并发编程最佳实践作业疑问

问题描述：

1、lock := make(chan content) 需要加buffer吗？试了一下不加程序也不会挂掉，加了是不是可以防止channel阻塞？

2、go fetch(name, lock) 协程里面执行http请求，如果http请求超时，会不会导致 c := <-lock 代码处阻塞？

3、下图代码还有没有其它问题？

相关代码：

package main

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

type content struct {
    name string
    url  string
    body []byte
}

func main() {
    urls := []string{
        "baidu.com",
        "bing.com",
    }

    lock := make(chan content)
    for _, name := range urls {
        go fetch(name, lock)
    }
    c := <-lock
    writeToFile(c.name, c.url, c.body)
}

func fetch(name string, lock chan content) {
    url := fmt.Sprintf("https://%s", name)
    resp, err := http.Get(url)
    if err != nil {
        panic("request failed")
    }
    defer resp.Body.Close()

    body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        panic("Failed to read buffer data")
    }

    content := content{
        name: name,
        url:  url,
        body: body,
    }
    lock <- content
}

func writeToFile(name, url string, body []byte) {
    if err := ioutil.WriteFile("./"+name+".html", body, 0644); err != nil {
        panic("Failed to write to file")
    }
}

qq_Tto_0 2021-07-06

源自：Go 高级工程师实战营 1-14 Go 并发编程最佳实践

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1回答

Xargin 回答被采纳获得+3积分 2021-07-06 22:59:14

按生产标准来写的话，你这里超时就会导致 goroutine 泄露~

生产环境向外发请求一定要加超时，不要直接用 http.Get 这种 API

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qq_Tto_0 提问者 #1

明白了，谢谢曹大，我又改了一版

package main

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

type Handle struct {
   client *http.Client
   lock   chan content
}

func NewClient() *Handle {
   client := &http.Client{
      Timeout: 30 * time.Second,
   }
   lock := make(chan content)
   return &Handle{client, lock}
}

type content struct {
   name string
   url  string
   body []byte
}

func main() {
   n := NewClient()
   urls := []string{
      "baidu.com",
      "bing.com",
   }

   for _, name := range urls {
      go n.fetch(name)
   }
   c := <-n.lock;
   n.writeToFile(c.name, c.url, c.body)
}

func (n *Handle) fetch(name string) {
   url := fmt.Sprintf("https://%s", name)
   req, _ := http.NewRequest(http.MethodGet, url, nil)
   resp, err := n.client.Do(req)
   if err != nil {
      fmt.Printf("request error, err:%s", err)
      return
   }
   defer resp.Body.Close()
   if resp.StatusCode != http.StatusOK {
      fmt.Printf("response err status code: %d,url: %s\n", resp.StatusCode, req.URL)
      return
   }

   body, err := ioutil.ReadAll(resp.Body)
   if err != nil {
      log.Fatalf("Failed to read buffer data, err:%s", err)
   }

   content := content{
      name: name,
      url:  url,
      body: body,
   }
   n.lock <- content
}

func (n *Handle) writeToFile(name, url string, body []byte) {
   if err := ioutil.WriteFile("./"+name+".html", body, 0644); err != nil {
      fmt.Printf("Failed to write to file, err:%s\n", err)
   }
}