Terraform arrives

.gitignore

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+*.gem
+.bundle
+Gemfile.lock
+pkg/*

Gemfile

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+source "http://rubygems.org"
+
+# Specify your gem's dependencies in terraform.gemspec
+gemspec

README.markdown

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+Terraform is a small goal-oriented DSL for setting up a machine, similar in purpose to Chef and
+Puppet. Its design is inspired by Babushka, but it's simpler and tailored specifically for provisioning a machine for a webapp.
+
+Usage
+-----
+
+    require "terraform_dsl"
+    include TerraformDsl
+    dep "my library" do
+      met? { (check if your dependency is met) }
+      meet { (install your dependency) }
+    end
+
+A more detailed README is coming shortly.
+
+Contribute
+----------
+When editing this gem, to test your changes, you can load your local copy of the gem in your project by using this in your Gemfile:
+
+gem "terraform", :path => "~/p/terraform"
+
+Credits
+-------
+Dmac -- thanks for the name!

Rakefile

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+require "bundler/gem_tasks"

lib/terraform.rb

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+require "terraform/version"
+require "fileutils"
+
+module Terraform
+  # Writes the terraform_dsl.rb to the given file or directory.
+  def self.write_dsl_file(path)
+    path = File.join(path, "terraform_dsl.rb") if File.directory?(path)
+    FileUtils.cp(File.expand_path(File.join(File.dirname(__FILE__), "terraform/terraform_dsl.rb")), path)
+  end
+end

lib/terraform/terraform_dsl.rb

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+# This is small goal-oriented DSL for installing system components, similar in purpose to Chef and Puppet.
+# Its design is inspired by Babushka but it's simpler and tailored specifically for provisioning a machine
+# for a webapp.
+#
+# Usage:
+#
+# require "terraform_dsl"
+# include TerraformDsl
+# dep "my library" do
+#   met? { (check if your dependency is met) }
+#   meet { (install your dependency) }
+# end
+
+require "fileutils"
+require "digest/md5"
+
+module TerraformDsl
+  def dep(name)
+    @dependencies ||= []
+    # If a dep gets required or defined twice, only run it once.
+    return if @dependencies.find { |dep| dep[:name] == name }
+    @dependencies.push(@current_dependency = { :name => name })
+    yield
+  end
+  def met?(&block) @current_dependency[:met?] = block end
+  def meet(&block) @current_dependency[:meet] = block end
+  def in_path?(command) `which #{command}`.size > 0 end
+  def fail_and_exit(message) puts message; exit 1 end
+
+  # Runs a command and raises an exception if its exit status was nonzero.
+  # - silent: if false, log the command being run and its stdout. False by default.
+  # - check_exit_code: raises an error if the command had a non-zero exit code. True by default.
+  def shell(command, options = {})
+    silent = (options[:silent] != false)
+    puts command unless silent
+    output = `#{command}`
+    puts output unless output.empty? || silent
+    raise "#{command} had a failure exit status of #{$?.to_i}" unless $?.to_i == 0
+    true
+  end
+
+  def satisfy_dependencies
+    STDOUT.sync = true # Ensure that we flush logging output as we go along.
+    @dependencies.each do |dep|
+      unless dep[:met?].call
+        puts "* Dependency #{dep[:name]} is not met. Meeting it."
+        dep[:meet].call
+        fail_and_exit %Q("met?" for #{dep[:name]} is still false after running "meet".) unless dep[:met?].call
+      end
+    end
+  end
+
+  #
+  # These are very common tasks which are needed by almost everyone, and so they're bundled with this DSL.
+  #
+
+  def package_installed?(package) `dpkg -s #{package} 2> /dev/null | grep Status`.match(/\sinstalled/) end
+  def install_package(package)
+    # Specify a noninteractive frontend, so dpkg won't prompt you for info. -q is quiet; -y is "answer yes".
+    shell "sudo DEBIAN_FRONTEND=noninteractive apt-get install -qy #{package}"
+  end
+
+  def ensure_packages(*packages) packages.each { |package| ensure_package(package) } end
+  def ensure_package(package)
+    dep package do
+      met? { package_installed?(package) }
+      meet { install_package(package) }
+    end
+  end
+
+  def gem_installed?(gem) `gem list '#{gem}'`.include?(gem) end
+
+  def ensure_gem(gem)
+    dep gem do
+      met? { gem_installed?(gem) }
+      meet { shell "gem install #{gem} --no-ri --no-rdoc" }
+    end
+  end
+
+  # Ensures the file at dest_path is exactly the same as the one in source_path.
+  # Invokes the given block if the file is changed. Use this block to restart a service, for instance.
+  def ensure_file(source_path, dest_path, &on_change)
+    dep dest_path do
+      met? do
+        raise "This file does not exist: #{source_path}" unless File.exists?(source_path)
+        File.exists?(dest_path) && (Digest::MD5.file(source_path) == Digest::MD5.file(dest_path))
+      end
+      meet do
+        FileUtils.cp(source_path, dest_path)
+        on_change.call if on_change
+      end
+    end
+  end
+
+  def ensure_rbenv
+    ensure_package "git-core"
+    dep "rbenv" do
+      met? { in_path?("rbenv") }
+      meet do
+        # These instructions are from https://github.com/sstephenson/rbenv/wiki/Using-rbenv-in-Production
+        shell "wget -q -O - https://raw.github.com/fesplugas/rbenv-installer/master/bin/rbenv-installer | bash"
+        # We need to run rbenv init after install, which adjusts the path. If exec is causing us problems
+        # down the road, we can perhaps simulate running rbenv init without execing.
+        unless ARGV.include?("--forked-after-rbenv") # To guard against an infinite forking loop.
+          exec "bash -c 'source ~/.bashrc; #{$0} --forked-after-rbenv'" # $0 is the current process's name.
+        end
+      end
+    end
+  end
+
+  # ruby_version is a rbenv ruby version string like "1.9.2-p290".
+  def ensure_rbenv_ruby(ruby_version)
+    ensure_rbenv
+    ensure_packages "curl", "build-essential", "libxslt1-dev", "libxml2-dev", "libssl-dev"
+
+    dep "rbenv ruby #{ruby_version}" do
+      met? { `which ruby`.include?("rbenv") && `ruby -v`.include?(ruby_version.gsub("-", "")) }
+      meet do
+        puts "Compiling Ruby will take a few minutes."
+        shell "rbenv install #{ruby_version}"
+        shell "rbenv rehash"
+      end
+    end
+  end
+end

lib/terraform/version.rb

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+module Terraform
+  VERSION = "0.0.1"
+end

terraform.gemspec

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+# -*- encoding: utf-8 -*-
+$:.push File.expand_path("../lib", __FILE__)
+require "terraform/version"
+
+Gem::Specification.new do |s|
+  s.name        = "terraform"
+  s.version     = Terraform::VERSION
+  s.authors     = ["Phil Crosby"]
+  s.email       = ["phil.crosby@gmail.com"]
+  s.homepage    = "http://github.com/philc/terraform"
+  s.summary     = %q{Set up a cold, inhospitable system using Terraform.}
+  # s.description = %q{TODO: Write a gem description}
+
+  s.rubyforge_project = "terraform"
+
+  s.files         = `git ls-files`.split("\n")
+  s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
+  s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
+  s.require_paths = ["lib"]
+end