statics_controller.rb

class StaticsController < ActionController::Base
  def render_404
    if real_404?
      send_detailed_disaster_mail(request)
    end

    respond_to do |format|
      format.json do
        render json: "", status: 404
      end

      format.js do
        render text: "", status: 404
      end

      format.html do
        render template: "statics/404", status: 404, layout: 'application'
      end
    end
  end

  private

  def real_404?
    # code to reject known 404s (like browser bugs)
  end

  def send_detailed_disaster_mail(req)
    message = "#{req.method}: #{req.url}"
    subject = "[404] RoutingError #{message}"
    max = req.env.keys.map(&:size).max
    req.env.each do |key, value|
      message << "\n#{key.rjust(max)} : #{value}"
    end

    if Rails.env.development?
      logger.debug message
    else
      ::Mailer.disaster(subject, message).deliver
    end
  end
end