summary refs log tree commit diff
path: root/synapse/state/__init__.py
blob: 4b136b3054c49962748a0165b29904e31d157aee (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 New Vector 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.

import logging
from collections import namedtuple

from six import iteritems, itervalues

import attr
from frozendict import frozendict
from prometheus_client import Histogram

from twisted.internet import defer

from synapse.api.constants import EventTypes
from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, StateResolutionVersions
from synapse.events.snapshot import EventContext
from synapse.state import v1, v2
from synapse.util.async_helpers import Linearizer
from synapse.util.caches import get_cache_factor_for
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.util.logutils import log_function
from synapse.util.metrics import Measure

logger = logging.getLogger(__name__)


# Metrics for number of state groups involved in a resolution.
state_groups_histogram = Histogram(
    "synapse_state_number_state_groups_in_resolution",
    "Number of state groups used when performing a state resolution",
    buckets=(1, 2, 3, 5, 7, 10, 15, 20, 50, 100, 200, 500, "+Inf"),
)


KeyStateTuple = namedtuple("KeyStateTuple", ("context", "type", "state_key"))


SIZE_OF_CACHE = 100000 * get_cache_factor_for("state_cache")
EVICTION_TIMEOUT_SECONDS = 60 * 60


_NEXT_STATE_ID = 1

POWER_KEY = (EventTypes.PowerLevels, "")


def _gen_state_id():
    global _NEXT_STATE_ID
    s = "X%d" % (_NEXT_STATE_ID,)
    _NEXT_STATE_ID += 1
    return s


class _StateCacheEntry(object):
    __slots__ = ["state", "state_group", "state_id", "prev_group", "delta_ids"]

    def __init__(self, state, state_group, prev_group=None, delta_ids=None):
        # dict[(str, str), str] map  from (type, state_key) to event_id
        self.state = frozendict(state)

        # the ID of a state group if one and only one is involved.
        # otherwise, None otherwise?
        self.state_group = state_group

        self.prev_group = prev_group
        self.delta_ids = frozendict(delta_ids) if delta_ids is not None else None

        # The `state_id` is a unique ID we generate that can be used as ID for
        # this collection of state. Usually this would be the same as the
        # state group, but on worker instances we can't generate a new state
        # group each time we resolve state, so we generate a separate one that
        # isn't persisted and is used solely for caches.
        # `state_id` is either a state_group (and so an int) or a string. This
        # ensures we don't accidentally persist a state_id as a stateg_group
        if state_group:
            self.state_id = state_group
        else:
            self.state_id = _gen_state_id()

    def __len__(self):
        return len(self.state)


class StateHandler(object):
    """Fetches bits of state from the stores, and does state resolution
    where necessary
    """

    def __init__(self, hs):
        self.clock = hs.get_clock()
        self.store = hs.get_datastore()
        self.hs = hs
        self._state_resolution_handler = hs.get_state_resolution_handler()

    @defer.inlineCallbacks
    def get_current_state(self, room_id, event_type=None, state_key="",
                          latest_event_ids=None):
        """ 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
        """
        if not latest_event_ids:
            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)

        logger.debug("calling resolve_state_groups from get_current_state")
        ret = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
        state = ret.state

        if event_type:
            event_id = state.get((event_type, state_key))
            event = None
            if event_id:
                event = yield self.store.get_event(event_id, allow_none=True)
            defer.returnValue(event)
            return

        state_map = yield self.store.get_events(list(state.values()),
                                                get_prev_content=False)
        state = {
            key: state_map[e_id] for key, e_id in iteritems(state) if e_id in state_map
        }

        defer.returnValue(state)

    @defer.inlineCallbacks
    def get_current_state_ids(self, room_id, latest_event_ids=None):
        """Get the current state, or the state at a set of events, for a room

        Args:
            room_id (str):

            latest_event_ids (iterable[str]|None): if given, the forward
                extremities to resolve. If None, we look them up from the
                database (via a cache)

        Returns:
            Deferred[dict[(str, str), str)]]: the state dict, mapping from
                (event_type, state_key) -> event_id
        """
        if not latest_event_ids:
            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)

        logger.debug("calling resolve_state_groups from get_current_state_ids")
        ret = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
        state = ret.state

        defer.returnValue(state)

    @defer.inlineCallbacks
    def get_current_users_in_room(self, room_id, latest_event_ids=None):
        """
        Get the users who are currently in a room.

