Who is Goroutine

轻量级线程-协程

How to use Goroutine

https://dave.cheney.net/practical-go/presentations/qcon-china.html#_concurrency

  • Keep yourself busy or do the work yourself
    • 如果你的Goroutine在另一个Goroutine获得结果之前无法取得进展，那么通常情况下，自己做，比委派出去更简单
  • Never satart a Goroutine without knowing when it will stop
    • 如果要委派出去Goroutine，应该感知到Goroutine结束
  • Leave concurrency to the caller
    • 并发交给调用者

      Rule

      每次执行 go xxx 思考

  1. 什么时候Goroutine结束？
  2. 如何让某个Goroutine结束？
  3. Goroutine由调用者 go

Bad Code

  1. func main() {
  2.     go func() {
  3.         test()
  4.     }()
  5.     select {}
  6. }
  8. func test() {
  9.     // xxxx xxxx xxxx
  10. }
  1. func main() {
  2.     Go(test)
  3.     select {}
  4. }
  6. func test() {
  7.     // xxxx xxxx xxxx
  8. }
  10. func Go(f func()) {
  11.     go func() {
  12.         if err := recover(); err != nil {
  13.             fmt.Println(err)
  14.         }
  15.         f()
  16.     }()
  17. }
  1. func main() {
  2.     http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
  3.         fmt.Fprintln(w, "Hello")
  4.     })
  5.     go func() {
  6.         if err := http.ListenAndServe(":8080", nil); err != nil {
  7.             log.Fatal(err)
  8.         }
  9.     }()
  11.     select {}
  12. }
  1. func main() {
  2.     mux := http.NewServeMux()
  3.     mux.HandleFunc("/", func(resp http.ResponseWriter, req *http.Request) {
  4.         fmt.Fprintln(resp, "Hello, QCon!")
  5.     })
  6.     go http.ListenAndServe("127.0.0.1:8001", http.DefaultServeMux) // debug
  7.     http.ListenAndServe("0.0.0.0:8080", mux)                       // app traffic
  8. }
  1. // API servie 接收一个service
  2. func service() {
  3.     go Go(doSometing())
  4. }
  6. func doSometing() {
  7.     // xxxxxx
  8. }
  10. func Go(f func()) {
  11.     if err := recover(); err != nil {
  12.         fmt.Println(err)
  13.     }
  14.     f()
  15. }

Example

  • 异步执行某个东西 ```go func main() { go Go(test) select {} }

func test() { // xxxx xxxx xxxx }

func Go(f func()) { if err := recover(); err != nil { fmt.Println(err) } f() }

  2. - 启动一个http服务
  3. ```go
  4. func main() {
  5.     http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
  6.         fmt.Fprintln(w, "Hello, GopherCon SG")
  7.     })
  8.     if err := http.ListenAndServe(":8080", nil); err != nil {
  9.         log.Fatal(err)
  10.     }
  11. }

  • 同时启动2个http监听2个端口 ```go func main() { stop := make(chan struct{}) errs := make(chan error) stoped := false // 启动server1 go func() { // Rule.3 go 由调用者发起

    1.   errs <- server(":10000", stop)

    }() // 启动server2 go func() {

    1.   errs <- server(":10001", stop)

    }()

    for i := 0; i < cap(errs); i++ {

    1.   if err := <-errs; err != nil {
    2.       fmt.Printf("err:%s", err)
    3.   }
    4.   if !stopped {
    5.       stopped = true
    6.       close(stop) // Rule.2 明确goroutine怎么退出
    7.   }

    } }

func server(addr string, stop <-chan struct{}) error { s := http.Server{Addr: addr} // 监听退出信号 // Rule.1 明确goroutine什么时候退出；close关闭时 go func() { <-stop s.ShutDown(context.Background()) // Rule.2 明确server作为异步出去的goroutine怎么退出 }() return s.ListenAndServe() }

  2. - 发送异步更新数据
  3. ```go
  4. func main() {
  5.     logCh := make(chan string, 10)
  6.     go subLog(logCh)
  7.     for i := 0; i < 1000; i++ {
  8.         pub(logCh)
  9.     }
  10.     time.Sleep(10 * time.Second)
  11.     close(logCh)
  12. }
  14. func pub(ch chan<- string) {
  15.     i := strconv.Itoa(rand.Intn(10000))
  16.     ch <- i
  17. }
  19. func subLog(ch <-chan string) {
  20.     for s := range ch {
  21.         fmt.Println("log:", s)
  22.     }
  23. }