runserver child started via autoreload won't always exit cleanly

[santtu]

When using django.utils.autoreload (for example, runserver with use_reloader option enabled) it is possible to get into a situation where you might think the server has been killed, but actually is not and is listening to the port.

Steps to reproduce:

1. Start application, when use_reloader is enabled (manage.py runserver)
2. Search for a pair of the manage.py processes (ps -aef --forest | grep runserver etc.), make a note of which is the parent and which is the child
3. Kill the parent using command-line kill "kill -INT <parent pid>"
4. Look at ps output, and you'll find the child still alive, and via lsof -i | grep LISTEN you can see it is still listening on the server port.

Normally if you use runserver from a terminal, pressing control-C will send SIGINT to the whole foreground process group. Both the parent and child will thus receive SIGINT and will exit cleanly.

If you however kill the *parent* only, the child will not receive any signal, and thus will happily keep running.

This is a bit of a bummer when doing test automation, which tries to clean up the test environment by killing the parent -- but the child won't go away, and keeping server port reserved.

It is possible to do a semi-work-around by spawning runserver in its own process group, but it requires some careful environment crafting (and I haven't been able to get it reliably working on macos -- there are apparently some semantic differences in setpgrp wrt/ linux and macos). And of course is hardly obvious for anyone encountering this problem for the first time.

I have a patch for this and I'll make a pull request and link to that when I have a ticket id..

[anonymous]

BTW, there is also another obvious work-around when doing test automation: disable autoreloader.

[santtu]

Here's the pull request: ​https://github.com/django/django/pull/448

[Ramiro Morales]

#16982 was closed as duplicate of this one.

Feedback about how things work on Mac OS X and Windows once the PR has been applied is welcome.

[fabiofz@…]

This patch doesn't seem to work on windows.

On a quick search I found: ​http://danielkaes.wordpress.com/2009/06/04/how-to-catch-kill-events-with-python/ (the last comment implies that killing a process with the task manager in windows will kill all threads, giving no further chance to actually treat the exception, in which case, a signal-based approach won't work on windows).

[Tim Graham]

Setting patch needs improvement since it doesn't work on Windows according to the previous comment.

[Tim Graham]

I think we should focus on gunicorn integration (#21978) rather than what seems to be an obscure issue.

Actually, I think this may be fixed by #21773.