go语言设计模式之Concurrency barrier

Posted 2020-11-22 aguncn

barrier.go

package barrier

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"time"
)

var timeoutMillseconds int = 5000

type barrierResp struct {
	Err  error
	Resp string
}

func barrier(endpoints ...string) {
	requestNumber := len(endpoints)

	in := make(chan barrierResp, requestNumber)
	defer close(in)

	responses := make([]barrierResp, requestNumber)

	for _, endpoint := range endpoints {
		go makeRequest(in, endpoint)
	}

	var hasError bool
	for i := 0; i < requestNumber; i++ {
		resp := <-in
		if resp.Err != nil {
			fmt.Println("ERROR: ", resp.Err)
			hasError = true
		}
		responses[i] = resp
	}

	if !hasError {
		for _, resp := range responses {
			fmt.Println(resp.Resp)
		}
	}
}

func makeRequest(out chan<- barrierResp, url string) {
	res := barrierResp{}
	client := http.Client{
		Timeout: time.Duration(time.Duration(timeoutMillseconds) *
			time.Microsecond),
	}

	resp, err := client.Get(url)
	if err != nil {
		res.Err = err
		out <- res
		return
	}

	byt, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		res.Err = err
		out <- res
		return
	}

	res.Resp = string(byt)
	out <- res
}

　　

barrier_test.go

package barrier

import (
	"bytes"
	"io"
	"os"
	"strings"
	"testing"
)

func TestBarrier(t *testing.T) {
	t.Run("Correct endpoints", func(t *testing.T) {
		endpoints := []string{"https://www.baidu.com/",
			"https://www.sina.com.cn/"}

		result := captureBarrierOutput(endpoints...)

		if !strings.Contains(result, "Accept-Encoding") {
			t.Fail()
		}
		t.Log(result)
	})

	t.Run("One endpoints incorrect", func(t *testing.T) {
		endpoints := []string{"http://malformed-url",
			"http://httpbin.org/User-Agent"}

		result := captureBarrierOutput(endpoints...)

		if !strings.Contains(result, "ERROR") {
			t.Fail()
		}
		t.Log(result)
	})

	t.Run("Very short timeout", func(t *testing.T) {
		endpoints := []string{"http://httpbin.org/headers",
			"http://httpbin.org/User-Agent"}
		//timeoutMilliseconds := 1
		result := captureBarrierOutput(endpoints...)
		if !strings.Contains(result, "Timeout") {
			t.Fail()
		}
		t.Log(result)
	})
}

func captureBarrierOutput(endpoints ...string) string {
	reader, writer, _ := os.Pipe()
	os.Stdout = writer
	out := make(chan string)

	go func() {
		var buf bytes.Buffer
		io.Copy(&buf, reader)
		out <- buf.String()
	}()

	barrier(endpoints...)

	writer.Close()
	temp := <-out
	return temp
}