What is gunicorn.sock?

Question

I am a newbie following the gunicorn-django tutorial by Michal Karzynski. I am using Django 1.7.4 on Ubuntu 14 and my setup for the gunicorn script is as follows

#!/bin/bash

NAME="mytestapp"                                  # Name of the application
DJANGODIR=/var/www/testapp/src             # Django project directory
SOCKFILE=/var/www/testapp/run/gunicorn.sock  # we will communicte using this unix socket
USER=ubuntu                                        # the user to run as
GROUP=ubuntu                                     # the group to run as
NUM_WORKERS=3                                     # how many worker processes should Gunicorn spawn
DJANGO_SETTINGS_MODULE=testapp.settings             # which settings file should Django use
DJANGO_WSGI_MODULE=testapp.wsgi                     # WSGI module name

echo "Starting $NAME as `whoami`"

# Activate the virtual environment
cd $DJANGODIR
export DJANGO_SETTINGS_MODULE=$DJANGO_SETTINGS_MODULE
export PYTHONPATH=$DJANGODIR:$PYTHONPATH

# Create the run directory if it doesn't exist
RUNDIR=$(dirname $SOCKFILE)
test -d $RUNDIR || mkdir -p $RUNDIR

# Start your Django Unicorn
# Programs meant to be run under supervisor should not daemonize themselves (do not use --daemon)
exec gunicorn ${DJANGO_WSGI_MODULE}:application \
  --name $NAME \
  --workers $NUM_WORKERS \
  --user=$USER --group=$GROUP \
  --bind=0.0.0.0:8000 \
  --log-level=debug \
  --log-file=-

When I change the bind setting to unix:$SOCKFILE, my script still runs but I am unable to connect with my browser. In this question I have read that it's not wise to deploy 0.0.0.0:8000 on a production server.

I know a bit about unix sockets, but I don't know understand how I can use the unix socket file to serve my site. I have tried to edit the socket file as the superuser, but the OS doesn't let me open it.

How can I setup the socket file to allow me to serve my pages?

PS: Here is my nginx configuration file

upstream hello_app_server {
# fail_timeout=0 means we always retry an upstream even if it failed
# to return a good HTTP response (in case the Unicorn master nukes a
# single worker for timing out).

server 127.0.0.1:8000 fail_timeout=0;
} 

server {

    listen   80;
    server_name test.com;

    client_max_body_size 4G;

    access_log /var/www/testapp/src/logs/nginx-access.log;
    error_log /var/www/testapp/src/logs/nginx-error.log;

    location /static/ {
        alias   /var/www/testapp/src/static/static_dirs/;
    }

    location /media/ {
        alias   /var/www/testapp/src/static/media/;
    }

    location / {
        # an HTTP header important enough to have its own Wikipedia entry:
        #   http://en.wikipedia.org/wiki/X-Forwarded-For
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

        # enable this if and only if you use HTTPS, this helps Rack
        # set the proper protocol for doing redirects:
        # proxy_set_header X-Forwarded-Proto https;

        # pass the Host: header from the client right along so redirects
        # can be set properly within the Rack application
        proxy_set_header Host $http_host;

        # we don't want nginx trying to do something clever with
        # redirects, we set the Host: header above already.
        proxy_redirect off;

        # set "proxy_buffering off" *only* for Rainbows! when doing
        # Comet/long-poll stuff.  It's also safe to set if you're
        # using only serving fast clients with Unicorn + nginx.
        # Otherwise you _want_ nginx to buffer responses to slow
        # clients, really.
        # proxy_buffering off;

        # Try to serve static files from nginx, no point in making an
        # *application* server like Unicorn/Rainbows! serve static files.

        if (!-f $request_filename) {
            proxy_pass http://hello_app_server;
            break;
        }

    }

    # Error pages
    error_page 500 502 503 504 /500.html;
    location = /500.html {
        root /var/www/testapp/src/static/;
    }
}

Answer 1

You're supposed to use a reverse proxy like nginx to sit in front of gunicorn, and that's what actually serves your site. They communicate via the socket.

The gunicorn docs have a sample nginx configuration which does exactly that, although obviously you should make the sockfile match what you've put in your gunicorn config.