运行此代码时,我必须等待10秒才能打印s.Locations,而要等待60+秒才能打印n.Titles。是什么原因造成的?

有关如何解决此问题的提示将很有帮助,即查看完成某些代码行需要多长时间。新手入门,所以不确定如何精确执行此操作。

我已确保关闭连接。由于我计算机上的所有其他内容都非常快,因此我认为通过http.Get访问互联网应该不会很慢。

package main

import (
    "encoding/xml"
    "fmt"
    "io/ioutil"
    "net/http"
    "strings"
)

// SitemapIndex is the root xml
type SitemapIndex struct {
    Locations []string `xml:"sitemap>loc"`
}

// News is the individual categories
type News struct {
    Titles    []string `xml:"url>news>title"`
    Keywords  []string `xml:"url>news>keywords"`
    Locations []string `xml:"url>loc"`
}

// NewsMap is the
type NewsMap struct {
    Keywords string
    Location string
}

func main() {
    var s SitemapIndex
    var n News
    // np := make(map[string]NewsMap)
    resp, _ := http.Get("https://www.washingtonpost.com/news-sitemaps/index.xml")
    bytes, _ := ioutil.ReadAll(resp.Body)
    xml.Unmarshal(bytes, &s)
    resp.Body.Close()

    for i := range s.Locations {
        s.Locations[i] = strings.TrimSpace(s.Locations[i])
    }

    fmt.Println(s.Locations) // slice of data

    for _, Location := range s.Locations {
        resp, _ := http.Get(Location)
        bytes, _ := ioutil.ReadAll(resp.Body)
        xml.Unmarshal(bytes, &n)
        resp.Body.Close()
    }

    fmt.Println(n.Titles)
}

我得到了输出,但我必须等待10秒才能找到s.Locations,而要等待60+秒才能看到n.Titles

最佳答案



从简单的事情开始,一次测量一件事,一次科学实验。

使用curl衡量基本响应时间。

$ curl https://www.google.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  7246    0  7246    0     0  94103      0 --:--:-- --:--:-- --:--:-- 94103
$ curl https://www.nytimes.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   934  100   934    0     0     61      0  0:00:15  0:00:15 --:--:--   230
$ curl https://www.washingtonpost.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  3360  100  3360    0     0    133      0  0:00:25  0:00:25 --:--:--   869
$

Google刻不容缓。纽约时报有15秒的延迟。 《华盛顿邮报》有25秒的延迟。

在Go中,确认《华盛顿邮报》有25秒的延迟。
$ go run wapo.go
25.174366651s
$ cat wapo.go
package main

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

func main() {
    start := time.Now()
    resp, err := http.Get("https://www.washingtonpost.com/news-sitemaps/index.xml")
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    _, err = ioutil.ReadAll(resp.Body)
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    resp.Body.Close()
    fmt.Fprintln(os.Stderr, time.Since(start))
}
$

接下来,尝试使用其他计算机上的其他ISP。
$ curl https://www.google.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  7246    0  7246    0     0  27343      0 --:--:-- --:--:-- --:--:-- 27343
$ curl https://www.nytimes.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   934  100   934    0     0   2017      0 --:--:-- --:--:-- --:--:--  2017
$ curl https://www.washingtonpost.com/robots.txt -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  3360  100  3360    0     0    356      0  0:00:09  0:00:09 --:--:--   840
$ curl https://www.washingtonpost.com/news-sitemaps/index.xml -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1101  100  1101    0     0    104      0  0:00:10  0:00:10 --:--:--   266
$

$ go run wapo.go
8.378458882s
$

Google刻不容缓。纽约时报有一点延迟。 《华盛顿邮报》有9秒的延迟。

Go代码和编译器相同:
$ go version
go version devel +a25c2878c7 Sat Jul 27 23:29:18 2019 +0000 linux/amd64
$ cat wapo.go
package main

import (
    "fmt"
    "net/http"
    "os"
    "time"
)

func main() {
    start := time.Now()
    resp, err := http.Get("https://www.washingtonpost.com/news-sitemaps/index.xml")
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    resp.Body.Close()
    fmt.Fprintln(os.Stderr, time.Since(start))
}
$

因此,重点关注网络和站点因素。

09-18 12:49