jiffy.rb

#!/usr/bin/env ruby

begin
  require 'aws'
rescue LoadError => e
  abort "Unable to load library: #{e.message}"
end

require 'Forwardable'

class SandBox < AWS::EC2::Instance
  attr_reader :instance, :key, :key_name, :username

  extend Forwardable
  def_delegators :@instance, :dns_name, :id, :status

  SSH_PORT = 22

  def initialize(ami_id)
    read_config
    @ec2 = AWS::EC2.new(:ec2_endpoint => ec2_endpoint)
    key_setup
    @instance = @ec2.instances.create(:image_id => ami_id, :key_name => @key_name)
  end

  def ec2_endpoint
    ec2_url = ENV['EC2_URL'] || 'https://ec2.us-east-1.amazonaws.com'
    ec2_url.split('/').last
  end

  def key_setup
    unless @key = ENV['EC2_KEYPAIR']
      abort 'You must export EC2_KEYPAIR'
    end
    unless @key_name = ENV['EC2_KEYPAIR_NAME']
      abort 'You must export EC2_KEYPAIR_NAME'
    end
    @username = ENV['EC2_USER'] || 'root'
  end

  def read_config
    config_path = File.expand_path(File.join(Dir.home, '.ec2', 'jiffy.yml'))
    unless File.exists?(config_path)
      abort "#{config_path} must contain :access_key id and :secret_access_key"
    end
    AWS.config(YAML.load(File.read(config_path)))
  end

  def tcp_test_ssh
    tcp_socket = TCPSocket.new(dns_name, SSH_PORT)
    readable = IO.select([tcp_socket], nil, nil, 5)
    if readable
      yield
      true
    else
      false
    end
  rescue SocketError, Errno::ECONNREFUSED, Errno::EHOSTUNREACH, Errno::ENETUNREACH, IOError
    sleep 2
    false
  rescue Errno::EPERM, Errno::ETIMEDOUT
    false
  ensure
    tcp_socket && tcp_socket.close
  end

  def wait_for_sshd
    STDOUT.print(".") until tcp_test_ssh do
      sleep @initial_sleep_delay ||= 2
      puts("done")
    end
  end
end

if __FILE__ == $0
  if ARGV.length != 1
    abort "Usage: #{__FILE__} ami-id"
  end
  ami_id = ARGV[0]
  unless ami_id =~ /^ami-[0-9a-f]{8}$/
    abort "Malformed AMI id"
  end
  i = SandBox.new(ami_id)
  puts "Instance [#{i.id}] created"
  print '... waiting for boot ...'
  until i.status == :running
    print('.')
    sleep @initial_sleep_delay ||= 2
  end
  puts("done")
  print '... waiting for sshd ...'
  i.wait_for_sshd
  exec('ssh', '-oForwardAgent=yes', '-oUserKnownHostsFile=/dev/null', '-oStrictHostKeyChecking=no', '-l', i.username, '-i', i.key, i.dns_name)
end