Accurate timer in Nodejs

Question

I'm building a live chess app, and I'm trying to add a timer to it. However, I am struggling to find a way to make the timer accurate. I have run some tests, and setInterval and setTimeout are extremely inaccurate, with a ten minute timeout being off by over three minutes. I also tried using setInterval with in interval of 100ms, but even that was off by over minute, when the tab was not active. That was just with the javascript window.setInterval; with nodejs, it hasn't been more than 10ms off, but I'm afraid it will if the server gets busy. I'm hoping to find a way to have the game end within at least a tenth of a second of the real time.

Any suggestions? Thanks!

If your timeout is so large, why not just check the current time and subtract from the start time using Date API? OS timers are notoriously not accurate. — JBaczuk, Mar 03 '22 at 21:10
I agree with using the date API. I would use Date.now() for the unix timestamp and compare it to the previous Date.now() — Cal Irvine, Mar 03 '22 at 21:17
Adding on to everyone's comments, it's important that you never trust the timestamp sent from the client, although you can run it on the client just to display the UI. — code, Mar 03 '22 at 22:18
I am using the Date API, but how can I use that to trigger a response at a set time? If the callback in the timeout gets called even a second behind, knowing the time since the start time won't be helpful. (if you know what I mean) Should I maybe have an interval of 100ms that updates the time? Or would it still be prone to large inaccuracies? — jjroley, Mar 03 '22 at 22:26
Please provide enough code so others can better understand or reproduce the problem. — Community, Mar 04 '22 at 05:42

score 1 · Accepted Answer · answered Mar 10 '22 at 16:40

an ideal approach would be to use absolute clock time to get time elapsed and timer to have that check.

Something like code below.

const startTime = new Date();

const maxTime = 5 * 1000; // 60 seconds
setInterval(() => {
  checkExpired();
}, 300);

function checkExpired() {
  const curTime = new Date();

  timeDifference = Math.abs(curTime.getTime() - startTime.getTime());

  if (timeDifference > maxTime) {
    console.log("time up");
  }
}

The browser will not run setInterval as required due to performance reason. https://usefulangle.com/post/280/settimeout-setinterval-on-inactive-tab

If you need to run timer with required interval then it can be run in worker thread.

some info here. How can I make setInterval also work when a tab is inactive in Chrome?

But my guess is increased granularity is fine for non active tab.

Accurate timer in Nodejs

1 Answers1