Dan, > On Jun 18, 2024, at 09:44, Dan Shelton via Cygwin <cygwin@cygwin.com> wrote: > > On Mon, 17 Jun 2024 at 18:03, Dale Lobb (Sys Admin) via Cygwin > <cygwin@cygwin.com> wrote: >> >> Greetings, Nicholas; >> >>> From: Cygwin <cygwin-bounces+dale.lobb=bryanhealth....@cygwin.com> On >>> Behalf Of Andrey Repin via Cygwin >>> Sent: Monday, June 17, 2024 2:58 AM >>> To: Nicholas Williams <nicholas.willi...@zaxiom.com>; cygwin@cygwin.com >>> Cc: Andrey Repin <anrdae...@yandex.ru> >>> Subject: EXTERNAL SENDER: Re: Cygwin outputting message to stderr on dofork >>> EAGAIN failure even when Python exception is caught and handled >>> >>> Greetings, Nicholas Williams! > 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 >>> >>> Greetings, Nicholas Williams! >>> >>>> 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] > > Does python require fork(), or can it use posix_spawn() in this case?
I imagine this would be question for the CPython development team. While I have a basic understanding of C programming in Python (for the purposes of writing extensions), I do not know why subprocess.Popen is written in this way, and I do not know enough to question their choice here. It uses fork, and for now I have to live with that. Thanks, Nick -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
