Continuous Outlier Mining of Streaming Data in Flink
This work addresses the need for scalable outlier detection in streaming environments for data analytics applications, representing an incremental advancement by adapting existing methods to a parallel setting.
The authors tackled the problem of mining distance-based outliers in streaming data by transferring state-of-the-art techniques to Apache Flink, achieving speed-ups of up to 117 times over naive parallel solutions and 2076 times over non-parallel ones on a four-core machine, with further improvements up to 510 times on a three-machine cluster.
In this work, we focus on distance-based outliers in a metric space, where the status of an entity as to whether it is an outlier is based on the number of other entities in its neighborhood. In recent years, several solutions have tackled the problem of distance-based outliers in data streams, where outliers must be mined continuously as new elements become available. An interesting research problem is to combine the streaming environment with massively parallel systems to provide scalable streambased algorithms. However, none of the previously proposed techniques refer to a massively parallel setting. Our proposal fills this gap and investigates the challenges in transferring state-of-the-art techniques to Apache Flink, a modern platform for intensive streaming analytics. We thoroughly present the technical challenges encountered and the alternatives that may be applied. We show speed-ups of up to 117 (resp. 2076) times over a naive parallel (resp. non-parallel) solution in Flink, by using just an ordinary four-core machine and a real-world dataset. When moving to a three-machine cluster, due to less contention, we manage to achieve both better scalability in terms of the window slide size and the data dimensionality, and even higher speed-ups, e.g., by a factor of 510. Overall, our results demonstrate that oulier mining can be achieved in an efficient and scalable manner. The resulting techniques have been made publicly available as open-source software.