alive

What

alive waits for subtasks, coordinate graceful or fast shutdown. sync.WaitGroup on steroids.

Usage

Key takeaways:

• go get github.com/temoto/alive
• Zero value of alive.Alive{} is not usable ever, you must use NewAlive() constructor.

    srv := MyServer{ alive: alive.NewAlive() }

• Call .Add(n) and .Done() just as with WaitGroup, monitor .IsRunning().

    for srv.alive.IsRunning() {
        task := <-queue
        srv.alive.Add(1)
        go func() {
            // be useful
            srv.alive.Done()
        }()
    }

• Call .Stop() to switch IsRunning and stop creating new tasks if programmed so.

    sigShutdownChan := make(chan os.Signal, 1)
    signal.Notify(sigShutdownChan, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
    go func(ch <-chan os.Signal) {
        <-ch
        log.Printf("graceful stop")
        sdnotify("READY=0\nSTATUS=stopping\n")
        srv.alive.Stop()
    }(sigShutdownChan)

• Call .Wait() to synchronize on all subtasks .Done(), just as with WaitGroup.

func main() {
    // ...
    srv.alive.Wait()
}

• .StopChan() lets your observe .Stop() call from another place. A better option to IsRunning() poll.

    stopch := srv.alive.StopChan()
    for {
        select {
        case job := <-queue:
            // be useful
        case <-stopch:
            // break for loop
        }
    }

• .WaitChan() is select-friendly version of .Wait().
• Incorrect API usage .Stop() ; .Add() will panic. Please tell me how to remove it while staying interface compatible with WaitGroup.
• There are few more panic() which should never happen, like debug-build assertions. But please tell me if you find a way to trigger "Bug in package"

Flair