英文:
Leaking goroutine when a non-blocking readline hangs
问题
假设你有这样的结构：
ch := make(chan string)
errCh := make(chan error)
go func() {
line, _, err := bufio.NewReader(r).ReadLine()
if err != nil {
errCh <- err
} else {
ch <- string(line)
}
}()
select {
case err := <-errCh:
return "", err
case line := <-ch:
return line, nil
case <-time.After(5 * time.Second):
return "", TimeoutError
}
在5秒超时的情况下，goroutine会一直挂起，直到ReadLine返回，这可能永远不会发生。我的项目是一个长时间运行的服务器，所以我不希望出现堆积的挂起goroutine。
英文:
Assuming you have a structure like this:
ch := make(chan string)
errCh := make(chan error)
go func() {
line, _, err := bufio.NewReader(r).ReadLine()
if err != nil {
errCh <- err
} else {
ch <- string(line)
}
}()
select {
case err := <-errCh:
return "", err
case line := <-ch:
return line, nil
case <-time.After(5 * time.Second):
return "", TimeoutError
}
In the case of the 5 second timeout, the goroutine hangs until ReadLine returns, which may never happen. My project is a long-running server, so I don't want a buildup of stuck goroutines.
答案1
得分: 3
ReadLine方法在进程退出或读取到一行数据之前不会返回。管道没有截止时间或超时机制。
如果ReadLine方法在超时后返回，goroutine将会阻塞。可以通过使用带缓冲的通道来解决这个问题：
ch := make(chan string, 1)
errCh := make(chan error, 1)
应用程序应该调用Wait方法来清理与命令相关的资源。在goroutine中调用Wait方法是一个好的选择：
go func() {
line, _, err := bufio.NewReader(r).ReadLine()
if err != nil {
errCh <- err
} else {
ch <- string(line)
}
cmd.Wait() // <-- 添加这一行
}()
这将导致goroutine阻塞，这正是你想要避免的。另一种情况是应用程序会为每个命令泄漏资源。
英文:
ReadLine will not return until either the process exits or the method reads a line. There's no deadline or timeout mechanism for pipes.
The goroutine will block if the call to ReadLine returns after the timeout. This can be fixed by using buffered channels:
ch := make(chan string, 1)
errCh := make(chan error, 1)
The application should call Wait to cleanup resources associated with the command. The goroutine is a good place to call it:
go func() {
line, _, err := bufio.NewReader(r).ReadLine()
if err != nil {
errCh <- err
} else {
ch <- string(line)
}
cmd.Wait() // <-- add this line
}()
This will cause the goroutine to block, the very thing you are trying to avoid. The alternative is that the application leaks resources for each command.
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