The HTTP Load Balancer is a web server plug-in that accepts HTTP and HTTPS requests and distributes them to application server instances in a cluster. This allows the HTTP Binding Component to be scaled horizontally, running on multiple instances in a Sun Java System Application Server cluster.
The advantages of clustering are many:
Increases overall system throughput by distributing workload among multiple physical machines
Servers with different hardware capacities can have the work load distributed in favor of more powerful hosts
In the event that one particular application server instance is overloaded or becomes unavailable, requests can be re-routed to the least loaded application server instances
Clustering is invisible to the client. As far as the client is concerned, all HTTP requests are directed to the web server instance where the load balancer is configured
The HTTP Load Balancer includes the following features:
Sticky Round Robin load balancing algorithm
Support for multiple clusters
Configurable health failover capability (less than 30ms)
Checks and reloads for dynamic changes made to the load balancer configuration
Support for quiescence - enabling rolling web service upgrades
Automatic retry of failed requests for idempotent URLs
Configurable error pages