Towards Adaptive Replication Reconfiguration for QoS

Replication is a technique widely used for large networked software systems to provide qualities such as reliability, availability, performance and scalability to their clients. There are various configurations of replica control protocols that provide various levels of these qualities. Existing replication protocols implement a single configuration that is suitable for achieving the quality goal for a given external situation. If the situation changes, the quality will deteriorate. In this paper we present the MARR middleware that supports multiple replication configurations in a system. MARR can be set up during deployment to start in a particular configuration according to the anticipated external situation. This allows the same middleware to be used for different replication needs. If the situation changes during production MARR is designed to dynamically adapt and reconfigure the replication to maintain the service qualities. For example, if the request pattern from the clients changes from read intensive to update intensive, MARR can adapt from a single master configuration to a multi-master in order to maintain system performance.