lib/hirefire/middleware.rb
def get_path_prefix
      if defined?(Rails) && Rails.application.config.relative_url_root
        Regexp.new("^" + Regexp.escape(Rails.application.config.relative_url_root))
      end
    end
def get_path_prefix
      if defined?(Rails) && Rails.application.config.relative_url_root
        Regexp.new("^" + Regexp.escape(Rails.application.config.relative_url_root))
      end
    end
Configures the @path_prefix in order to handle apps
 mounted under RAILS_RELATIVE_URL_ROOT.