Group Membership and View Synchrony in Partitionable Asynchronous Distributed Systems: Specifications

Abstract

Transient failures, unknown scheduling strategies and variable loads on the computing and communication resources give rise to an asynchronous and partitionable characterization for practical distributed systems with large geographic extent. We consider the group membership problem in partitionable asynchronous systems and give a formal specification that guarantees liveness and prevents capricious view splitting. Our work is based on the notion of reachability as an appropriate characterization of failures in partitionable systems in that it subsumes both process crashes and communication failures. The group membership problem is formulated in the context of view synchrony that includes a reliable multicast service for communication within the group. Our specification is modular and includes properties governing group membership separately from those governing reliable multicasts. It can be taken either partially for defining a group membership service alone, or taken as a whole for defining view synchrony.