Kaqudai: A Dependable Web Infrastructure Made Out of Existing Components

An internet application typically consists of a business logic complemented by additional concerns, such as communication, security and higher level features such as dependability. We advocate the use of aspect orientation as an advanced concern separation technology, ensuring higher modularity and reusability of code. In this paper we show how such an approach can be put into practice, by enhancing an existing web application with a dependability layer, addressing availability, reliability and data integrity concerns. Specifically, we have produced a set of aspects and other suitable components which can be smoothly integrated into an existing web server, endowing it with the ability to redirect service requests under excessive load. Redirection may target either cloud-powered lightweight replicas of the main web server, or publicly exposed browsing caches from clients. Experiments were conducted on the W3C Jigsaw web server.