https://github.com/python/cpython/commit/6b282e18877ec84e927b381b4ce187eaf4b... commit: 6b282e18877ec84e927b381b4ce187eaf4ba3dd7 branch: master author: Bar Harel <bzvi7919@gmail.com> committer: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> date: 2019-06-01T02:19:09-07:00 summary: bpo-36813: Fix QueueListener to call task_done() upon termination. (GH-13113) Fixed QueueListener in order to avoid random deadlocks. Unable to add regression tests atm due to time constraints, will add it in a bit. Regarding implementation, although it's nested, it does not cause performance issues whatsoever, and does not call task_done() in case of an exception (which is the right thing to do IMHO). https://bugs.python.org/issue36813 files: A Misc/NEWS.d/next/Library/2019-05-06-18-28-38.bpo-36813.NXD0KZ.rst M Lib/logging/handlers.py M Lib/test/test_logging.py diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py index 3727bf0677cd..a913d27389ab 100644 --- a/Lib/logging/handlers.py +++ b/Lib/logging/handlers.py @@ -1477,6 +1477,8 @@ def _monitor(self): try: record = self.dequeue(True) if record is self._sentinel: + if has_task_done: + q.task_done() break self.handle(record) if has_task_done: diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py index b884753ad397..50148dc2f252 100644 --- a/Lib/test/test_logging.py +++ b/Lib/test/test_logging.py @@ -3633,6 +3633,16 @@ def test_no_messages_in_queue_after_stop(self): [m.msg if isinstance(m, logging.LogRecord) else m for m in items])) + def test_calls_task_done_after_stop(self): + # Issue 36813: Make sure queue.join does not deadlock. + log_queue = queue.Queue() + listener = logging.handlers.QueueListener(log_queue) + listener.start() + listener.stop() + with self.assertRaises(ValueError): + # Make sure all tasks are done and .join won't block. + log_queue.task_done() + ZERO = datetime.timedelta(0) diff --git a/Misc/NEWS.d/next/Library/2019-05-06-18-28-38.bpo-36813.NXD0KZ.rst b/Misc/NEWS.d/next/Library/2019-05-06-18-28-38.bpo-36813.NXD0KZ.rst new file mode 100644 index 000000000000..e89358aa4051 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2019-05-06-18-28-38.bpo-36813.NXD0KZ.rst @@ -0,0 +1,2 @@ +Fix :class:`~logging.handlers.QueueListener` to call ``queue.task_done()`` +upon stopping. Patch by Bar Harel.