Example deploy.rb for use with Engine Yard Cloud

deploy.rb

task :production do
  set :rails_env, "production"
  role :app, "example.com", :master => true
  role(:app) { |opts| compute_ec2_addresses(:app, opts) }
  role(:db, :master => true) { |opts| compute_ec2_addresses(:db, opts) }
end

task :staging do
  set :rails_env, "staging"
  role :app, "staging.example.com", :master => true
  role(:app) { |opts| compute_ec2_addresses(:app, opts) }
  role(:db, :master => true) { |opts| compute_ec2_addresses(:db, opts) }
end

# =============================================================================
def compute_ec2_addresses(role, opts)
  role = "#{role}_master" if opts[:master] == true
    
  unless roles[:app].respond_to? :static_servers
    roles[:app].class.send(:define_method, :static_servers) { @static_servers }
  end
  app_master = roles[:app].static_servers.detect{|server| server.options[:master] == true }.host

  unless @dna
    require 'rubygems'
    require 'json'

    @dna = JSON.parse(capture("sudo cat /etc/chef/dna.json", :hosts => [app_master]))
  end

  instances = @dna["engineyard"]["environment"]["instances"]
  instance = instances.detect {|instance| instance["role"] == role.to_s }
  instance ? instance["public_hostname"] : nil
end