[openstack-dev] [all] [designate] [heat] [python3] deadlock with eventlet and ThreadPoolExecutor in py3.7

Joshua Harlow harlowja at fastmail.com
Wed Jul 25 16:54:00 UTC 2018

Have you tried the following instead of threadpoolexecutor (which 
honestly should work as well, even under eventlet + eventlet patching).


If you have the ability to specify which executor your code is using, 
and you are running under eventlet I'd give preference to the green 
thread pool executor under that situation (and if not running under 
eventlet then prefer the threadpool executor variant).

As for @tomoto question; honestly openstack was created before asyncio 
was a thing so that was a reason and assuming eventlet patching is 
actually working then all the existing stdlib stuff should keep on 
working under eventlet (including concurrent.futures); otherwise 
eventlet.monkey_patch isn't working and that's breaking the eventlet 
api. If their contract is that only certain things work when monkey 
patched, that's fair, but that needs to be documented somewhere 
(honestly it's time imho to get the hell off eventlet everywhere but 
that likely requires rewrites of a lot of things, oops...).


Corey Bryant wrote:
> Hi All,
> I'm trying to add Py3 packaging support for Ubuntu Rocky and while there
> are a lot of issues involved with supporting Py3.7, this is one of the
> big ones that I could use a hand with.
> With py3.7, there's a deadlock when eventlet monkeypatch of stdlib
> thread modules is combined with use of ThreadPoolExecutor. I know this
> affects at least designate. The same or similar also affects heat
> (though I've not dug into the code the traceback after canceling tests
> matches that seen with designate). And it may affect other projects that
> I haven't touched yet.
> How to recreate [1]:
> * designate: Add a tox.ini py37 target and run
> designate.tests.test_workers.test_processing.TestProcessingExecutor.test_execute_multiple_tasks
> * heat: Add a tox.ini py37 target and run tests
> * general: Run bpo34173-recreate.py
> <https://bugs.python.org/file47709/bpo34173-recreate.py> from issue
> 34173 (see below).
> [1] ubuntu cosmic has py3.7
> In issue 508 (see below) @tomoto asks "Eventlet and asyncio solve same
> problem. Why would you want concurrent.futures and eventlet in same
> application?"
> I told @tomoto that I'd seek input to that question from upstream. I
> know there've been efforts to move away from eventlet but I just don't
> have the knowledge to  provide a good answer to him.
> Here are the bugs/issues I currently have open for this:
> https://github.com/eventlet/eventlet/issues/508
> <https://github.com/eventlet/eventlet/issues/508>
> https://bugs.launchpad.net/designate/+bug/1782647
> <https://bugs.launchpad.net/designate/+bug/1782647>
> https://bugs.python.org/issue34173 <https://bugs.python.org/issue34173>
> Any help with this would be greatly appreciated!
> Thanks,
> Corey
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