Buffered Channels and Worker Pools

原文链接:https://golangbot.com/buffered-channels-worker-pools/

buffered channels

• 带有缓冲区的channel 只有在缓冲区满之后 channel才会阻塞

WaitGroup

• 如果有多个 goroutine在后台执行 那么需要在主线程中 多次等待 可以有一个简单的方法 就是 通过WaitGroup 可以控制 Goroutines 直到它们都执行完成

例子

import (  
    "fmt"
    "sync"
    "time"
)

func process(i int, wg *sync.WaitGroup) {  
    fmt.Println("started Goroutine ", i)
    time.Sleep(2 * time.Second)
    fmt.Printf("Goroutine %d ended
", i)
    wg.Done()
}

func main() {  
    no := 3
    var wg sync.WaitGroup
    for i := 0; i < no; i++ {
        wg.Add(1)
        go process(i, &wg)
    }
    wg.Wait()![](https://images2018.cnblogs.com/blog/736597/201803/736597-20180312115109926-1714494090.png)


    fmt.Println("All go routines finished executing")
}

Worker Pool Implementation

先贴一下个人理解的 程序执行的流程图

import (
	"fmt"
	"math/rand"
	"sync"
	"time"
)

type Job struct {
	id       int
	randomno int
}
type Result struct {
	job         Job
	sumofdigits int
}

var jobs = make(chan Job, 10)
var results = make(chan Result, 10)

func digits(number int) int {
	sum := 0
	no := number
	for no != 0 {
		digit := no % 10
		sum += digit
		no /= 10
	}
	time.Sleep(5 * time.Second)
	return sum
}
func worker(wg *sync.WaitGroup) {
	for job := range jobs {
		output := Result{job, digits(job.randomno)}
		results <- output
	}
	wg.Done()
}
func createWorkerPool(noOfWorkers int) {
	var wg sync.WaitGroup
	for i := 0; i < noOfWorkers; i++ {
		wg.Add(1)
		go worker(&wg)
	}
	wg.Wait()
	close(results)
}
func allocate(noOfJobs int) {
	for i := 0; i < noOfJobs; i++ {
		randomno := rand.Intn(999)
		job := Job{i, randomno}
		jobs <- job
	}
	close(jobs)
}
func result(done chan bool) {
	for result := range results {
		fmt.Printf("Job id %d, input random no %d , sum of digits %d
", result.job.id, result.job.randomno, result.sumofdigits)
	}
	done <- true
}

func main() {
	startTime := time.Now()

	noOfJobs := 100
	go allocate(noOfJobs)

	done := make(chan bool)
	go result(done)
	noOfWorkers := 10
	createWorkerPool(noOfWorkers)
	<-done

	endTime := time.Now()


	diff := endTime.Sub(startTime)
	fmt.Println("total time taken ", diff.Seconds(), "seconds")
}