Book Image

Puppet 5 Essentials - Third Edition

By : Martin Alfke, Felix Frank
Book Image

Puppet 5 Essentials - Third Edition

By: Martin Alfke, Felix Frank

Overview of this book

Puppet is a configuration management tool that allows you to automate all your IT configurations, giving you control over what you do to each Puppet Agent in a network, and when and how you do it. In this age of digital delivery and ubiquitous Internet presence, it's becoming increasingly important to implement scaleable and portable solutions, not only in terms of software, but also the system that runs it. This book gets you started quickly with Puppet and its tools in the right way. It highlights improvements in Puppet and provides solutions for upgrading. It starts with a quick introduction to Puppet in order to quickly get your IT automation platform in place. Then you learn about the Puppet Agent and its installation and configuration along with Puppet Server and its scaling options. The book adopts an innovative structure and approach, and Puppet is explained with flexible use cases that empower you to manage complex infrastructures easily. Finally, the book will take readers through Puppet and its companion tools such as Facter, Hiera, and R10k and how to make use of tool chains.
Table of Contents (10 chapters)

Fetching data from classes

Looking up a key value in Hiera is easy. Puppet comes with a very straightforward function for this:

$plugins = hiera('reporting::plugins') 

Whenever the compiler encounters such a call in the manifest of the current agent node, it triggers a search in the hierarchy. The specific data sources are determined by the hierarchy in your hiera.yaml file. It will almost always rely on fact values provided by the agent to make flexible data source selections.

If the named key cannot be found in the agent's hierarchy, the master aborts the catalog compilation with an error. To prevent this, it is often sensible to supply a default value with the lookup:

$plugins = hiera('reporting::plugins', []) 

In this case, Puppet uses an empty array if the hierarchy mentions no plugins.

On the other hand, you can purposefully omit the default value...