Upgrading distributed applications with the version manager

Abstract: "Developers and managers of distributed systems today face a difficult choice. To provide for the evolution of their systems, they can either require that the software running on all nodes is inter-operable, or they can shut down the entire system when an upgrade is required. The former complicates the life of system developers, while the latter annoys users. We propose Version Manager, a middle ground between these approaches: an upgrade framework that limits the the [sic] extent of support required for interoperability, while also providing availability during upgrades. We evaluate the feasibility of our approach by applying it to two existing distributed systems: the Cooperative File System [11], and IrisLog [3]. Our proposal enables the upgrade of these systems while maintaining system availability, and without requiring code modifications."