timers: expose rearm()

[mscdex]

• Version: all
• Platform: n/a
• Subsystem: timers

It would be nice if timers exported rearm() or at least a variant of it suitable for public consumption. One use case for this is to allow for easier and/or more efficient keepalive mechanisms where a timer needs to be reset after a packet is sent/received.

Currently the only two solutions to achieve this are to constantly start/clear a normal Timeout or use an Interval timer and have some extra logic in the Interval callback to determine whether you should actually execute the real callback (and even then you can lose accuracy). Being able to just rearm(timer) simplifies all of this greatly and has much less overhead than clearTimeout() followed by setTimeout() for every packet.

[XadillaX]

@mscdex Could you give some code to show how to use this feature? Assume function rearm() is already finished and you can use this function in your code.

[tniessen]

@XadillaX I think what @mscdex suggests is something like this. Instead of having to write code such as

function someAsyncWork(callback) {
  console.log('Doing something which must not be done more than once per second');
  setTimeout(callback, 50);
}

let timeout;
function doSomethingPeriodically() {
  someAsyncWork((err) => {
    timeout = setTimeout(doSomethingPeriodically, 1000);
  });
}

timeout = setTimeout(doSomethingPeriodically, 1000);

it would be nice to just write

let timeout;
function doSomethingPeriodically() {
  someAsyncWork((err) => {
    timeout.rearm(); // or timers.rearm(timeout)
  });
}

timeout = setTimeout(doSomethingPeriodically, 1000);

[Fishrock123]

Not sure I agree with exposing rearm(), but the behavior you are looking for already exists: just call timers.active() on the timer.

Related to #11736

[Fishrock123]

@mscdex does that solve what you are looking for, or?

See https://github.com/nodejs/node/pull/11154/files#diff-e6ef024c3775d787c38487a6309e491dR240 for an example in practice.

[mscdex]

@Fishrock123 I haven't tested yet, it may be.

[targos]

should this stay open?

[Fishrock123]

My refresh PR solves this better, I think.

Certainly rearm() should not be used to refresh timers.

[Fishrock123]

Timeout#refresh() is now a public API in Node 10 (afaik) - see 46d335c