Filterfresh: Hot Replication of Java RMI Server Objects

This paper presents the design and implementation of a Java package called Filterfresh for building replicated fault-tolerant servers. Maintaining the correctness and integrity of replicated servers is supported by a GroupManager object instantiated with each replica to form a logical group. The Group Managers use a Group Membership algorithm to maintain a consistent group view and a Reliable Multicast mechanism to communicate with other GroupManagers. We then demonstrate how Filterfresh can be integrated into the Java RMI facilities. First we use the GroupManager class to construct a faulttolerant RMI registry called FT Registry|a group of replicated RMI registry servers. Second, we describe our implementation of the FT Unicast|a client-side mechanism that tolerates and masks server failures below the stub layer, transparent to the client. We also present initial performance results, and discuss how general purpose RMI servers can be made highly available using the Filterfresh package.