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