synapse-product/synapse/state.py

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# -*- coding: utf-8 -*-
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# Copyright 2014, 2015 OpenMarket Ltd
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#
# 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.
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from twisted.internet import defer
from synapse.util.logutils import log_function
from synapse.util.async import run_on_reactor
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from synapse.api.constants import EventTypes
from synapse.api.errors import AuthError
from synapse.events.snapshot import EventContext
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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):
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""" Responsible for doing state conflict resolution.
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"""
def __init__(self, hs):
self.store = hs.get_datastore()
# self.auth = hs.get_auth()
self.hs = hs
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@defer.inlineCallbacks
def get_current_state(self, room_id, event_type=None, state_key=""):
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""" Returns the current state for the room as a list. 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`.
"""
events = yield self.store.get_latest_events_in_room(room_id)
event_ids = [
e_id
for e_id, _, _ in events
]
res = yield self.resolve_state_groups(event_ids)
if event_type:
defer.returnValue(res[1].get((event_type, state_key)))
return
defer.returnValue(res[1].values())
@defer.inlineCallbacks
def compute_event_context(self, event, old_state=None):
""" 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()
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yield run_on_reactor()
if old_state:
context.current_state = {
(s.type, s.state_key): s for s in old_state
}
context.state_group = None
if hasattr(event, "auth_events") and event.auth_events:
auth_ids = zip(*event.auth_events)[0]
context.auth_events = {
k: v
for k, v in context.current_state.items()
if v.event_id in auth_ids
}
else:
context.auth_events = {}
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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
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context.prev_state_events = []
defer.returnValue(context)
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if event.is_state():
ret = yield self.resolve_state_groups(
[e for e, _ in event.prev_events],
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event_type=event.type,
state_key=event.state_key,
)
else:
ret = yield self.resolve_state_groups(
[e for e, _ in event.prev_events],
)
group, curr_state, prev_state = ret
context.current_state = curr_state
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context.state_group = group if not event.is_state() else None
prev_state = yield self.store.add_event_hashes(
prev_state
)
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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
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if hasattr(event, "auth_events") and event.auth_events:
auth_ids = zip(*event.auth_events)[0]
context.auth_events = {
k: v
for k, v in context.current_state.items()
if v.event_id in auth_ids
}
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else:
context.auth_events = {}
context.prev_state_events = prev_state
defer.returnValue(context)
@defer.inlineCallbacks
@log_function
def resolve_state_groups(self, event_ids, event_type=None, state_key=""):
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""" Given a list of event_ids this method fetches the state at each
event, resolves conflicts between them and returns them.
Return format is a tuple: (`state_group`, `state_events`), where the
first is the name of a state group if one and only one is involved,
otherwise `None`.
"""
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state_groups = yield self.store.get_state_groups(
event_ids
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)
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
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prev_states = [prev_state]
else:
prev_states = []
defer.returnValue((name, state, prev_states))
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state = {}
for group, g_state in state_groups.items():
for s in g_state:
state.setdefault(
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(s.type, s.state_key),
{}
)[s.event_id] = s
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unconflicted_state = {
k: v.values()[0] for k, v in state.items()
if len(v.values()) == 1
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}
conflicted_state = {
k: v.values()
for k, v in state.items()
if len(v.values()) > 1
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}
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 (EventTypes.Create, EventTypes.Member, EventTypes.PowerLevels,)
}
try:
resolved_state = self._resolve_state_events(
conflicted_state, auth_events
)
except:
logger.exception("Failed to resolve state")
raise
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new_state = unconflicted_state
new_state.update(resolved_state)
defer.returnValue((None, new_state, prev_states))
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@log_function
def _resolve_state_events(self, conflicted_state, auth_events):
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""" This is where we actually decide which of the conflicted state to
use.
We resolve conflicts in the following order:
1. power levels
2. memberships
3. other events.
:param conflicted_state:
:param auth_events:
:return:
"""
resolved_state = {}
power_key = (EventTypes.PowerLevels, "")
if power_key in conflicted_state.items():
power_levels = conflicted_state[power_key]
resolved_state[power_key] = self._resolve_auth_events(power_levels)
auth_events.update(resolved_state)
for key, events in conflicted_state.items():
if key[0] == EventTypes.Member:
resolved_state[key] = self._resolve_auth_events(
events,
auth_events
)
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auth_events.update(resolved_state)
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for key, events in conflicted_state.items():
if key not in resolved_state:
resolved_state[key] = self._resolve_normal_events(
events, auth_events
)
return resolved_state
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def _resolve_auth_events(self, events, auth_events):
reverse = [i for i in reversed(self._ordered_events(events))]
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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
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except AuthError:
pass
# Oh dear.
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)