英文:
Child goroutine is not stopped after its parent gorutine exits
问题
我有这段代码：
func sleep(d time.Duration, ch chan<- int) {
fmt.Println("睡眠中...")
time.Sleep(d)
fmt.Println("醒来了...")
ch <- 0
}
func parent(ctx context.Context) int {
ch := make(chan int, 1)
go sleep(3*time.Second, ch)
select {
case <-ctx.Done():
return 1
case <-ch:
return 0
}
}
func app(wg *sync.WaitGroup) {
defer wg.Done()
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
res := parent(ctx)
fmt.Println(res)
}
func main() {
var wg sync.WaitGroup
wg.Add(1)
go app(&wg)
wg.Wait()
time.Sleep(2 * time.Second)
}
在这个例子中，我有一个带有2秒超时的ctx。childFunc需要3秒才能结束其进程。2秒后，parent函数返回1，因为case <-ctx.Done()。但在主线程中，我再睡眠2秒，我发现childFunc还没有退出，它继续执行其过程，并打印出"醒来了..."。为什么childFunc在其父goroutine结束时没有退出？
以下是输出结果：
睡眠中...
1
醒来了...
英文:
I have this code:
func sleep(d time.Duration, ch chan<- int) {
fmt.Println("Sleeping...")
time.Sleep(d)
fmt.Println("Awake...")
ch <- 0
}
func parent(ctx context.Context) int {
ch := make(chan int, 1)
go sleep(3*time.Second, ch)
select {
case <-ctx.Done():
return 1
case <-ch:
return 0
}
}
func app(wg *sync.WaitGroup) {
defer wg.Done()
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
res := parent(ctx)
fmt.Println(res)
}
func main() {
var wg sync.WaitGroup
wg.Add(1)
go app(&wg)
wg.Wait()
time.Sleep(2 * time.Second)
}
In this example, I have a ctx with 2 seconds timeout.
It takes 3 seconds for childFunc to end its process.
After 2 seconds the parent func returns 1 because of case <-ctx.Done().
But in the main thread I sleep for 2 more seconds and I see the childFund hasn't exited and is continuing its process and the Awake... will be printed.
Why childFunc doesn't exit when its parent goroutine finishes?
Here is the output:
Sleeping...
1
Awake...
答案1
得分: 2
我认为你在问为什么一个 goroutine 在创建它的 goroutine 退出时不会退出。除了主 goroutine（当它退出时，包括所有 goroutine 在内的整个程序都会退出），goroutine 在启动时是独立的 - 它们没有“父级”，也没有办法从外部停止它们，包括终止启动它们的 goroutine。如果你想要一个 goroutine 可以被终止，那么你必须自己编写代码，例如在传入的上下文被取消时从 goroutine 中返回。
英文:
I think you're asking why a goroutine doesn't exit when the goroutine that created it exits. Except for the main goroutine (which when it exits, the whole program including all goroutines exit), goroutines are independent when they launch -- they don't have a "parent" and there's no way to stop them from outside, including termination of the goroutine that launched them. If you want a goroutine to be killable then you have to code it yourself, for example by returning from the goroutine when the passed-in context is cancelled.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论