Distributed Shared State with History Maintenance

Abstract

Shared mutable state is challenging to maintain in a distributed environment. We develop a technique, based on the Operational Transform, that guides independent agents into producing consistent states through inconsistent but equivalent histories of operations. Our technique, history maintenance, extends and streamlines the Operational Transform for general distributed systems. We describe how to use history maintenance to create eventually-consistent, strongly-consistent, and hybrid systems whose correctness is easy to reason about.