HowtoMatrix

This article explains how to set up a two-node load balancer in an active/passive configuration with HAProxy
and heartbeat on Debian Lenny. The load balancer sits between the user
and two (or more) backend Apache web servers that hold the same
content. Not only does the load balancer distribute the requests to the
two backend Apache servers, it also checks the health of the backend
servers. If one of them is down, all requests will automatically be
redirected to the remaining backend server. In addition to that, the
two load balancer nodes monitor each other using heartbeat, and if the
master fails, the slave becomes the master, which means the users will
not notice any disruption of the service. HAProxy is session-aware,
which means you can use it with any web application that makes use of
sessions (such as forums, shopping carts, etc.).

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