Pangea: an eager database replication middleware guaranteeing snapshot isolation without modification of database servers

• Authors: Takeshi Mishima;Hiroshi Nakamura
• Venue: Proceedings of the VLDB Endowment
• Year: 2009

Recently, several middleware-based approaches have been proposed. If we implement all functionalities of database replication only in a middleware layer, we can avoid the high cost of modifying existing database servers or scratch-building. However, it is a big challenge to propose middleware which can enhance performance and scalability without modification of database servers because the restriction may cause extra overhead. Unfortunately, many existing middleware-based approaches suffer from several shortcomings, i.e., some cause a hidden deadlock, some provide only table-level locking, some rely on total order communication tools, and others need to modify existing database servers. In this paper, we propose Pangea, a new eager database replication middleware guaranteeing snapshot isolation that solves the drawbacks of existing middleware by exploiting the property of the first updater wins rule. We have implemented the prototype of Pangea on top of PostgreSQL servers without modification. An advantage of Pangea is that it uses less than 2000 lines of C code. Our experimental results with the TPC-W benchmark reveal that, compared to an existing middleware guaranteeing snapshot isolation without modification of database servers, Pangea provides better performance in terms of throughput and scalability.