Welcome to this first edition of Spark: The Definitive Guide! We are excited to bring you the most complete resource on Apache Spark today, focusing especially on the new generation of Spark APIs introduced in Spark 2.0. Apache Spark is currently one of the most popular systems for large-scale data processing, with APIs in multiple programming languages and a wealth of built-in and third-party libraries. Although the project has existed for multiple years—first as a research project started at UC Berkeley in 2009, then at the Ap ache Software Foundation since 2013—the open source community is continuing to build more powerful APIs and high-level libraries over Spark, so there is still a lot to write about the project. We decided to write this book for two reasons. First, we wanted to present the most comprehensive book on Apache Spark, covering all of the fundamental use cases with easy-to-run examples. Second, we especially wanted to explore the higher-level “structured” APIs that were finalized in Apache Spark 2.0—namely DataFrames, Datasets, Spark SQL, and Structured Streaming—which older books on Spark don’t always include. We hope this book gives you a solid foundation to write modern Apache Spark applications using all the available tools in the project. In this preface, we’ll tell you a little bit about our background, and explain who this book is for and how we have organized the material. We also want to thank the numerous people who helped edit and review this book, without whom it would not have been possible.