Matthew Hodgson
ac26cfac83
Let me give you a clear summary of where this project stands:
...
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Summary: Synapse Twisted → asyncio Migration
What's been built (Phases 0-7) — 10 new files, ~3200 lines, 96 tests
Every Twisted component has an asyncio-native replacement ready:
┌──────────────────┬───────────────────────────────────────────────┬─────────────────────────────────────────────────────────┬───────────────────────────────────────────────┐
│ Component │ Twisted Original │ asyncio Replacement │ File │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ LoggingContext │ threading.local + Deferred callbacks │ ContextVar + asyncio Task │ synapse/logging/context.py (native functions) │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Async primitives │ ObservableDeferred, Linearizer, ReadWriteLock │ ObservableFuture, NativeLinearizer, NativeReadWriteLock │ synapse/util/async_helpers.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Cache │ DeferredCache │ FutureCache │ synapse/util/caches/future_cache.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Clock │ Clock (Twisted reactor) │ NativeClock (asyncio) │ synapse/util/clock.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Database │ adbapi.ConnectionPool │ NativeConnectionPool (ThreadPoolExecutor) │ synapse/storage/native_database.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ HTTP Client │ treq + Twisted Agent │ aiohttp.ClientSession │ synapse/http/native_client.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ HTTP Server │ JsonResource + Twisted Site │ NativeJsonResource + aiohttp.web │ synapse/http/native_server.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Replication │ LineOnlyReceiver (Twisted Protocol) │ asyncio.StreamReader/Writer │ synapse/replication/tcp/native_protocol.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Event loop │ ISynapseReactor │ ISynapseEventLoop │ synapse/types/__init__.py │
├──────────────────┼───────────────────────────────────────────────┼─────────────────────────────────────────────────────────┼───────────────────────────────────────────────┤
│ Test helper │ — │ FakeAsyncioLoop │ tests/async_helpers.py │
└──────────────────┴───────────────────────────────────────────────┴─────────────────────────────────────────────────────────┴───────────────────────────────────────────────┘
What's been wired in safely — 224 files changed, 0 regressions
- MemoryReactor type hint → Any across 198 test files (cosmetic)
- synapse/http/server.py — catches both Twisted and asyncio CancelledError
- All 4530 tests still pass (minus the 2 pre-existing failures)
What remains for the flag day
The actual switchover requires rewriting 5 core files simultaneously, then running a migration script across ~500 files:
1. tests/unittest.py + tests/server.py — switch from twisted.trial.TestCase to unittest.TestCase, MemoryReactorClock to FakeAsyncioLoop, get_success() to asyncio run_until_complete()
2. synapse/logging/context.py — switch current_context() to ContextVar, make_deferred_yieldable() to async, run_in_background() to create_task()
3. synapse/util/async_helpers.py — rename Native* classes to canonical names, remove Deferred-based originals
4. Migration script — update all CancelledError, defer.*, Deferred imports across ~500 files
5. pyproject.toml — remove Twisted dependency
This is an atomic change because: ContextVar can't coexist with Twisted's reactor callbacks, make_deferred_yieldable's signature change breaks all callers, and CancelledError is a different
class between Twisted and asyncio.
2026-03-21 16:17:04 +00:00
Eric Eastwood
5a9ca1e3d9
Introduce Clock.call_when_running(...) to include logcontext by default ( #18944 )
...
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
2025-09-22 10:27:59 -05:00
