Django: How to run a function when server exits?

Question

I am writing a Django project where several processes are opened using Popen. Right now, when the server exits, these processes are orphaned. I have a function to terminate these processes, and I wish to organise it so that this function is called automatically when the server quits.

Any help would be greatly appreciated.

Answer 1

Since you haven't specified which HTTP server you are using (uWSGI, nginx, apache etc.), you can test this recipe out on a simple dev server.

What you can try is to register a cleanup function via atexit module that will be called at process termination. You can do this easily by overriding django's builtin runserver command.

Create a file named runserver.py and put that in $PATH_TO_YOUR_APP/management/commands/ directory.

Assuming PROCESSES_TO_KILL is a global list holding references to orphan processes that will be killed upon server termination.

import atexit
import signal
import sys

from django.core.management.commands.runserver import BaseRunserverCommand

class NewRunserverCommand(BaseRunserverCommand):
    def __init__(self, *args, **kwargs):
        atexit.register(self._exit)
        signal.signal(signal.SIGINT, self._handle_SIGINT)
        super(Command, self).__init__(*args, **kwargs)

    def _exit(self):
        for process in PROCESSES_TO_KILL:
            process.terminate()

    def _handle_SIGINT(signal, frame):
        self._exit()
        sys.exit(0)

Just be aware that this works great for normal termination of the script, but it won't get called in all cases (e.g. fatal internal errors).

Hope this helps.