running nginx/postgres with supervisord - required?

Question

In all standard django productions setup templates I've seen, gunicorn is run with supervisor, whereas nginx/postgres are not configured under supervisor.

Any reason? Is this required for a production system? If not, why not?

Answer 1

In this architecture, Gunicorn works as the application server which runs our Django code. Supervisor is just a process management utility which restarts the Gunicorn server if it crashes. The Gunicorn server may crash due to our bad code, but nginx and postgres remain intact . So in the basic config we only look after the gunicorn process through supervisor. Though we could do the same for nginx and postgres too.

Answer 2

You need supervisor for gunicorn because it's an simply server without any tools to restart it, run it at system startup, stop it at system shutdown or reload when it crashes.

Postgresql and nginx can take care of themselves in that aspect, so there is no need for them to be running under supervisor.

Actually, you can just use init.d, upstart or system.d to start, stop and restart gunicorn, supervisor is just easier way to handle such small servers like gunicorn.

Consider also that it is common to run multiple django apps on one system, and that requires multiple separated instances of gunicorn. Supervisor will handle them better than init, upstart or system.d

There is also uWSGI server that won't need supervisor, because it has built-in features to handle multiple instances, starting, stopping and also auto-reloading on code change. Look at uWSGI emperor system.