worker pool的设计常用来加速处理执行较耗时的重任务，且为了避免goroutine的过度创建，需要指定工作池的大小。使用golang的goroutine与chan，数行代码即可实现一个简单的工作池。
<br />
<strong>1 简单 worker pool</strong>
<br />
如下代码中，新建两个channel，一个是works chan，一个是results chan，然后调用startWorkerPool启动指定goroutine个数的工作池。放入5个work到works后关闭通道，然后从results中等待结果即可。
<pre>
package main
import (
"fmt"
"time"
)
func do(work int, goroutine int) int {
time.Sleep(time.Second)
fmt.Printf("goroutine %d done work %d\n", goroutine, work)
return work
}
func worker(works <-chan int, results chan<- int, goroutine int) {
for work := range works {
results <- do(work, goroutine)
}
}
func startWorkerPool(works <-chan int, results chan<- int, size int) {
for i := 0; i < size; i++ {
go worker(works, results, i)
}
}
func main() {
works := make(chan int, 10)
results := make(chan int, 10)
startWorkerPool(works, results, 2)
for i := 0; i < 5; i++ {
works <- i
}
close(works)
// waiting for results
for i := 0; i < 5; i++ {
<-results
}
}
</pre>
运行结果为：
<code>goroutine 0 done work 1
goroutine 1 done work 0
goroutine 0 done work 2
goroutine 1 done work 3
goroutine 0 done work 4
</code>
<br />
<strong>2 worker pool封装</strong>
<br />
1中所示的代码难以满足真实业务场景需求，我们需要对worker pool作一层抽象，封装的更通用一点。如下代码封装了一个worker pool，WorkerPool的创建需要传入要处理的任务列表及指定pool的大小，Task为任务的封装，需提供该任务的实现。创建完worker pool，调用pool.Start()即进入多goroutine处理，调用pool.Results()即会阻塞等待所有任务的执行结果。
<pre>
package main
import (
"errors"
"fmt"
"time"
)
type Task struct {
Id int
Err error
f func() error
}
func (task *Task) Do() error {
return task.f()
}
type WorkerPool struct {
PoolSize int
tasksSize int
tasksChan chan Task
resultsChan chan Task
Results func() []Task
}
func NewWorkerPool(tasks []Task, size int) *WorkerPool {
tasksChan := make(chan Task, len(tasks))
resultsChan := make(chan Task, len(tasks))
for _, task := range tasks {
tasksChan <- task
}
close(tasksChan)
pool := &WorkerPool{PoolSize: size, tasksSize: len(tasks), tasksChan: tasksChan, resultsChan: resultsChan}
pool.Results = pool.results
return pool
}
func (pool *WorkerPool) Start() {
for i := 0; i < pool.PoolSize; i++ {
go pool.worker()
}
}
func (pool *WorkerPool) worker() {
for task := range pool.tasksChan {
task.Err = task.Do()
pool.resultsChan <- task
}
}
func (pool *WorkerPool) results() []Task {
tasks := make([]Task, pool.tasksSize)
for i := 0; i < pool.tasksSize; i++ {
tasks[i] = <-pool.resultsChan
}
return tasks
}
func main() {
t := time.Now()
tasks := []Task{
{Id: 0, f: func() error { time.Sleep(2 * time.Second); fmt.Println(0); return nil }},
{Id: 1, f: func() error { time.Sleep(time.Second); fmt.Println(1); return errors.New("error") }},
{Id: 2, f: func() error { fmt.Println(2); return errors.New("error") }},
}
pool := NewWorkerPool(tasks, 2)
pool.Start()
tasks = pool.Results()
fmt.Printf("all tasks finished, timeElapsed: %f s\n", time.Now().Sub(t).Seconds())
for _, task := range tasks {
fmt.Printf("result of task %d is %v\n", task.Id, task.Err)
}
}
</pre>
运行结果为：
<br />
<code>1
2
0
all tasks finished, timeElapsed: 2.006011 s
result of task 1 is error
result of task 2 is error
result of task 0 is nil
</code>
<br />
本文代码托管地址：<a href="https://github.com/olzhy/go-excercises/tree/master/worker_pool" target="blank">https://github.com/olzhy/go-excercises/tree/master/worker_pool</a>
原文地址：https://leileiluoluo.com/posts/golang-worker-pool.html
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