Balancer: IP Hash
The IP Hash load balancer module distributes the incoming requests among the upstreams based on the IP address of the client. This method guarantees that the client request will always be transferred to the same server.
In case one of the back-end servers were detected as inoperative, it would be disabled for a period of time. After this safety time, it would be reactivated. Meanwhile, the requests that would have normally targeted the off-lined server would be delivered to another one.
The only thing needed to configure this balancer is a list of information sources. At least one must be selected in order for this to work.