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Diffstat (limited to 'synapse/state.py')
| -rw-r--r-- | synapse/state.py | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/synapse/state.py b/synapse/state.py new file mode 100644 index 0000000000..439c0b519a --- /dev/null +++ b/synapse/state.py @@ -0,0 +1,223 @@ +# -*- coding: utf-8 -*- +# Copyright 2014 matrix.org +# +# 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 +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): + """ 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) + + results = yield self.store.get_latest_pdus_in_context( + event.room_id + ) + + event.prev_events = [ + encode_event_id(p_id, origin) for p_id, origin, _ in results + ] + event.prev_events = [ + e for e in event.prev_events if e != event.event_id + ] + + if results: + event.depth = max([int(v) for _, _, v in results]) + 1 + else: + event.depth = 0 + + current_state = yield self.store.get_current_state( + key.context, key.type, key.state_key + ) + + 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) + + yield self.store.update_current_state( + pdu_id=event.event_id, + origin=self.server_name, + 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) + + 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 = 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 not current_branch: + # There is no current state + defer.returnValue(True) + return + + if new_branch[-1] == current_branch[-1]: + # We have all the PDUs we need, so we can just do the conflict + # resolution. + + if len(current_branch) == 1: + # This is a direct clobber so we can just... + defer.returnValue(True) + + 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 = algo(new_branch, current_branch) + + if new_res < curr_res: + defer.returnValue(False) + elif new_res > curr_res: + defer.returnValue(True) + + raise Exception("Conflict resolution failed.") + + else: + # We need to ask for PDUs. + missing_prev = max( + new_branch[-1], current_branch[-1], + key=lambda x: x.depth + ) + + yield self._replication.get_pdu( + destination=missing_prev.origin, + pdu_origin=missing_prev.prev_state_origin, + pdu_id=missing_prev.prev_state_id, + outlier=True + ) + + updated_current = yield self._handle_new_state(new_pdu) + defer.returnValue(updated_current) + + def _do_power_level_conflict_res(self, new_branch, current_branch): + max_power_new = max( + new_branch[:-1], + key=lambda t: t.power_level + ).power_level + + max_power_current = max( + current_branch[:-1], + key=lambda t: t.power_level + ).power_level + + return (max_power_new, max_power_current) + + def _do_chain_length_conflict_res(self, new_branch, current_branch): + return (len(new_branch), len(current_branch)) + + def _do_hash_conflict_res(self, new_branch, current_branch): + 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() + ) |