Supervisor is a monitoring tool that can monitor your processes. It can restart the process if the process dies or gets killed for some reason.

In production, I use gunicorn as web server. I started a gunicorn process as a daemon and logged out from the server. My site ran as expected for few days. All of a sudden, we started getting ‘502 Bad Gateway’ and I had no idea why. I had to ssh to the server to find out what went wrong. After ps aux | grep gunicorn, I found out gunicorn wasn’t running anymore. My gunicorn process died on its own, and I had no idea when and why. Had I used supervisor, supervisor would have been controlling the gunicorn process. It must have recieved a signal when gunicorn died and it would have created a new gunicorn process in such scenario. And my site would have kept running as expected.

Read More: https://www.agiliq.com/blog/2014/05/supervisor-with-django-and-gunicorn/