笔记：Google I/O 2012 - Go Concurrency Patterns

[wisecsj]

Google I/O 2012 - Go Concurrency Patterns

Rob Pike:

Go was designed for building system software

1. Go runtime holds waiting FIFO queue for receivers (goroutines ready to receive on the particular channel)

2. 多个goroutine产生 channel value 最终汇聚到某个 channel （fan-in）

3. 某个channel的值分发到多个goroutine (worker pattern)

Patterns

1. Generator:funciton that returns a channel

func boring(msg string) <-chan string { // Returns receive-only channel of strings.
    c := make(chan string)
    go func() { // We launch the goroutine from inside the function.
        for i := 0; ; i++ {
            c <- fmt.Sprintf("%s %d", msg, i)
            time.Sleep(time.Duration(rand.Intn(1e3)) * time.Millisecond)
        }
    }()
    return c // Return the channel to the caller.
}

2. Timeout using select

func main() {
    c := boring("Joe")
    for {
        select {
        case s := <-c:
            fmt.Println(s)
        case <-time.After(1 * time.Second):
            fmt.Println("You're too slow.")
            return
        }
    }
}

3. Timeout for whole conversation using select

   Create the timer once, outside the loop, to time out the entire conversation.

func main() {
    c := boring("Joe")
    timeout := time.After(5 * time.Second)
    for {
        select {
        case s := <-c:
            fmt.Println(s)
        case <-timeout:
            fmt.Println("You talk too much.")
            return
        }
    }
}

4. Daisy-chain
   

func f(left, right chan int) {
    left <- 1 + <-right
}

func main() {
    const n = 10000
    leftmost := make(chan int)
    right := leftmost
    left := leftmost
    for i := 0; i < n; i++ {
        right = make(chan int)
        go f(left, right)
        left = right
    }
    go func(c chan int) { c <- 1 }(right)
    fmt.Println(<-leftmost)
}

Google Search ,Example

1. 同步阻塞方式
2. fan-in 方式
3. fan-in + timeout
4. avoid discarding results from slow servers.Send requests to multiple replicas, and use the first response(对提供相同服务的多个服务器发送请求，取最快的那个)

Links

[wisecsj]

talk slide