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.

1 files changed, 8 insertions, 4 deletions

diff --git a/tests/unittest.py b/tests/unittest.py

index 8816a4d152..439174dbfc 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -38,7 +38,11 @@ from synapse.config.ratelimiting import FederationRateLimitConfig
 from synapse.federation.transport import server as federation_server
 from synapse.http.server import JsonResource
 from synapse.http.site import SynapseRequest, SynapseSite
-from synapse.logging.context import LoggingContext
+from synapse.logging.context import (
+    SENTINEL_CONTEXT,
+    current_context,
+    set_current_context,
+)
 from synapse.server import HomeServer
 from synapse.types import Requester, UserID, create_requester
 from synapse.util.ratelimitutils import FederationRateLimiter
@@ -97,10 +101,10 @@ class TestCase(unittest.TestCase):
         def setUp(orig):
             # if we're not starting in the sentinel logcontext, then to be honest
             # all future bets are off.
-            if LoggingContext.current_context() is not LoggingContext.sentinel:
+            if current_context():
                 self.fail(
                     "Test starting with non-sentinel logging context %s"
-                    % (LoggingContext.current_context(),)
+                    % (current_context(),)
                 )
 
             old_level = logging.getLogger().level
@@ -122,7 +126,7 @@ class TestCase(unittest.TestCase):
             # force a GC to workaround problems with deferreds leaking logcontexts when
             # they are GCed (see the logcontext docs)
             gc.collect()
-            LoggingContext.set_current_context(LoggingContext.sentinel)
+            set_current_context(SENTINEL_CONTEXT)
 
             return ret