fu.get("/latest_message", function (req, res) {
  var since = parseInt(qs.parse(url.parse(req.url).query).since);

  if(since < latestMessageReceived) // new message since client last requested
    sendLatestMessageToClient(res); // send it straight to them
  else
    messageRequests.push({ callback: sendLatestMessageToClient, res: res }); // queue up the requst
});