DEBS grand challenge: real-time detection of air quality improvement with Apache Flink

ABSTRACTThe topic of the DEBS Grand Challenge 2021 is to develop a solution for detecting areas in which the air quality index (AQI) improved the most when compared to the previous year. The solution must run two given continuous queries in parallel on the incoming sensor data stream which must return the following: 1) a top 50 cities in terms of AQI improvement with their current AQIs and 2) a histogram of the longest streaks of good AQI. The incoming data is accessed through an API which provides streaming sensor measurements in batches. We present our solution based on Apache Flink, a distributed stream processing framework for the cluster. We opted for Flink since its applications can easily be scaled horizontally and vertically by adding computation nodes or increasing available resources, respectively. Flink allows us to divide the given queries into smaller tasks which can be run concurrently on different nodes in order to reduce the overall processing time and thus improve the performance of our solution. In more detail, the following performance intensive tasks are run in parallel on distributed nodes: 1) retrieving measurement batches, 2) assigning a city to each measurement and 3) calculating air quality index per city. We also discuss the main optimizations we have used to improve the performance and present an experimental evaluation of our solution.