Grape: Efficient Spatiotemporal Prediction Services with Stale Sensing Streams

Emerging cyber-physical systems have embraced a large number of IoT devices spanning geo-distributed, which generate and consume massive volumes of data continuously. Accurate and timely spatiotemporal predictions (STP) over these streaming sensor data are critical and, in growing demand, ubiquitous across various edge scenarios such as traffic flow forecasting. Towards that, recent advanced systems have developed sophisticated optimizations among STP pipelines, aiming at optimal prediction performance. However, based on our empirical studies in real-world settings, we identify a previously overlooked bottleneck of end-to-end STP performance: data staleness. To mitigate this issue, in this work, we investigate a new task, namely stream interception, which deliberately terminates the acceptance of incoming sensor data and anticipates model execution with imputed missing features. We propose a novel dynamic interception strategy to determine the time slot to exit waiting and present Grape, an STP system that implements it with practical system designs. Extensive evaluations on real-world traces show that Grape can strike a superior tradeoff between prediction accuracy and serving latency, achieving 1.69-1.90× speedup against traditional all-waiting baselines across various STP services with high prediction accuracy on par with offline optimal cases.