Multi-tier caching of dynamic content for database-driven Web sites
Cox, Alan L.
Doctor of Philosophy
Web sites have gradually shifted from delivering just static html pages and images to customized, user-specific content and plethora of online services. The new features and facilities are made possible by dynamic content which is produced at request time. Multi-tiered database-driven web sites form the predominant infrastructure for most structured and scalable approaches to dynamic content delivery. However, even with these scalable approaches, the request-time computation and high resource demands for dynamic content generation result in significantly higher latencies and lower throughputs than for sites with just static content. This thesis proposes the caching of dynamic content as the solution for improving the performance of web sites with significant amount of dynamic content. This work shows that there is significant locality in the data accesses and computations for content generation which can be exploited by caching to improve performance. This work introduces a novel multi-tier caching architecture that incorporates multiple, independent caching components to enable easy deployment and effective performance over the prevalent multi-tiered database-driven architecture for dynamic content delivery. The dynamic content infrastructure and the proposed caching strategy is evaluated with e-commerce workloads from the TPC-W benchmark. The evaluation of the system without caching shows that content generation overheads are dominated by the database component for e-commerce workloads. With multi-tier caching, each caching component overcomes specific overheads during content generation while the combination provides overall improvements in performance significantly greater than the individual contributions. The increased peak throughputs with caching range from 1.58 to 8.72 times the peak throughputs without caching at similar or significantly reduced average response times. At the same load as for the peak throughputs without caching, the response times were reduced by 90% to 97% with caching. The evaluations also establish the effectiveness of the strategy in relation to variation in platform and site configurations. Overall, the proposed multi-tier caching strategy brings about dramatic improvements in performance for dynamic content delivery.