Dependency management with Puppet

Hi, I’m Richard Crowley

• Equal opportunity technology hater
• DevStructure’s operator and UNIX hacker

Installing Puppet

• apt-get install puppet

• or

• gem install puppet

• You really want 2.6 or better.

Resources

• The smallest unit of configuration.
• Have a type, a name, and attributes.

Packages

• The obvious resource type.
• Abstract differences between
  package managers.

Package resources

package { "nginx":
    ensure => "0.7.67-3ubuntu1",
}

package {
    "mysql2":
        ensure   => "0.2.6",
        provider => gem;
    "rails":
        ensure   => "3.0.1",
        provider => gem;
}

A bug!

package {
    "mysql2":
        ensure   => "0.2.6",
        provider => gem;
}

• Missing libmysqlclient-dev package which is needed to build mysql2 gem.

Declare all dependencies

package {
    "libmysqlclient-dev":
        ensure => "5.1.49-1ubuntu8";
    "mysql2":
        ensure   => "0.2.6",
        provider => gem;
}

Nondeterminism!

package {
    "libmysqlclient-dev":
        ensure => "5.1.49-1ubuntu8";
    "mysql2":
        ensure   => "0.2.6",
        provider => gem;
}

Declare that dep

package {
    "libmysqlclient-dev":
        ensure => "5.1.49-1ubuntu8";
    "mysql2":
        ensure   => "0.2.6",
        provider => gem,
        require  =>
            Package["libmysqlclient-dev"];
}

Realistic example

Ruby and RubyGems

stage { "pre": before => Stage["main"] }
class pre {
    package {
        "build-essential": ensure => latest;
        "ruby": ensure => "4.5"; # Ruby 1.8.7
        "ruby-dev": ensure => "4.5"; # Ruby 1.8.7
        "rubygems": ensure => "1.3.7-2";
    }
}
class { "pre": stage => "pre" }

Running Puppet

• sudo puppet apply deps.pp

• Bring a new server up to speed.

• Incrementally manage your devbox.

• https://gist.github.com/668403

Thank you

• richard@devstructure.com or @rcrowley
• P.S. use DevStructure.