ReverseProxy取决于请求。戈朗的尸体

Question

我想构建一个http反向代理，它检查http主体，然后向其上游服务器发送http请求。你怎么能在围棋中做到这一点？

初始尝试（随后）失败，因为ReverseProxy复制传入请求，修改并发送请求，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正文读入字节。读卡器，并使用它检查正文内容，在发送到上游服务器之前查找开头部分。但是接下来我必须重新实现我想要避免的ReverseProxy。还有其他优雅的方式吗？

Answer 1

编辑：

如上所述，在这种情况下，解析的表单将为空。您需要从主体中手动解析表单。

请求。Body是一个io。ReaderCloser，因为它描述了tcp连接的rx部分。但是在您的用例中，您需要阅读所有内容，因为您正在将主体解析为表单。这里的技巧是使用io重新分配r.Body。ReaderCloser从已读数据派生的对象。下面是我要做的：

  // before calling r.ParseForm(), get the body
  // as a byte slice
  body, err := ioutil.ReadAll(r.Body)

  // after calling r.ParseForm(), reassign body
  r.Body = ioutil.NopCloser(bytes.NewBuffer(body))

字节。NewBuffer（body）将主体字节片转换为io。Reader和ioutil。NopCler转换一个io。读取到io。带有nop方法的ReaderCloser方法。

  package main

  import "net/http"
  import "net/http/httputil"
  import "net/url"
  import "net/http/httptest"
  import "fmt"
  import "log"
  import "bytes"
  import "io/ioutil"

  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) {
            // read out body into a slice
            body, err := ioutil.ReadAll(r.Body)
            if err != nil {
                http.Error(w, fmt.Sprintf("Error reading body: %s", err), 500)
                return
            }

            // inspect current body here
            if err := r.ParseForm(); err != nil {
                http.Error(w, fmt.Sprintf("ParseForm: %s", err), 500)
                return
            }

            // assign a new body with previous byte slice
            r.Body = ioutil.NopCloser(bytes.NewBuffer(body))
            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)
  }

Answer 2

您可以将导演处理程序设置为http putil。ReverseProxy文档：https://golang.org/pkg/net/http/httputil/#ReverseProxy

下面是一个示例代码，它从请求中读取内容正文，并从localhost:8080到localhost:3333

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))
}