WIP: use a contextvar to store the logcontext

CHANGES.md

@@ -1,47 +1,3 @@
-# Synapse 1.137.0 (2025-08-26)
-
-No significant changes since 1.137.0rc1.
-
-
-
-
-# Synapse 1.137.0rc1 (2025-08-19)
-
-### Bugfixes
-
-- Fix a bug which could corrupt auth chains making it impossible to perform state resolution. ([\#18746](https://github.com/element-hq/synapse/issues/18746))
-- Fix error message in `register_new_matrix_user` utility script for empty `registration_shared_secret`. ([\#18780](https://github.com/element-hq/synapse/issues/18780))
-- Allow enabling [MSC4108](https://github.com/matrix-org/matrix-spec-proposals/pull/4108) when the stable Matrix Authentication Service integration is enabled. ([\#18832](https://github.com/element-hq/synapse/issues/18832))
-
-### Improved Documentation
-
-- Include IPv6 networks in `denied-peer-ips` of coturn setup. Contributed by @litetex. ([\#18781](https://github.com/element-hq/synapse/issues/18781))
-
-### Internal Changes
-
-- Update tests to ensure all database tables are emptied when purging a room. ([\#18794](https://github.com/element-hq/synapse/issues/18794))
-- Instrument the `encode_response` part of Sliding Sync requests for more complete traces in Jaeger. ([\#18815](https://github.com/element-hq/synapse/issues/18815))
-- Tag Sliding Sync traces when we `wait_for_events`. ([\#18816](https://github.com/element-hq/synapse/issues/18816))
-- Fix `portdb` CI by hardcoding the new `pg_dump` restrict key that was added due to [CVE-2025-8714](https://nvd.nist.gov/vuln/detail/cve-2025-8714). ([\#18824](https://github.com/element-hq/synapse/issues/18824))
-
-
-
-### Updates to locked dependencies
-
-* Bump actions/add-to-project from 5b1a254a3546aef88e0a7724a77a623fa2e47c36 to 0c37450c4be3b6a7582b2fb013c9ebfd9c8e9300. ([\#18557](https://github.com/element-hq/synapse/issues/18557))
-* Bump actions/cache from 4.2.3 to 4.2.4. ([\#18799](https://github.com/element-hq/synapse/issues/18799))
-* Bump actions/checkout from 4.2.2 to 4.3.0. ([\#18800](https://github.com/element-hq/synapse/issues/18800))
-* Bump actions/download-artifact from 4.3.0 to 5.0.0. ([\#18801](https://github.com/element-hq/synapse/issues/18801))
-* Bump docker/metadata-action from 5.7.0 to 5.8.0. ([\#18773](https://github.com/element-hq/synapse/issues/18773))
-* Bump mypy from 1.16.1 to 1.17.1. ([\#18775](https://github.com/element-hq/synapse/issues/18775))
-* Bump phonenumbers from 9.0.10 to 9.0.11. ([\#18797](https://github.com/element-hq/synapse/issues/18797))
-* Bump pygithub from 2.6.1 to 2.7.0. ([\#18779](https://github.com/element-hq/synapse/issues/18779))
-* Bump serde_json from 1.0.141 to 1.0.142. ([\#18776](https://github.com/element-hq/synapse/issues/18776))
-* Bump slab from 0.4.10 to 0.4.11. ([\#18809](https://github.com/element-hq/synapse/issues/18809))
-* Bump tokio from 1.47.0 to 1.47.1. ([\#18774](https://github.com/element-hq/synapse/issues/18774))
-* Bump types-pyyaml from 6.0.12.20250516 to 6.0.12.20250809. ([\#18798](https://github.com/element-hq/synapse/issues/18798))
-* Bump types-setuptools from 80.9.0.20250529 to 80.9.0.20250809. ([\#18796](https://github.com/element-hq/synapse/issues/18796))
-
 # Synapse 1.136.0 (2025-08-12)
 
 Note: This release includes the security fixes from `1.135.2` and `1.136.0rc2`, detailed below.

changelog.d/18746.bugfix

@@ -0,0 +1 @@
+Fix a bug which could corrupt auth chains making it impossible to perform state resolution.

