An experimental prototype for scalable server selection

An experimental prototype for server selection using an independent brokerage service is described This prototype is composed of four main components: instrumented Apache Web servers, monitoring agents, a QoS broker, and client emulator. The role of the broker is to distribute client sessions to a set of replicated servers. It is designed to support different types of selection policies and hay the capability to collect performance data from the servers. We include in our description the technique used to instrument Apache servers and our implementation of the server-broker protocol that we have developed. Our implementation of the QoS broker and the technique used to collect data for the performance parameters of interest are also described. We use our prototype to study the performance of server selection algorithms under realistic conditions. The experimental environment and an analysis of the experimental results are presented.