func createRenderResponse(metrics pb.MultiFetchResponse, missing interface{}) []map[string]interface{} {

	var response []map[string]interface{}

	for _, metric := range metrics.GetMetrics() {

		var pvalues []interface{}
		for i, v := range metric.Values {
			if metric.IsAbsent[i] {
				pvalues = append(pvalues, missing)
			} else {
				pvalues = append(pvalues, v)
			}
		}

		// create the response
		presponse := map[string]interface{}{
			"start":  metric.StartTime,
			"step":   metric.StepTime,
			"end":    metric.StopTime,
			"name":   metric.Name,
			"values": pvalues,
		}
		response = append(response, presponse)
	}

	return response
}

func handleRenderPB(w http.ResponseWriter, req *http.Request, format string, responses []serverResponse) {

	metrics := make(map[string][]pb.FetchResponse)

	for _, r := range responses {
		var d pb.MultiFetchResponse
		err := proto.Unmarshal(r.response, &d)
		if err != nil {
			logger.Logf("error decoding protobuf response from server:%s: req:%s: err=%s", r.server, req.URL.RequestURI(), err)
			logger.Traceln("\n" + hex.Dump(r.response))
			Metrics.RenderErrors.Add(1)
			continue
		}
		for _, m := range d.Metrics {
			metrics[m.GetName()] = append(metrics[m.GetName()], *m)
		}
	}

	var multi pb.MultiFetchResponse

	if len(metrics) == 0 {
		err := fmt.Sprintf("no decoded responses to merge for req: %s", req.URL.RequestURI())
		logger.Logln(err)
		http.Error(w, err, http.StatusInternalServerError)
		Metrics.RenderErrors.Add(1)
		return
	}

	for name, decoded := range metrics {

		logger.Tracef("request: %s: %q %+v", req.URL.RequestURI(), name, decoded)

		if len(decoded) == 1 {
			logger.Debugf("only one decoded responses to merge for req: %q %s", name, req.URL.RequestURI())
			m := decoded[0]
			multi.Metrics = append(multi.Metrics, &m)
			continue
		}

		// Use the metric with the highest resolution as our base
		var highest int
		for i, d := range decoded {
			if d.GetStepTime() < decoded[highest].GetStepTime() {
				highest = i
			}
		}
		decoded[0], decoded[highest] = decoded[highest], decoded[0]

		metric := decoded[0]

		mergeValues(req, &metric, decoded)
		multi.Metrics = append(multi.Metrics, &metric)
	}

	returnRender(w, format, multi)
}

func MarshalProtobuf(results []*MetricData) ([]byte, error) {
	response := pb.MultiFetchResponse{}
	for _, metric := range results {
		response.Metrics = append(response.Metrics, &((*metric).FetchResponse))
	}
	b, err := response.Marshal()
	if err != nil {
		return nil, err
	}

	return b, nil
}

func marshalProtobuf(results []*metricData) []byte {
	response := pb.MultiFetchResponse{}
	for _, metric := range results {
		response.Metrics = append(response.Metrics, &((*metric).FetchResponse))
	}
	b, err := response.Marshal()
	if err != nil {
		logger.Logf("proto.Marshal: %v", err)
	}

	return b
}

func returnRender(w http.ResponseWriter, format string, metrics pb.MultiFetchResponse) {

	switch format {
	case "protobuf":
		w.Header().Set("Content-Type", "application/protobuf")
		b, _ := metrics.Marshal()
		w.Write(b)

	case "json":
		presponse := createRenderResponse(metrics, nil)
		w.Header().Set("Content-Type", "application/json")
		e := json.NewEncoder(w)
		e.Encode(presponse)

	case "", "pickle":
		presponse := createRenderResponse(metrics, pickle.None{})
		w.Header().Set("Content-Type", "application/pickle")
		e := pickle.NewEncoder(w)
		e.Encode(presponse)
	}

}

func fetchHandler(wr http.ResponseWriter, req *http.Request) {
	// URL: /render/?target=the.metric.name&format=pickle&from=1396008021&until=1396022421

	Metrics.RenderRequests.Add(1)
	req.ParseForm()
	metric := req.FormValue("target")
	format := req.FormValue("format")
	from := req.FormValue("from")
	until := req.FormValue("until")

	t0 := time.Now()

