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
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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`.".
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- 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
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* [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))
Follows: #19365
Part of: MSC4354 Sticky Events (experimental feature #19409)
This PR introduces a `spam_checker_spammy` flag, analogous to
`policy_server_spammy`, as an explicit flag
that an event was decided to be spammy by a spam-checker module.
The original Sticky Events PR (#18968) just reused
`policy_server_spammy`, but it didn't sit right with me
because we (at least appear to be experimenting with features that)
allow users to opt-in to seeing
`policy_server_spammy` events (presumably for moderation purposes).
Keeping these flags separate felt best, therefore.
As for why we need this flag: soon soft-failed status won't be
permanent, at least for sticky events.
The spam checker modules currently work by making events soft-failed.
We want to prevent spammy events from getting
reconsidered/un-soft-failed, so it seems like we need
a flag to track spam-checker spamminess *separately* from soft-failed.
Should be commit-by-commit friendly, but is also small.
---------
Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>
During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.
Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
This allows trailing commas in multi-line arg lists.
Minor, but we might as well keep our formatting current with regard to
our minimum supported Python version.
Signed-off-by: Dan Callahan <danc@element.io>
The CI appears to use the latest version of isort, which is a problem when isort gets a major version bump. Rather than try to pin the version, I've done the necessary to make isort5 happy with synapse.
* Factor out functions for injecting events into database
I want to add some more flexibility to the tools for injecting events into the
database, and I don't want to clutter up HomeserverTestCase with them, so let's
factor them out to a new file.
* Rework TestReplicationDataHandler
This wasn't very easy to work with: the mock wrapping was largely superfluous,
and it's useful to be able to inspect the received rows, and clear out the
received list.
* Fix AssertionErrors being thrown by EventsStream
Part of the problem was that there was an off-by-one error in the assertion,
but also the limit logic was too simple. Fix it all up and add some tests.
Paul Chobert