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

问题描述

这是一个后续问题，在go中，如何检查写入http.ResponseWriter的http响应？，因为那里的解决方案需要伪造一个请求，这对单元测试非常有用，但不适用于直播服务器。

我想转储HTTP响应，我的web服务响应它从用户接收到的请求而返回到日志文件（或控制台）中。输出应该告诉我头是什么和JSON有效载荷。

这是怎么回事？

如果有一个httputil.DumpResponse等价物将http.ResponseWriter作为参数而不是http.Response，那么这将是完美的，但目前我只能从http.ResponseWriter访问Header

  r = mux.NewRouter（）
 r.HandleFunc（/ path，func（w http.ResponseWriter，r * http.Request）{
 
 fmt.Printf（r.HandleFunc / path \\\
）
 
 resp：= server.NewResponse（）
 defer resp.Close（）
 
 r.ParseForm（）
 
 //服务器在这里做一些工作
 // ... 
 
 //在这里插入调试代码，类似于
 // 
 // dump = http.DumpResponseFromWriter（w）
 // fmt.Printf（％s \ n，dump）
}）; 
 http.Handle（/ path，r）
  

解决方案

中间件链接

这个问题的常见解决方案是所谓的中间件链。有几个库提供这种功能，例如。

这是一种延续形式，在这里写下你的中间件函数的样式（取自negroni的自述文件）：

  func MyMiddleware （rw http.ResponseWriter，r * http.Request，next http.HandlerFunc）{
 //在
 next（rw，r）
之前做一些事情//在$ b之后做一些事
 $ b  

然后negroni为您提供一个HTTP处理程序，以正确的顺序调用您的中间件。 / p>

我们可以稍微不同的方式实现这个解决方案，这个方法的功能不如神奇功能更强大（如函数式编程）方法。定义处理程序组合子如下：

  func NewFooHandler（next http.HandlerFunc）http.HandlerFunc {
 return func（w http：//ResponseWriter，r * http.Request）{
 //在
 next（r，w）
之前做一些事情//在
之后做一些事情
 } 
  

然后将您的连锁店定义为一个组合：

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

现在 h 是一个 http.HandlerFunc ，它会执行foo，然后是bar，然后是baz。 Sink 只是一个空的最后一个处理程序，它什么都不做（用来完成链接。）

应用这个解决您的问题

定义处理程序组合器：

  func NewResponseLoggingHandler （下一个http.HandlerFunc）http.HandlerFunc {
返回func（w http.ResponseWriter，r * http.Request）{
 
 //转出记录器的响应编写器
 //所有后续处理程序
c：= httptest.NewRecorder（）
 next（c，r）
 
 //将所有内容从响应记录器
 //复制到实际响应编写器
 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的所有链。为此，您可以再次使用组合器（这与Negroni的 Classic（）方法）相当：

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


之后，每当你开始这样的连锁时：

  h：= NewDefaultHandler（...）
  

它会自动包含响应记录和所有默认的东西你在 NewDefaultHandler 中定义的。

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.

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.

How does one go about that?

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)

解决方案

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.

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
}

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

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
    }
}

Then define your chain as a combination:

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

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.)

Applying this solution to your problem

Define a handler combinator:

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)

    }
}

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))
}

After this, whenever you start a chain like this:

h := NewDefaultHandler(...)

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

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