Multi-Cache Coherence Protocol for Distributed Internet Services

Multi-tier architectures provide a means for building scalable distributed services. Caching is a classical technique for enhancing the performance of systems (e.g. database servers, or web servers). Although caching solutions have been successfully studied for individual tiers of multi-tier systems, if collectively applied, these solutions may violate the coherence of cached data. This paper precisely addresses this issue. It presents e-Caching, an end-to-end caching system for multi-tier services aimed at guaranteeing data consistency across caches. The paper describes a novel caching protocol to automatically detect data dependencies and apply inter-cache invalidations. The implemented protocol is evaluated with the TPC-W online multi-tier bookstore service. The evaluation shows that e-Caching improves service performance compared to regular caching techniques while guaranteeing global data consistency in multi-tier systems.