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Run subprocess-starting tests on separate runners#30278

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jkseppan wants to merge 6 commits into
matplotlib:mainfrom
jkseppan:separate-subprocess-test-runners
Closed

Run subprocess-starting tests on separate runners#30278
jkseppan wants to merge 6 commits into
matplotlib:mainfrom
jkseppan:separate-subprocess-test-runners

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@jkseppan

@jkseppan jkseppan commented Jul 9, 2025

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I suspect that we are running out of process IDs, or the scheduler
is not letting all subprocesses execute, leading to timeouts in
tests that start subprocesses when other long-running tests are
executing. This happens often with Python 3.14 tests for some reason.

Add a new pytest marker for the tests that start a subprocess at
top level, and run these tests in separate runners without
pytest-xdist parallelization.

I suspect that we are running out of process IDs, or the scheduler
is not letting all subprocesses execute, leading to timeouts in
tests that start subprocesses when other long-running tests are
executing. This happens often with Python 3.14 tests for some reason.

Add a new pytest marker for the tests that start a subprocess at
top level, and run these tests in separate runners without
pytest-xdist parallelization.
jkseppan added 5 commits July 9, 2025 11:10
- set PYTHONUNBUFFERED=1 to make the subprocess Python unbuffered
- set bufsize=0 making the parent process pipe unbuffered
- because that can return short reads, check if the subprocess
  exited, and if not, yield the CPU
- set stdin to DEVNULL and stderr to STDOUT to avoid blocking
  related to those
@QuLogic

QuLogic commented Jun 20, 2026

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Our timeouts are mostly fixed now.

@QuLogic QuLogic closed this Jun 20, 2026
@QuLogic

QuLogic commented Jun 20, 2026

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Our timeouts are mostly fixed now.

@QuLogic QuLogic reopened this Jun 20, 2026
@QuLogic QuLogic closed this Jun 20, 2026
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2 participants