Puppet Language Intro

“It’s not programming, it’s declaring your intentions to the universe. The universe just happens to be made of servers.”

Overview

The Puppet language (also called the Puppet DSL) is a declarative, domain-specific language designed for one thing: describing the desired state of your infrastructure. You don’t tell Puppet how to do something — you tell it what you want, and it figures out the rest.

If you’re coming from scripting of any kind, this requires a small shift in thinking. Instead of writing:

# Imperative (shell): HOW to do it
source /etc/os-release
if $ID == 'rhel'; then
  if ! rpm -q httpd; then
    yum install -y httpd
  fi
  systemctl enable httpd
  systemctl start httpd
elsif $ID == 'ubuntu'; then
  if ! dpkg-query -W -f='${Status}' apache 2>/dev/null | grep -q "ok installed"; then
    apt install -y apache
  fi
  systemctl enable apache
  systemctl start apache
elseif .....
  # ....
fi

You write:

# Declarative (Puppet): WHAT you want
package { 'httpd':
  ensure => installed,
}

service { 'httpd':
  ensure => running,
  enable => true,
}

puppet apply manifest.pp

Same result, but the Puppet version is idempotent, cross-platform (mostly), and self-documenting. You might get excited and want to go writing a bunch of Puppet code now, but let’s go another layer deeper. What if you didn’t even have to write any of this yourself?

The Puppet Forge

One of the strengths of the OpenVox community is the vast amount of pre-written modules. For example, let’s say that you wanted to manage a simple nginx reverse proxy. First, install the module:

puppet module install puppet/nginx

Then declare the resources exposed by the nginx module:

# set up nginx itself
include nginx

# then declare the resource you want to manage
nginx::resource::server { 'kibana.example.com':
  listen_port => 80,
  proxy       => 'http://localhost:5601',
}

puppet apply nginx_reverse_proxy.pp

Many users won’t need to learn more of the Puppet Language. Instead, the roles and profiles design pattern makes it easy to build a composable and maintainable codebase with component modules sourced from the Pupept Forge.

If you do end up needing to write your own modules, then you can go further learning the language. Let’s dive in.