[mnarayan01]

  // check if we're toobusy() - note, this call is extremely fast, and returns
  // state that is calculated asynchronously.  
  if (toobusy()) res.send(503, "I'm busy right now, sorry.");

Saying it is calculated "asynchronously" seems pretty confusing in this context. Maybe "is cached at a fixed interval"?

[firefoxman1]

Side note: caching at a fixed interval is a great way to save CPU cycles. If you're serving 100req/s and you had to grab the current time within 1sec accuracy for them, you could have 1/100th the amount of Date calls by getting the time each second instead of each request.

[lloydhilaiel]

I agree. /me fixes

[wereHamster]

Nope, it is literally calculated asynchronously. Look at https://github.com/lloyd/node-toobusy/blob/master/toobusy.cc... and lines 91/92 which sets up the background timer.