Puppet Best Practices

Chapter 10. Extending Puppet

One of Puppet’s strengths is its extreme extensibility. Even though a basic deployment of Puppet includes a fairly comprehensive set of resource types, facts, and function calls, it’s fairly simple and incredibly common to extend Puppet’s functionality.

This chapter is not intended to provide detailed API documentation for Puppet; instead, we look at a lot of the approaches, best practices, and pitfalls of extension development.

The Cost of Extending Puppet

Before writing custom extensions for Puppet, it’s a good idea to consider the ongoing costs associated with creating and maintaining in-house customizations to Puppet.

Although all code (including Puppet manifests) carries some maintenance costs, native Ruby extensions to Puppet carry somewhat higher overhead than the Puppet language code.

Minimizing Development Costs

Development of extensions beyond basic facts is generally considered a specialty skill that many Puppet users will not have. Creating Puppet extensions requires a higher degree of familiarity with Ruby and Puppet’s internal APIs than is required by simply using the built-in language features. Although the new resource API will make developing extensions easier than ever before, choosing to build your own extensions has an unavoidable effort cost that can only be borne by senior developers. It can be difficult to find developers capable of maintaining internally built extensions in the long term.

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The cost of developing extensions ...