The traffic load/availability related to a website is a major concern that requires a load balancer. That can be deployed in form of an appliance, service or software. The software format is usually the one that has free open source options like Nginx, Stunnel and Pound.

The demo is about Pound, that is available under GPL license (free to use, copy and distribute, but with no warranty nor tech support). Unlike Apache and Nginx, it does not perform as HTTP server so this makes it possible to be a very light software with simple configuration.
Pound knows which servers are up from keepalive messages so it can distribute the HTTP(S) requests among them. In case of a basic configuration, there´s no priority for any backend server and the default predictor will be random.

During the demo a user requires a content via an application virtual IP on port 8082 and this request is answered by Pound that has this service/port on listening mode. It then forward this request to a web server via port 80. Just after the content is delivered back to Pound it redirects that to the client. In other words, Pound acts as a reverse proxy distributing the requests among the backend server isolating them from the client.

No favicon was included in the application so this request will return a 404 status. But all other content (PHP) reaches its way to the client thanks to Pound. Wireshark could check the distribution randomness that Pound performed.

Requests from client to index.php: (10 in sum):

• Requests from Pound to server 1: 5 (50%)
• Requests from Pound to server 2: 1 (10%)
• Requests from Pound to server 3: 4 (40%)

Requests from client to registros.php (12 in sum):

• Requests from Pound to server 1: 3 (25%)
• Requests from Pound to server 2: 3 (25%)
• Requests from Pound to server 3: 6 (50%)

In general Pound is deployed very rapidly and has also very easy configuration.
 

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