在http.HandleFunc内记录对传入HTTP请求的响应 [英] Logging responses to incoming HTTP requests inside http.HandleFunc

问题描述

这是对

This is a follow-up question to In go, how to inspect the http response that is written to http.ResponseWriter? since the solution there requires faking a request, which works great for a unit test but not on a live server.

我想将我的Web服务针对从用户收到的请求返回的HTTP响应转储到日志文件(或控制台)中.输出应该告诉我标题是什么以及JSON有效负载.

I would like to dump out HTTP response that my web service is returning in response to requests it receives from users into a log file (or to console). The output should tell me what the headers are and the JSON payload.

那怎么办?

如果有一个使用http.ResponseWriter作为参数而不是http.Response的httputil.DumpResponse等效项，那将是完美的，但是目前我只能从http.ResponseWriter访问标头

If there were a httputil.DumpResponse equivalent that takes a http.ResponseWriter as argument rather than http.Response it would be perfect, but currently I can only access the Header from http.ResponseWriter

r = mux.NewRouter()
r.HandleFunc("/path", func (w http.ResponseWriter, r *http.Request) {

    fmt.Printf("r.HandleFunc /path\n")

    resp := server.NewResponse()
    defer resp.Close()

    r.ParseForm()

    // Server does some work here
    // ...

    // Insert debug code here, something like
    //
    // dump = http.DumpResponseFromWriter(w)
    // fmt.Printf("%s\n", dump)
});
http.Handle("/path", r)

推荐答案

中间件链接

一个常见的解决方案是所谓的中间件链.有几个提供此功能的库，例如 negroni .

Middleware Chaining

A common solution to this problem is the so called middleware chain. There are several libraries that provide this functionality e.g. negroni.

这是一种延续传递样式的形式，您可以编写这样的 middleware 函数(取自negroni的自述文件):

It's a form of continuation-passing style where you write your middleware functions like this (taken from negroni's readme):

func MyMiddleware(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
  // do some stuff before
  next(rw, r)
  // do some stuff after
}

然后negroni为您提供一个HTTP处理程序，该处理程序以正确的顺序调用您的中间件.

And then negroni gives you an HTTP handler that calls your middlewares in the right order.

我们可以以一种不太神奇且功能更多的方式(如功能编程)来实现该解决方案.定义处理程序组合器，如下所示:

We could implement this solution slightly differently to a less magical and more functional (as in functional programming) approach. Define handler combinators as follows:

func NewFooHandler(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        // do some stuff before
        next(r,w)
        // do some stuff after
    }
}

然后将您的链定义为组合:

Then define your chain as a combination:

h := NewFooHandler(NewBarHandler(NewBazHandler(Sink)))

现在，h是一个http.HandlerFunc，它执行foo，然后执行bar，然后执行baz. Sink只是一个空的最后一个处理程序，不执行任何操作(以完成"链条.)

Now h is an http.HandlerFunc that does foo, then bar, then baz. Sink is just an empty last handler, that does nothing (to "finish" the chain.)

定义处理程序组合器:

func NewResponseLoggingHandler(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {

        // switch out response writer for a recorder
        // for all subsequent handlers
        c := httptest.NewRecorder()
        next(c, r)

        // copy everything from response recorder
        // to actual response writer
        for k, v := range c.HeaderMap {
            w.Header()[k] = v
        }
        w.WriteHeader(c.Code)
        c.Body.WriteTo(w)

    }
}

现在问题归结为处理程序管理.您可能希望将此处理程序应用于某个类别中的所有链.为此，您可以再次使用组合器(这在一定程度上等同于negroni的Classic()方法):

Now the problem boils down to handler management. You'll probably want this handler applied to all chains in a certain category. For this, you can use combinators again (this is somewhat equivalent to negroni's Classic() method):

func NewDefaultHandler(next http.HandlerFunc) http.HandlerFunc {
    return NewResponseLoggingHandler(NewOtherStuffHandler(next))
}

在此之后，每当您启动这样的链条时:

After this, whenever you start a chain like this:

h := NewDefaultHandler(...)

它将自动包括响应日志记录和您在NewDefaultHandler中定义的所有默认内容.

It will automatically include response logging and all the default stuff that you defined in NewDefaultHandler.

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