code: function bubble(ask, layer) {
    ask.server.stack[layer](ask.req, ask.res, function next() {
      if (ask.server.stack.length > layer + 1) bubble(ask, layer + 1);
      else {
        ask.res.statusCode = 500;
        ask.res.end('Internal Server Error\n');
      }
    });
  }
docs: The bubble goes through each layer of the stack until it reaches the surface. The surface is a Server Error, btw.