[How To] Using NGinx as a Load Balancer

NGinx is an asynchronous event-driven web-server which has become immensely popular in recent years for its performance advantages. NGinx can be used is a reverse proxy to load balance HTTP requests among back-end servers. Here is how this can be achieved on a standard Ubuntu server:

Setup

                                                         ------------------------------
                                              |----------|  Back-end Server 1 (BES1)  |
                                              |          ------------------------------
             ----------------------           |
  Internet   |  Front-end server  |-----------'          ------------------------------
-------------|   Running NGinx    |----------------------|  Back-end Server 2 (BES2)  |
             |       (FES)        |------------          ------------------------------
             ----------------------           |
                                              |          ------------------------------
                                              '----------|  Back-end Server 3 (BES3)  |
                                                         ------------------------------

In this sample setup, we have a front-end server (FES) on which NGinx is installed and listens on the external interface. We have three back-end servers (BES1, BES2 and BES3) on which our web-application is hosted using any standard HTTP server which listens on the internal interface. Now the front-end server is configured to forward the HTTP requests on the external interface to the three back-end servers, hence acting as a reverse proxy cum HTTP load balancer.

• Front-end server (FES)

  NIC1-> eth0 with public IP xxx.xxx.xxx.xxx
  NIC2-> eth1 with internal IP 192.168.1.2
  Runs NGinx listening on xxx.xxx.xxx.xxx:80

• Back-end server 1 (BES1)

  NIC1-> eth1 with internal IP 192.168.1.3
  Runs any http server (Eg: apache2) listening on 192.168.1.3:8080

• Back-end server 2 (BES2)

  NIC1-> eth1 with internal IP 192.168.1.4
  Runs any http server (Eg: apache2) listening on 192.168.1.4:8080

• Back-end server 3 (BES3)

  NIC1-> eth1 with internal IP 192.168.1.5
  Runs any http server (Eg: apache2) listening on 192.168.1.5:8080

Configuration

1. Install NGinx on the front-end server (FES):

   apt-get install nginx
   

2. Edit the file /etc/nginx/sites-enabled/default to look like the following:

   upstream lb_units {
         server 192.168.1.3:8080 weight=10 max_fails=3 fail_timeout=30s; # Reverse proxy to  BES1
         server 192.168.1.4:8080 weight=10 max_fails=3 fail_timeout=30s; # Reverse proxy to  BES2
         server 192.168.1.5:8080 weight=10 max_fails=3 fail_timeout=30s; # Reverse proxy to  BES3
   }
   server {
    listen xxx.xxx.xxx.xxx:80; # Listen on the external interface
    server_name  my.domain-name.com; # The server name
    access_log  /var/log/nginx/nginx.access.log;
    error_log  /var/log/nginx/nginx_error.log debug;
    location / {
     proxy_pass         http://lb_units; # Load balance the URL location "/" to the upstream lb_units
    }
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
     root   /var/www/nginx-default;
    }
   }
   

3. Reload NGinx

   /etc/init.d/nginx reload
   

Thats it, now my.domain-name.com is load balanced using FES on to the back-end servers BES1, BES2 and BES3.

Hope this “How To” was helpful.