bpo-35726: Prevented QueueHandler formatting from affecting other handlers (GH-11537)

QueueHandler.prepare() now makes a copy of the record before modifying and enqueueing it, to avoid affecting other handlers in the chain.

1 files changed, 3 insertions, 0 deletions

diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py
index e213e438c3..3727bf0677 100644
--- a/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@ -27,6 +27,7 @@ import logging, socket, os, pickle, struct, time, re
 from stat import ST_DEV, ST_INO, ST_MTIME
 import queue
 import threading
+import copy
 
 #
 # Some constants...
@@ -1377,6 +1378,8 @@ class QueueHandler(logging.Handler):
         # exc_info and exc_text attributes, as they are no longer
         # needed and, if not None, will typically not be pickleable.
         msg = self.format(record)
+        # bpo-35726: make copy of record to avoid affecting other handlers in the chain.
+        record = copy.copy(record)
         record.message = msg
         record.msg = msg
         record.args = None