        Args:
            room_id (str): The ID of the room.
            latest_event_ids (List[str]|None): Precomputed list of latest
                event IDs. Will be computed if None.
        Returns:
            Deferred[Dict[str,ProfileInfo]]: Dictionary of user IDs to their
                profileinfo.
        """
        if not latest_event_ids:
            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
        logger.debug("calling resolve_state_groups from get_current_users_in_room")
        entry = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
        joined_users = yield self.store.get_joined_users_from_state(room_id, entry)
        defer.returnValue(joined_users)

    @defer.inlineCallbacks
    def get_current_hosts_in_room(self, room_id, latest_event_ids=None):
        if not latest_event_ids:
            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
        logger.debug("calling resolve_state_groups from get_current_hosts_in_room")
        entry = yield self.resolve_state_groups_for_events(room_id, latest_event_ids)
        joined_hosts = yield self.store.get_joined_hosts(room_id, entry)
        defer.returnValue(joined_hosts)

    @defer.inlineCallbacks
    def compute_event_context(self, event, old_state=None):
        """Build an EventContext structure for the event.

        This works out what the current state should be for the event, and
        generates a new state group if necessary.

        Args:
            event (synapse.events.EventBase):
            old_state (dict|None): The state at the event if it can't be
                calculated from existing events. This is normally only specified
                when receiving an event from federation where we don't have the
                prev events for, e.g. when backfilling.
        Returns:
            synapse.events.snapshot.EventContext:
        """

        if event.internal_metadata.is_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:
                prev_state_ids = {
                    (s.type, s.state_key): s.event_id for s in old_state
                }
                if event.is_state():
                    current_state_ids = dict(prev_state_ids)
                    key = (event.type, event.state_key)
                    current_state_ids[key] = event.event_id
                else:
                    current_state_ids = prev_state_ids
            else:
                current_state_ids = {}
                prev_state_ids = {}

            # We don't store state for outliers, so we don't generate a state
            # group for it.
            context = EventContext.with_state(
                state_group=None,
                current_state_ids=current_state_ids,
                prev_state_ids=prev_state_ids,
            )

            defer.returnValue(context)

        if old_state:
            # We already have the state, so we don't need to calculate it.
            # Let's just correctly fill out the context and create a
            # new state group for it.

            prev_state_ids = {
                (s.type, s.state_key): s.event_id for s in old_state
            }

            if event.is_state():
                key = (event.type, event.state_key)
                if key in prev_state_ids:
                    replaces = prev_state_ids[key]
                    if replaces != event.event_id:  # Paranoia check
                        event.unsigned["replaces_state"] = replaces
                current_state_ids = dict(prev_state_ids)
                current_state_ids[key] = event.event_id
            else:
                current_state_ids = prev_state_ids

            state_group = yield self.store.store_state_group(
                event.event_id,
                event.room_id,
                prev_group=None,
                delta_ids=None,
                current_state_ids=current_state_ids,
            )

            context = EventContext.with_state(
                state_group=state_group,
                current_state_ids=current_state_ids,
                prev_state_ids=prev_state_ids,
            )

            defer.returnValue(context)

        logger.debug("calling resolve_state_groups from compute_event_context")

        entry = yield self.resolve_state_groups_for_events(
            event.room_id, event.prev_event_ids(),
        )

        prev_state_ids = entry.state
        prev_group = None
        delta_ids = None

        if event.is_state():
            # If this is a state event then we need to create a new state
            # group for the state after this event.

            key = (event.type, event.state_key)
            if key in prev_state_ids:
                replaces = prev_state_ids[key]
                event.unsigned["replaces_state"] = replaces

            current_state_ids = dict(prev_state_ids)
            current_state_ids[key] = event.event_id

            if entry.state_group:
                # If the state at the event has a state group assigned then
                # we can use that as the prev group
                prev_group = entry.state_group
                delta_ids = {
                    key: event.event_id
                }
            elif entry.prev_group:
                # If the state at the event only has a prev group, then we can
                # use that as a prev group too.
                prev_group = entry.prev_group
                delta_ids = dict(entry.delta_ids)
                delta_ids[key] = event.event_id

            state_group = yield self.store.store_state_group(
                event.event_id,
                event.room_id,
                prev_group=prev_group,
                delta_ids=delta_ids,
                current_state_ids=current_state_ids,
            )
        else:
            current_state_ids = prev_state_ids
            prev_group = entry.prev_group
            delta_ids = entry.delta_ids

            if entry.state_group is None:
                entry.state_group = yield self.store.store_state_group(
                    event.event_id,
                    event.room_id,
                    prev_group=entry.prev_group,
                    delta_ids=entry.delta_ids,
                    current_state_ids=current_state_ids,
                )
                entry.state_id = entry.state_group

            state_group = entry.state_group

        context = EventContext.with_state(
            state_group=state_group,
            current_state_ids=current_state_ids,
            prev_state_ids=prev_state_ids,
            prev_group=prev_group,
            delta_ids=delta_ids,
        )

        defer.returnValue(context)

    @defer.inlineCallbacks
    def resolve_state_groups_for_events(self, room_id, event_ids):
        """ Given a list of event_ids this method fetches the state at each
        event, resolves conflicts between them and returns them.

