func fetchMetricFamilies(url string, ch chan<- *dto.MetricFamily) {
	defer close(ch)
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		log.Fatalf("creating GET request for URL %q failed: %s", url, err)
	}
	req.Header.Add("Accept", acceptHeader)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatalf("executing GET request for URL %q failed: %s", url, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		log.Fatalf("GET request for URL %q returned HTTP status %s", url, resp.Status)
	}

	mediatype, params, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))
	if err == nil && mediatype == "application/vnd.google.protobuf" &&
		params["encoding"] == "delimited" &&
		params["proto"] == "io.prometheus.client.MetricFamily" {
		for {
			mf := &dto.MetricFamily{}
			if _, err = pbutil.ReadDelimited(resp.Body, mf); err != nil {
				if err == io.EOF {
					break
				}
				log.Fatalln("reading metric family protocol buffer failed:", err)
			}
			ch <- mf
		}
	} else {
		// We could do further content-type checks here, but the
		// fallback for now will anyway be the text format
		// version 0.0.4, so just go for it and see if it works.
		var parser expfmt.TextParser
		metricFamilies, err := parser.TextToMetricFamilies(resp.Body)
		if err != nil {
			log.Fatalln("reading text format failed:", err)
		}
		for _, mf := range metricFamilies {
			ch <- mf
		}
	}
}

func (c *textFileCollector) parseTextFiles() []*dto.MetricFamily {
	error := 0.0
	var metricFamilies []*dto.MetricFamily
	mtimes := map[string]time.Time{}

	// Iterate over files and accumulate their metrics.
	files, err := ioutil.ReadDir(c.path)
	if err != nil && c.path != "" {
		log.Errorf("Error reading textfile collector directory %s: %s", c.path, err)
		error = 1.0
	}
	for _, f := range files {
		if !strings.HasSuffix(f.Name(), ".prom") {
			continue
		}
		path := filepath.Join(c.path, f.Name())
		file, err := os.Open(path)
		if err != nil {
			log.Errorf("Error opening %s: %v", path, err)
			error = 1.0
			continue
		}
		var parser expfmt.TextParser
		parsedFamilies, err := parser.TextToMetricFamilies(file)
		if err != nil {
			log.Errorf("Error parsing %s: %v", path, err)
			error = 1.0
			continue
		}
		// Only set this once it has been parsed, so that
		// a failure does not appear fresh.
		mtimes[f.Name()] = f.ModTime()
		for _, mf := range parsedFamilies {
			if mf.Help == nil {
				help := fmt.Sprintf("Metric read from %s", path)
				mf.Help = &help
			}
			metricFamilies = append(metricFamilies, mf)
		}
	}

	// Export the mtimes of the successful files.
	if len(mtimes) > 0 {
		mtimeMetricFamily := dto.MetricFamily{
			Name:   proto.String("node_textfile_mtime"),
			Help:   proto.String("Unixtime mtime of textfiles successfully read."),
			Type:   dto.MetricType_GAUGE.Enum(),
			Metric: []*dto.Metric{},
		}

		// Sorting is needed for predictable output comparison in tests.
		filenames := make([]string, 0, len(mtimes))
		for filename := range mtimes {
			filenames = append(filenames, filename)
		}
		sort.Strings(filenames)

		for _, filename := range filenames {
			mtimeMetricFamily.Metric = append(mtimeMetricFamily.Metric,
				&dto.Metric{
					Label: []*dto.LabelPair{
						&dto.LabelPair{
							Name:  proto.String("file"),
							Value: proto.String(filename),
						},
					},
					Gauge: &dto.Gauge{Value: proto.Float64(float64(mtimes[filename].UnixNano()) / 1e9)},
				},
			)
		}
		metricFamilies = append(metricFamilies, &mtimeMetricFamily)
	}
	// Export if there were errors.
	metricFamilies = append(metricFamilies, &dto.MetricFamily{
		Name: proto.String("node_textfile_scrape_error"),
		Help: proto.String("1 if there was an error opening or reading a file, 0 otherwise"),
		Type: dto.MetricType_GAUGE.Enum(),
		Metric: []*dto.Metric{
			&dto.Metric{
				Gauge: &dto.Gauge{Value: &error},
			},
		},
	})

	return metricFamilies
}

// Parse returns a slice of Metrics from a text representation of a
// metrics
func (p *PrometheusParser) Parse(buf []byte) ([]telegraf.Metric, error) {
	var metrics []telegraf.Metric
	var parser expfmt.TextParser
	// parse even if the buffer begins with a newline
	buf = bytes.TrimPrefix(buf, []byte("\n"))
	// Read raw data
	buffer := bytes.NewBuffer(buf)
	reader := bufio.NewReader(buffer)

