Book Image

Learning Apache Flink

By : Tanmay Deshpande
Book Image

Learning Apache Flink

By: Tanmay Deshpande

Overview of this book

<p>With the advent of massive computer systems, organizations in different domains generate large amounts of data on a real-time basis. The latest entrant to big data processing, Apache Flink, is designed to process continuous streams of data at a lightning fast pace.</p> <p>This book will be your definitive guide to batch and stream data processing with Apache Flink. The book begins with introducing the Apache Flink ecosystem, setting it up and using the DataSet and DataStream API for processing batch and streaming datasets. Bringing the power of SQL to Flink, this book will then explore the Table API for querying and manipulating data. In the latter half of the book, readers will get to learn the remaining ecosystem of Apache Flink to achieve complex tasks such as event processing, machine learning, and graph processing. The final part of the book would consist of topics such as scaling Flink solutions, performance optimization and integrating Flink with other tools such as ElasticSearch.</p> <p>Whether you want to dive deeper into Apache Flink, or want to investigate how to get more out of this powerful technology, you’ll find everything you need inside.</p>
Table of Contents (17 chapters)
Learning Apache Flink
About the Author
About the Reviewers
Customer Feedback

Data sources

Sources are places where the DataSet API expects to get its data from. It could in the form of a file or from Java collections. This is the second step in the Flink program's anatomy. DataSet API supports a number of pre-implemented data source functions. It also supports writing custom data source functions so anything that is not supported can be programmed easily. First let's try to understand the built-in source functions.


Flink supports reading data from files. It reads data line by line and returns it as strings. The following are built-in functions you can use to read data:

  • readTextFile(Stringpath): This reads data from a file specified in the path. By default it will read TextInputFormat and will read strings line by line.

  • readTextFileWithValue(Stringpath): This reads data from a file specified in the path. It returns StringValues. StringValues are mutable strings.

  • readCsvFile(Stringpath): This reads data from comma separated files. It returns the Java POJOs or...