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GeezerVison is showing github.com — gh-139462: Make the ProcessPoolExecutor BrokenProcessPool exception report which child process terminated by jberg5 · Pull Request #139486 · python/cpython

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@jberg5

@jberg5 jberg5 commented Oct 1, 2025 •
edited by bedevere-app Bot
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See #139462 for more context.

Short summary: prior to this change, if a child process segfaulted when running in a concurrent.futures.ProcessPoolExecutor, the user would get a BrokenProcessPool exception with no information about which child process terminated or why.

In order to improve the debugging experience, this change attempts to report which child process terminated and with what exit code. For instance, if I have a worker process that segfaults, I'll now see something like:

Lib.concurrent.futures.process._RemoteTraceback: Process 48939 terminated abruptly with exit code -11

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
...
Lib.concurrent.futures.process.BrokenProcessPool: A process in the process pool was terminated abruptly while the future was running or pending.
  • Issue: Hard to debug subprocess crashes when using concurrent.futures.ProcessPoolExecutor #139462

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@jberg5
Report which process terminated as cause of BPE
e9c07b5
@bedevere-app

bedevere-app Bot commented Oct 1, 2025

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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@python-cla-bot

python-cla-bot Bot commented Oct 1, 2025 •
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@bedevere-app bedevere-app Bot added the awaiting review label Oct 1, 2025
@bedevere-app bedevere-app Bot mentioned this pull request Oct 1, 2025
Hard to debug subprocess crashes when using concurrent.futures.ProcessPoolExecutor #139462
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@gpshead gpshead self-assigned this Oct 1, 2025
gpshead
gpshead reviewed Oct 1, 2025
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Comment thread Lib/concurrent/futures/process.py Resolved

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ZeroIntensity
ZeroIntensity reviewed Oct 1, 2025
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Per the bot, please add a news entry, and please also update the "What's New in Python 3.15" document.

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Comment thread Lib/concurrent/futures/process.py Resolved

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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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@jberg5
PR feedback
0ece422
@bedevere-app

bedevere-app Bot commented Oct 2, 2025

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.
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jberg5 added 2 commits October 2, 2025 22:30
@jberg5
Add a NEWS entry
c8fc9de
@jberg5
Add to whats new in python
f81efde
@jberg5
jberg5 requested a review from AA-Turner as a code owner October 2, 2025 21:39
jberg5 added 2 commits October 2, 2025 22:48
@jberg5
merge
c86be73
@jberg5
add back hack to get merge conflict checker to pass
206dfc4
ZeroIntensity
ZeroIntensity reviewed Oct 2, 2025
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Just down to docs nitpicks for me. The rest looks good.

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Comment thread Doc/whatsnew/3.15.rst Resolved

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Comment thread Misc/NEWS.d/next/Library/2025-10-02-22-29-00.gh-issue-139462.VZXUHe.rst Resolved

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@jberg5

jberg5 commented Oct 2, 2025

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There was a fun issue where the precommit merge conflict checker thought that a perfectly legitimate string was a problem:

check for merge conflicts................................................Failed
Doc/whatsnew/3.15.rst:680: Merge conflict string '=======' found

I removed one of the = and it was happy again :) (and then added it back after)
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@jberg5
PR comments for docs
d80ebf1
@jberg5

jberg5 commented Oct 2, 2025

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Thanks @ZeroIntensity, appreciate all the feedback!
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ZeroIntensity
ZeroIntensity approved these changes Oct 2, 2025
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Thanks, this looks good to me. I'll wait for @gpshead as the multiprocessing expert to decide on the weird triple-quotes in the message.

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting review labels Oct 2, 2025
@ZeroIntensity

ZeroIntensity commented Oct 2, 2025

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Hmm, something seems to be causing the tests to hang.
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ZeroIntensity
ZeroIntensity reviewed Oct 2, 2025
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Comment thread Lib/test/test_concurrent_futures/test_process_pool.py Resolved

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@jberg5
Simplify tests slightly and try fresh pool
a5d3266
@jberg5

jberg5 commented Oct 6, 2025

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Hi @ZeroIntensity and @gpshead! Tests are passing, let me know if there are any other changes you'd like me to make, or if this is good to go.
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YvesDup
YvesDup reviewed Oct 7, 2025
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Comment thread Lib/concurrent/futures/process.py Resolved

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@jberg5
better comment
208ea75
@jberg5
jberg5 requested a review from gpshead October 8, 2025 20:22
@jberg5

jberg5 commented Oct 14, 2025

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@AA-Turner @ZeroIntensity @gpshead thanks for all the feedback thus far! Let me know if there's anything else you'd like me to change here.
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@gpshead
Merge branch 'main' into jb-139462
5e04081
@gpshead
gpshead enabled auto-merge (squash) November 11, 2025 21:49
@gpshead
gpshead merged commit 9e7340c into python:main Nov 11, 2025
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@bedevere-app bedevere-app Bot removed the awaiting merge label Nov 11, 2025
@jberg5
jberg5 deleted the jb-139462 branch November 11, 2025 22:11
StanFromIreland pushed a commit to StanFromIreland/cpython that referenced this pull request Dec 6, 2025
@jberg5 @StanFromIreland
pythongh-139462: Make the ProcessPoolExecutor BrokenProcessPool excep…
76a1b47 
…tion report which child process terminated (pythonGH-139486)

Report which process terminated as cause of BPE
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Reviewers

@ZeroIntensity ZeroIntensity ZeroIntensity approved these changes
@AA-Turner AA-Turner Awaiting requested review from AA-Turner AA-Turner is a code owner
@gpshead gpshead Awaiting requested review from gpshead
+1 more reviewer
@YvesDup YvesDup YvesDup left review comments
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4 participants

@jberg5 @ZeroIntensity @gpshead @YvesDup
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