Puppet Module Design

A Puppet module is a reusable policy package. It manages one technology or responsibility and gives other code a stable way to declare that policy.

Good design is not measured by how many classes fit in the module. It is measured by how clearly the module separates its public contract from its implementation.

Start with one responsibility

A component module should answer one question: what system capability does it own?

An nginx module can own package installation, service state, configuration files, and related virtual hosts. It should not also define an organization's entire web application role, database backup policy, and monitoring stack.

Keep business-specific composition in profiles and roles:

role -> profiles -> component modules

A role describes one complete node purpose. Profiles combine component modules into a site-specific layer. Component modules manage technologies through reusable interfaces.

This boundary lets you upgrade or replace a component without rewriting every node classification.

Design the public interface first

A module's public classes and defined types are its API. Users should be able to understand the supported inputs without reading private manifests.

Use typed parameters: