Aspectizing a Web Server for Adaptation

Web servers are exposed to extremely changing runtime requirements. Going offline to adjust policies and configuration parameters in order to cope with such requirements is not an available choice for long running Web servers. Many of the policies that need to be adapted are crosscutting in nature. Aspect-oriented programming (AOP) provides mechanisms to encapsulate the crosscutting policies as aspects. This paper describes the integration of a statically configurable Web server with our dynamic aspect weaving infrastructure. This integration transformed the server to a dynamically adaptable one that could adjust its policies and configuration parameters at runtime according to the changing requirements. This paper further provides a comprehensive analysis of the memory and runtime costs associated with this transformation, and explains how our dynamic aspect weaving infrastructure via its tailored support facilitates to minimise these costs.