Session-Based Overload Control in QoS-Aware Web Servers

Abstract — With the explosive use of Internet, contemporary web servers are susceptible to overloads and their services deteriorate drastically and often cause denial of services. In this paper, we proposed two methods to prevent and control overloads in web servers by utilizing session-based relationship among HTTP requests. We first exploited the dependence among session-based requests by analyzing and predicting the reference patterns. Using the dependency relationships, we have derived traffic conformation functions that can be used for capacity planning and overload prevention in web servers. Second, we have proposed a dynamic weighted fairing sharing (DWFS) scheduling algorithm to control overloads in web servers. DWFS is distinguished from other scheduling algorithms in the sense that it aims to avoid processing of requests that belong to sessions that are likely to be aborted in the near future. The experimental results demonstrate that DWFS can improve server responsiveness by as high as 50 % while providing QoS support through service differentiation for a class of application environment. Index Terms—Capacity planning, Dynamic weighted fair sharing, Overload control, Quality of service, Scheduling algorithm, Service differentiation, Session-based control, Web server