Credit Where It's Due

This is a re-invention of Ben Hoskings's excellent Babushka.

There are a bunch of things I love about Babushka, and a bunch of other things that really don't fit with the way we want to use it at Envato. Tango is an experiment in changing around a few of Babushka's fundamentals to try to find a better fit.

Bootstrapping Ubuntu

sudo apt-get install -y ruby irb rdoc

# Use the real rubygems, not the silly apt version. 
wget http://production.cf.rubygems.org/rubygems/rubygems-1.6.2.tgz
tar -zxvf rubygems-1.6.2.tgz
cd rubygems-1.6.2
sudo ruby setup.rb --no-format-executable

sudo gem install tango

Example Runner

require 'tango'

class AptInstaller < Tango::Runner
  def installed?(package)
    shell("dpkg-query", "--status", package, :echo => false).output !~ /not.installed|deinstall/
  end

  step :install do |package|
    met? { installed?(package) }
    meet { shell!("apt-get", "install", "-y", package) }
  end
end

class GemInstaller < Tango::Runner
  def installed?(gem)
    shell("gem", "query", "--installed", "--name-matches", gem, :echo => false).output =~ /true/
  end

  step :install do |gem|
    met? { installed?(gem) }
    meet { shell!("gem", "install", gem) }
  end
end

class ExampleInstaller < Tango::Runner
  def initialize
    @apt = AptInstaller.new
    @gem = GemInstaller.new
  end

  step :install do
    @apt.install "build-essential"

    @apt.install "mysql-server"
    @apt.install "libmysqlclient-dev"

    @apt.install "git-core"

    @gem.install "bundler"
  end
end

Running the Example

The normal way to do this is to use Rake as a front-end for Tango, so have a Rakefile like this:

require 'example_installer'

desc "Install MySQL, Git, and bundler."
task :example_install do
  ExampleInstaller.new.install
end

And then run:

rake example_install

Useful Helper Methods

Running Shell Commands

step :install_something do
  result = shell("apt-get", "install", "something")
  if result.succeeded?
    write("/tmp/something-install.log", result.output)
  end
end

Use shell! to raise an exception if the command exits with non-zero status.

Writing Config Files

step :configure_foo do
  @log_directory = "/var/log/foo.log"
  write "/etc/foo.conf", <<-EOF
    # Config file for foo
    log_file <%= @log_file %>
  end
end

Fetching a Remote URL

step :install do
  cd "/tmp" do
    fetch "http://example.com/something.tar.gz"
  end
end

Chainable Helper Methods

You can use these together like this:

in_directory("/tmp").with_umask(0022) do
  ...
end

Changing the Working Directory

step :migrate do
  in_directory "/rails_apps/blog" do
    shell "rake db:migrate"
  end
end

Changing the Umask

step :install do
  with_umask 0077 do
    shell "make install"
  end
end

Running As Another User

step :install do
  as_user "fred" do
    FileUtils.touch("/home/fred/fred_woz_ere")
  end
end

Copyright

Copyright © 2011 Envato & Pete Yandell. See LICENSE for details.