Chapter 5. Workflow Management with Python
The most popular workflow scheduler to manage Hadoop jobs is arguably Apache Oozie. Like many other Hadoop products, Oozie is written in Java, and is a server-based web application that runs workflow jobs that execute Hadoop MapReduce and Pig jobs. An Oozie workflow is a collection of actions arranged in a control dependency directed acyclic graph (DAG) specified in an XML document. While Oozie has a lot of support in the Hadoop community, configuring workflows and jobs through XML attributes has a steep learning curve.
Luigi is a Python alternative, created by Spotify, that enables complex pipelines of batch jobs to be built and configured. It handles dependency resolution, workflow management, visualization, and much more. It also has a large community and supports many Hadoop technologies.
This chapter begins with the installation of Luigi and a detailed description of a workflow. Multiple examples then show how Luigi can be used to control MapReduce and Pig jobs.
Luigi is distributed through PyPI and can be installed using
$ pip install luigi
Or it can be installed from source:
$ git clone https://github.com/spotify/luigi $ python setup.py install
Within Luigi, a workflow consists of a pipeline of actions, called tasks. Luigi tasks are nonspecific, that is, they can be anything that can be written in Python. The locations of input and output data for a task are known as targets. Targets typically ...