Refactoring of Go Channels http://talks.golang.org/2012/concurrency/support/google2.2.go to simulate concurrent downloads

concurrentDownloads

package main

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

type Result string
type Download func() Result

func FanInDownloads(files []string) (results []Result) {
	c := make(chan Result)

	for i := 0; i < len(files); i++ {
		fileName := files[i]
		go func() { c <- nexusDownload(fileName)() }()
	}

	timeout := time.After(11000 * time.Millisecond)
	for i := 0; i < len(files); i++ {
		select {
		case result := <-c:
			fmt.Println("FINISHED: " + result)
			results = append(results, result)

		case <-timeout:
			fmt.Println("timed out")
			return
		}
	}
	return
}

func nexusDownload(artifactId string) Download {
	return func() Result {
		duration := rand.Intn(10000)
		fmt.Println(fmt.Sprintf("Will start downloading %s... It might take %d", artifactId, duration))
		time.Sleep(time.Duration(duration) * time.Millisecond)
		return Result(fmt.Sprintf("%s downloaded in %d", artifactId, duration))
	}
}

func main() {
	rand.Seed(time.Now().UnixNano())
	start := time.Now()

	files := []string{"file1", "file2", "file3"}

	results := FanInDownloads(files)
	elapsed := time.Since(start)
	fmt.Println(results)
	fmt.Println(elapsed)
}

Go Parallel Downloads using Channels

mdesales@ubuntu [11/30/201423:36:56] ~/dev/github-intuit/docker-images/platform/mule-3.4/source (master *) $ go run trying.go
Will start downloading file1... It might take 3787
Will start downloading file2... It might take 8639
Will start downloading file3... It might take 5633
FINISHED: file1 downloaded in 3787
FINISHED: file3 downloaded in 5633
FINISHED: file2 downloaded in 8639
[file1 downloaded in 3787 file3 downloaded in 5633 file2 downloaded in 8639]
8.641097774s