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# -*- 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()
)
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