This PR fixes the issue described as comment here:
https://github.com/element-hq/synapse/issues/18793#issuecomment-3502202379
In Element Call, this shows up as ghost participants: someone who left
the call keeps being displayed until a later state change refreshes the
room.
The bug is not specific to Element Call: any state event can be
affected, RTC membership just changes often enough to make it visible.
## What happens
Alice has a client syncing against a homeserver where events are
persisted by one worker (the event persister) and `/sync` is served by
another (the sync worker). Her client is parked in a long-poll: `GET
/sync?since=s99&timeout=30000`.
Bob joins a call at the same moment Carol sends a message. Carol's
message reaches the persister first; Bob's `m.call.member` arrives while
that write is still in flight, so the per-room persist queue groups them
into one transaction:
```
events (each gets its own stream ordering):
stream_ordering 100: m.room.message Carol
stream_ordering 101: m.call.member Bob (state)
current_state_delta_stream (how state_after finds state changes):
stream_id 100 ────► (m.call.member, @bob) -> $bob_join_call
▲
└─ stamped with the batch MINIMUM (100), not the event's own 101
(see `_update_current_state_txn`)
```
The transaction commits: both events and the delta row are now in the
database, atomically.
The persister then announces the new events over replication, one RDATA
token per stream ordering — rows are only merged into one token when
they share a position, and 100 and 101 don't. So the sync worker's
events-stream position steps 99 → 100 → 101, and on reaching 100 it
pokes the notifier.
Alice's long-poll wakes at exactly that moment. Her response is built at
the worker's *current* position — `end = 100` — with RDATA 101 still in
the queue:
```
Sync A (since=99, end=100):
timeline: events 99 < ordering ≤ 100 → [Carol's message]
state_after: deltas 99 < stream_id ≤ 100 → [$bob_join_call] ← delivered EARLY
next_batch: s100 ← mid-batch token
```
No race on the client's side is needed: the server *hands out* the
mid-batch token as `next_batch`. Alice's client re-polls with it, as
every sync client does. The worker has meanwhile processed RDATA 101:
```
Sync B (since=100, end=101):
timeline: events 100 < ordering ≤ 101 → [Bob's m.call.member @101] ✓
state_after: deltas 100 < stream_id ≤ 101 → [] row is stamped 100 ✗
```
A state event in the timeline with an empty `state_after`. An MSC4222
client trusts `state_after` over timeline state events, so Alice's copy
of Bob's call membership never updates from this response.
On a single process this cannot happen: the batch's stream IDs are
released as a whole, so the position visible to `/sync` jumps 99 → 101
and `s100` is never handed out. Only a process that learns its position
from replication — any sync worker — ticks through the middle of a
batch.
### Pull Request Checklist
<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->
* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
- Use markdown where necessary, mostly for `code blocks`.
- End with either a period (.) or an exclamation mark (!).
- Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct (run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))
## The bug
With the experimental
[MSC4222](https://github.com/matrix-org/matrix-spec-proposals/pull/4222)
implementation enabled (`use_state_after`) and lazy-loading of room
members, an incremental `/sync` could disclose state from **after** the
user's leave in a left room's `state_after`.
1. Alice syncs with `lazy_load_members: true` and
`use_state_after=true`.
2. Bob sends a message in a room they share.
3. Alice leaves the room.
4. Bob updates his per-room displayname
5. Alice does an incremental sync covering steps 2–3. Alice's
`state_after` contains Bob's post-leave membership event from step 4
Alice should not see the new per-room display name of Bob.
## The fix
Copy what has been done for `_compute_state_delta_for_full_sync`: pass
`joined` down and, for rooms the user is no longer joined to, fetch the
memberships as of `end_token` via state groups (`get_state_ids_at`)
instead of current state.
Introduce `Clock.call_when_running(...)` to wrap startup code in a
logcontext, ensuring we can identify which server generated the logs.
Background:
> Ideally, nothing from the Synapse homeserver would be logged against the `sentinel`
> logcontext as we want to know which server the logs came from. In practice, this is not
> always the case yet especially outside of request handling.
