Classes & defined types

Group and parameterize resources.

A class groups related resources under a name so you can include them as a unit — the nginx class contains the package, config, and service. Classes are declared once and included wherever needed (include nginx), and Puppet ensures a class is only applied once per node no matter how many times it is included. Parameterized classes take inputs, so the same class configures differently per node.

class nginx (
  Integer $workers = 4,
  Integer $port    = 80,
) {
  package { 'nginx': ensure => installed }
  file { '/etc/nginx/nginx.conf':
    ensure  => file,
    content => epp('nginx/nginx.conf.epp', { 'workers' => $workers, 'port' => $port }),
    notify  => Service['nginx'],
  }
  service { 'nginx': ensure => running, enable => true }
}

Defined types repeat a pattern

Where a class is a singleton (applied once per node), a defined type is a reusable pattern you can instantiate many times with different titles — a vhost defined type to create ten virtual hosts, a user-with-dotfiles type per developer. It looks like a class but uses define, and each instance is distinct. Classes for “the node has nginx,” defined types for “the node has these N of something.”

define nginx::vhost (String $server_name, Integer $port = 80) {
  file { "/etc/nginx/sites/${title}.conf":
    ensure  => file,
    content => epp('nginx/vhost.epp', { 'name' => $server_name, 'port' => $port }),
    notify  => Service['nginx'],
  }
}
# instantiate many:
nginx::vhost { 'app':  server_name => 'app.acme.internal' }
nginx::vhost { 'api':  server_name => 'api.acme.internal', port => 8080 }