Group-Enhanced Remote Method Invocations

We present a specification for Jgroup, an extension to the Java distributed object model based on group communication. Jgroup is particularly suited for developing dependable network applications that are to be deployed in environments subject to voluntary or involuntary network partitionings. Jgroup adapts view synchrony semantics, typically defined for message-based group communication systems, to remote method invocations on objects. Unlike existing object group systems that mix two different paradigms (message passing within groups and remote method invocations outside), Jgroup presents a single uniform programming interface based entirely on remote method invocations. Furthermore, Jgroup extends view synchrony semantics that govern interactions within the group to external clients of the group without requiring them to become full-fledgedmembers. In this manner, the higher costs associated with providing strong guarantees on method invocations are limited to (typically small number of) group members while guarantees for clients can be light-weight and thus incur smaller costs.