DTA: Dynamic topology algorithms in content-based Publish/Subscribe

Publish/Subscribe (Pub/Sub) has been used in many large-scale distributed systems owing to its scalability and loose coupling, and most of the existing Pub/Sub systems are built on the basis of the acyclic topology because the routing algorithm can be simplified. However, the flexibility is limited and the robustness is also a big problem. This paper proposes a dynamic topology algorithm to facilitate the adaptation to the dynamic change of the network conditions, which is composed of two parts: Topology Generation Algorithm (TGA) and Topology Transformation Algorithm (TTA). The topology can switch between cyclic topology and acyclic topology automatically, and the advantages of both the cyclic topology and the acyclic topology can thus be exploited. In addition, the efficiency and scalability can also be guaranteed when the topology changes. The topology of a Pub/Sub system will be transformed into a cyclic one to enhance robustness when the network condition gets worse, while into the acyclic pattern when the network condition is getting better. Experiments show that average number of edges in the topology reduces by 12% and subscription notification delivery time improves by 20%.