networking - Golang反向代理到nginx背后的app

Question

我正在使用 Golang 编写一个简单的反向代理。代码如下:

func NewMultiHostProxy(target_urls []string) gin.HandlerFunc {
    var urls []*url.URL
    for i := 0; i < len(target_urls); i++ {
        target, err := url.Parse(target_urls[i])
        if err != nil {
            fmt.Errorf("Error parsing url")
            return nil
        }
        urls = append(urls, target)
    }
    return func(c *gin.Context) {
        director := func(req *http.Request) {
            target := urls[rand.Int()%len(urls)]
            r := c.Request
            req = r
            req.URL.Scheme = target.Scheme
            req.URL.Host = target.Host
            req.URL.Path = target.Path
            req.Header.Set("X-GoProxy", "GoProxy")
            if target.RawQuery == "" || req.URL.RawQuery == "" {
                req.URL.RawQuery = target.RawQuery + req.URL.RawQuery
            } else {
                req.URL.RawQuery = target.RawQuery + "&" + req.URL.RawQuery
            }
            log.Print(req.URL)
        }
        proxy := &httputil.ReverseProxy{Director: director}
        proxy.ServeHTTP(c.Writer, c.Request)
    }
}

当我尝试将一个请求代理到 Nginx 后面的 REST api 时，Nginx 总是返回 404。但是，如果我直接访问 REST api，它会正确返回结果。这是我的 Nginx 配置:

server {
    listen       80;
    server_name  myservername;

    location /api {
        proxy_pass http://127.0.0.1:5000;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}

我可以知道如何调试这个问题吗？是Nginx配置引起的吗？

Answer 1

来自 https://golang.org/pkg/net/http/httputil/#ReverseProxy :

    // Director must be a function which modifies
    // the request into a new request to be sent
    // using Transport. Its response is then copied
    // back to the original client unmodified.
    // Director must not access the provided Request
    // after returning.
    Director func(*http.Request)

也就是&httputil.ReverseProxy{Director: director}中用来构造ReverseProxy的函数

但是您的主管从不修改原始req 指向的http.Request。它用 req = r 重新分配指针。改为修改不相关的 http.Request。