Dependency management with Puppet

Hi, I’m Richard Crowley

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

Installing Puppet

sudo apt-get update
sudo apt-get -y install ruby ruby-dev \
    rubygems libopenssl-ruby \
    libshadow-ruby1.8

sudo gem install rubygems-update
PATH=$PATH:/var/lib/gems/1.8/bin \
    sudo update_rubygems

sudo gem install puppet

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 => "0.7.65-1ubuntu2",
}

package {
    "mysql2":
        ensure   => "0.2.4",
        provider => gem;
    "rails":
        ensure   => "3.0.0",
        provider => gem;
}

A bug!

package {
    "mysql2":
        ensure   => "0.2.4",
        provider => gem;
}

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

Declare all dependencies

package {
    "libmysqlclient-dev":
        ensure => "5.1.41-3ubuntu12.3";
    "mysql2":
        ensure   => "0.2.4",
        provider => gem;
}

Nondeterminism!

package {
    "libmysqlclient-dev":
        ensure => "5.1.41-3ubuntu12.3";
    "mysql2":
        ensure   => "0.2.4",
        provider => gem;
}

Declare that dep

package {
    "libmysqlclient-dev":
        before => Package["mysql2"],
        ensure => "5.1.41-3ubuntu12.3";
    "mysql2":
        ensure   => "0.2.4",
        provider => gem;
}

Classes

• Singletons.
• Collections of resources.
• May be named as dependencies.

Running Puppet

sudo puppet apply deps.pp

• Bring a new server up to speed.
• Incrementally manage your devbox.

Thank you

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