AOP-Based Caching of Dynamic Web Content: Experience with J2EE Applications

Caching dynamic web content is an appealing approach to reduce Internet latency and server load. In aspect-oriented programming, caching is usually presented as an orthogonal aspect that could be automatically integrated to an application. A classical AOP motivating example is adding caching of static data with no underlying consistency. But what about caching dynamic data? In this paper, we explore the feasibility of aspectizing consistent caching of dynamically generated web documents. We use two J2EE web applications to validate our experiments: the TPC-W on-line bookstore and the RUBiS auction site. To the question “Can we consider consistent caching of dynamic web content as a separate aspect that could be transparently and efficiently integrated to a dynamic web application?”, our conclusions are the following: (a) Just as in the classic AOP caching example having no consistency management, AOP provides a modular way to add caching having a strong consistency policy. (b) However, maintaining strong consistency on web pages results in prohibitively expensive run-time processing and, thus, any straightforward implementation in AOP is too slow. We propose an optimization that essentially eliminates all the run-time overhead in practice. (c) Furthermore, we identify instances where consistent web caching may not be orthogonal to J2EE applications, especially for those applications that rely on sophisticated web techniques (e.g., cookies). In summary, adding caching supporting strong consistency using AOP turned out to be an unexpected challenge.