Adaptive Channel-Based Routing in Content-Based Pub/Sub Systems

Content-based Pub/Sub systems enable various applications especially in the field of Internet of Things (IoT) to capture the events interested by the users. However, the event/subscription routing approaches in the Pub/Sub systems must adapt to the diversity and skew ness of the events/subscriptions. Only on this basis, performance improvement and quality of service required by the users can be considered. In the face of changing event/subscription loads, this paper presents an adaptive approach to channel management in the channel-based routing. Our approach exploits the historical information of the subscriptions and events as well as the covering relationship between subscriptions to accomplish channel splitting and joining. Due to properly utilizing the differencing method of set partitioning, our approach can guarantee that the difference between loads of two resultant brokers is as small as possible at the granularity of a subscription tree after a channel splitting operation on an overloaded broker. Moreover, it can work with any content-based subscription language without any limitation imposed on the specifications of subscriptions. The experimental results show that our approach is adaptable and elastic in terms of standard deviation of loads of brokers and also has acceptable offloading time.