Network–wide complex event processing over geographically distributed data sources

In this paper we focus on Complex Event Processing (CEP) applications where the data is generated by sites that are geographically dispersed across large regions. This geographic distribution, combined with the size of the collected data, imposes severe communication and computation challenges. To attack these challenges, we propose a novel approach for geographically distributed CEP, which combines algorithmic and systems contributions. At an algorithmic level, our work combines an in-network processing approach, which pushes parts of the processing (i.e., CEP operators) towards the sources of their input events, along with a push–pull paradigm, in order to reduce the amount of communicated events. We present optimal (but computationally expensive) solutions which seek to minimize the maximum bandwidth consumption given input latency constraints for detecting events, as well as efficient greedy and heuristic algorithmic variations for our problem. At a systems level, we explain how existing CEP engines can support, with minimal modifications, our algorithms. Our experimental evaluation, using mainly real datasets and network topologies, demonstrates that the power of our techniques lies in the combination of the in-network with the push–pull paradigm, thus allowing our algorithms to significantly outperform related centralized push–pull or conventional in-network processing approaches.