在继续之前要求 Go 运行所有 goroutines

Question

我需要 Golang 调度程序在继续之前运行所有 goroutine，runtime.Gosched() 没有解决。

问题是 go 例程运行得如此之快以至于 start() 中的“select”在 de stopStream() 中的“select”之后运行，然后是“case <-chanStopStream:" receiver is not ready to the sender "case retChan <- true:". The result is that when this happen the result is the same behavior from when stopStream() hangs

运行这段代码https://go.dev/play/p/DQ85XqjU2Q_z 很多时候你会看到这两个回应 不挂起时的预期响应：

2009/11/10 23:00:00 Start
2009/11/10 23:00:00 receive chan
2009/11/10 23:00:03 end

挂起时的预期响应，但不是这么快：

2009/11/10 23:00:00 Start
2009/11/10 23:00:00 default
2009/11/10 23:00:01 TIMER
2009/11/10 23:00:04 end

代码

package main

import (
    "log"
    "runtime"
    "sync"
    "time"
)

var wg sync.WaitGroup

func main() {
    wg.Add(1)
    //run multiples routines on a huge system
    go start()
    wg.Wait()
}
func start() {
    log.Println("Start")
    chanStopStream := make(chan bool)
    go stopStream(chanStopStream)
    select {
    case <-chanStopStream:
        log.Println("receive chan")
    case <-time.After(time.Second): //if stopStream hangs do not wait more than 1 second
        log.Println("TIMER")
        //call some crash alert
    }
    time.Sleep(3 * time.Second)
    log.Println("end")
    wg.Done()
}

func stopStream(retChan chan bool) {
    //do some work that can be faster then caller or not
    runtime.Gosched()
    //time.Sleep(time.Microsecond) //better solution then runtime.Gosched()
    //time.Sleep(2 * time.Second) //simulate when this routine hangs more than 1 second
    select {
    case retChan <- true:
    default: //select/default is used because if the caller times out this routine will hangs forever
        log.Println("default")
    }
}

Answer 1

通过更改

chanStopStream

缓冲频道来修复。这允许

stopStream

在所有场景中发送一个值。

func start() {
    log.Println("Start")
    chanStopStream := make(chan bool, 1) // <--- buffered channel
    go stopStream(chanStopStream)
    ...
}

func stopStream(retChan chan bool) {
    ...
    // Always send. No select/default needed.
    retChan <- true
}

https://go.dev/play/p/xWg42TO_fIW

替代修复：关闭通道而不是发送值。发送者总是可以关闭通道。在关闭的通道上接收返回通道值类型的零值。

func start() {
    log.Println("Start")
    chanStopStream := make(chan bool) // buffered channel not required
    go stopStream(chanStopStream)
    ...

func stopStream(retChan chan bool) {
    ...
    close(retChan)
}

https://go.dev/play/p/lNfT6qzrMmO