Clean up some LoggingContext stuff (#7120)

* Pull Sentinel out of LoggingContext

... and drop a few unnecessary references to it

* Factor out LoggingContext.current_context

move `current_context` and `set_context` out to top-level functions.

Mostly this means that I can more easily trace what's actually referring to
LoggingContext, but I think it's generally neater.

* move copy-to-parent into `stop`

this really just makes `start` and `stop` more symetric. It also means that it
behaves correctly if you manually `set_log_context` rather than using the
context manager.

* Replace `LoggingContext.alive` with `finished`

Turn `alive` into `finished` and make it a bit better defined.

changelog.d/7120.misc

@@ -0,0 +1 @@
+Clean up some LoggingContext code.

docs/log_contexts.md

@@ -29,14 +29,13 @@ from synapse.logging import context         # omitted from future snippets
 def handle_request(request_id):
     request_context = context.LoggingContext()
 
-    calling_context = context.LoggingContext.current_context()
-    context.LoggingContext.set_current_context(request_context)
+    calling_context = context.set_current_context(request_context)
     try:
         request_context.request = request_id
         do_request_handling()
         logger.debug("finished")
     finally:
-        context.LoggingContext.set_current_context(calling_context)
+        context.set_current_context(calling_context)
 
 def do_request_handling():
     logger.debug("phew")  # this will be logged against request_id

synapse/crypto/keyring.py

@@ -43,8 +43,8 @@
     SynapseError,
 )
 from synapse.logging.context import (
-    LoggingContext,
     PreserveLoggingContext,
+    current_context,
     make_deferred_yieldable,
     preserve_fn,
     run_in_background,
@@ -236,7 +236,7 @@ def _start_key_lookups(self, verify_requests):
         """
 
         try:
-            ctx = LoggingContext.current_context()
+            ctx = current_context()
 
             # map from server name to a set of outstanding request ids
             server_to_request_ids = {}

synapse/federation/federation_base.py

@@ -32,8 +32,8 @@
 from synapse.events.utils import prune_event
 from synapse.http.servlet import assert_params_in_dict
 from synapse.logging.context import (
-    LoggingContext,
     PreserveLoggingContext,
+    current_context,
     make_deferred_yieldable,
 )
 from synapse.types import JsonDict, get_domain_from_id
@@ -78,7 +78,7 @@ def _check_sigs_and_hashes(
         """
         deferreds = _check_sigs_on_pdus(self.keyring, room_version, pdus)
 
-        ctx = LoggingContext.current_context()
+        ctx = current_context()
 
         def callback(_, pdu: EventBase):
             with PreserveLoggingContext(ctx):

synapse/handlers/sync.py

@@ -26,7 +26,7 @@
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.filtering import FilterCollection
 from synapse.events import EventBase
-from synapse.logging.context import LoggingContext
+from synapse.logging.context import current_context
 from synapse.push.clientformat import format_push_rules_for_user
 from synapse.storage.roommember import MemberSummary
 from synapse.storage.state import StateFilter
@@ -301,7 +301,7 @@ async def _wait_for_sync_for_user(
         else:
             sync_type = "incremental_sync"
 
-        context = LoggingContext.current_context()
+        context = current_context()
         if context:
             context.tag = sync_type
 

synapse/http/request_metrics.py

@@ -19,7 +19,7 @@
 
 from prometheus_client.core import Counter, Histogram
 
-from synapse.logging.context import LoggingContext
+from synapse.logging.context import current_context
 from synapse.metrics import LaterGauge
 
 logger = logging.getLogger(__name__)
@@ -148,7 +148,7 @@ def _get_in_flight_counts():
 class RequestMetrics(object):
     def start(self, time_sec, name, method):
         self.start = time_sec
-        self.start_context = LoggingContext.current_context()
+        self.start_context = current_context()
         self.name = name
         self.method = method
 
@@ -163,7 +163,7 @@ def stop(self, time_sec, response_code, sent_bytes):
         with _in_flight_requests_lock:
             _in_flight_requests.discard(self)
 
-        context = LoggingContext.current_context()
+        context = current_context()
 
         tag = ""
         if context:

synapse/logging/_structured.py

@@ -42,7 +42,7 @@
     TerseJSONToConsoleLogObserver,
     TerseJSONToTCPLogObserver,
 )
-from synapse.logging.context import LoggingContext
+from synapse.logging.context import current_context
 
 
 def stdlib_log_level_to_twisted(level: str) -> LogLevel:
@@ -86,7 +86,7 @@ def __call__(self, event: dict) -> None:
             ].startswith("Timing out client"):
                 return
 
-        context = LoggingContext.current_context()
+        context = current_context()
 
         # Copy the context information to the log event.
         if context is not None: