Ruby on Rails Lightweight

config.ru

require "rails"
require "action_controller/railtie"

class RoRLightweight < Rails::Application
  routes.append do
    get "/welcome" => "welcome#index"
  end

  config.cache_classes = true
  config.middleware.delete "Rack::Lock"
  config.middleware.delete "ActionDispatch::Flash"
  config.middleware.delete "ActionDispatch::BestStandardsSupport"
  config.secret_token = "1542f8fae401d3ec3a736b10e2cb11ec6a7ad0da11dfe7d94a453b4579184fd7aefe1f0500bdb74f5bfdb8b062163b83abed94c53b901a4a0219458f8f47fce6"
end

class WelcomeController < ActionController::Metal
  include ActionController::Rendering

  def index
    render :text => "Hello world!"
  end
end

RoRLightweight.initialize!

run RoRLightweight

Gemfile

source :rubygems

gem "actionpack", "~> 4.0"
gem "railties",   "~> 4.0"
gem "tzinfo"

gem "thin"