# -*- coding: utf-8 -*- # Copyright 2014, 2015 OpenMarket 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. from twisted.internet import defer from synapse.util.logutils import log_function from synapse.util.async import run_on_reactor from synapse.api.constants import EventTypes from synapse.api.errors import AuthError from synapse.events.snapshot import EventContext from collections import namedtuple import logging import hashlib logger = logging.getLogger(__name__) def _get_state_key_from_event(event): return event.state_key KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key")) class StateHandler(object): """ Responsible for doing state conflict resolution. """ def __init__(self, hs): self.store = hs.get_datastore() # self.auth = hs.get_auth() self.hs = hs @defer.inlineCallbacks def get_current_state(self, room_id, event_type=None, state_key=""): """ Returns the current state for the room as a list. This is done by calling `get_latest_events_in_room` to get the leading edges of the event graph and then resolving any of the state conflicts. This is equivalent to getting the state of an event that were to send next before receiving any new events. If `event_type` is specified, then the method returns only the one event (or None) with that `event_type` and `state_key`. """ events = yield self.store.get_latest_events_in_room(room_id) event_ids = [ e_id for e_id, _, _ in events ] res = yield self.resolve_state_groups(event_ids) if event_type: defer.returnValue(res[1].get((event_type, state_key))) return defer.returnValue(res[1].values()) @defer.inlineCallbacks def compute_event_context(self, event, old_state=None): """ Fills out the context with the `current state` of the graph. The `current state` here is defined to be the state of the event graph just before the event - i.e. it never includes `event` If `event` has `auth_events` then this will also fill out the `auth_events` field on `context` from the `current_state`. Args: event (EventBase) Returns: an EventContext """ context = EventContext() yield run_on_reactor() if old_state: context.current_state = { (s.type, s.state_key): s for s in old_state } context.state_group = None if hasattr(event, "auth_events") and event.auth_events: auth_ids = zip(*event.auth_events)[0] context.auth_events = { k: v for k, v in context.current_state.items() if v.event_id in auth_ids } else: context.auth_events = {} if event.is_state(): key = (event.type, event.state_key) if key in context.current_state: replaces = context.current_state[key] if replaces.event_id != event.event_id: # Paranoia check event.unsigned["replaces_state"] = replaces.event_id context.prev_state_events = [] defer.returnValue(context) if event.is_state(): ret = yield self.resolve_state_groups( [e for e, _ in event.prev_events], event_type=event.type, state_key=event.state_key, ) else: ret = yield self.resolve_state_groups( [e for e, _ in event.prev_events], ) group, curr_state, prev_state = ret context.current_state = curr_state context.state_group = group if not event.is_state() else None prev_state = yield self.store.add_event_hashes( prev_state ) if event.is_state(): key = (event.type, event.state_key) if key in context.current_state: replaces = context.current_state[key] event.unsigned["replaces_state"] = replaces.event_id if hasattr(event, "auth_events") and event.auth_events: auth_ids = zip(*event.auth_events)[0] context.auth_events = { k: v for k, v in context.current_state.items() if v.event_id in auth_ids } else: context.auth_events = {} context.prev_state_events = prev_state defer.returnValue(context) @defer.inlineCallbacks @log_function def resolve_state_groups(self, event_ids, event_type=None, state_key=""): """ Given a list of event_ids this method fetches the state at each event, resolves conflicts between them and returns them. Return format is a tuple: (`state_group`, `state_events`), where the first is the name of a state group if one and only one is involved, otherwise `None`. """ state_groups = yield self.store.get_state_groups( event_ids ) group_names = set(state_groups.keys()) if len(group_names) == 1: name, state_list = state_groups.items().pop() state = { (e.type, e.state_key): e for e in state_list } prev_state = state.get((event_type, state_key), None) if prev_state: prev_state = prev_state.event_id prev_states = [prev_state] else: prev_states = [] defer.returnValue((name, state, prev_states)) state = {} for group, g_state in state_groups.items(): for s in g_state: state.setdefault( (s.type, s.state_key), {} )[s.event_id] = s unconflicted_state = { k: v.values()[0] for k, v in state.items() if len(v.values()) == 1 } conflicted_state = { k: v.values() for k, v in state.items() if len(v.values()) > 1 } if event_type: prev_states_events = conflicted_state.get( (event_type, state_key), [] ) prev_states = [s.event_id for s in prev_states_events] else: prev_states = [] auth_events = { k: e for k, e in unconflicted_state.items() if k[0] in (EventTypes.Create, EventTypes.Member, EventTypes.PowerLevels,) } try: resolved_state = self._resolve_state_events( conflicted_state, auth_events ) except: logger.exception("Failed to resolve state") raise new_state = unconflicted_state new_state.update(resolved_state) defer.returnValue((None, new_state, prev_states)) @log_function def _resolve_state_events(self, conflicted_state, auth_events): """ This is where we actually decide which of the conflicted state to use. We resolve conflicts in the following order: 1. power levels 2. memberships 3. other events. :param conflicted_state: :param auth_events: :return: """ resolved_state = {} power_key = (EventTypes.PowerLevels, "") if power_key in conflicted_state.items(): power_levels = conflicted_state[power_key] resolved_state[power_key] = self._resolve_auth_events(power_levels) auth_events.update(resolved_state) for key, events in conflicted_state.items(): if key[0] == EventTypes.Member: resolved_state[key] = self._resolve_auth_events( events, auth_events ) auth_events.update(resolved_state) for key, events in conflicted_state.items(): if key not in resolved_state: resolved_state[key] = self._resolve_normal_events( events, auth_events ) return resolved_state def _resolve_auth_events(self, events, auth_events): reverse = [i for i in reversed(self._ordered_events(events))] auth_events = dict(auth_events) prev_event = reverse[0] for event in reverse[1:]: auth_events[(prev_event.type, prev_event.state_key)] = prev_event try: # FIXME: hs.get_auth() is bad style, but we need to do it to # get around circular deps. self.hs.get_auth().check(event, auth_events) prev_event = event except AuthError: return prev_event return event def _resolve_normal_events(self, events, auth_events): for event in self._ordered_events(events): try: # FIXME: hs.get_auth() is bad style, but we need to do it to # get around circular deps. self.hs.get_auth().check(event, auth_events) return event except AuthError as e: pass # Oh dear. return event def _ordered_events(self, events): def key_func(e): return -int(e.depth), hashlib.sha1(e.event_id).hexdigest() return sorted(events, key=key_func)