changelog.d/18780.bugfix

@@ -0,0 +1 @@
+Fix error message in `register_new_matrix_user` utility script for empty `registration_shared_secret`.

changelog.d/18781.doc

@@ -0,0 +1 @@
+Include IPv6 networks in denied-peer-ips of coturn setup. Contributed by @litetex.

changelog.d/18794.misc

@@ -0,0 +1 @@
+Update tests to ensure all database tables are emptied when purging a room.

changelog.d/18815.misc

@@ -0,0 +1 @@
+Instrument the `encode_response` part of Sliding Sync requests for more complete traces in Jaeger.

changelog.d/18816.misc

@@ -0,0 +1 @@
+Tag Sliding Sync traces when we `wait_for_events`.

changelog.d/18824.misc

@@ -0,0 +1 @@
+Fix portdb CI by hardcoding the new pg_dump restrict key that was added due to CVE-2025-8714.

changelog.d/18832.bugfix

@@ -0,0 +1 @@
+Allow enabling MSC4108 when the stable Matrix Authentication Service integration is enabled.

debian/changelog

@@ -1,15 +1,3 @@
-matrix-synapse-py3 (1.137.0) stable; urgency=medium
-
-  * New Synapse release 1.137.0.
-
- -- Synapse Packaging team <packages@matrix.org>  Tue, 26 Aug 2025 10:23:41 +0100
-
-matrix-synapse-py3 (1.137.0~rc1) stable; urgency=medium
-
-  * New Synapse release 1.137.0rc1.
-
- -- Synapse Packaging team <packages@matrix.org>  Tue, 19 Aug 2025 10:55:22 +0100
-
 matrix-synapse-py3 (1.136.0) stable; urgency=medium
 
   * New Synapse release 1.136.0.

pyproject.toml

@@ -101,7 +101,7 @@ module-name = "synapse.synapse_rust"
 
 [tool.poetry]
 name = "matrix-synapse"
-version = "1.137.0"
+version = "1.136.0"
 description = "Homeserver for the Matrix decentralised comms protocol"
 authors = ["Matrix.org Team and Contributors <packages@matrix.org>"]
 license = "AGPL-3.0-or-later"

schema/synapse-config.schema.yaml

@@ -1,5 +1,5 @@
 $schema: https://element-hq.github.io/synapse/latest/schema/v1/meta.schema.json
-$id: https://element-hq.github.io/synapse/schema/synapse/v1.137/synapse-config.schema.json
+$id: https://element-hq.github.io/synapse/schema/synapse/v1.136/synapse-config.schema.json
 type: object
 properties:
   modules:

synapse/logging/context.py

@@ -34,6 +34,7 @@ import logging
 import threading
 import typing
 import warnings
+from contextvars import ContextVar
 from types import TracebackType
 from typing import (
     TYPE_CHECKING,
@@ -660,13 +661,12 @@ class PreserveLoggingContext:
                 )
 
 
-_thread_local = threading.local()
-_thread_local.current_context = SENTINEL_CONTEXT
+_current_context: ContextVar[LoggingContextOrSentinel] = ContextVar("current_context")
 
 
 def current_context() -> LoggingContextOrSentinel:
     """Get the current logging context from thread local storage"""
-    return getattr(_thread_local, "current_context", SENTINEL_CONTEXT)
+    return _current_context.get(SENTINEL_CONTEXT)
 
 
 def set_current_context(context: LoggingContextOrSentinel) -> LoggingContextOrSentinel:
@@ -687,7 +687,7 @@ def set_current_context(context: LoggingContextOrSentinel) -> LoggingContextOrSe
     if current is not context:
         rusage = get_thread_resource_usage()
         current.stop(rusage)
-        _thread_local.current_context = context
+        _current_context.set(context)
         context.start(rusage)
 
     return current
@@ -803,7 +803,6 @@ def run_in_background(
     CRITICAL error about an unhandled error will be logged without much
     indication about where it came from.
     """
-    current = current_context()
     try:
         res = f(*args, **kwargs)
     except Exception:
@@ -832,23 +831,6 @@ def run_in_background(
         # optimise out the messing about
         return d
 
