ErrGroup和WaitGroup性能测试对比

var wg sync.WaitGroup

type Result struct {
	path string
	data [md5.Size]byte
}

func md5AllByWaitGroup(root string) (map[string][md5.Size]byte,error)  {
	ctx,cancel := context.WithCancel(context.Background())
	defer cancel()

	paths := make(chan string)

	wg.Add(1)
	go getPath(paths,root,ctx)

	ret := make(chan Result)
	for i :=0;i<20;i++{
		wg.Add(1)
		go func(paths chan string,ret chan Result) {
			defer wg.Done()
			for path := range paths{
				data,err := ioutil.ReadFile(path)
				if err !=nil{
					return
				}
				select {
				case ret <- Result{path: path,data: md5.Sum(data)}:
				case <-ctx.Done():
					return
				}
			}
		}(paths,ret)
	}

	go func() {
		wg.Wait()
		close(ret)
	}()

	m1 := make(map[string][md5.Size]byte)
	for v := range ret{
		m1[v.path] = v.data
	}

	return m1,nil

}

func getPath(paths chan string,root string,ctx context.Context)  {
	defer wg.Done()
	defer close(paths)
	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
		if err !=nil{
			return err
		}
		if !info.Mode().IsRegular(){
			return nil
		}
		select {
		case paths<- path:
		case <-ctx.Done():
			return ctx.Err()
		}
		return nil
	})
}

func WaitGroupDemo()  {
	m,err := md5AllByWaitGroup(".")
	if err !=nil{
		log.Fatal(err)
	}
	for k,sum := range m{
		fmt.Printf("%s:\t %x\n",k,sum)
	}
}

func md5AllByErrGroup(ctx context.Context,root string) (map[string][md5.Size]byte,error) {
	g,ctx := errgroup.WithContext(ctx)

	paths := make(chan string)

	g.Go(func() error {
		defer close(paths)
		return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
			if err !=nil{
				return err
			}
			if !info.Mode().IsRegular(){
				return nil
			}
			select {
			case paths <-path:
			case <-ctx.Done():
				return ctx.Err()
			}
			return nil
		})
	})

	c :=make(chan Result)
	for i:=0;i<20;i++{
		g.Go(func() error {
			for path := range paths{
				data,err := ioutil.ReadFile(path)
				if err !=nil{
					return err
				}
				select {
				case c <- Result{path: path,data: md5.Sum(data)}:
				case <-ctx.Done():
					return ctx.Err()
				}
			}
			return nil
		})
	}

	go func() {
		g.Wait()
		close(c)
	}()

	m := make(map[string][md5.Size]byte)
	for v := range c{
		m[v.path] = v.data
	}

	if err := g.Wait();err !=nil{
		return nil,err
	}
	return m,nil
}

func ErrGroupDemo()  {
	m,err := md5AllByErrGroup(context.Background(),".")
	if err !=nil{
		log.Fatal(err)
	}
	for k,sum := range m{
		fmt.Printf("%s:\t %x\n",k,sum)
	}
}