ticker.md

Time Ticker and Sleep

Tickers are for when you want to do something repeatedly at regular intervals.

But what if the something task takes time longer than interval?

Let's test it:

package main

import (
    "fmt"
    "time"
)

func main() {
    ticker := time.NewTicker(time.Second)
    defer ticker.Stop()
    done := make(chan bool)
    go func() {
        time.Sleep(10 * time.Second)
        done <- true
    }()
    for {
        select {
        case <-done:
            fmt.Println("Done!")
            return
        case t := <-ticker.C:
            fmt.Println("Current time: ", t)
            time.Sleep(time.Second * 10)
            fmt.Println("After a tick 2s", time.Now())
        }
    }
}

The result is interesting, the ticker has to wait until the interrupt Sleep is done but the returned tick doesn't include the Sleep time.

Current time:  2020-07-10 09:03:37.70405479 +0700 +07 m=+1.000134765
After a tick 2s 2020-07-10 09:03:39.704664613 +0700 +07 m=+3.000744605
Current time:  2020-07-10 09:03:38.704132675 +0700 +07 m=+2.000212636
After a tick 2s 2020-07-10 09:03:41.7048811 +0700 +07 m=+5.000961093
Current time:  2020-07-10 09:03:40.704144127 +0700 +07 m=+4.000224096
After a tick 2s 2020-07-10 09:03:43.705124327 +0700 +07 m=+7.001204329
Current time:  2020-07-10 09:03:42.704140894 +0700 +07 m=+6.000220865
After a tick 2s 2020-07-10 09:03:45.705391382 +0700 +07 m=+9.001471372
Current time:  2020-07-10 09:03:44.704143883 +0700 +07 m=+8.000223851
After a tick 2s 2020-07-10 09:03:47.705639864 +0700 +07 m=+11.001719857
Current time:  2020-07-10 09:03:46.704047296 +0700 +07 m=+10.000127260
After a tick 2s 2020-07-10 09:03:49.705904585 +0700 +07 m=+13.001984508
Done!