The Research On Web QoS Of Web Server Cluster System Based On Cluster Dispatcher

As the HTTP requests are growing exponentially and the E-commerce applications are booming rapidly, it is an increasingly critical issue for Web-server systems to handle the ever-growing client demands as well as provide performance assurance and service differentiation to different requests or customers. To that end, besides network, Web server systems must also have mechanisms and policies for establishing and supporting Quality of Service(QoS). In fact, Web QoS is a key component in delivering end-to-end QoS to end-users. Presently, more and more attention has been paid to Web QoS by the international researchers or companies, while in China, few researches and no products or patents on Web QoS can be found.This dissertation investigates the policies, modeling and performance analysis of Web QoS control based on the local Web server cluster architecture; and dynamic Web content adaptation is implemented based on MVC model in single Web server. The contributions of this dissertation are presented as follows.(1) A new mechanism is proposed to correlate customer and contents priorities of incoming HTTP requests used for server process scheduling with the load balancing policies for Web-server clusters. Based on this methodology, a QoS-aware integrated scheme of request distribution is proposed based on the SP and FSPF schemes. An architecture of Web server clusters that is suited to implement the QoS-aware integrated policies is proposed by adopting a customer-aware request dispatcher. Based on this architectures, a Multiserver Multiqueue(MSMQ) system model is proposed for the Web server cluster. Stochastic high-level Petri net is used for modeling and performance analysis of the system model. A SHLPN performance model with Poisson arrivals is also put forward to analys the performance.Numerical results of performance analysis show that the QoS-aware integrated strategies can provide differentiated Web QoS to different types of request or custormers,in comparison with the QoS-unaware police(FSPF).(2) A Web server prototype with dynamic Web content adaptation policy by meanse of MVC model is implemented for single server, and we use the httperf tool to test its performanse.The testing results show that the Apache server that implement the Web content adaptation policy can provide different types of requests or customers with differentiated Web QoS, in comparison with the popular QoS-unaware Apache.