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
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Custom functions


Functions are an important area where we can extend Puppet. They are used when Puppet parses our manifests and can greatly enhance our ability to fetch data from custom sources, filter, and manipulate it.

We can distribute a function just by placing a file at lib/puppet/parser/<function_name>.rb in a module of ours.

Even if they are automatically distributed to all our clients, it's important to remember that being used only during the catalog compilation, functions are needed only on the Puppet Master.

Note

Note that since they are loaded in the memory when Puppet starts, if we change a function on the Master, we have to restart its service in order to load the latest version.

There are two kinds of functions:

  • :rvalue functions return a value, they are typically assigned to a variable or a resource argument. Sample core rvalue functions are template, hiera, regsubst, versioncmp, and inline_template.

  • :statement functions perform an action without returning any value. Samples...