LLM summary:
func only ever needs to be moved to a thread and called there sequentially, never shared by & across threads:
- In the erasure, func is captured by-move into the Box<dyn Fn ... + Send> callback (only Send is required to box it that way).
- The Python pool moves that callback into the runInteraction DB-thread closure and calls it there; the Rust pool calls it within a single async task. Neither sends &func to multiple threads concurrently.
Prompt:
```
Compare this with a previous approach that was swapped out in `d9a111bdfaf51cd4cadfdc071f9956eec47aea43` (look at the removals). Anything we should change/simplify or something you like better/worse about that one? Give the new approach a review and simplify and make things more clear as necessary
```
Changes made (LLM summary):
1. #[async_trait] on the object-safe method. The core trait method is now async fn run_interaction_erased(...) -> ErasedResult instead of a hand-rolled fn ... -> BoxFuture<'a, _>. This is the convention already used by Transaction in the same file, and it removed the async move { ... }.boxed() wrapper (plus the BoxFuture/FutureExt imports) from both pool impls — their bodies are now plain async fns again.
2. Dropped the constrain / erase_interaction helper. I'd over-engineered the closure erasure out of a worry that higher-ranked-lifetime inference would fail. The previous code proved a direct let erased: ErasedInteraction = Box::new(move |txn| {...}) compiles — the type annotation on the binding is enough. ~30 lines gone.
3. Dropped the unneeded + Sync on the erased callback type. ErasedInteraction is + Send only now; the boxed callback is moved to a single DB thread and called there, never shared by reference.
```
[ERROR]
Traceback (most recent call last):
File "/home/eric/.cache/pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.14/lib/python3.14/site-packages/twisted/trial/runner.py", line 711, in loadByName
return self.suiteFactory([self.findByName(name, recurse=recurse)])
File "/home/eric/.cache/pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.14/lib/python3.14/site-packages/twisted/trial/runner.py", line 474, in findByName
obj = reflect.namedModule(searchName)
File "/home/eric/.cache/pypoetry/virtualenvs/matrix-synapse-xCtC9ulO-py3.14/lib/python3.14/site-packages/twisted/python/reflect.py", line 156, in namedModule
topLevel = __import__(name)
File "/home/eric/Documents/github/element/synapse/tests/__init__.py", line 24, in <module>
from synapse.util.patch_inline_callbacks import do_patch
File "/home/eric/Documents/github/element/synapse/synapse/__init__.py", line 31, in <module>
from synapse.util.rust import check_rust_lib_up_to_date
File "/home/eric/Documents/github/element/synapse/synapse/util/__init__.py", line 41, in <module>
from synapse.types import JsonDict
File "/home/eric/Documents/github/element/synapse/synapse/types/__init__.py", line 63, in <module>
from synapse.api.errors import Codes, SynapseError
File "/home/eric/Documents/github/element/synapse/synapse/api/errors.py", line 33, in <module>
from synapse.util.json import json_decoder
File "/home/eric/Documents/github/element/synapse/synapse/util/json.py", line 23, in <module>
from synapse.synapse_rust.events import JsonObject
File "/home/eric/Documents/github/element/synapse/synapse/logging/context.py", line 55, in <module>
from synapse.util.stringutils import random_string_insecure_fast
File "/home/eric/Documents/github/element/synapse/synapse/util/stringutils.py", line 31, in <module>
from synapse.api.errors import Codes, SynapseError
builtins.ImportError: cannot import name 'Codes' from partially initialized module 'synapse.api.errors' (most likely due to a circular import) (/home/eric/Documents/github/element/synapse/synapse/api/errors.py)
```
After looking into it, just a couple of things to pick a bone at in the
old wording,
which I thought could be clarified for when I next come to look at this
again.
- the claim that there's a fundamental difference; I'd argue there isn't
really, it's just by convention
on some mainstream distros. So I have changed this to 'typically'
- statements that some distros fetch dependencies at build time
(probably does happen, but
traditional distros make a point of not doing this for the reasons you'd
expect).
- This was probably meant to be talking about Debian, but my observation
based on sample size of 3 is that some crates are packaged natively,
others are vendored in the respective application's source package (like
they do for us) and sometime they patch the bounds a bit
There could probably be room to talk about how distros vendoring
packages is a maintenance burden on them,
but I guess it's a bit moot as we would struggle to conform to wide
enough bounds to make everyone
happy (and anyway; I expect the distros that vendor packages have the
tooling to make this easy to
update and we do keep on top of security updates and release
frequently...)
---
Spawning from discussion in
[`#element-backend-internal:matrix.org`](https://matrix.to/#/!SGNQGPGUwtcPBUotTL:matrix.org/$VttYPPUevn2S_W_rrzg2ZOXWI6aKebk2ganTgrLEWUc?via=jki.re&via=element.io&via=matrix.org)
---------
Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>
Follows: #19487
Part of: MSC4354 whose experimental feature tracking issue is #19409
This PR implements the Sliding Sync (MSC4186) extension described in
MSC4354, allowing sliding sync clients
to receive sticky events in a reliable way.
The logic is much the same as for oldschool sync (implementation in
#19487),
although in the sliding sync extension, the client can choose their own
limit
and must control their own pagination through an extra token in the
extension request/response bodies.
Note this does not yet send down existing sticky events in the
room when the room has been newly-joined.
This newly-discovered gap is tracked at #19662 and will be addressed for
both current sync and MSC4186 SSS soon.
---------
Signed-off-by: Olivier 'reivilibre <oliverw@matrix.org>
Co-authored-by: Eric Eastwood <erice@element.io>
Bringing it up to parity with the other 404 StoreErrors naming the table
name already.
More helpful response when debugging issues with incomplete relations.
Concretly: a user that got partly removed and then reinstated, missing
an entry in 'profiles' table.
This should also contribute to a better understanding of #2807 and #2173
Eric Eastwood