gistfile1.rb

require 'ohai'
require 'json'
o = Ohai::System.new
o.all_plugins
chef_config = JSON.parse(o[:ec2][:userdata])
if chef_config.kind_of?(Array)
  chef_config = chef_config[o[:ec2][:ami_launch_index]]
end
Chef::Log.info(chef_config["app_role"])
if chef_config["app_role"] == "primary"
  execute "start delayed job daemon" do  
    cwd "#{node[:deploy_root]}/current"
    command "script/delayed_job start"
    user "amsrv"
  end 
  execute "whenever script " do
    #....
  end 
end