- Keep an unchanged device stream's position. The tokens are read after
the change check, so moving to them could skip a message that arrived
in between.
- Decode cross-signing keys as leniently as Python does, including
URL-safe base64.
- Mark the transaction open before awaiting BEGIN, so a dropped task
still rolls back.
- Tell modules about delivered events before the database writes, as
Python does.
- Update the stream change cache before its listeners, and log a
listener that fails.
- Check the metrics through a registry scrape, with a fresh event.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R5b7Ruy4cgt27Mjq6Ptxbb
On the native Postgres driver, the Rust queues' `NativeHooks` read the
device EDUs and record finished transactions through `FederationStore`,
on tokio. A transaction then takes no trip to the reactor, unless it
finishes a sticky event batch or a module wants to hear about delivered
events. Catch-up and the sticky event backlog stay Python. SQLite and
the Python Postgres driver keep the Python hooks.
Python skips the device queries for destinations with nothing new by
asking two stream change caches. Rust keeps a mirror of each, per
destination, fed by a new `StreamChangeCache.add_listener`, so it hears
of every change the caches do. The current stream positions live in
Python's ID generators, and are read under the GIL (without a reactor
trip) only when a destination has changed.
The loops now count their transactions, EDUs and requests in Rust.
`synapse.metrics.pre_collect_hooks` adds the counts to the Python
metrics when they are collected. This removes a GIL crossing on every
failed send, and from `_rust_complete`.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R5b7Ruy4cgt27Mjq6Ptxbb
This is particularly a problem in a state reset scenario where the membership
might change without a corresponding event.
This PR is targeting a scenario where a state reset happens which causes
room membership to change. Previously, the cache would just hold onto
stale data and now we properly bust the cache in this scenario.
We have a few tests for these scenarios which you can see are now fixed
because we can remove the `FIXME` where we were previously manually
busting the cache in the test itself.
This is a general Synapse thing so by it's nature it helps out Sliding
Sync.
Fix https://github.com/element-hq/synapse/issues/17368
Prerequisite for https://github.com/element-hq/synapse/issues/17929
---
Match when are busting `_curr_state_delta_stream_cache`
There is a bug with the `StreamChangeCache` where it would incorrectly
return that all entities had changed if asked for entities changed
*since* the earliest stream position.
Note that for streams we use the inequalities: `$min_stream_id <
stream_id <= $max_stream_id`, i.e. when we ask the stream change cache
for all things that have changed since `$stream_id` we don't care for
events that happened *at* `$stream_id`.
Specifically: `_earliest_known_stream_pos` is the position at which we
know that we'll have entries for all changes since that point, we can
use the cache for any stream IDs that equal
`_earliest_known_stream_pos`.
`_earliest_known_stream_pos` is set in three places:
- On startup we set it either to:
- the current maximum stream ID, with not prefilled values; or
- the minimum of the latest N values we pulled from the DB
- When we evict items from the bottom, we set it to the stream ID of the
evicted items.
This was changed in https://github.com/matrix-org/synapse/pull/14435,
but I think we were overly conservative there.
---------
Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
When there have been lots of changes compared with the number of
entities, we can do a fast(er) path.
Locally I ran some benchmarking, and the comparison seems to give the
best determination of which method we use.
An empty cache does not mean the entity has no changed, if
it is earlier than the earliest known stream position return that
the entity *has* changed since the cache cannot accurately
answer that query.
The internal methods of the StreamChangeCache were inconsistently
treating the earliest known stream position as valid. It is now treated as
invalid, meaning the cache cannot determine if an entity at the earliest
known stream position has changed or not.
First some background: StreamChangeCache is used to keep track of what "entities" have
changed since a given stream ID. So for example, we might use it to keep track of when the last
to-device message for a given user was received [1], and hence whether we need to pull any to-device messages from the database on a sync [2].
Now, it turns out that StreamChangeCache didn't support more than one thing being changed at
a given stream_id (this was part of the problem with #7206). However, it's entirely valid to send
to-device messages to more than one user at a time.
As it turns out, this did in fact work, because *some* methods of StreamChangeCache coped
ok with having multiple things changing on the same stream ID, and it seems we never actually
use the methods which don't work on the stream change caches where we allow multiple
changes at the same stream ID. But that feels horribly fragile, hence: let's update
StreamChangeCache to properly support this, and add some typing and some more tests while
we're at it.
[1]: https://github.com/matrix-org/synapse/blob/release-v1.12.3/synapse/storage/data_stores/main/deviceinbox.py#L301
[2]: https://github.com/matrix-org/synapse/blob/release-v1.12.3/synapse/storage/data_stores/main/deviceinbox.py#L47-L51
