Log Request Body for Debugging (golang)

gistfile1.txt

		buf, bodyErr := ioutil.ReadAll(r.Body)
		if bodyErr != nil {
			log.Print("bodyErr ", bodyErr.Error())
			http.Error(w, bodyErr.Error(), http.StatusInternalServerError)
			return
		}
		
		rdr1 := ioutil.NopCloser(bytes.NewBuffer(buf))
		rdr2 := ioutil.NopCloser(bytes.NewBuffer(buf))
		log.Printf("BODY: %q", rdr1)
		r.Body = rdr2

nice snippet! Thanks for sharing!

nice

Thank you, this pointed me in the right direction. But it seems this is dangerous code. From the docs for NewBuffer():

NewBuffer creates and initializes a new Buffer using buf as its initial contents. The new Buffer takes ownership of buf, and the caller should not use buf after this call.

But this code is using buf twice. Moreover, while you need to construct a NopCloser to make the stored content readable, is there really any reason to construct a second one just to log it?

I got what I needed with the following code, which only creates one NopCloser and also doesn't violate the directive to not use the byte buffer after calling bytes.Newbuffer() (this uses zerolog logging syntax but hopefully the difference is still clear):

	buf, err := ioutil.ReadAll(r.Body)
	if err != nil {
		log.Error().Msgf("Error reading request body: %v", err.Error())
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	log.Debug().Msgf("Request body: %v", string(buf))

	reader := ioutil.NopCloser(bytes.NewBuffer(buf))
	r.Body = reader

Thanks @nstansby -- you're right, a second NopCloser not needed since you can just log the message as you've demonstrated above, then create just the one NopCloser for r.Body to continue on.

Mine was mainly a quick paste-in for debugging, so I didn't invest too much time in it.

Yours is nicer and could be used for debugging or production logging. Thanks again for adding your improvements!

It helps a lot, thanks