是否有一些优雅的方式来暂停和恢复任何其他 goroutine？

Question

就我而言，我有数千个 goroutine 同时作为 work() 工作。我还有一个sync() goroutine。当sync 启动时，我需要任何其他 goroutine 在同步作业完成后暂停一段时间。这是我的代码：

var channels []chan int
var channels_mutex sync.Mutex

func work() {
  channel := make(chan int, 1)
  channels_mutex.Lock()  
  channels = append(channels, channel)
  channels_mutex.Unlock()
  for {
    for {
      sync_stat := <- channel // blocked here
      if sync_stat == 0 { // if sync complete
        break  
      }
    }
    // Do some jobs
    if (some condition) {
      return
    }
  }
}

func sync() {
  channels_mutex.Lock()
  // do some sync

  for int i := 0; i != len(channels); i++ {
    channels[i] <- 0
  }
  channels_mutex.Unlock()
}

现在的问题是，由于<- 总是在读取时阻塞，所以每次去sync_stat := <- channel 都是阻塞的。我知道如果频道关闭了它不会被阻止，但是由于我必须在work()退出之前使用这个频道，并且我没有找到任何方法来重新打开已关闭的频道。

我怀疑自己走错路了，因此感谢您的帮助。是否有一些“优雅”的方式来暂停和恢复任何其他 goroutine？

Answer 1

如果我理解正确，您需要 N 个工人和一个控制器，可以随意暂停、恢复和停止工人。下面的代码就可以做到这一点。

package main

import (
    "fmt"
    "runtime"
    "sync"
)

// 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, 1)

        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
    setState(workers, Running)

    // Pause workers.
    setState(workers, Paused)

    // Unpause workers.
    setState(workers, Running)

    // Shutdown workers.
    setState(workers, Stopped)
}

// setState changes the state of all given workers.
func setState(workers []chan int, state int) {
    for _, w := range workers {
        w <- state
    }
}