Request rate adaptive dispatching architecture for scalable Internet server

A scalable web server is one of popular information replication methods to accomodate the rapidly growing World Wide Web. It is basically a server clustering technique which supplies information from several servers with the illusion of one serving entity. Request distribution among the back-end servers is crucial work for the scalable web server performance. One popular approach for request distribution is using centralized scheduler such as dispatcher. It provides full control of scheduling and fine-grained load balancing but it suffers from potential bottleneck. DNS based approach utilizes name resolution process for request distribution. It is simple and low overhead scheduling method but it has limited control of load balancing because of the name resolution caching in the intermediate name servers. Another approach such as server based scheme has released the bottleneck problem by distributing the scheduling ability to all participating servers. However, the dispatching efficiency degrades because the redirection process shares resources with data processing jobs. We have developed an adaptive load balancing method that changes the number of scheduling entities according to different workload. It behaves exactly like dispatcher based scheme with low or intermediate workload, taking advantage of fine-grained load balancing. When the dispatcher is overloaded, the dispatching job is partially distributed to other entities such as DNS servers and back-end servers. In this way, we have relaxed hot spot of dispatcher. At the same time, we have preserved the balanced load state through estimation of client domain load rate. We have shown that the adaptive dispatching method improves overall performance in realistic workload simulation.