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self.state = state
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self.state_group = state_group
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class StateHandler(object):
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""" Responsible for doing state conflict resolution.
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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.hs = hs
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# dict of set of event_ids -> _StateCacheEntry.
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self._state_cache = None
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def start_caching(self):
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logger.debug("start_caching")
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self._state_cache = ExpiringCache(
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cache_name="state_cache",
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clock=self.clock,
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max_len=SIZE_OF_CACHE,
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expiry_ms=EVICTION_TIMEOUT_SECONDS*1000,
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reset_expiry_on_get=True,
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)
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self._state_cache.start()
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@defer.inlineCallbacks
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def get_current_state(self, room_id, event_type=None, state_key=""):
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""" Returns the current state for the room as a list. 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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"""
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events = yield self.store.get_latest_events_in_room(room_id)
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event_ids = [
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e_id
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for e_id, _, _ in events
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]
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cache = None
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if self._state_cache is not None:
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cache = self._state_cache.get(frozenset(event_ids), None)
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if cache:
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cache.ts = self.clock.time_msec()
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state = cache.state
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else:
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res = yield self.resolve_state_groups(event_ids)
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state = res[1]
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if event_type:
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defer.returnValue(state.get((event_type, state_key)))
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return
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defer.returnValue(state)
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@defer.inlineCallbacks
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def compute_event_context(self, event, old_state=None):
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""" Fills out the context with the `current state` of the graph. The
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`current state` here is defined to be the state of the event graph
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just before the event - i.e. it never includes `event`
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If `event` has `auth_events` then this will also fill out the
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`auth_events` field on `context` from the `current_state`.
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Args:
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event (EventBase)
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Returns:
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an EventContext
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"""
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context = EventContext()
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yield run_on_reactor()
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if old_state:
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context.current_state = {
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(s.type, s.state_key): s for s in old_state
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}
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context.state_group = None
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if event.is_state():
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key = (event.type, event.state_key)
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if key in context.current_state:
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replaces = context.current_state[key]
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if replaces.event_id != event.event_id: # Paranoia check
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event.unsigned["replaces_state"] = replaces.event_id
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context.prev_state_events = []
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defer.returnValue(context)
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if event.is_state():
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ret = yield self.resolve_state_groups(
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[e for e, _ in event.prev_events],
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event_type=event.type,
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state_key=event.state_key,
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)
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else:
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ret = yield self.resolve_state_groups(
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[e for e, _ in event.prev_events],
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)
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group, curr_state, prev_state = ret
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context.current_state = curr_state
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context.state_group = group if not event.is_state() else None
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prev_state = yield self.store.add_event_hashes(
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prev_state
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)
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if event.is_state():
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key = (event.type, event.state_key)
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if key in context.current_state:
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replaces = context.current_state[key]
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event.unsigned["replaces_state"] = replaces.event_id
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context.prev_state_events = prev_state
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defer.returnValue(context)
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@defer.inlineCallbacks
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@log_function
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def resolve_state_groups(self, event_ids, event_type=None, state_key=""):
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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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Return format is a tuple: (`state_group`, `state_events`), where the
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first is the name of a state group if one and only one is involved,
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otherwise `None`.
