This is the final part of my tutorial on Flask Server Deployment. In the last section we configured our Gunicorn WSGI server and controlled it via Supervisor. In this section we will place our WSGI server behind a Proxy server.

Content of this Tutorial

• Part 1: Choosing the right webservice provider
• Part 2: Flask Development Server
• Part 3: Gunicorn WSGI Server
• Part 4: Nginx Proxy Server

Why use a Proxy Server

This is the question I asked me first when I read in the Gunicorn documentation that one should put the Gunicorn application server behind a proxy. Mainly the main advantages of a proxy seem to be:

• you can run more than one WSGI server with different web applications and assign them to individual routes or ports
• the proxy takes care of static content while the WSGI server handles the dynamic stuff
• it frees your Gunicorn server from serving slow clients

The guys from Gunicorn recommend Nginx as a proxy so I decided to follow this recommendation. One could also use Apache here.

Install and configure Nginx

We install Nginx via apt-get:

apt-get install nginx

The configuration happens mainly via the /etc/nginx/nginx.conf file. We open it with our editor and add our server configuration:

server {
    listen 80;

    server_name _;

    access_log  /var/log/nginx/flaskapp.log;
    error_log  /var/log/nginx/flaskapp_err.log;

    location / {
        proxy_pass         http://127.0.0.1:8000/;
        proxy_redirect     off;

        proxy_set_header   Host             $host;
        proxy_set_header   X-Real-IP        $remote_addr;
        proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
    }
}

What we do now is listen on port 80 for any requests. Those requests are passed on to port 8000 of our localhost. This is where our Gunicorn server will serve our flasktest app. The proxy_set_header directives are used to rewrite the headers so that our application works behind a proxy. Before we start of with our new proxy configuration make sure you changed the port in our Gunicorn startup script /home/apps/run_flaskapp.py from 80 to 8000 and restart it with

supervisorctl restart flasktest

Now we restart our nginx server:

service nginx restart

Now we will see our "Hello World" statement served from a WSGI application server behind a proxy.

Useful Links

• Gunicorn Documentation - Deploying Gunicorn: Comprehensive documentation with an example Nginx config file
• Flask Documentation - Proxy Setups