Go并发HTTP请求中"no such host"错误与文件描述符限制解析

package main

import (
    "fmt"
    "io/ioutil"
    "net/http"
    "sync" // 引入sync包用于等待所有goroutine完成
)

func get(url string) ([]byte, error) {
    // 建议使用http.DefaultClient或自定义client，此处为示例
    client := &http.Client{}
    req, err := http.NewRequest("GET", url, nil)
    if err != nil {
        fmt.Printf("Error creating request for %s: %v\n", url, err)
        return nil, err
    }

    res, err := client.Do(req)
    if err != nil {
        // 这里的错误可能就是"no such host"
        fmt.Printf("Error doing request for %s: %v\n", url, err)
        return nil, err
    }
    defer res.Body.Close() // 确保响应体被关闭

    bytes, read_err := ioutil.ReadAll(res.Body)
    if read_err != nil {
        fmt.Printf("Error reading response body for %s: %v\n", url, read_err)
        return nil, read_err
    }

    // fmt.Println(string(bytes)) // 打印内容可能过多，此处注释
    return bytes, nil
}

func main() {
    const parallelNum = 1040 // 模拟高并发数量
    var wg sync.WaitGroup

    fmt.Printf("Starting %d parallel HTTP requests...\n", parallelNum)

    for i := 0; i < parallelNum; i++ {
        wg.Add(1)
        go func(idx int) {
            defer wg.Done()
            url := fmt.Sprintf("http://www.httpbin.org/get?a=%d", idx)
            _, err := get(url)
            if err != nil {
                // 仅打印错误，不中断主程序
            }
        }(i)
    }

    wg.Wait() // 等待所有goroutine完成
    fmt.Println("All requests finished.")
}

$ ulimit -a
-t: cpu time (seconds)         unlimited
-f: file size (blocks)         unlimited
-d: data seg size (kbytes)     unlimited
-s: stack size (kbytes)        8192
-c: core file size (blocks)    0
-v: address space (kb)         unlimited
-l: locked-in-memory size (kb) unlimited
-u: processes                  709
-n: file descriptors           2560

$ ulimit -n
2560

$ ulimit -n 5000

$ ulimit -n
5000

sudo nano /etc/security/limits.conf

*   soft    nofile  65535
*   hard    nofile  65535