From 55e6bdf28798153de5c2a6cf9bf0a6618f59168a Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Mon, 20 Aug 2018 18:20:07 +0100
Subject: [PATCH] Robustness fix for logcontext filter

Make the logcontext filter not explode if it somehow ends up with a logcontext
of None, since that infinite-loops the whole logging system.
---
 synapse/util/logcontext.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index 07e83fadda..848765e530 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