[New-bugs-announce] [issue42769] concurrent.futures.ProcessPoolExecutor is unable to forward exceptions with state.

[Damien Levac]

New submission from Damien Levac <damien.levac at gmail.com>:

When running tasks on a `ProcessPoolExecutor`, exceptions raised by the dispatched function should be pickled and accessible to the parent process through the `Future.exception` method.

On Python 3.9.1 (Linux ryzen3950x 5.4.0-58-generic #64-Ubuntu SMP Wed Dec 9 08:16:25 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux) the behavior works with exceptions which are stateless but not if they hold state.

I suspect it is related to the multiprocessing/pickle bug mentioned in the release notes to 3.9.1 but I didn't dig much deeper.

Let me know if I can assist in any way or if any pertinent information is missing: it is my first time reporting a bug here :)

Thank you for your hard work!

----------
components: Library (Lib)
files: repro.py
messages: 383903
nosy: damien.levac
priority: normal
severity: normal
status: open
title: concurrent.futures.ProcessPoolExecutor is unable to forward exceptions with state.
type: behavior
versions: Python 3.9
Added file: https://bugs.python.org/file49703/repro.py

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue42769>
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