Although HAProxy has several prominent features, this article focuses on how to setup HAProxy to “proxy” your web application.

Installing HAProxy

Since Ubuntu 14.04 does not ship with HAProxy 1.5 (latest stable release at time of writing), we will have to use a PPA to be able to install it using apt-get:

add-apt-repository ppa:vbernat/haproxy-1.5

Next, update the system:

apt-get update
apt-get dist-upgrade

Now install HAProxy with the following command:

apt-get install haproxy

If everything is successful, then you have finished installing HAProxy and can proceed to the next step.

Configuring HAProxy

The HA Proxy configuration file is split up into two sections – “global”, and “proxies”. One deals with process-wide configuration, while the other consists of default configuration, frontend, and backend sections.

Global Section

With your favorite text editor, open /etc/haproxy/haproxy.cfg and you will notice the predefined sections: “global” and “defaults”. The first thing that you may want to do is increase the maxconn to a reasonable size, as this affects the connections that HAProxy allows. Too many connections may cause your web service to crash due to many requests. You will need to adjust the size to see what works for you. In the global section, add or change maxconn to 3072.

In the default section, add the following lines under mode http:

option forwardfor
option http-server-close

This will add X-Forwarded-For headers to each request, as well as reduce the latency between HAProxy and to preserve client persistent connections.

Proxies Section

Frontend and Backend

Commonly, the first thing when it comes to using is to setup a frontend to handle HTTP connections. Add the following:

frontend http-frontend
    bind public_ip:80
    reqadd X-Forwarded-Proto:\ http
    default_backend wwwbackend

Note: Be sure to replace public_ip with your domain or your public ip. Otherwise, this entire setup will not work.

After you have finished configuring the frontend, you can now add your backend by adding the following lines to the end of your configuration:

backend wwwbackend
    server 1-www private_ip_1:80 check
    server 2-www private_ip_2:80 check
    server 3-www private_ip_3:80 check

The backend configuration used here creates a connection named X-www to private_ip_X:80 (Replace X with 1 – 3. and replace private_ip_X with your private or public ip). This will allow you to load balance between each server set (assuming you have more than one server). The check option makes the load balancer perform health checks on the server.

When you are done, save the configuration file, then restart HAProxy by running:

service haproxy restart

If everything is working, then you will be able to connect to http://public_ip/ (replacing it with your AKLWEB Host VPS IP) and view your website.