Moira: A Goal-Oriented Incremental Machine Learning Approach to Dynamic Resource Cost Estimation in Distributed Stream Processing Systems.

The need for real-time analysis is still spreading and the number of available streaming sources is increasing. The recent literature has plenty of works on Data Stream Processing (DSP). In a streaming environment, the data incoming rate varies over time. The challenge is how to efficiently deploy these applications in a cluster. Several works have been conducted on improving the latency of the system or to minimize the allocated resources per application through time. However, to the best of our knowledge, none of the existing works takes into consideration the user needs for a specific application, which is different from one user to another. In this paper, we propose Moria, a goal-oriented framework for dynamically optimizing the resource allocation built on top of Apache Flink. The system takes actions based on the user application and on the incoming data characteristics (i.e., input rate and window size). Starting from an initial estimation of the resources needed for the user query, at each iteration we improve our cost function with the collected metrics from the monitored system about the incoming data, to fulfill the user needs. We present a series of experiments that show in which cases our dynamic estimation outperforms the baseline Apache Flink and the thumb rule estimation alone performed at the deployment of the applications.