Merge tag 'v0.33.3rc2' into develop

Bugfixes
--------

- Fix bug in v0.33.3rc1 which caused infinite loops and OOMs
([\#3723](https://github.com/matrix-org/synapse/issues/3723))

1 files changed, 10 insertions, 2 deletions

diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py

index 07e83fadda..a0c2d37610 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -385,7 +385,13 @@ class LoggingContextFilter(logging.Filter):
         context = LoggingContext.current_context()
         for key, value in self.defaults.items():
             setattr(record, key, value)
-        context.copy_to(record)
+
+        # context should never be None, but if it somehow ends up being, then
+        # we end up in a death spiral of infinite loops, so let's check, for
+        # robustness' sake.
+        if context is not None:
+            context.copy_to(record)
+
         return True
 
 
@@ -396,7 +402,9 @@ class PreserveLoggingContext(object):
 
     __slots__ = ["current_context", "new_context", "has_parent"]
 
-    def __init__(self, new_context=LoggingContext.sentinel):
+    def __init__(self, new_context=None):
+        if new_context is None:
+            new_context = LoggingContext.sentinel
         self.new_context = new_context
 
     def __enter__(self):