# -*- coding: utf-8 -*-
# Copyright 2014-2016 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.caches.expiringcache import ExpiringCache
from synapse.api.constants import EventTypes
from synapse.api.errors import AuthError
from synapse.api.auth import AuthEventTypes
from synapse.events.snapshot import EventContext
from collections import namedtuple
import logging
import hashlib
logger = logging.getLogger(__name__)
KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))
SIZE_OF_CACHE = 1000
EVICTION_TIMEOUT_SECONDS = 20
class _StateCacheEntry(object):
def __init__(self, state, state_group, ts):
self.state = state
self.state_group = state_group
class StateHandler(object):
""" Responsible for doing state conflict resolution.
"""
def __init__(self, hs):
self.clock = hs.get_clock()
self.store = hs.get_datastore()
self.hs = hs
# dict of set of event_ids -> _StateCacheEntry.
self._state_cache = None
def start_caching(self):
logger.debug("start_caching")
self._state_cache = ExpiringCache(
cache_name="state_cache",
clock=self.clock,
max_len=SIZE_OF_CACHE,
expiry_ms=EVICTION_TIMEOUT_SECONDS * 1000,
reset_expiry_on_get=True,
)
self._state_cache.start()
@defer.inlineCallbacks
def get_current_state(self, room_id, event_type=None, state_key=""):
""" Retrieves the current state for the room. 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`.
:returns map from (type, state_key) to event
"""
event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
cache = None
if self._state_cache is not None:
cache = self._state_cache.get(frozenset(event_ids), None)
if cache:
cache.ts = self.clock.time_msec()
state = cache.state
else:
res = yield self.resolve_state_groups(room_id, event_ids)
state = res[1]
if event_type:
defer.returnValue(state.get((event_type, state_key)))
return
defer.returnValue(state)
@defer.inlineCallbacks
def compute_event_context(self, event, old_state=None, outlier=False):
""" 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()
if outlier:
# If this is an outlier, then we know it shouldn't have any current
# state. Certainly store.get_current_state won't return any, and
# persisting the event won't store the state group.
if old_state:
context.current_state = {
(s.type, s.state_key): s for s in old_state
}
else:
context.current_state = {}
context.prev_state_events = []
context.state_group = None
defer.returnValue(context)
if old_state:
context.current_state = {
(s.type, s.state_key): s for s in old_state
}
context.state_group = None
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(
event.room_id, [e for e, _ in event.prev_events],
event_type=event.type,
state_key=event.state_key,
)
else:
ret = yield self.resolve_state_groups(
event.room_id, [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
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
context.prev_state_events = prev_state
defer.returnValue(context)
@defer.inlineCallbacks
@log_function
def resolve_state_groups(self, room_id, 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.
:returns a Deferred tuple of (`state_group`, `state`, `prev_state`).
`state_group` is the name of a state group if one and only one is
involved. `state` is a map from (type, state_key) to event, and
`prev_state` is a list of event ids.
"""
logger.debug("resolve_state_groups event_ids %s", event_ids)
if self._state_cache is not None:
cache = self._state_cache.get(frozenset(event_ids), None)
if cache and cache.state_group:
cache.ts = self.clock.time_msec()
prev_state = cache.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(
(cache.state_group, cache.state, prev_states)
)
state_groups = yield self.store.get_state_groups(
room_id, event_ids
)
logger.debug(
"resolve_state_groups state_groups %s",
state_groups.keys()
)
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 = []
if self._state_cache is not None:
cache = _StateCacheEntry(
state=state,
state_group=name,
ts=self.clock.time_msec()
)
self._state_cache[frozenset(event_ids)] = cache
defer.returnValue((name, state, prev_states))
new_state, prev_states = self._resolve_events(
state_groups.values(), event_type, state_key
)
if self._state_cache is not None:
cache = _StateCacheEntry(
state=new_state,
state_group=None,
ts=self.clock.time_msec()
)
self._state_cache[frozenset(event_ids)] = cache
defer.returnValue((None, new_state, prev_states))
def resolve_events(self, state_sets, event):
if event.is_state():
return self._resolve_events(
state_sets, event.type, event.state_key
)
else:
return self._resolve_events(state_sets)
def _resolve_events(self, state_sets, event_type=None, state_key=""):
"""
:returns a tuple (new_state, prev_states). new_state is a map
from (type, state_key) to event. prev_states is a list of event_ids.
:rtype: (dict[(str, str), synapse.events.FrozenEvent], list[str])
"""
state = {}
for st in state_sets:
for e in st:
state.setdefault(
(e.type, e.state_key),
{}
)[e.event_id] = e
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 AuthEventTypes
}
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)
return 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. join rules
3. memberships
4. other events.
"""
resolved_state = {}
power_key = (EventTypes.PowerLevels, "")
if power_key in conflicted_state:
events = conflicted_state[power_key]
logger.debug("Resolving conflicted power levels %r", events)
resolved_state[power_key] = self._resolve_auth_events(
events, auth_events)
auth_events.update(resolved_state)
for key, events in conflicted_state.items():
if key[0] == EventTypes.JoinRules:
logger.debug("Resolving conflicted join rules %r", events)
resolved_state[key] = self._resolve_auth_events(
events,
auth_events
)
auth_events.update(resolved_state)
for key, events in conflicted_state.items():
if key[0] == EventTypes.Member:
logger.debug("Resolving conflicted member lists %r", events)
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:
logger.debug("Resolving conflicted state %r:%r", key, events)
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:
pass
# Use the last event (the one with the least depth) if they all fail
# the auth check.
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)