CoCache: Query Processing Based on Collaborative Caching in P2P Systems

In this paper, we propose CoCache, a P2P query processing architecture that enables sophisticated optimization techniques. CoCache is different from existing P2P query processing systems in three ways. First, a coordinator overlay network (CON) maintaining the summary of the whole system is constructed by applying DHT technique to query plan trees. CON protocol ensures the efficiency for handling dynamic environments. Second, a preliminary cost-based optimization technique for retrieving appropriate cached copies of data is studied. With the help of CON, we show the possibility of fine optimization in even large scale and dynamic environments. Third, the collaborative caching strategy is presented, with which even small portion of cache storage on each peer may result in great improvement on query processing performance. Extensive experiments over real-world and synthetic settings show the effectiveness and efficiency of CoCache.