	// Make sure we log which metric caused a panic()
	defer func() {
		if r := recover(); r != nil {
			var buf [1024]byte
			runtime.Stack(buf[:], false)
			logger.Logf("panic handling request: %s\n%s\n", req.RequestURI, string(buf[:]))
		}
	}()

	if format != "json" && format != "pickle" && format != "protobuf" {
		Metrics.RenderErrors.Add(1)
		logger.Logf("dropping invalid uri (format=%s): %s",
			format, req.URL.RequestURI())
		http.Error(wr, "Bad request (unsupported format)",
			http.StatusBadRequest)
		return
	}

	files, leafs := expandGlobs(metric)

	var badTime bool

	i, err := strconv.Atoi(from)
	if err != nil {
		logger.Debugf("fromTime (%s) invalid: %s (in %s)", from, err, req.URL.RequestURI())
		badTime = true
	}
	fromTime := int(i)
	i, err = strconv.Atoi(until)
	if err != nil {
		logger.Debugf("untilTime (%s) invalid: %s (in %s)", from, err, req.URL.RequestURI())
		badTime = true
	}
	untilTime := int(i)

	if badTime {
		Metrics.RenderErrors.Add(1)
		http.Error(wr, "Bad request (invalid from/until time)", http.StatusBadRequest)
		return
	}

	var multi pb.MultiFetchResponse
	for i, metric := range files {

		if !leafs[i] {
			log.Printf("skipping directory = %q\n", metric)
			// can't fetch a directory
			continue
		}

		path := config.WhisperData + "/" + strings.Replace(metric, ".", "/", -1) + ".wsp"
		w, err := whisper.Open(path)
		if err != nil {
			// the FE/carbonzipper often requests metrics we don't have
			// We shouldn't really see this any more -- expandGlobs() should filter them out
			Metrics.NotFound.Add(1)
			log.Printf("error opening %q: %v\n", path, err)
			continue
		}

		points, err := w.Fetch(fromTime, untilTime)
		w.Close()
		if err != nil {
			Metrics.RenderErrors.Add(1)
			logger.Logf("failed to fetch points from %s: %s", path, err)
			continue
		}

		if points == nil {
			Metrics.NotFound.Add(1)
			logger.Debugf("Metric time range not found: metric=%s from=%d to=%d ", metric, fromTime, untilTime)
			continue
		}

		values := points.Values()

		fromTime := int32(points.FromTime())
		untilTime := int32(points.UntilTime())
		step := int32(points.Step())
		response := pb.FetchResponse{
			Name:      proto.String(metric),
			StartTime: &fromTime,
			StopTime:  &untilTime,
			StepTime:  &step,
			Values:    make([]float64, len(values)),
			IsAbsent:  make([]bool, len(values)),
		}

//.........这里部分代码省略.........

func renderHandler(w http.ResponseWriter, req *http.Request) {

	Metrics.FetchRequests.Add(1)

	target := req.FormValue("target")
	format := req.FormValue("format")
	from := req.FormValue("from")
	until := req.FormValue("until")

	frint, _ := strconv.Atoi(from)
	unint, _ := strconv.Atoi(until)

	if format != "json" && format != "protobuf" {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	matches := findMetrics(target)

	var multi pb.MultiFetchResponse

	for _, m := range matches {

		target := m.GetPath()

		var metric string
		if prefix, _, ok := parseTopK(target); ok {
			metric = prefix
		} else {
			metric = target
		}

		metrics := Whispers.Fetch(metric)
		if metrics == nil {
			continue
		}
		points := metrics.Fetch(metric, int32(frint), int32(unint))

		if points == nil {
			continue
		}

		fromTime := int32(points.From)
		untilTime := int32(points.Until)
		step := int32(points.Step)
		response := pb.FetchResponse{
			Name:      &target,
			StartTime: &fromTime,
			StopTime:  &untilTime,
			StepTime:  &step,
			Values:    make([]float64, len(points.Values)),
			IsAbsent:  make([]bool, len(points.Values)),
		}

		for i, p := range points.Values {
			if math.IsNaN(p) {
				response.Values[i] = 0
				response.IsAbsent[i] = true
			} else {
				response.Values[i] = p
				response.IsAbsent[i] = false
			}
		}

		multi.Metrics = append(multi.Metrics, &response)
	}

	var b []byte
	switch format {
	case "json":
		w.Header().Set("Content-Type", "application/json")
		b, _ = json.Marshal(multi)
	case "protobuf":
		w.Header().Set("Content-Type", "application/protobuf")
		b, _ = proto.Marshal(&multi)
	}
	w.Write(b)
}