Partitionable Virtual Synchrony Using Extended Virtual Synchrony

View-oriented group communication systems (GCSs) are powerful tools for building distributed applications. Over the past fifteen years, group communication researchers developed a multitude of group communication semantics and implementations. Today, researchers commonly design their group communication algorithms on top of simple existing services such as a network membership service or a reliable FIFO multicast framework. A natural extension of this idea is to implement one set of group communication semantics using another. This approach is not usually utilized due to the expensive overhead of running one set of group communication algorithms on top of another. This thesis argues that the Extended Virtual Synchrony (EVS) model of group communication, implemented using a client-daemon architecture, is of such high performance that the overhead of constructing another group communication model on top of it is acceptable. It demonstrates that the strong safety properties provided by the EVS model can be leveraged to create very simple algorithms that implement more powerful group communication models. This thesis presents several EVS algorithms for implementing a partitionable Virtual Synchrony (VS) model of group communication. It first explicitly defines the VS and EVS models through the presentation of their safety and liveness properties. Then, one simple algorithm is formally proved to implement the VS model by utilizing the safety and liveness properties of the underlying EVS system. Finally, the paper discusses several other simple variants and algorithms that were developed during the course of this work. iii Acknowledgments