Freshness-driven adaptive caching for dynamic content Web sites

Both response time and content freshness are essential to e-commerce applications on the Web. One option to achieve good response time is to build a high performance Web site by deploying the state of art IT infrastructures with large network and server capacities. With such a system architecture, freshness of the content delivered is limited by the network latency since when users receive the contents, the contents may have changed at the server. With the wide availability of content delivery networks, many e-commerce Web applications utilize edge cache servers to cache and deliver dynamic contents at locations much closer to users, avoiding network latency. By caching a large number of dynamic content pages in the edge cache servers, response time can be reduced, benefiting from higher cache hit rates. However, this is achieved at the expense of higher invalidation cost. On the other hand, a higher invalidation cost leads to a longer invalidation cycle (time to perform invalidation check on the pages in caches) at the expense of freshness of cached dynamic content. In this paper, we propose a freshness-driven adaptive dynamic content caching technique, which monitors response time and invalidation cycle length and dynamically adjusts caching policies. We have implemented the proposed technique within NEC s CachePortal Web acceleration solution. We have conducted experiments to evaluate effectiveness of the proposed freshness-driven adaptive dynamic content caching technique. The experimental results show that the proposed technique consistently maintains the best content freshness to users. The experimental results also show that even a Web site with dynamic content caching enabled can further benefit from deployment of our solution with improvement of * Corresponding author. Tel.: +1-408-863-6008; fax: +1-408-863-6099. E-mail addresses: [email protected] (W.-S. Li), [email protected] (O. Po), [email protected] (W.-P. Hsiung), [email protected] (K. Selc uk Candan), [email protected] (D. Agrawal). 0169-023X/$ see front matter 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0169-023X(03)00093-4 270 W.-S. Li et al. / Data & Knowledge Engineering 47 (2003) 269–296 its content freshness up to 10 times especially during heavy user request traffic and long network latency delay. 2003 Elsevier B.V. All rights reserved.