time.Ticker's behavior

[Kai Zhang]

Hello,

      I'm using ticker to do some batch works.But I found why tickers runs not as expect.why the second ticker is 100 Millisecond.code is here

thanks,

zhangkai

2020-05-25

[Brian Candler]

You asked for ticks at 100ms intervals, but your receiver has a time.Sleep(1*time.Second).

See https://golang.org/pkg/time/#NewTicker

"It adjusts the intervals or drops ticks to make up for slow receivers."

[Jake Montgomery]

I'll take a crack at it. The behavior you see is one tick about 100ms after start, a second one marked as 200ms after start, then one 1200ms, one at 2200, and another at 3200ms after start.

The key is in the documentation for NewTicker: "It adjusts the intervals or drops ticks to make up for slow receivers."

If you add a bit more info to your app it becomes clearer: https://play.golang.org/p/gHZXgyIuYw7

Here is what is happening:

100ms - The ticker fires and sends a tick timestamped 100ms.

100ms - Your goroutine wakes, receives the tick timestamped 100ms.

100+ms - Your goroutine goes to sleep at line 30 (for one second).

200ms - The ticker fires again, but your goroutine is asleep.

300ms - Since the last tick has not been processed, the ticker waits, as described in the docs: "It adjusts the intervals or drops ticks to make up for slow receivers."

1100ms - Your goroutine wakes, receives the tick timestamped 200ms.

1100+ms Your goroutine goes to sleep at line 30 (for one second).

1200ms - Since the tick was processed the ticker sends its next tick.

1300ms - Since the last tick has not been processed, the ticker waits, as described in the docs: "It adjusts the intervals or drops ticks to make up for slow receivers."

2100ms - Your goroutine wakes, receives the tick timestamped 1200ms

2100ms - Your goroutine goes to sleep at line 30 (for one second).

2200ms - Since the tick was processed the ticker sends its next tick.

2300ms - Since the last tick has not been processed, the ticker waits, as described in the docs: "It adjusts the intervals or drops ticks to make up for slow receivers."

It continues on like that until the program exits after 3600ms.

Hope this helps.

[Kai Zhang]

Hello,

    It really help,I scan the go source and I can see the ticker.C is 1-element channel.maybe I should just treate it as a normal channel.but the value in channel is Time.Now I am seek how the later ticker be dropped.because the source code said 

// NewTicker returns a new Ticker containing a channel that will send the // time with a period specified by the duration argument. // It adjusts the intervals or drops ticks to make up for slow receivers. // The duration d must be greater than zero; if not, NewTicker will panic. // Stop the ticker to release associated resources. func NewTicker(d Duration) *Ticker {         if d <= 0 {                 panic(errors.New("non-positive interval for NewTicker"))         }         // Give the channel a 1-element time buffer.         // If the client falls behind while reading, we drop ticks         // on the floor until the client catches up.         c := make(chan Time, 1)         t := &Ticker{                 C: c,                 r: runtimeTimer{                         when:   when(d),                         period: int64(d),                         f:      sendTime,                         arg:    c,                 },         }         startTimer(&t.r)         return t }

在 2020年5月25日星期一 UTC+8下午7:22:15，Jake Montgomery写道：