Question

我在Go中编写了一个URL监控程序，但经过一段时间后，我在netstat -nao|grep 80找到了许多ESTABLISHED条目。

getHttpStatusCode func：

    HttpClient = &http.Client{
        Transport: &http.Transport{
            Dial: func(netw, addr string) (net.Conn, error) {
                deadline := time.Now().Add(30 * time.Second)
                c, err := net.DialTimeout(netw, addr, 20*time.Second)
                if err != nil {
                    return nil, err
                }

                c.SetDeadline(deadline)
                c.SetReadDeadline(deadline)
                c.SetWriteDeadline(deadline)
                return c, nil
            },
        },
    }

// ...

func getHttpStatusCode(url string) int {
    if url == "" {
        return 200
    }

    req, err := http.NewRequest("GET", url, nil)
    if err != nil {
        return 0
    }

    req.Close = true
    req.Header.Add("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_3) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.57 Safari/537.17")
    resp, err := HttpClient.Do(req)
    if err != nil {
        return 0
    }

    defer resp.Body.Close()
    return resp.StatusCode
}

我检查了Go手册，找不到像req.Close（）这样的东西，只是推迟resp.Body.Close（）。

以下是netstat -nao | grep 80的输出：

tcp 1343352 0 192.168.2.33:29581 220.181.155.19:80 ESTABLISHED off（0.00 / 0/0）

tcpdump tcp port 80的输出：

14:32:54.085095 IP 113.12.80.13.http > wk_0_mysql.KIDC90805.zw.39174: Flags [.], seq 17376:18824, ack 1, win 42, options [nop,nop,TS val 4236145017 ecr 204896351], length 1448
14:32:54.109206 IP wk_0_mysql.KIDC90805.zw.25834 > 220.181.90.8.http: Flags [S], seq 714805337, win 14600, options [mss 1460,sackOK,TS val 204896416 ecr 0,nop,wscale 9], length 0
14:32:54.223349 IP 220.181.155.22.http > wk_0_mysql.KIDC90805.zw.19262: Flags [.], seq 864939135:864940583, ack 1630899997, win 42, options [nop,nop,TS val 1570834172 ecr 204896529], length 1448
14:32:54.223352 IP wk_0_mysql.KIDC90805.zw.19262 > 220.181.155.22.http: Flags [.], ack 1448, win 1301, options [nop,nop,TS val 204896530 ecr 1570834172], length 0
14:32:54.223432 IP 220.181.155.10.http > wk_0_mysql.KIDC90805.zw.27376: Flags [.], seq 3889371684:3889373132, ack 1106685068, win 42, options [nop,nop,TS val 3866364254 ecr 204896529], length 1448
14:32:54.223436 IP wk_0_mysql.KIDC90805.zw.27376 > 220.181.155.10.http: Flags [.], ack 1448, win 594, options [nop,nop,TS val 204896530 ecr 3866364254], length 0
14:32:54.275774 IP 121.12.101.130.http > wk_0_mysql.KIDC90805.zw.63329: Flags [.], seq 1314475629:1314477089, ack 642951590, win 54, length 1460

Answer 1

HTTP客户端默认使用保持活动连接，您可以通过调用transport.CloseIdleConnections（来自docs）关闭它们。

我不确定req.Close对客户端请求做了什么，它可能只针对服务器。

URL监视器在netstat中生成多个ESTABLISHED（连接）条目

1 个答案: