Load balancing and control for distributed World Wide Web servers

We describe an admission control and load balancing scheme for multicomputer World Wide Web servers. The scheme consists of a frontend admission control function which regulates requests sent to backend Web server using periodic load measurements passed from the backends to the frontends. The aims of scheme are two-fold: to ensure that traffic offered to backends can be serviced promptly, and to make full use of the backend capacity. We describe simulation results and an Erlang based implementation of the scheme. It is shown that the algorithm is trivial to implement, has negligible computational complexity, and provides effective load balancing and control. The scheme has now been implemented in the Eddie open source project, an Ericsson sponsored effort aimed at delivering commercial grade, quality of service driven Web server solutions.