一种动态的客户端负载均衡机制

Web applications' traffic demand fluctuates widely and usually unpredictably. The common practice of provisioning a fixed capacity would either result in unsatisfied customers (when the resources allocated to a specific customer are too low) or waste valuable capital investment (when the resources allocated to a specific customer are too much). By leveraging an infrastructure cloud's on-demand, pay-per-use capabilities, we finally can match the system's capacity with the demand in real time. Although the static client-side load balancing mechanism has been used by many clusters, it does not suit the cluster which needs to change nodes and load balancing policies in runtime. This paper proposes a dynamic client-side load balancing mechanism. By integrating technologies such as distributed cluster-view maintenance and control flow, this mechanism not only has good scalability but also introduces many dynamic features into the client-side load balancing, providing effective support for the nodes' dynamic join and exit as well as the adaptive adjustment of the load balancing policies. Since the framework has been implemented in an open-source JEE application server named PKUAS, this paper also describes some key implementation features and analyzes the evaluation results of the experiments to show the effectiveness of the mechanism from different aspects.