http - ReverseProxy 依赖于 golang 中的 request.Body

Question

我想构建一个 http 反向代理来检查 HTTP 正文，然后将 HTTP 请求发送到它的上游服务器。你怎么能在 go 中做到这一点？

初始尝试(如下)失败，因为 ReverseProxy 复制传入请求、修改它并发送，但正文已被读取。

func main() {
    backendServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        b, err := ioutil.ReadAll(r.Body)
        if err != nil {
            http.Error(w, fmt.Sprintf("ioutil.ReadAll: %s", err), 500)
            return
        }
        // expecting to see hoge=fuga
        fmt.Fprintf(w, "this call was relayed by the reverse proxy, body: %s", string(b))
    }))
    defer backendServer.Close()

    rpURL, err := url.Parse(backendServer.URL)
    if err != nil {
        log.Fatal(err)
    }

    proxy := func(u *url.URL) http.Handler {
        p := httputil.NewSingleHostReverseProxy(u)
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if err := r.ParseForm(); err != nil {
                http.Error(w, fmt.Sprintf("ParseForm: %s", err), 500)
                return
            }
            p.ServeHTTP(w, r)
        })
    }(rpURL)
    frontendProxy := httptest.NewServer(proxy)
    defer frontendProxy.Close()

    resp, err := http.Post(frontendProxy.URL, "application/x-www-form-urlencoded", bytes.NewBufferString("hoge=fuga"))
    if err != nil {
        log.Fatalf("http.Post: %s", err)
    }

    b, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        log.Fatalf("ioutil.ReadAll: %s", err)
    }

    fmt.Printf("%s", b)
}
// shows: "http: proxy error: http: ContentLength=9 with Body length 0"

然后我的下一个尝试是将整个主体读入 bytes.Reader 并使用它来检查主体内容，并在发送到上游服务器之前查找到开头。但是后来我必须重新实现我想避免的 ReverseProxy。还有其他优雅的方式吗？

Answer 1

您可以将 Director 处理程序设置为 httputil.ReverseProxy文档:https://golang.org/pkg/net/http/httputil/#ReverseProxy

这是一个示例代码，它从 localhost:8080 到 localhost:3333 的请求和代理中读取内容正文

package main

import (
    "bytes"
    "io/ioutil"
    "log"
    "net/http"
    "net/http/httputil"
)

func main() {
    director := func(req *http.Request) {
        if req.Body != nil {
            // read all bytes from content body and create new stream using it.
            bodyBytes, _ := ioutil.ReadAll(req.Body)
            req.Body = ioutil.NopCloser(bytes.NewBuffer(bodyBytes))

            // create new request for parsing the body
            req2, _ := http.NewRequest(req.Method, req.URL.String(), bytes.NewReader(bodyBytes))
            req2.Header = req.Header
            req2.ParseForm()
            log.Println(req2.Form)
        }

        req.URL.Host = "localhost:3333"
        req.URL.Scheme = "http"
    }
    proxy := &httputil.ReverseProxy{Director: director}
    log.Fatalln(http.ListenAndServe(":8080", proxy))
}