Database Replication Policies for Dynamic Content Applications

摘要

The database tier of dynamic content servers at large Internet sites is typically hosted on centralized and expensive hardware. Recently, research prototypes have proposed using database replication on commodity clusters as a more economical scaling solution. In this paper, we propose using database replication to support multiple applications on a shared cluster. Our system dynamically allocates replicas to applications in order to maintain application-level performance in response to either peak loads or failure conditions. This approach allows unifying load and fault management functionality. The main challenge in the design of our system is the time taken to add database replicas. We present replica allocation policies that take this time delay into account and also design an efficient replica addition method that has minimal impact on other applications. We evaluate our dynamic replication system on a commodity cluster with two standard benchmarks: the TPC-W e-commerce benchmark and the RUBIS auction benchmark. Our evaluation shows that dynamic replication requires fewer resources than static partitioning or full overlap replication policies and provides over 90% latency compliance to each application under a range of load and failure scenarios.