[Python-checkins] gh-89087: Update logging.QueueHandler documentation to clarify record… (GH-96527)

[vsajip]

https://github.com/python/cpython/commit/e5823bf9b594937290ddd3c0f3e42f5c534f58d1
commit: e5823bf9b594937290ddd3c0f3e42f5c534f58d1
branch: main
author: Vinay Sajip <vinay_sajip at yahoo.co.uk>
committer: vsajip <vinay_sajip at yahoo.co.uk>
date: 2022-09-03T13:02:19+01:00
summary:

gh-89087: Update logging.QueueHandler documentation to clarify record… (GH-96527)

files:
M Doc/library/logging.handlers.rst

diff --git a/Doc/library/logging.handlers.rst b/Doc/library/logging.handlers.rst
index a0129279f4db..f3b26e726aaf 100644
--- a/Doc/library/logging.handlers.rst
+++ b/Doc/library/logging.handlers.rst
@@ -1060,6 +1060,20 @@ possible, while any potentially slow operations (such as sending an email via
       the record to a dict or JSON string, or send a modified copy
       of the record while leaving the original intact.
 
+      .. note:: The base implementation formats the message with arguments, sets
+         the ``message`` and ``msg`` attributes to the formatted message and
+         sets the ``args`` and ``exc_text`` attributes to ``None`` to allow
+         pickling and to prevent further attempts at formatting. This means
+         that a handler on the :class:`QueueListener` side won't have the
+         information to do custom formatting, e.g. of exceptions. You may wish
+         to subclass ``QueueHandler`` and override this method to e.g. avoid
+         setting ``exc_text`` to ``None``. Note that the ``message`` / ``msg``
+         / ``args`` changes are related to ensuring the record is pickleable,
+         and you might or might not be able to avoid doing that depending on
+         whether your ``args`` are pickleable. (Note that you may have to
+         consider not only your own code but also code in any libraries that
+         you use.)
+
    .. method:: enqueue(record)
 
       Enqueues the record on the queue using ``put_nowait()``; you may