Author: Falko Timme <ft [at] falkotimme [dot] com>
Last edited 05/26/2007
Since Apache 2.1, a new module called mod_proxy_balancer is available which lets you turn a system that has Apache installed into a loadbalancer. This loadbalancer retrieves requested pages from two or more backend webservers and delivers them to the user’s computer. Users get the impression that they deal with just one server (the loadbalancer) when in fact there are multiple systems behind the loadbalancer that process the users’ requests. By using a loadbalancer, you can lower the load average on your webservers. One important feature of mod_proxy_balancer is that it can keep track of sessions which means that a single user always deals with the same backend webserver. Most websites are database-driven nowadays with user logins etc., and you’d get weird results if a user logs in on one backend webserver, and then his next request goes to another backend webserver, meaning he’d get logged out again. You can avoid this by using mod_proxy_balancer’s session-awareness.