Effective Multicast Programming in Large Scale Distributed Systems

Many distributed applications have a strong requirement for efficient dissemination of large amounts of information to widely spread consumers in large networks. These include applications in e-commerce and telecommunication. Publish/subscribe is considered one of the most important interaction styles to model communication at large scale. Producers publish information for a topic and consumers subscribe to the topics they wish to be informed of. The decoupling of producers and consumers in time, space, and flow makes the publish/subscribe paradigm very attractive for large scale distribution, especially in environments like the Internet. This paper describes the architecture and implementation of DACE (Distributed Asynchronous Computing Environment), a framework for publish/subscribe communication based on an object-oriented programming abstraction in the form of Distributed Asynchronous Collection (DAC). DACs capture the different variations of publish/subscribe, without blurring their respective advantages. The architecture we present is tolerant to network partitions and crash failures. The underlying model is based on the notion of Topic Membership: a weak membership for the parties involved in a topic. We present how Topic Membership enables the realization of a robust and efficient reliable multicast for large scale. The protocol ensures that, inside a topic, even a subscriber that is temporarily partitioned away eventually receives a published message.