-    # The function may have reset the context before returning, so
-    # we need to restore it now.
-    ctx = set_current_context(current)
-
-    # The original context will be restored when the deferred
-    # completes, but there is nothing waiting for it, so it will
-    # get leaked into the reactor or some other function which
-    # wasn't expecting it. We therefore need to reset the context
-    # here.
-    #
-    # (If this feels asymmetric, consider it this way: we are
-    # effectively forking a new thread of execution. We are
-    # probably currently within a ``with LoggingContext()`` block,
-    # which is supposed to have a single entry and exit point. But
-    # by spawning off another deferred, we are effectively
-    # adding a new exit point.)
-    d.addBoth(_set_context_cb, ctx)
     return d
 
 
@@ -868,65 +850,19 @@ def run_coroutine_in_background(
     cannot change the log contexts.
     """
 
-    current = current_context()
-    d = defer.ensureDeferred(coroutine)
-
-    # The function may have reset the context before returning, so
-    # we need to restore it now.
-    ctx = set_current_context(current)
-
-    # The original context will be restored when the deferred
-    # completes, but there is nothing waiting for it, so it will
-    # get leaked into the reactor or some other function which
-    # wasn't expecting it. We therefore need to reset the context
-    # here.
-    #
-    # (If this feels asymmetric, consider it this way: we are
-    # effectively forking a new thread of execution. We are
-    # probably currently within a ``with LoggingContext()`` block,
-    # which is supposed to have a single entry and exit point. But
-    # by spawning off another deferred, we are effectively
-    # adding a new exit point.)
-    d.addBoth(_set_context_cb, ctx)
-    return d
+    return defer.ensureDeferred(coroutine)
 
 
 T = TypeVar("T")
 
 
 def make_deferred_yieldable(deferred: "defer.Deferred[T]") -> "defer.Deferred[T]":
-    """Given a deferred, make it follow the Synapse logcontext rules:
-
-    If the deferred has completed, essentially does nothing (just returns another
-    completed deferred with the result/failure).
-
-    If the deferred has not yet completed, resets the logcontext before
-    returning a deferred. Then, when the deferred completes, restores the
-    current logcontext before running callbacks/errbacks.
-
-    (This is more-or-less the opposite operation to run_in_background.)
-    """
-    if deferred.called and not deferred.paused:
-        # it looks like this deferred is ready to run any callbacks we give it
-        # immediately. We may as well optimise out the logcontext faffery.
-        return deferred
-
-    # ok, we can't be sure that a yield won't block, so let's reset the
-    # logcontext, and add a callback to the deferred to restore it.
-    prev_context = set_current_context(SENTINEL_CONTEXT)
-    deferred.addBoth(_set_context_cb, prev_context)
     return deferred
 
 
 ResultT = TypeVar("ResultT")
 
 
-def _set_context_cb(result: ResultT, context: LoggingContextOrSentinel) -> ResultT:
-    """A callback function which just sets the logging context"""
-    set_current_context(context)
-    return result
-
-
 def defer_to_thread(
     reactor: "ISynapseReactor", f: Callable[P, R], *args: P.args, **kwargs: P.kwargs
 ) -> "defer.Deferred[R]":
@@ -998,18 +934,6 @@ def defer_to_threadpool(
         A Deferred which fires a callback with the result of `f`, or an
             errback if `f` throws an exception.
     """
-    curr_context = current_context()
-    if not curr_context:
-        logger.warning(
-            "Calling defer_to_threadpool from sentinel context: metrics will be lost"
-        )
-        parent_context = None
-    else:
-        assert isinstance(curr_context, LoggingContext)
-        parent_context = curr_context
-
-    def g() -> R:
-        with LoggingContext(str(curr_context), parent_context=parent_context):
-            return f(*args, **kwargs)
-
-    return make_deferred_yieldable(threads.deferToThreadPool(reactor, threadpool, g))
+    return make_deferred_yieldable(
+        threads.deferToThreadPool(reactor, threadpool, f, *args, **kwargs)
+    )