        Args:
            room_id (str)
            event_ids (list[str])
            explicit_room_version (str|None): If set uses the the given room
                version to choose the resolution algorithm. If None, then
                checks the database for room version.

        Returns:
            Deferred[_StateCacheEntry]: resolved state
        """
        logger.debug("resolve_state_groups event_ids %s", event_ids)

        # map from state group id to the state in that state group (where
        # 'state' is a map from state key to event id)
        # dict[int, dict[(str, str), str]]
        state_groups_ids = yield self.store.get_state_groups_ids(
            room_id, event_ids
        )

        if len(state_groups_ids) == 0:
            defer.returnValue(_StateCacheEntry(
                state={},
                state_group=None,
            ))
        elif len(state_groups_ids) == 1:
            name, state_list = list(state_groups_ids.items()).pop()

            prev_group, delta_ids = yield self.store.get_state_group_delta(name)

            defer.returnValue(_StateCacheEntry(
                state=state_list,
                state_group=name,
                prev_group=prev_group,
                delta_ids=delta_ids,
            ))

        room_version = yield self.store.get_room_version(room_id)

        result = yield self._state_resolution_handler.resolve_state_groups(
            room_id, room_version, state_groups_ids, None,
            state_res_store=StateResolutionStore(self.store),
        )
        defer.returnValue(result)

    @defer.inlineCallbacks
    def resolve_events(self, room_version, state_sets, event):
        logger.info(
            "Resolving state for %s with %d groups", event.room_id, len(state_sets)
        )
        state_set_ids = [{
            (ev.type, ev.state_key): ev.event_id
            for ev in st
        } for st in state_sets]

        state_map = {
            ev.event_id: ev
            for st in state_sets
            for ev in st
        }

        with Measure(self.clock, "state._resolve_events"):
            new_state = yield resolve_events_with_store(
                room_version, state_set_ids,
                event_map=state_map,
                state_res_store=StateResolutionStore(self.store),
            )

        new_state = {
            key: state_map[ev_id] for key, ev_id in iteritems(new_state)
        }

        defer.returnValue(new_state)


class StateResolutionHandler(object):
    """Responsible for doing state conflict resolution.

    Note that the storage layer depends on this handler, so all functions must
    be storage-independent.
    """
    def __init__(self, hs):
        self.clock = hs.get_clock()

        # dict of set of event_ids -> _StateCacheEntry.
        self._state_cache = None
        self.resolve_linearizer = Linearizer(name="state_resolve_lock")

        self._state_cache = ExpiringCache(
            cache_name="state_cache",
            clock=self.clock,
            max_len=SIZE_OF_CACHE,
            expiry_ms=EVICTION_TIMEOUT_SECONDS * 1000,
            iterable=True,
            reset_expiry_on_get=True,
        )

    @defer.inlineCallbacks
    @log_function
    def resolve_state_groups(
        self, room_id, room_version, state_groups_ids, event_map, state_res_store,
    ):
        """Resolves conflicts between a set of state groups

        Always generates a new state group (unless we hit the cache), so should
        not be called for a single state group

        Args:
            room_id (str): room we are resolving for (used for logging)
            room_version (str): version of the room
            state_groups_ids (dict[int, dict[(str, str), str]]):
                 map from state group id to the state in that state group
                (where 'state' is a map from state key to event id)

            event_map(dict[str,FrozenEvent]|None):
                a dict from event_id to event, for any events that we happen to
                have in flight (eg, those currently being persisted). This will be
                used as a starting point fof finding the state we need; any missing
                events will be requested via state_res_store.

                If None, all events will be fetched via state_res_store.

            state_res_store (StateResolutionStore)

        Returns:
            Deferred[_StateCacheEntry]: resolved state
        """
        logger.debug(
            "resolve_state_groups state_groups %s",
            state_groups_ids.keys()
        )

        group_names = frozenset(state_groups_ids.keys())

        with (yield self.resolve_linearizer.queue(group_names)):
            if self._state_cache is not None:
                cache = self._state_cache.get(group_names, None)
                if cache:
                    defer.returnValue(cache)

            logger.info(
                "Resolving state for %s with %d groups", room_id, len(state_groups_ids)
            )

            state_groups_histogram.observe(len(state_groups_ids))

            # start by assuming we won't have any conflicted state, and build up the new
            # state map by iterating through the state groups. If we discover a conflict,
            # we give up and instead use `resolve_events_with_store`.
            #
            # XXX: is this actually worthwhile, or should we just let
            # resolve_events_with_store do it?
            new_state = {}
            conflicted_state = False
            for st in itervalues(state_groups_ids):
                for key, e_id in iteritems(st):
                    if key in new_state:
                        conflicted_state = True
                        break
                    new_state[key] = e_id
                if conflicted_state:
                    break

            if conflicted_state:
                logger.info("Resolving conflicted state for %r", room_id)
                with Measure(self.clock, "state._resolve_events"):
                    new_state = yield resolve_events_with_store(
                        room_version,
                        list(itervalues(state_groups_ids)),
                        event_map=event_map,
                        state_res_store=state_res_store,
                    )

