Distributed Low-Latency Out-of-Order Event Processing for High Data Rate Sensor Streams

Event-based Systems (EBS) are used to detect and analyze meaningful events in surveillance, sports, finances and many other areas. With rising data and event rates and with correlations among these events, sequential event processing becomes infeasible and needs to be distributed. Existing approaches cannot deal with the ubiquity of out-of-order event arrival that is introduced by network delays when distributing EBS. Order-less event processing may result in a system failure. We present a low-latency approach based on K-slack that achieves ordered event processing on high data rate sensor and event streams without a-priori knowledge. Slack buffers are dynamically adjusted to fit the disorder in the streams without using local or global clocks. The middleware transparently reorders the event input streams so that events can still be aggregated and processed to a granularity that satisfies the demands of the application. On a Realtime Locating System (RTLS) our system performs accurate low-latency event detection under the predominance of out-of-order event arrival and with a close to linear performance scale-up when the system is distributed over several threads and machines.