简陋的协程池

simple-goroutine-pool.go

package main

import (
	"fmt"
	"sync"
)

// https://play.golang.org/p/jooMMwYID54
// 一个简单的协程池
// 关键问题是：range 读取 closed retCh 时才不会报错
// 何时关闭 retCh 才是关键，我修改原始代码增加了 WaitGroup
// https://mp.weixin.qq.com/s/fINhzg3eNi9YFi5qZ_JzGA
func main() {

	totalTask := 20

	var wg sync.WaitGroup
	wg.Add(totalTask)

	jobCh := make(chan int, totalTask)
	go func() {
		for i := 0; i < totalTask; i++ {
			jobCh <- i
		}
		close(jobCh)
	}()

	retCh := make(chan string, 20)

	// 启动 5 个协程梳理
	workerPool(5, jobCh, retCh, &wg)
	wg.Wait()
	close(retCh)

	for ret := range retCh {
		fmt.Println(ret)
	}
}

// 启动一个协程池
// n 为最多协程数量
// jobCh 为写入队列，协程从 jobCh 读取读取内容
// retCh 为结果队列，协程把结果写入到 retCh 中
func workerPool(n int, jobCh <-chan int, retCh chan<- string, wg *sync.WaitGroup) {
	for i := 0; i < n; i++ {
		go worker(i, jobCh, retCh, wg)
	}
}

func worker(id int, jobCh <-chan int, retCh chan<- string, wg *sync.WaitGroup) {
	for job := range jobCh {
		ret := fmt.Sprintf("worker %d processed job: %d", id, job)
		retCh <- ret
		wg.Done()
	}
}