The rack application role.

rack_application.js

{
    // Some settings that are necessary for the Chef Solo to work
    // as expected. If you use the Ruby DSL rather than JSON you
    // can omit a few of these.
    "name": "rack_application",
    "description": "A simple role for a Rack application.",
    "chef_type": "role",
    "json_class": "Chef::Role",

    // All of the recipes that we want to load into the VM.
    "run_list": [
        "recipe[ruby_build]",
        "recipe[rbenv::system]"
    ],

    "default_attributes": {
        "rbenv": {
            "rubies": ["1.9.3-p392"],
            "global": "1.9.3-p392",
            "gems": {
                "1.9.3-p392": [
                    { "name": "bundler" },
                    { "name": "foreman" },
                    { "name": "unicorn" },
                    { "name": "rack" }
                ]
            }
        }
    }
}