coredns/middleware/recorder.go

package middleware

import (
	"time"

	"github.com/miekg/dns"
)

// ResponseRecorder is a type of ResponseWriter that captures
// the rcode code written to it and also the size of the message
// written in the response. A rcode code does not have
// to be written, however, in which case 0 must be assumed.
// It is best to have the constructor initialize this type
// with that default status code.
type ResponseRecorder struct {
	dns.ResponseWriter
	rcode int
	size  int
	start time.Time
}

// NewResponseRecorder makes and returns a new responseRecorder,
// which captures the DNS rcode from the ResponseWriter
// and also the length of the response message written through it.
func NewResponseRecorder(w dns.ResponseWriter) *ResponseRecorder {
	return &ResponseRecorder{
		ResponseWriter: w,
		rcode:          0,
		start:          time.Now(),
	}
}

// WriteMsg records the status code and calls the
// underlying ResponseWriter's WriteMsg method.
func (r *ResponseRecorder) WriteMsg(res *dns.Msg) error {
	r.rcode = res.Rcode
	r.size = res.Len()
	return r.ResponseWriter.WriteMsg(res)
}

// Write is a wrapper that records the size of the message that gets written.
func (r *ResponseRecorder) Write(buf []byte) (int, error) {
	n, err := r.ResponseWriter.Write(buf)
	if err == nil {
		r.size += n
	}
	return n, err
}

// Size returns the size.
func (r *ResponseRecorder) Size() int {
	return r.size
}

// Rcode returns the rcode.
func (r *ResponseRecorder) Rcode() int {
	return r.rcode
}

// Start returns the start time of the ResponseRecorder.
func (r *ResponseRecorder) Start() time.Time {
	return r.start
}

// Hijack implements dns.Hijacker. It simply wraps the underlying
// ResponseWriter's Hijack method if there is one, or returns an error.
func (r *ResponseRecorder) Hijack() {
	r.ResponseWriter.Hijack()
	return
}