Use Mongrel as the default Rails server in Rails 3.2.x instead of WEBrick

mongrel.rb

# config/initializers/mongrel.rb
# This will make Mongrel the default server in development
module Rack
  module Handler
    def self.default(options = {})
      # Guess.
      if ENV.include?("PHP_FCGI_CHILDREN")
        # We already speak FastCGI
        options.delete :File
        options.delete :Port

        Rack::Handler::FastCGI
      elsif ENV.include?("REQUEST_METHOD")
        Rack::Handler::CGI
      else
        begin
          Rack::Handler::Thin
        rescue LoadError
          if Rails.env.development?
            # use Mongrel as default
            Rack::Handler::Mongrel
          else
            # keep WEBrick as the default
            Rack::Handler::WEBrick
          end
        end
      end
    end
  end
end