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, 5 insertions, 8 deletions

diff --git a/synapse/logging/scopecontextmanager.py b/synapse/logging/scopecontextmanager.py
index 4eed4f2338..dc3ab00cbb 100644
--- a/synapse/logging/scopecontextmanager.py
+++ b/synapse/logging/scopecontextmanager.py
@@ -19,7 +19,7 @@ from opentracing import Scope, ScopeManager
 
 import twisted
 
-from synapse.logging.context import LoggingContext, nested_logging_context
+from synapse.logging.context import current_context, nested_logging_context
 
 logger = logging.getLogger(__name__)
 
@@ -49,11 +49,8 @@ class LogContextScopeManager(ScopeManager):
             (Scope) : the Scope that is active, or None if not
             available.
         """
-        ctx = LoggingContext.current_context()
-        if ctx is LoggingContext.sentinel:
-            return None
-        else:
-            return ctx.scope
+        ctx = current_context()
+        return ctx.scope
 
     def activate(self, span, finish_on_close):
         """
@@ -70,9 +67,9 @@ class LogContextScopeManager(ScopeManager):
         """
 
         enter_logcontext = False
-        ctx = LoggingContext.current_context()
+        ctx = current_context()
 
-        if ctx is LoggingContext.sentinel:
+        if not ctx:
             # We don't want this scope to affect.
             logger.error("Tried to activate scope outside of loggingcontext")
             return Scope(None, span)