Adaptive Topology for Scalability and Immediacy in Distributed Publish/Subscribe Messaging

Publish/subscribe is a communication model for exchanging messages via a broker while providing loose coupling. So far, several studies have been conducted to address load concentration on the broker by forming distributed brokers. However, although they achieve higher throughput by load distribution among multiple brokers, these existing studies require an increased latency for message delivery. In this paper, we propose a novel method to construct and maintain an adaptive topology that features both scalability and immediacy in distributed publish/subscribe messaging. The proposed method is for topic-based publish/subscribe systems and uses a number of brokers to form an overlay network. Its topology changes dynamically to compose a subgraph for each topic in a single-hop or multi-hop manner according to the topic load (i.e., the number of clients). The experimental results show that compared to existing studies, the proposed method reduces the delivery path length, which is a principal factor that affects latency. Especially for low load topics, the reduction rate of the proposed method reaches values greater than 60%.