OverFly-A Client-Enhanced Publish-Subscribe System

This paper presents OverFly, a large-scale publish-subscribe system developed to support our grid middleware, Vega grid operating system, short as GOS. OverFly differs from most existing publish-subscribe systems in three ways. First, it introduces a message store at the client-side which enables clients to be more resilient to intermittent system faults such as intermittent network partitions and intermittent event broker errors. The client message store also enables further optimizations, such as messages packing and compression. Second, it proposes a transparent topic location and relocation design scheme, with which OverFly can tolerate permanent event broker crashes. Third, it provides a delegation model for sending and receiving messages. Besides flexibility, the delegation model can optimize system usages in single machine environments as well as interconnected environments.