I have a multiprocessed python application which is being run as an EXE on windows. Upon selecting to shutdown the operating system the applications throws a number of exceptions as a result of the processes being shutdown.
Is there a way to capture the system shutdown request by windows so I may handle the closure of the multiprocesses myself?
A nabble.com page suggests using win32api.SetConsoleCtrlHandler:
“I need to do something when windows shuts down, as when someone presses the power button. I believe this is a window message, WM_QUERYENDSESSION or WM_ENDSESSION. I can't find any way to trap this in python. atexit() does not work. Using the signal module to trap SIGBREAK or SIGTERM does not work either.”
You might be able to use win32api.SetConsoleCtrlHandler and catch the CTRL_SHUTDOWN_EVENT that's sent to the console.
Also see Python windows shutdown events, which says, “When using win32api.setConsoleCtrlHandler() I'm able to receive shutdown/logoff/etc events from Windows, and cleanly shut down my app” etc.
Related
I run ffmpeg from python script and need to shutdown recording on demand.
In Linux I just send SIGTERM. But in Windows as I understand SIGTERM replaced by SIGKILL so records needs to be remixed to play properly.
After googling I found that I should use CTRL_BREAK_EVENT but this signal terminate my parent script too.
What should I use?
I have a Python app that uses websockets and gevent. It's quite a big application in my personal experience.
I've encountered a problem with it: when I run it on Windows (with 'pipenv run python myapp'), it can (suddenly but very rarily) freeze, and stop accepting messages. If I then enter CTRL+C in cmd, it starts reacting to all the messages, that were issued when it was hanging.
I understand, that it might block somewhere, but I don't know how to debug theses types of errors, because I don't see anything in the code, that could do it. And it happens very rarily on completely different stages of the application's runtime.
What is the best way to debug it? And to actually see what goes behind the scenes? My logs show no indication of a problem.
Could it be an error with cmd and not my app?
Your answer may be as simple as adding timeouts to some of your spawns or gevent calls. Gevent is still single threaded, and so if an IO bound resource hangs, it can't context switch until it's been received. Setting a timeout might help bypass these issues and move your app forward?
I am using a custom Django runserver command that is supposed to run a bunch of cleanup functions upon termination. This works fine as long as I don't use the autoreloader: by server catches the KeyboardInterrupt exception properly and exits gracefully.
However, if I use Django's autoreloader, the reloader seems to simply kill the server thread without properly terminating it (as far as I can tell, it doesn't have any means to do this).
This seems inherently unsafe, so I can't really believe that there's not a better way of handling this.
Can I somehow use the autoreloader functionality without having my server thread be killed uncleanly?
Try using the atexit module to catch the termination. It should work for everything which acts like SIGINT or SIGTERM, SIGKILL cannot be interrupted (but should not be sent by any auto-restart script without sending SIGTERM before).
I would like to attach gdb to a dying process, because the program runs in production and I need to debug it there, if I open the program with gdb it slows down and the computers are not that great. I tried to catch signals in the application and attach gdb there but it just works if I send them signals myself. When the program stalls (multi-threaded program, and the main thread gets a deadlock or somehow gets stuck (or apparently stuck)), and the user forces it to quit in the Desktop Environment (LXDE), I can't catch no signal. The program is all python with PySide for the graphical interface. Just care about linux.
My idea is to create a kernel driver and try too hook process termination or signals sending in there but since it would be much of a hassle I would like to ask if there is some tool for this kind of thing or some information that I could make use of. Thanks.
There might be a way to do what you want, but if you can't perhaps it would be sufficient to freeze the program and inspect its memory image?
Enable core dump file generation before it starts, and then once the process is hosed, terminate it with kill. Then use gdb to open the core file and analyze what was happening.
I'm working on a project that spins off several long-running workers as processes. Child workers catch SIGINT and clean up after themselves - based on my research, this is considered a best practice, and works as expected when terminating scripts.
I am actively developing this project, which means that I am regularly testing changes in the interpreter. When I'm working in an interpreter, I often hit CTRL+C to clear currently written text and get a fresh prompt. Unfortunately, if I do this while a subprocess is running, SIGINT is sent to that worker, causing it to terminate.
Is there a solution to this problem other than "never hit CTRL+C in your interpreter"?
One option is to set a variable (e.g. environment variable, commandline option) when debugging.