无法在中间件中跟踪 HTTP 响应代码

Question

我正在使用 go-openapi 从 swagger 配置生成一个 http 服务器并处理所有处理程序。我的中间件的模式是 request -> override func -> do http stuff -> logs response code -> response.

这是我的中间件：

func (pm *PrometheusMetrics) HTTPMiddleware(h http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        start := time.Now()
        statusRecoder := &utils.StatusRecorder{ResponseWriter: w, StatusCode: 200}
        logrus.Infof("--> %v %v", r.Method, r.URL.Path)
        // statusRecoder := negroni.NewResponseWriter(w) <-- tried this solution, didn't worked

        h.ServeHTTP(statusRecoder, r)

        logrus.Infof("<-- %v", statusRecoder.Status()) // should display status code
        duration := time.Since(start)
        statusCode := strconv.Itoa(statusRecoder.Status())

        pm.PushHTTPMetrics(r.URL.Path, statusCode, duration.Seconds())
    })
}

下面是我传递中间件的方式：

func setupGlobalMiddleware(handler http.Handler, promMetrics *apihandlers.PrometheusMetrics) http.Handler {
    middle := interpose.New()
    middle.UseHandler(handler)

    recoveryMiddleware := recovr.New()
    middle.Use(recoveryMiddleware)

    logrusMiddleware := interposeMiddleware.NegroniLogrus()
    middle.Use(logrusMiddleware)
    middle.Use(func(h http.Handler) http.Handler {
        return promMetrics.HTTPMiddleware(h)
    })

    corsMiddleware := cors.New(cors.Options{
        AllowedHeaders:     []string{"*"},
        AllowedOrigins:     []string{"*"},
        AllowedMethods:     []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
        MaxAge:             1000,
        OptionsPassthrough: false,
    })
    if log.GetLevel() >= log.DebugLevel {
        corsMiddleware.Log = log.StandardLogger()
    }

    return corsMiddleware.Handler(middle)
}

最后，我调用 setupGlobalMiddleware 函数的地方：

func configureAPI(api *operations.KubeesAPI) http.Handler { // operations is package generated by go-openapi
    // Some setup...
    return setupGlobalMiddleware(api.Serve(setupMiddlewares), promMetrics)
}

statusRecoder的覆盖：

type StatusRecorder struct {
    http.ResponseWriter
    StatusCode int
}

// WriteHeader is the fake function to record status code
func (rec *StatusRecorder) WriteHeader(statusCode int) {
    logrus.Infof("hello there: %v", statusCode)
    rec.StatusCode = statusCode
    rec.ResponseWriter.WriteHeader(statusCode)
}

如您所见，我重写了 http.Handler 中的 WriteHeader 函数以仅存储状态代码并在外部访问它，然后调用原始 WriteHeader 函数。这里的问题是，我的函数 WriteHeader 从未被调用过。并且无法弄清楚为什么不是。

Answer 1

The problem here, is that my function WriteHeader is never called. And can't figure out why it's not.

因为 Go 使用组合，而不是继承。 WriteHeader 最常被第一次调用 Write() 自动调用。来自 http.ResponseWriter documentation:

// Write writes the data to the connection as part of an HTTP reply.
//
// If WriteHeader has not yet been called, Write calls
// WriteHeader(http.StatusOK) before writing the data. If the Header
// does not contain a Content-Type line, Write adds a Content-Type set
// to the result of passing the initial 512 bytes of written data to
// DetectContentType. Additionally, if the total size of all written
// data is under a few KB and there are no Flush calls, the
// Content-Length header is added automatically.

但是由于您还没有定义自己的 Write 方法，因此调用了嵌入式方法（由 http.ResponseWriter 的嵌入式实例提供）。当那个 Write() 方法被调用，然后调用 WriteHeader 时，它调用原始的 WriteHeader 方法，而不是你的版本。

解决方案是也提供你自己的Write方法，它包装了原来的，并在需要时调用你的WriteHeader版本。

type StatusRecorder struct {
    http.ResponseWriter
    StatusCode int
    written bool
}

// WriteHeader is the fake function to record status code
func (rec *StatusRecorder) WriteHeader(statusCode int) {
    rec.written = true
    logrus.Infof("hello there: %v", statusCode)
    rec.StatusCode = statusCode
    rec.ResponseWriter.WriteHeader(statusCode)
}

func (rec *StatusRecorder) Write(p []byte) (int, error) {method
    if !rec.written {
        rec.WriteHeader(http.StatusOK)
    }
    return rec.Write(p)
}

Answer 2

好吧，如果您没有完整的软件包列表，那么答案会稍微复杂一些。
问题是 go-openapi 和 go-swagger 在代码中实现中间件并处理它们的方式。许多其他已安装的软件包都有这个问题。
为了确保我正确检索状态代码，我将中间件放在中间件声明的右下角。

代码：

func setupGlobalMiddleware(handler http.Handler, promMetrics *apihandlers.PrometheusMetrics) http.Handler {
    middle := interpose.New()
    middle.UseHandler(handler)

    recoveryMiddleware := recovr.New()
    middle.Use(recoveryMiddleware)

    logrusMiddleware := interposeMiddleware.NegroniLogrus()
    middle.Use(logrusMiddleware)

    // the old declaration was here

    corsMiddleware := cors.New(cors.Options{
        AllowedHeaders:     []string{"*"},
        AllowedOrigins:     []string{"*"},
        AllowedMethods:     []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
        MaxAge:             1000,
        OptionsPassthrough: false,
    })
    if log.GetLevel() >= log.DebugLevel {
        corsMiddleware.Log = log.StandardLogger()
    }

    // notice the changement where the promMetrics.HTTPMiddleware is now in the bottom
    return corsMiddleware.Handler(promMetrics.HTTPMiddleware(middle))
    // return corsMiddleware.Handler(middle) <-- old line
}

无法在中间件中跟踪 HTTP 响应代码

Can't track HTTP response code in middleware

http

go

server

wrapper

middleware