Star Merge and Divide-and-Conquer Algorithms for Publish/Subscribe Topic-connected Overlay Design

Overlay network design for topic-based publish/subscribe systems is of primary importance because the overlay directly impacts the system’s performance. Determining a topic-connected overlay, in which for every topic the graph induced by nodes interested in the topic is connected, is a fundamental problem. Existing algorithms for this problem suffer from three key drawbacks: (1) prohibitively high running time cost, (2) requirement of full system knowledge and centralized operation, and (3) constructing overlay from scratch. From a practical point of view, these are all significant limitations. To address these concerns, in this paper, we develop novel algorithms that efficiently solve the problem of dynamically joining two or more topic-connected overlays. Inspired from the divide-and-conquer character of our approach, we derive an algorithm that solves the original problem at a fraction (up to 1.7%) of the running time cost of alternative solutions, but at the expense of an empirically insignificant increase in the average node degree.