>
> Global things outside of Synapse (e.g. Twisted reactor code) should run in the
> `sentinel` logcontext. It's only when it calls into application code that a logcontext
> gets activated. This means the reactor should be started in the `sentinel` logcontext,
> and any time an awaitable yields control back to the reactor, it should reset the
> logcontext to be the `sentinel` logcontext. This is important to avoid leaking the
> current logcontext to the reactor (which would then get picked up and associated with
> the next thing the reactor does).
>
> *-- `docs/log_contexts.md`
Also adds a lint to prefer `Clock.call_when_running(...)` over
`reactor.callWhenRunning(...)`
Part of https://github.com/element-hq/synapse/issues/18905
The notifier is quite inefficient when it has to wake up many user
streams all at once
From a silly benchmark this takes the time to notify 1M user streams
from ~30s to ~5s
Update `filters.is_encrypted` and `filters.types`/`filters.not_types` to
be robust when dealing with remote invite rooms in Sliding Sync.
Part of
[MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575):
Sliding Sync
Follow-up to https://github.com/element-hq/synapse/pull/17434
We now take into account current state, fallback to stripped state
for invite/knock rooms, then historical state. If we can't determine
the info needed to filter a room (either from state or stripped state),
it is filtered out.
Rather than always including all rooms in range.
Also adds a pre-filter to rooms that checks the stream change cache to
see if anything might have happened.
Based on #17447
---------
Co-authored-by: Eric Eastwood <eric.eastwood@beta.gouv.fr>
The basic idea is that we introduce a new token for a sliding sync
connection, which stores the mapping of room to room "status" (i.e. have
we sent the room down?). This token allows us to handle duplicate
requests properly. In future it can be used to store more
"per-connection" information safely.
In future this should be migrated into the DB, so its important that we
try to reduce the number of syncs where we need to update the
per-connection information. In this PoC this only happens when we: a)
send down a set of room for the first time, or b) we have previously
sent down a room and there are updates but we are not sending the room
down the sync (due to not falling in a list range)
Co-authored-by: Eric Eastwood <eric.eastwood@beta.gouv.fr>
Backfill events have a negative stream ordering, and so its not useful
to use to compare with other (positive) stream orderings.
Plus, the Rust SDK currently assumes `bump_stamp` is positive.
Add room subscriptions to Sliding Sync `/sync`
Based on
[MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575):
Sliding Sync
Currently, you can only subscribe to rooms you have had *any* membership
in before.
In the future, we will allow `world_readable` rooms to be subscribed to
without joining.
`bump_stamp` corresponds to the `stream_ordering` of the latest `DEFAULT_BUMP_EVENT_TYPES` in the room. This helps clients sort more readily without them needing to pull in a bunch of the timeline to determine the last activity. `bump_event_types` is a thing because for example, we don't want display name changes to mark the room as unread and bump it to the top. For encrypted rooms, we just have to consider any activity as a bump because we can't see the content and the client has to figure it out for themselves.
Outside of Synapse, `bump_stamp` is just a free-form counter so other implementations could use `received_ts`or `origin_server_ts` (see the [*Security considerations* section in MSC3575 about the potential pitfalls of using `origin_server_ts`](https://github.com/matrix-org/matrix-spec-proposals/blob/kegan/sync-v3/proposals/3575-sync.md#security-considerations)). It doesn't have any guarantee about always going up. In the Synapse case, it could go down if an event was redacted/removed (or purged in cases of retention policies).
In the future, we could add `bump_event_types` as [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) mentions if people need to customize the event types.
---
In the Sliding Sync proxy, a similar [`timestamp` field was added](https://github.com/matrix-org/sliding-sync/pull/247) for the same purpose but the name is not obvious what it pertains to or what it's for.
The `timestamp` field was also added to Ruma in https://github.com/ruma/ruma/pull/1622
Fixes https://github.com/element-hq/synapse/issues/17274, hopefully.