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"""
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logger.debug("resolve_state_groups event_ids %s", event_ids)
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if self._state_cache is not None:
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cache = self._state_cache.get(frozenset(event_ids), None)
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if cache and cache.state_group:
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cache.ts = self.clock.time_msec()
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prev_state = cache.state.get((event_type, state_key), None)
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if prev_state:
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prev_state = prev_state.event_id
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prev_states = [prev_state]
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else:
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prev_states = []
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defer.returnValue(
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(cache.state_group, cache.state, prev_states)
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)
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state_groups = yield self.store.get_state_groups(
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event_ids
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)
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logger.debug(
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"resolve_state_groups state_groups %s",
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state_groups.keys()
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)
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group_names = set(state_groups.keys())
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if len(group_names) == 1:
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name, state_list = state_groups.items().pop()
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state = {
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(e.type, e.state_key): e
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for e in state_list
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}
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prev_state = state.get((event_type, state_key), None)
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if prev_state:
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prev_state = prev_state.event_id
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prev_states = [prev_state]
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else:
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prev_states = []
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if self._state_cache is not None:
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cache = _StateCacheEntry(
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state=state,
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state_group=name,
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ts=self.clock.time_msec()
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)
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self._state_cache[frozenset(event_ids)] = cache
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defer.returnValue((name, state, prev_states))
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new_state, prev_states = self._resolve_events(
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state_groups.values(), event_type, state_key
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)
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if self._state_cache is not None:
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cache = _StateCacheEntry(
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state=new_state,
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state_group=None,
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ts=self.clock.time_msec()
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)
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self._state_cache[frozenset(event_ids)] = cache
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defer.returnValue((None, new_state, prev_states))
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def resolve_events(self, state_sets, event):
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if event.is_state():
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return self._resolve_events(
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state_sets, event.type, event.state_key
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)
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else:
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return self._resolve_events(state_sets)
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def _resolve_events(self, state_sets, event_type=None, state_key=""):
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state = {}
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for st in state_sets:
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for e in st:
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state.setdefault(
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(e.type, e.state_key),
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{}
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)[e.event_id] = e
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unconflicted_state = {
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k: v.values()[0] for k, v in state.items()
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if len(v.values()) == 1
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}
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conflicted_state = {
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k: v.values()
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for k, v in state.items()
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if len(v.values()) > 1
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}
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if event_type:
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prev_states_events = conflicted_state.get(
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(event_type, state_key), []
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)
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prev_states = [s.event_id for s in prev_states_events]
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else:
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prev_states = []
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auth_events = {
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k: e for k, e in unconflicted_state.items()
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if k[0] in AuthEventTypes
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}
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try:
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resolved_state = self._resolve_state_events(
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conflicted_state, auth_events
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)
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except:
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logger.exception("Failed to resolve state")
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raise
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new_state = unconflicted_state
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new_state.update(resolved_state)
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return new_state, prev_states
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@log_function
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def _resolve_state_events(self, conflicted_state, auth_events):
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""" This is where we actually decide which of the conflicted state to
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use.
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We resolve conflicts in the following order:
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1. power levels
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2. memberships
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3. other events.
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"""
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resolved_state = {}
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power_key = (EventTypes.PowerLevels, "")
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if power_key in conflicted_state.items():
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power_levels = conflicted_state[power_key]
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resolved_state[power_key] = self._resolve_auth_events(power_levels)
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auth_events.update(resolved_state)
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for key, events in conflicted_state.items():
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if key[0] == EventTypes.JoinRules:
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resolved_state[key] = self._resolve_auth_events(
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events,
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auth_events
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)
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auth_events.update(resolved_state)
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for key, events in conflicted_state.items():
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if key[0] == EventTypes.Member:
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resolved_state[key] = self._resolve_auth_events(
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events,
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auth_events
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)
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auth_events.update(resolved_state)
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for key, events in conflicted_state.items():
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if key not in resolved_state:
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resolved_state[key] = self._resolve_normal_events(
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events, auth_events
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)
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return resolved_state
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def _resolve_auth_events(self, events, auth_events):
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reverse = [i for i in reversed(self._ordered_events(events))]
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auth_events = dict(auth_events)
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prev_event = reverse[0]
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for event in reverse[1:]:
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auth_events[(prev_event.type, prev_event.state_key)] = prev_event
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try:
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# FIXME: hs.get_auth() is bad style, but we need to do it to
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# get around circular deps.
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self.hs.get_auth().check(event, auth_events)
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prev_event = event
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except AuthError:
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return prev_event
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return event
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def _resolve_normal_events(self, events, auth_events):
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for event in self._ordered_events(events):
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try:
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# FIXME: hs.get_auth() is bad style, but we need to do it to
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# get around circular deps.
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self.hs.get_auth().check(event, auth_events)
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return event
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except AuthError:
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pass
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# Use the last event (the one with the least depth) if they all fail
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# the auth check.
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return event
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def _ordered_events(self, events):
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def key_func(e):
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return -int(e.depth), hashlib.sha1(e.event_id).hexdigest()
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return sorted(events, key=key_func)
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