golang scheduled stop

More and more software systems require periodic operations, such as data backup, log cleaning, scheduled tasks, etc. When implementing these periodic operations, we usually need to use timers. Golang provides a built-in timer, but when performing timing operations, how can we stop the timer at the required time?

Generally speaking, we can use the time package provided by golang to generate a timer. For example:

timer1 := time.NewTimer(time.Second * 5)
<-timer1.C
fmt.Println("Timer 1 expired")

The above code will output "Timer 1 expired" after 5 seconds. The program here will receive a time signal from the timer channel (timer1.C) after waiting for 5 seconds, thereby realizing the timer's task. It should be noted that the timer created using the time.NewTimer() function will automatically repeat by default. You need to use timer.Stop() to end the timer, otherwise the timer will keep running.

But what if we need to stop the timer within a specified time? For example, when we are backing up data, if the specified backup time is exceeded, we need to forcefully stop the timer and end the backup task. At this time, we need to bind the stop signal when the timer is generated, and send abort information to the signal when it needs to be stopped.

// 定时任务函数
func doDataBackup(stopSignal chan bool){
    // 模拟数据备份，并每10秒执行一遍
    for {
        select {
        case <-time.After(time.Second * 10):
            backupData()
        case stop := <-stopSignal:
            if stop {
                fmt.Println("Data backup stopped.")
                return
            }
        }
    }
}

func main() {
    stopSignal := make(chan bool)
    // 每10秒备份一次数据，规定备份时间为50秒
    go doDataBackup(stopSignal)
    time.Sleep(time.Second * 50)
    // 操纵停止信号，结束任务
    stopSignal <- true
}

In the above code, we added a stop signal stopSignal in the doDataBackup() function to accept forced stop information. When we need to stop the backup task, we only need to send true to the stopSignal channel, and the backup task will be forcibly stopped.

It should be noted that before sending a stop signal to the stopSignal channel, some necessary operations such as data saving and resource release may be required. These operations need to be performed before sending a stop signal to the channel, otherwise problems such as data loss may occur.

It should be emphasized that the above backup tasks are performed within a single coroutine. If we need to execute tasks regularly in multiple coroutines and need to stop them regularly, we can use golang's sync.WaitGroup and context packages to achieve this. For example:

func doTask(ctx context.Context, wg *sync.WaitGroup, id int){
    defer wg.Done()
    fmt.Printf("goroutine %d started.
", id)
    for {
        select {
        case <-time.After(time.Second * 1):
            fmt.Printf("goroutine %d is working.
", id)
        case <-ctx.Done():
            fmt.Printf("goroutine %d is stopped.
", id)
            return
        }
    }
}

func main() {
    wg := sync.WaitGroup{}
    ctx, cancel := context.WithTimeout(context.Background(), time.Second * 5)
    defer cancel()
    for i := 0; i < 3; i++ {
        wg.Add(1)
        go doTask(ctx, &wg, i)
    }
    wg.Wait()
    fmt.Println("Task completed.")
}

In the above code, we created three coroutines. Each coroutine will perform a task regularly and control the closing of the coroutine through the incoming context. Use sync.WaitGroup to ensure that all coroutine tasks are completed before ending the program. Use the WithTimeout() function in the context, which stipulates that the maximum time for the task to run is 5 seconds. If the task is not completed within 5 seconds, the task will be forcibly stopped and the coroutine will exit.

The above is how to use timers in golang and how to implement scheduled stops. Using these methods, we can easily implement various periodic tasks and accurately control the running time and stop time of the tasks when needed.

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