Book Image

Extending Puppet - Second Edition

By : Alessandro Franceschi, Jaime Soriano Pastor
Book Image

Extending Puppet - Second Edition

By: Alessandro Franceschi, Jaime Soriano Pastor

Overview of this book

Puppet has changed the way we manage our systems, but Puppet itself is changing and evolving, and so are the ways we are using it. To tackle our IT infrastructure challenges and avoid common errors when designing our architectures, an up-to-date, practical, and focused view of the current and future Puppet evolution is what we need. With Puppet, you define the state of your IT infrastructure, and it automatically enforces the desired state. This book will be your guide to designing and deploying your Puppet architecture. It will help you utilize Puppet to manage your IT infrastructure. Get to grips with Hiera and learn how to install and configure it, before learning best practices for writing reusable and maintainable code. You will also be able to explore the latest features of Puppet 4, before executing, testing, and deploying Puppet across your systems. As you progress, Extending Puppet takes you through higher abstraction modules, along with tips for effective code workflow management. Finally, you will learn how to develop plugins for Puppet - as well as some useful techniques that can help you to avoid common errors and overcome everyday challenges.
Table of Contents (19 chapters)
Extending Puppet Second Edition
About the Authors
About the Reviewer

Using Hiera in Puppet

The data stored in Hiera can be retrieved by the Puppet Master while compiling the catalog using the Hiera functions. In our manifests, we can have something like the following:

$dns_servers = hiera("dns_servers")

Note that the name of the Puppet variable need not be the same as the Hiera one, so the preceding command can also be something like this:

$my_dns_servers = hiera("dns_servers")

This assigns the top value to the $my_dns_servers variable (the first one found while crossing the hierarchy of data sources) retrieved by Hiera for the key dns_servers.

We can also merge arrays and hashes here, so, in order to retrieve an array of all the values in the hierarchy's data sources of a given key and not just the first one, we can use hiera_array():

$my_dns_servers = hiera_array("dns_servers")

If we expect a hash value for a given key, we can use the hiera() function to retrieve the top value found, or hiera_hash() to merge all the found values in a single hash: