Apache Oozie

Chapter 2. Oozie Concepts

This chapter covers the basic concepts behind the workflow, coordinator, and bundle jobs, and how they relate to one another. We present a use case for each one of them. Throughout the book, we will elaborate on these concepts and provide more detailed examples. The last section of this chapter explains Oozie’s high-level architecture.

Oozie Applications

In Unix, the /bin/echo file is an executable. When we type /bin/echo Hello in a terminal session, it starts a process that prints Hello. Oozie applications are analogous to Unix executables, and Oozie jobs are analogous to Unix processes. Oozie users develop applications, and one execution of an application is called a job.

Note

Throughout the book, unless explicitly specified, we do not differentiate between applications and jobs. Instead, we simply call them a workflow, a coordinator, or a bundle.

Oozie Workflows

An Oozie workflow is a multistage Hadoop job. A workflow is a collection of action and control nodes arranged in a directed acyclic graph (DAG) that captures control dependency where each action typically is a Hadoop job (e.g., a MapReduce, Pig, Hive, Sqoop, or Hadoop DistCp job). There can also be actions that are not Hadoop jobs (e.g., a Java application, a shell script, or an email notification).

The order of the nodes in the workflow determines the execution order of these actions. An action does not start until the previous action in the workflow ends. Control nodes in a workflow are used to manage ...