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Ubuntu Server Setup Part 9 - Setup a Reverse Proxy with Nginx

16 Jun 2019

In the previous part we covered how to set-up Nginx as a web server to serve static content. In this part, we will configure Nginx as a reverse proxy (one of the main other use cases) to be able to access other services running locally on your server without opening up a dedicated port.

What is a Reverse Proxy?

A reverse proxy can be thought of as a simple ‘passthrough’, whereby specific requests made to your web server get routed to other applications running locally and their responses returned as though they were all handled by the one server. For example, you wanted to give public access to a Python server you have running on port 8080. Instead of directly opening up the port and thus increasing the overall attack surface, Nginx can be configured to proxy certain requests to that server instead. This also has the advantage of easily enabling HTTPS for all services without having to configure each application separately and you get all the other advantages of a high performance web server like load balancing etc.

Follow the steps in the previous tutorial to setup Nginx and also optionally enable HTTPS. The rest of this part assumes you have another server running on your machine listening on localhost under port 8080.

Configure NGINX

Open up the main configuration file for your site:

$ sudo nano /etc/nginx/sites-available/yourdomain.com

server {
  listen 80;
  listen [::]:80;

  server_name yourdomain.com;

  location /otherapp {
      proxy_pass http://localhost:8080/;
  }
}

The proxy_pass directive is what makes this configuration a reverse proxy. It specifies that all requests which match the location block (in this case the root /otherapp path) should be forwarded to port 8080 on localhost, where our other app is running.

Test the new configuration to see if there are any errors

$ sudo nginx -t

If there are no errors present, reload the Nginx config

$ sudo nginx -s reload

In a browser, navigate to your main public domain and append /otherapp to the end e.g. http://yourdomain.com/otherapp. Because the URL matches the location element in the config above, Nginx will forward the request to our other server running on port 8080.

Additional Options

For basic applications, the main proxy_pass directive should work just fine. However, as you would expect, Nginx offers a number of other options to further configure the behaviour of the reverse proxy.

In the below configuration, proxy buffering is switched off - this means that the request body will be forwarded to the proxied server immediately as it is received, which can be useful for some real-time apps. A custom header X-Original-IP is also set on the forwarded request, containing the IP from the original request (which can then be picked up by the other server as needed).

location /otherapp {
    proxy_pass http://localhost:8080/;
    proxy_buffering off;
    proxy_set_header X-Original-IP $remote_addr;
}

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