浅谈Go Channel 高级实践

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2019-06-20

channel æ¯ golang éç¸å½æè¶£çä¸ä¸ªåè½ï¼å¨æä½¿ç¨ golang ç¼ç çç»éªéï¼å¤§é¨åäºä»¶é½ä¼æ¯å¨äº«å channel å goroutine éåçä¹è¶£ãæä»¥æ¬æä¸»è¦ä»ç» channel çä¸äºæè¶£çç¨æ³ã

è¿éæ Oling Cat ç¿»è¯çGoç¼ç¨è¯è¨è§èéå³äº channelï¼ä¿¡éï¼çæè¿°ï¼

channel å®ç°çæºç ä¸å¤æï¼æ¨èéè¯»ï¼https://github.com/golang/go/blob/master/src/runtime/chan.go

channel æ¯å¹²ä»ä¹ç

æä¹ï¼channel æ¯ç¨æ¥éä¿¡ç

channel åºè¯¥ç¨å¨ä»ä¹å°æ¹

æ ¸å¿ï¼éè¦éä¿¡çå°æ¹

ä¾å¦ä»¥ä¸åºæ¯ï¼

éç¥å¹¿æ
äº¤æ¢æ°æ®
æ¾å¼åæ¥
å¹¶åæ§å¶
...

channel ç¨ä¾å®ç°

è¶æ¶æ§å¶

// å©ç¨ time.After å®ç°
func main() {
  done := do()
  select {
  case <-done:
    // logic
  case <-time.After(3 * time.Second):
    // timeout
  }
}

func do() <-chan struct{} {
  done := make(chan struct{})
  go func() {
    // do something
    // ...
    done <- struct{}{}
  }()
  return done
}

åæå¿«çç»æ

func main() {
  ret := make(chan string, 3)
  for i := 0; i < cap(ret); i++ {
    go call(ret)
  }
    fmt.Println(<-ret)
}

func call(ret chan<- string) {
  // do something
  // ...
  ret <- "result"
}

éå¶æå¤§å¹¶åæ°

// æå¤§å¹¶åæ°ä¸º 2
limits := make(chan struct{}, 2)
for i := 0; i < 10; i++ {
  go func() {
    // ç¼å²åºæ»¡äºå°±ä¼é»å¡å¨è¿
    limits <- struct{}{}
    do()
    <-limits
  }()
}

for...range ä¼å

for ... range c { do } è¿ç§åæ³ç¸å½äº if _, ok := <-c; ok { do }

func main() {
  c := make(chan int, 20)
  go func() {
    for i := 0; i < 10; i++ {
      c <- i
    }
    close(c)
  }()
  // å½ c è¢«å³éåï¼åå®éé¢çåç´ å°±ä¼è·³åºå¾ªç¯
  for x := range c {
    fmt.Println(x)
  }
}

å¤ä¸ª goroutine åæ¥ååº

å©ç¨ close å¹¿æ

func main() {
  c := make(chan struct{})
  for i := 0; i < 5; i++ {
    go do(c)
  }
  close(c)
}

func do(c <-chan struct{}) {
  // ä¼é»å¡ç´å°æ¶å° close
  <-c
  fmt.Println("hello")
}

éé»å¡ç select

select {
case <-done:
  return
default:  
}

for{select{}} ç»æ¢

for ok {
  select {
  case ch <- 0:
  case <-done:
    ok = false
  }
}

channel ç¹æ§

åºç¡ç¹æ§

æä½	å¼ä¸º nil ç channel	è¢«å³éç channel	æ£å¸¸ç channel
close	panic	panic	æåå³é
c<-	æ°¸è¿é»å¡	panic	é»å¡ææååé
<-c	æ°¸è¿é»å¡	æ°¸è¿ä¸é»å¡	é»å¡ææåæ¥æ¶

happens-before ç¹æ§

æ ç¼å²æ¶ï¼æ¥æ¶ happens-before åé
ä»»ä½æåµä¸ï¼åé happens-before æ¥æ¶
close happens-before æ¥æ¶

åè

https://go101.org/article/channel.html
https://golang.org/doc/effective_go.html#channels

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