2

该程序同时产生了许多 goroutines (getStock)，我相信这会导致远程服务器立即断开连接。我不是在尝试创建 DOS，但我仍然想积极地获取数据而不会出现“连接重置”错误。

有哪些策略最多只能有 N 个（例如 20 个）同时连接？golang Http 客户端中是否有内置的 GET 请求队列？我还在学习，如果有更好的设计模式来理解这种类型的代码，那就太好了。

输出

$ go run s1w.go 
sl(size): 1280
body: "AAPL",17.92
body: "GOOG",32.13
body: "FB",42.02
body: "AMZN",195.83
body: "GOOG",32.13
body: "AMZN",195.83
body: "GOOG",32.13
body: "FB",42.02
body: "AAPL",17.92
2017/07/26 00:01:23 NFLX: Get http://goanuj.freeshell.org/go/NFLX.txt: read tcp 192.168.86.28:56674->205.166.94.30:80: read: connection reset by peer
2017/07/26 00:01:23 AAPL: Get http://goanuj.freeshell.org/go/AAPL.txt: read tcp 192.168.86.28:56574->205.166.94.30:80: read: connection reset by peer
2017/07/26 00:01:23 NFLX: Get http://goanuj.freeshell.org/go/NFLX.txt: read tcp 192.168.86.28:56760->205.166.94.30:80: read: connection reset by peer
2017/07/26 00:01:23 FB: Get http://goanuj.freeshell.org/go/FB.txt: read tcp 192.168.86.28:56688->205.166.94.30:80: read: connection reset by peer
2017/07/26 00:01:23 AMZN: Get http://goanuj.freeshell.org/go/AMZN.txt: read tcp 192.168.86.28:56689->205.166.94.30:80: read: connection reset by peer
2017/07/26 00:01:23 AAPL: Get http://goanuj.freeshell.org/go/AAPL.txt: read tcp 192.168.86.28:56702->205.166.94.30:80: read: connection reset by peer

s1.go

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

// https://www.youtube.com/watch?v=f6kdp27TYZs (15m)
// Generator: function that returns a channel
func getStocks(sl []string) <-chan string {
        c := make(chan string)
        for _, s := range sl {
                go getStock(s, c)
        }
        return c
}

func getStock(s string, c chan string) {
        resp, err := http.Get("http://goanuj.freeshell.org/go/" + s + ".txt")
        if err != nil {
                log.Printf(s + ": " + err.Error())
                c <- err.Error() // channel send
                return
        }
        body, _ := ioutil.ReadAll(resp.Body)
        resp.Body.Close() // close ASAP to prevent too many open file desriptors
        val := string(body)
        //fmt.Printf("body: %s", val)
        c <- val // channel send
        return
}

func main() {
        start := time.Now()
        var sl = []string{"AAPL", "AMZN", "GOOG", "FB", "NFLX"}
        // creates slice of 1280 elements
        for i := 0; i < 8; i++ {
                sl = append(sl, sl...)
        }
        fmt.Printf("sl(size): %d\n", len(sl))

        // get channel that returns only strings
        c := getStocks(sl)
        for i := 0; i < len(sl); i++ {
                fmt.Printf("%s", <-c) // channel recv
        }

        fmt.Printf("main: %.2fs elapsed.\n", time.Since(start).Seconds())
}
4

2 回答 2

2

与其为每个请求启动新的 goroutine，不如在程序启动时创建一个固定池并通过共享通道传递订单。每个订单都是一个结构，对应于当前传递给的参数getStock。如果您需要能够杀死游泳池，事情会变得更加复杂，但这仍然不是那么难......

基本上，您的新处理程序将是一个循环，从所有处理程序共享的通道中读取订单，执行它，然后在订单的响应通道上发送结果。

于 2017-07-26T16:19:53.423 回答
0

您需要使用缓冲通道来限制并行操作的数量。在循环中开始一个新的 goroutine 之前，你需要发送到这个通道并在调用完成后从它接收，所以它会释放一个地方并且新的请求将能够开始。在操场上查看你修改过的代码

于 2017-07-26T22:10:01.003 回答