Hello,
We have a Python (installed and run through Cygwin) process running on Windows
Server 2022 that was very, very occasionally failing when
subprocess.check_output was called:
0 [main] python3 28481 dofork: child -1 - forked process 16856 died
unexpectedly, retry 0, exit code 0xC0000142, errno 11
…
subprocess.check_output(["cygpath", "-w", directory.name],
encoding="utf-8").strip()
File "/usr/lib/python3.9/subprocess.py", line 424, in check_output <>
<>return run(*popenargs, stdout=PIPE, timeout=timeout, check=True, <>
File "/usr/lib/python3.9/subprocess.py", line 505, in run <>
<>with Popen(*popenargs, **kwargs) as process: <>
File "/usr/lib/python3.9/subprocess.py", line 951, in __init__ <>
<>self._execute_child(args, executable, preexec_fn, close_fds, <>
File "/usr/lib/python3.9/subprocess.py", line 1754, in _execute_child
self.pid = _posixsubprocess.fork_exec(
BlockingIOError: [Errno 11] Resource temporarily unavailable
Setting aside for a minute the various reasons this might be happening
occasionally, which we cannot solve for at this moment, the error number
(EAGAIN) indicates that you should “try again.” So that’s exactly what we did.
We added a try/catch to the Python code to catch the BlockingIOError and, if
and only if the error number is EAGAIN, we try up to two more times. This fixed
the problem and caused the application to stop quitting. We output a warning to
our log so that we don’t forget about the problem, but the warning only ever
appears once, so retrying a single time seems to help.
However … even though Python handles the dofork error, turns it into a Python
exception, and our code catches the Python exception and handles it properly,
Cygwin (not Python … Cygwin) still outputs a message to stderr right before our
warning message. This Cygwin error message shows up as an error in our log
tracking:
0 [main] python3 15042 dofork: child -1 - forked process 6780 died
unexpectedly, retry 0, exit code 0xC0000142, errno 11
06/16 13:57:53. 87520: WARNING: Retrying command in 2 seconds due to EAGAIN:
[the command we’re running]
I’m sure there could be any number of things I might be missing, but IMO, if
the process calling dofork properly handles the error raised by dofork, Cygwin
should not be outputting an error message to stderr.
Thoughts?
Thanks,
Nick
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