Enriched view synchrony: a programming paradigm for partitionable asynchronous distributed systems

Distributed systems constructed using off-the-shelf communication infrastructures are becoming common vehicles for doing business in many important application domains. Large geographic extent due to increased globalization, increased probability of failures, and highly dynamic loads all contribute toward a partitionable and asynchronous characterization for these systems. In this paper, we consider the problem of developing reliable applications to be deployed in partitionable asynchronous distributed systems. What makes this task difficult is guaranteeing the consistency of shared state despite asynchrony, failures, and recoveries, including the formation and merging of partitions. While view synchrony within process groups is a powerful paradigm that can significantly simplify reasoning about asynchrony and failures, it is insufficient for coping with recoveries and merging of partitions after repairs. We first give an abstract characterization for shared state management in partitionable asynchronous distributed systems and then show how views can be enriched to convey structural and historical information relevant to the group´s activity. The resulting, paradigm, called enriched view synchrony, can be implemented efficiently and leads to a simple programming methodology for solving shared state management in the presence of partitions