            # if the new state matches any of the input state groups, we can
            # use that state group again. Otherwise we will generate a state_id
            # which will be used as a cache key for future resolutions, but
            # not get persisted.

            with Measure(self.clock, "state.create_group_ids"):
                cache = _make_state_cache_entry(new_state, state_groups_ids)

            if self._state_cache is not None:
                self._state_cache[group_names] = cache

            defer.returnValue(cache)


def _make_state_cache_entry(
    new_state,
    state_groups_ids,
):
    """Given a resolved state, and a set of input state groups, pick one to base
    a new state group on (if any), and return an appropriately-constructed
    _StateCacheEntry.

    Args:
        new_state (dict[(str, str), str]): resolved state map (mapping from
           (type, state_key) to event_id)

        state_groups_ids (dict[int, dict[(str, str), str]]):
                 map from state group id to the state in that state group
                (where 'state' is a map from state key to event id)

    Returns:
        _StateCacheEntry
    """
    # if the new state matches any of the input state groups, we can
    # use that state group again. Otherwise we will generate a state_id
    # which will be used as a cache key for future resolutions, but
    # not get persisted.

    # first look for exact matches
    new_state_event_ids = set(itervalues(new_state))
    for sg, state in iteritems(state_groups_ids):
        if len(new_state_event_ids) != len(state):
            continue

        old_state_event_ids = set(itervalues(state))
        if new_state_event_ids == old_state_event_ids:
            # got an exact match.
            return _StateCacheEntry(
                state=new_state,
                state_group=sg,
            )

    # TODO: We want to create a state group for this set of events, to
    # increase cache hits, but we need to make sure that it doesn't
    # end up as a prev_group without being added to the database

    # failing that, look for the closest match.
    prev_group = None
    delta_ids = None

    for old_group, old_state in iteritems(state_groups_ids):
        n_delta_ids = {
            k: v
            for k, v in iteritems(new_state)
            if old_state.get(k) != v
        }
        if not delta_ids or len(n_delta_ids) < len(delta_ids):
            prev_group = old_group
            delta_ids = n_delta_ids

    return _StateCacheEntry(
        state=new_state,
        state_group=None,
        prev_group=prev_group,
        delta_ids=delta_ids,
    )


def resolve_events_with_store(room_version, state_sets, event_map, state_res_store):
    """
    Args:
        room_version(str): Version of the room

        state_sets(list): List of dicts of (type, state_key) -> event_id,
            which are the different state groups to resolve.

        event_map(dict[str,FrozenEvent]|None):
            a dict from event_id to event, for any events that we happen to
            have in flight (eg, those currently being persisted). This will be
            used as a starting point fof finding the state we need; any missing
            events will be requested via state_map_factory.

            If None, all events will be fetched via state_map_factory.

        state_res_store (StateResolutionStore)

    Returns
        Deferred[dict[(str, str), str]]:
            a map from (type, state_key) to event_id.
    """
    v = KNOWN_ROOM_VERSIONS[room_version]
    if v.state_res == StateResolutionVersions.V1:
        return v1.resolve_events_with_store(
            state_sets, event_map, state_res_store.get_events,
        )
    else:
        return v2.resolve_events_with_store(
            room_version, state_sets, event_map, state_res_store,
        )


@attr.s
class StateResolutionStore(object):
    """Interface that allows state resolution algorithms to access the database
    in well defined way.

    Args:
        store (DataStore)
    """

    store = attr.ib()

    def get_events(self, event_ids, allow_rejected=False):
        """Get events from the database

        Args:
            event_ids (list): The event_ids of the events to fetch
            allow_rejected (bool): If True return rejected events.

        Returns:
            Deferred[dict[str, FrozenEvent]]: Dict from event_id to event.
        """

        return self.store.get_events(
            event_ids,
            check_redacted=False,
            get_prev_content=False,
            allow_rejected=allow_rejected,
        )

    def get_auth_chain(self, event_ids):
        """Gets the full auth chain for a set of events (including rejected
        events).

        Includes the given event IDs in the result.

        Note that:
            1. All events must be state events.
            2. For v1 rooms this may not have the full auth chain in the
               presence of rejected events

        Args:
            event_ids (list): The event IDs of the events to fetch the auth
                chain for. Must be state events.

        Returns:
            Deferred[list[str]]: List of event IDs of the auth chain.
        """

        return self.store.get_auth_chain_ids(event_ids, include_given=True)