Basically, old versions of Synapse could advance streams without
persisting anything in the DB (fixed in #17229). On restart those
updates would get lost, and so the position of the stream would revert
to an older position. If this happened across an upgrade to a later
Synapse version which included #17215, then sync could get blocked
indefinitely (until the stream advanced to the position in the token).
We fix this by bounding the stream positions we'll wait for to the
maximum position of the underlying stream ID generator.
Sort is no longer configurable and we always sort rooms by the `stream_ordering` of the last event in the room or the point where the user can see up to in cases of leave/ban/invite/knock.
Based on [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575): Sliding Sync
This iteration only focuses on returning the list of room IDs in the sliding window API (without sorting/filtering).
Rooms appear in the Sliding sync response based on:
- `invite`, `join`, `knock`, `ban` membership events
- Kicks (`leave` membership events where `sender` is different from the `user_id`/`state_key`)
- `newly_left` (rooms that were left during the given token range, > `from_token` and <= `to_token`)
- In order for bans/kicks to not show up, you need to `/forget` those rooms. This doesn't modify the event itself though and only adds the `forgotten` flag to `room_memberships` in Synapse. There isn't a way to tell when a room was forgotten at the moment so we can't factor it into the from/to range.
### Example request
`POST http://localhost:8008/_matrix/client/unstable/org.matrix.msc3575/sync`
```json
{
"lists": {
"foo-list": {
"ranges": [ [0, 99] ],
"sort": [ "by_notification_level", "by_recency", "by_name" ],
"required_state": [
["m.room.join_rules", ""],
["m.room.history_visibility", ""],
["m.space.child", "*"]
],
"timeline_limit": 100
}
}
}
```
Response:
```json
{
"next_pos": "s58_224_0_13_10_1_1_16_0_1",
"lists": {
"foo-list": {
"count": 1,
"ops": [
{
"op": "SYNC",
"range": [0, 99],
"room_ids": [
"!MmgikIyFzsuvtnbvVG:my.synapse.linux.server"
]
}
]
}
},
"rooms": {},
"extensions": {}
}
```
During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.
* Allow `AbstractSet` in `StrCollection`
Or else frozensets are excluded. This will be useful in an upcoming
commit where I plan to change a function that accepts `List[str]` to
accept `StrCollection` instead.
* `rooms_to_exclude` -> `rooms_to_exclude_globally`
I am about to make use of this exclusion mechanism to exclude rooms for
a specific user and a specific sync. This rename helps to clarify the
distinction between the global config and the rooms to exclude for a
specific sync.
* Better function names for internal sync methods
* Track a list of excluded rooms on SyncResultBuilder
I plan to feed a list of partially stated rooms for this sync to ignore
* Exclude partial state rooms during eager sync
using the mechanism established in the previous commit
* Track un-partial-state stream in sync tokens
So that we can work out which rooms have become fully-stated during a
given sync period.
* Fix mutation of `@cached` return value
This was fouling up a complement test added alongside this PR.
Excluding a room would mean the set of forgotten rooms in the cache
would be extended. This means that room could be erroneously considered
forgotten in the future.
Introduced in #12310, Synapse 1.57.0. I don't think this had any
user-visible side effects (until now).
* SyncResultBuilder: track rooms to force as newly joined
Similar plan as before. We've omitted rooms from certain sync responses;
now we establish the mechanism to reintroduce them into future syncs.
* Read new field, to present rooms as newly joined
* Force un-partial-stated rooms to be newly-joined
for eager incremental syncs only, provided they're still fully stated
* Notify user stream listeners to wake up long polling syncs
* Changelog
* Typo fix
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
* Unnecessary list cast
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
* Rephrase comment
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
* Another comment
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
* Fixup merge(?)
* Poke notifier when receiving un-partial-stated msg over replication
* Fixup merge whoops
Thanks MV :)
Co-authored-by: Mathieu Velen <mathieuv@matrix.org>
Co-authored-by: Mathieu Velten <mathieuv@matrix.org>
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>
This adds support for the stable identifiers of MSC2285 while
continuing to support the unstable identifiers behind the configuration
flag. These will be removed in a future version.
Eric Eastwood