Difference between time.NewTimer() and time.Reset() when "clear" timer

[fdin...@gmail.com]

Hi all:

I am writing something as a watch-dog, for example, a timer will be reseted to timing from 0 if something happened, otherwise after a const duration, it will timeout.

To re-timing the timer, there maybe 2 ways:

tmr := time.NewTimer(d)

// watcher
for {
    select {
    case <- tmr.C:
        // timeout! blablabla..
   
    case <- something-happened-notice-channel:
        // 2 ways to reset timer:
        // tmr.Reset(d)
        // tmr = time.NewTimer(d)
    }
}

These 2 different ways to reset timer seems do the same thing, except the latest is more expensive because of allocating new memory and may trigger GC-handling more frequently than the 1st way, especially when a huge amount of timer is allocated (this is just what I thought, maybe incorrect, please tell me more if anyone know the details).

But when I use it in my code, these 2 ways leads my code to different result. My related function is:

func (rf *Raft) newRandTimer() {
    rf.timeout = electionTimeoutGen()
    /*
    if rf.timer == nil {
        rf.timer = time.NewTimer(rf.timeout)
    } else {
        rf.timer.Reset(rf.timeout)
    }
    */
    rf.timer = time.NewTimer(rf.timeout)
}

When I use code in /* */, it cannot reset the timer and will expired, which is not correct, however, when I code as re-allocate timer, it goes well. Any tips please?

Thanks.

[pierre...@gmail.com]

Hello,

You should definitely use the Reset() method.

Using the first code sample you provided, everything works as expected, see http://play.golang.org/p/Zq50IYFPTO.

I am not sure why it fails in your full code, maybe try to isolate a non-working as expected sample?

[roger peppe]

Timer.Reset has unfortunate semantics and is awkward to use correctly.
Notably, calling Reset does not guarantee that you won't
receive a value on the channel from the last timer event.

You might find it worthwhile to read this thread:

https://groups.google.com/forum/#!topic/golang-dev/c9UUfASVPoU

and these issues:

https://github.com/golang/go/issues/11513
https://github.com/golang/go/issues/14038

In summary, you shouldn't call Timer.Reset without
checking its return value and receiving from the channel
if it returned false.

cheers,
rog.

> --
> You received this message because you are subscribed to the Google Groups
> "golang-nuts" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to golang-nuts...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.