这是@Jimt 编写的Go 中worker 和controller 模式的一个很好的例子，以回答“Golang 中是否有一些优雅的方式来暂停和恢复任何其他goroutine？ ”
package main
import (
"fmt"
"runtime"
"sync"
"time"
)
// Possible worker states.
const (
Stopped = 0
Paused = 1
Running = 2
)
// Maximum number of workers.
const WorkerCount = 1000
func main() {
// Launch workers.
var wg sync.WaitGroup
wg.Add(WorkerCount + 1)
workers := make([]chan int, WorkerCount)
for i := range workers {
workers[i] = make(chan int)
go func(i int) {
worker(i, workers[i])
wg.Done()
}(i)
}
// Launch controller routine.
go func() {
controller(workers)
wg.Done()
}()
// Wait for all goroutines to finish.
wg.Wait()
}
func worker(id int, ws <-chan int) {
state := Paused // Begin in the paused state.
for {
select {
case state = <-ws:
switch state {
case Stopped:
fmt.Printf("Worker %d: Stopped\n", id)
return
case Running:
fmt.Printf("Worker %d: Running\n", id)
case Paused:
fmt.Printf("Worker %d: Paused\n", id)
}
default:
// We use runtime.Gosched() to prevent a deadlock in this case.
// It will not be needed of work is performed here which yields
// to the scheduler.
runtime.Gosched()
if state == Paused {
break
}
// Do actual work here.
}
}
}
// controller handles the current state of all workers. They can be
// instructed to be either running, paused or stopped entirely.
func controller(workers []chan int) {
// Start workers
for i := range workers {
workers[i] <- Running
}
// Pause workers.
<-time.After(1e9)
for i := range workers {
workers[i] <- Paused
}
// Unpause workers.
<-time.After(1e9)
for i := range workers {
workers[i] <- Running
}
// Shutdown workers.
<-time.After(1e9)
for i := range workers {
close(workers[i])
}
}
但是这段代码也有一个问题：如果你想在退出workers时删除一个工作通道worker()，就会发生死锁。
如果你close(workers[i])，下次控制器写入它会导致恐慌，因为 go 无法写入关闭的通道。如果您使用一些互斥锁来保护它，那么它将被卡住，workers[i] <- Running因为worker它没有从通道读取任何内容并且写入将被阻塞，并且互斥锁将导致死锁。您也可以为通道提供更大的缓冲区作为解决方法，但这还不够好。
所以我认为解决这个问题的最好方法是worker()退出时关闭通道，如果控制器发现通道关闭，它将跳过它并且什么都不做。但是在这种情况下，我找不到如何检查通道是否已关闭。如果我尝试读取控制器中的通道，控制器可能被阻塞。所以我现在很困惑。
PS：恢复引发的恐慌是我尝试过的，但它会关闭引发恐慌的goroutine。在这种情况下，它将是控制器，所以没有用。
不过，我认为 Go 团队在下一个版本的 Go 中实现这个功能是有用的。