go cluster note

func HeavyWork(id int) {
	rand.Seed(int64(id))
	interval := time.Duration(rand.Intn(3)+1) * time.Second
	time.Sleep(interval)
	fmt.Printf("HeavyWork %-3d cost %v\n", id, interval)
}

// "talk is cheap, show me the code."
func main() {
	waitChan := make(chan int, 1)
	for i := 0; i < N; i++ {
		go func(n int) {
			HeavyWork(n)
			waitChan <- 1
		}(i)
	}
	cnt := 0
	for range waitChan {   //是用for 读取chan,如果不读取, go func 会阻塞, 主程序for 结束时,也就是并发结束时
		cnt++
		if cnt == N {
			break
		}
	}
	close(waitChan)
	fmt.Println("finished")
}

// "talk is cheap, show me the code."
// Add 用来添加 goroutine 的个数。Done 执行一次数量减 1。Wait 用来等待结束
func main() {
	wg := sync.WaitGroup{}
	for i := 0; i < N; i++ {
		wg.Add(1)
		go func(n int) {
			defer wg.Done()
			HeavyWork(n)
		}(i)
	}
	wg.Wait()
	fmt.Println("finished")
}

func main() {
	ok, quit := make(chan int, 1), make(chan int, 1)
	go func() {
		i := 0
		for {
			select {
			case <- quit:  //如果quit成功读到数据，则进行该case处理语句,如果不给 quit 传值,则不执行
				ok <- 1  //给chan ok 传值,如果没有读ok,则阻塞
				return
			default:
				HeavyWork(i)
				i++
			}
		}
	}()
	time.Sleep(5 * time.Second)
	quit <- 1  //不给quit值,会
	<-ok
}