Spark: The Definitive Guide

Chapter 20. Stream Processing Fundamentals

Stream processing is a key requirement in many big data applications. As soon as an application computes something of value—​say, a report about customer activity, or a new machine learning model—​an organization will want to compute this result continuously in a production setting. As a result, organizations of all sizes are starting to incorporate stream processing, often even in the first version of a new application.

Luckily, Apache Spark has a long history of high-level support for streaming. In 2012, the project incorporated Spark Streaming and its DStreams API, one of the first APIs to enable stream processing using high-level functional operators like map and reduce. Hundreds of organizations now use DStreams in production for large real-time applications, often processing terabytes of data per hour. Much like the Resilient Distributed Dataset (RDD) API, however, the DStreams API is based on relatively low-level operations on Java/Python objects that limit opportunities for higher-level optimization. Thus, in 2016, the Spark project added Structured Streaming, a new streaming API built directly on DataFrames that supports both rich optimizations and significantly simpler integration with other DataFrame and Dataset code. The Structured Streaming API was marked as stable in Apache Spark 2.2, and has also seen swift adoption throughout the Spark community.

In this book, we will focus only on the Structured Streaming API, which integrates ...