Puppet 4 :: Modules and Classes

Environments -> Modules -> classes -> parameters -> Inheritance -> Custom Resources

Environments & Modules

• Env: Support for Production and Development Code
• Env: puppet config print environment
• Env: Support for Isolation of Departmental Code
• Env: puppet config print environmentpath
• Env: Helps in using different versions of the module for each environment
• Module: Can be located in either the environment directory or a common shared directory
• Create environment in /etc/puppetlabs/code/environments/dev/{modules,manifests}
• Install module as follows puppet module install ntp --environment dev
• Module: To see the list puppet module list --environment dev
• Puppet configuration /etc/puppetlabs/puppet/puppet.conf
• To work under a environment puppet config set environment dev

Modules

• Puppet module is simply a directory tree with specific and predictable content
• Module contains
  • Name (ntp/)
    • manifests/init.pp
    • files/
    • lib/ # can contain facts
    • facts.d/ # external facts
    • templates/ # erb (embeded ruby file) | Puppet4 -> epb (embeded manifest file)
    • examples/
• manifest must contain a class with the same name as the module
• Modules Metadata
  • we can use puppet module generate skota/test # test = module name, skota = user name/ org name
    • this will start an interview process to collect other information i.e, version no, author etc..
  • To skip all we can use puppet module generate skota/test --skip-interview - This will use the defaults
  • stores data in metadata.json
  • This will help us in versioning our Modules
• tree module will list down the file structure

Sub Classes

ntp/manifests/config.pp    # create a file name under module's manifest folder

class ntp::config {        # class name should be prefixed by base class as shown (ntp::)
}

include ntp::config                # usage 1
notify => Class['ntp::config']     # usage 2

Parameterized Classes

• Examples below:

class test ($param = 'daily') {            # $param is a parameter and it's default value is 'daily'
  file {'temp':
    ensure => 'present',
    content => file("etc/${param}"),      # run-time error if "etc/daily" file doesn't exists
  }
}

class test (String $param = 'weekly') {     # Ensuring that only string type can be sent as $param 

# Including the class 
class { 'test': }

# Including the class - with parameter
class { 'test': 
  param => 'weekly',
} 

# using Include
include test
include ::test   # scope?

# same result
class {'test':}      # Declaring a class using Resource style
include test         # Declaring a class using Include style
include ::test

• Validation
  • we can use validation functions that are provided by puppetlabs/stdlib
    • Ex: validate_re(<string_to_test>, <regular_expression>)
  • Implementation example

class test ($param = 'daily') {
  $allowed = [
               '^daily$',    # starts with daily ^
               '^weekly$'      # ends with weekly $
             ]

  validate_re($param, $allowed)    # will print out a message saying the allowed param (daily, weekly)

  file {'temp':
    ensure => 'present',
    content => file("etc/${param}"),      # run-time error if "etc/daily" file doesn't exists
  }
}

• Parser validation puppet parser validate file.pp
• Inheritance

class ntp::config (
    $location = 'london',
    $admingroup =$ntp::params::admingroup,
    ) inherits ntp::params
{

}
class ntp::params {
  case $facts['os']['family'] {
    'RedHat': {
      $ntp_service = 'ntpd'
      $admingroup = 'wheel'
    }
    'RedHat': {
      $ntp_service = 'ntp'
      $admingroup = 'sudo'
    }
    default: {
      fail("Your ${facts['os']['family']} is not supported")
    }
  }
}