# -*- coding: utf-8 -*- # Copyright 2014 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.federation.pdu_codec import encode_event_id, decode_event_id from synapse.util.logutils import log_function 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): """ Repsonsible for doing state conflict resolution. """ def __init__(self, hs): self.store = hs.get_datastore() self._replication = hs.get_replication_layer() self.server_name = hs.hostname @defer.inlineCallbacks @log_function def handle_new_event(self, event, snapshot): """ Given an event this works out if a) we have sufficient power level to update the state and b) works out what the prev_state should be. Returns: Deferred: Resolved with a boolean indicating if we succesfully updated the state. Raised: AuthError """ # This needs to be done in a transaction. if not hasattr(event, "state_key"): return key = KeyStateTuple( event.room_id, event.type, _get_state_key_from_event(event) ) # Now I need to fill out the prev state and work out if it has auth # (w.r.t. to power levels) snapshot.fill_out_prev_events(event) event.prev_events = [ e for e in event.prev_events if e != event.event_id ] current_state = snapshot.prev_state_pdu if current_state: event.prev_state = encode_event_id( current_state.pdu_id, current_state.origin ) # TODO check current_state to see if the min power level is less # than the power level of the user # power_level = self._get_power_level_for_event(event) pdu_id, origin = decode_event_id(event.event_id, self.server_name) yield self.store.update_current_state( pdu_id=pdu_id, origin=origin, context=key.context, pdu_type=key.type, state_key=key.state_key ) defer.returnValue(True) @defer.inlineCallbacks @log_function def handle_new_state(self, new_pdu): """ Apply conflict resolution to `new_pdu`. This should be called on every new state pdu, regardless of whether or not there is a conflict. This function is safe against the race of it getting called with two `PDU`s trying to update the same state. """ # This needs to be done in a transaction. is_new = yield self._handle_new_state(new_pdu) logger.debug("is_new: %s %s %s", is_new, new_pdu.pdu_id, new_pdu.origin) if is_new: yield self.store.update_current_state( pdu_id=new_pdu.pdu_id, origin=new_pdu.origin, context=new_pdu.context, pdu_type=new_pdu.pdu_type, state_key=new_pdu.state_key ) defer.returnValue(is_new) def _get_power_level_for_event(self, event): # return self._persistence.get_power_level_for_user(event.room_id, # event.sender) return event.power_level @defer.inlineCallbacks @log_function def _handle_new_state(self, new_pdu): tree, missing_branch = yield self.store.get_unresolved_state_tree( new_pdu ) new_branch, current_branch = tree logger.debug( "_handle_new_state new=%s, current=%s", new_branch, current_branch ) if missing_branch is not None: # We're missing some PDUs. Fetch them. # TODO (erikj): Limit this. missing_prev = tree[missing_branch][-1] pdu_id = missing_prev.prev_state_id origin = missing_prev.prev_state_origin is_missing = yield self.store.get_pdu(pdu_id, origin) is None if not is_missing: raise Exception("Conflict resolution failed") yield self._replication.get_pdu( destination=missing_prev.origin, pdu_origin=origin, pdu_id=pdu_id, outlier=True ) updated_current = yield self._handle_new_state(new_pdu) defer.returnValue(updated_current) if not current_branch: # There is no current state defer.returnValue(True) return n = new_branch[-1] c = current_branch[-1] common_ancestor = n.pdu_id == c.pdu_id and n.origin == c.origin if common_ancestor: # We found a common ancestor! if len(current_branch) == 1: # This is a direct clobber so we can just... defer.returnValue(True) else: # We didn't find a common ancestor. This is probably fine. pass result = yield self._do_conflict_res( new_branch, current_branch, common_ancestor ) defer.returnValue(result) @defer.inlineCallbacks def _do_conflict_res(self, new_branch, current_branch, common_ancestor): conflict_res = [ self._do_power_level_conflict_res, self._do_chain_length_conflict_res, self._do_hash_conflict_res, ] for algo in conflict_res: new_res, curr_res = yield defer.maybeDeferred( algo, new_branch, current_branch, common_ancestor ) if new_res < curr_res: defer.returnValue(False) elif new_res > curr_res: defer.returnValue(True) raise Exception("Conflict resolution failed.") @defer.inlineCallbacks def _do_power_level_conflict_res(self, new_branch, current_branch, common_ancestor): new_powers_deferreds = [] for e in new_branch[:-1] if common_ancestor else new_branch: if hasattr(e, "user_id"): new_powers_deferreds.append( self.store.get_power_level(e.context, e.user_id) ) current_powers_deferreds = [] for e in current_branch[:-1] if common_ancestor else current_branch: if hasattr(e, "user_id"): current_powers_deferreds.append( self.store.get_power_level(e.context, e.user_id) ) new_powers = yield defer.gatherResults( new_powers_deferreds, consumeErrors=True ) current_powers = yield defer.gatherResults( current_powers_deferreds, consumeErrors=True ) max_power_new = max(new_powers) max_power_current = max(current_powers) defer.returnValue( (max_power_new, max_power_current) ) def _do_chain_length_conflict_res(self, new_branch, current_branch, common_ancestor): return (len(new_branch), len(current_branch)) def _do_hash_conflict_res(self, new_branch, current_branch, common_ancestor): new_str = "".join([p.pdu_id + p.origin for p in new_branch]) c_str = "".join([p.pdu_id + p.origin for p in current_branch]) return ( hashlib.sha1(new_str).hexdigest(), hashlib.sha1(c_str).hexdigest() )