	// Get format
	mediatype, params, err := mime.ParseMediaType(p.PromFormat["Content-Type"])
	// Prepare output
	metricFamilies := make(map[string]*dto.MetricFamily)
	if err == nil && mediatype == "application/vnd.google.protobuf" &&
		params["encoding"] == "delimited" &&
		params["proto"] == "io.prometheus.client.MetricFamily" {
		for {
			metricFamily := &dto.MetricFamily{}
			if _, err = pbutil.ReadDelimited(reader, metricFamily); err != nil {
				if err == io.EOF {
					break
				}
				return nil, fmt.Errorf("reading metric family protocol buffer failed: %s", err)
			}
			metricFamilies[metricFamily.GetName()] = metricFamily
		}
	} else {
		metricFamilies, err = parser.TextToMetricFamilies(reader)
		if err != nil {
			return nil, fmt.Errorf("reading text format failed: %s", err)
		}
		// read metrics
		for metricName, mf := range metricFamilies {
			for _, m := range mf.Metric {
				// reading tags
				tags := makeLabels(m)
				/*
					for key, value := range p.DefaultTags {
						tags[key] = value
					}
				*/
				// reading fields
				fields := make(map[string]interface{})
				if mf.GetType() == dto.MetricType_SUMMARY {
					// summary metric
					fields = makeQuantiles(m)
					fields["count"] = float64(m.GetSummary().GetSampleCount())
					fields["sum"] = float64(m.GetSummary().GetSampleSum())
				} else if mf.GetType() == dto.MetricType_HISTOGRAM {
					// historgram metric
					fields = makeBuckets(m)
					fields["count"] = float64(m.GetHistogram().GetSampleCount())
					fields["sum"] = float64(m.GetHistogram().GetSampleSum())

				} else {
					// standard metric
					fields = getNameAndValue(m)
				}
				// converting to telegraf metric
				if len(fields) > 0 {
					var t time.Time
					if m.TimestampMs != nil && *m.TimestampMs > 0 {
						t = time.Unix(0, *m.TimestampMs*1000000)
					} else {
						t = time.Now()
					}
					metric, err := telegraf.NewMetric(metricName, tags, fields, t)
					if err == nil {
						metrics = append(metrics, metric)
					}
				}
			}
		}
	}
	return metrics, err
}

// Push returns an http.Handler which accepts samples over HTTP and stores them
// in the MetricStore. If replace is true, all metrics for the job and instance
// given by the request are deleted before new ones are stored.
//
// The returned handler is already instrumented for Prometheus.
func Push(
	ms storage.MetricStore, replace bool,
) func(http.ResponseWriter, *http.Request, httprouter.Params) {
	var ps httprouter.Params
	var mtx sync.Mutex // Protects ps.

	instrumentedHandlerFunc := prometheus.InstrumentHandlerFunc(
		"push",
		func(w http.ResponseWriter, r *http.Request) {
			job := ps.ByName("job")
			labelsString := ps.ByName("labels")
			mtx.Unlock()

			labels, err := splitLabels(labelsString)
			if err != nil {
				http.Error(w, err.Error(), http.StatusBadRequest)
				return
			}
			if job == "" {
				http.Error(w, "job name is required", http.StatusBadRequest)
				return
			}
			labels["job"] = job

			if replace {
				ms.SubmitWriteRequest(storage.WriteRequest{
					Labels:    labels,
					Timestamp: time.Now(),
				})
			}

			var metricFamilies map[string]*dto.MetricFamily
			ctMediatype, ctParams, ctErr := mime.ParseMediaType(r.Header.Get("Content-Type"))
			if ctErr == nil && ctMediatype == "application/vnd.google.protobuf" &&
				ctParams["encoding"] == "delimited" &&
				ctParams["proto"] == "io.prometheus.client.MetricFamily" {
				metricFamilies = map[string]*dto.MetricFamily{}
				for {
					mf := &dto.MetricFamily{}
					if _, err = pbutil.ReadDelimited(r.Body, mf); err != nil {
						if err == io.EOF {
							err = nil
						}
						break
					}
					metricFamilies[mf.GetName()] = mf
				}
			} else {
				// We could do further content-type checks here, but the
				// fallback for now will anyway be the text format
				// version 0.0.4, so just go for it and see if it works.
				var parser expfmt.TextParser
				metricFamilies, err = parser.TextToMetricFamilies(r.Body)
			}
			if err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
			sanitizeLabels(metricFamilies, labels)
			ms.SubmitWriteRequest(storage.WriteRequest{
				Labels:         labels,
				Timestamp:      time.Now(),
				MetricFamilies: metricFamilies,
			})
			w.WriteHeader(http.StatusAccepted)
		},
	)

	return func(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
		mtx.Lock()
		ps = params
		instrumentedHandlerFunc(w, r)
	}
}

func ExampleGatherers() {
	reg := prometheus.NewRegistry()
	temp := prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Name: "temperature_kelvin",
			Help: "Temperature in Kelvin.",
		},
		[]string{"location"},
	)
	reg.MustRegister(temp)
	temp.WithLabelValues("outside").Set(273.14)
	temp.WithLabelValues("inside").Set(298.44)

	var parser expfmt.TextParser

	text := `
# TYPE humidity_percent gauge
# HELP humidity_percent Humidity in %.
humidity_percent{location="outside"} 45.4
humidity_percent{location="inside"} 33.2
# TYPE temperature_kelvin gauge
# HELP temperature_kelvin Temperature in Kelvin.
temperature_kelvin{location="somewhere else"} 4.5
`

	parseText := func() ([]*dto.MetricFamily, error) {
		parsed, err := parser.TextToMetricFamilies(strings.NewReader(text))
		if err != nil {
			return nil, err
		}
		var result []*dto.MetricFamily
		for _, mf := range parsed {
			result = append(result, mf)
		}
		return result, nil
	}

	gatherers := prometheus.Gatherers{
		reg,
		prometheus.GathererFunc(parseText),
	}

	gathering, err := gatherers.Gather()
	if err != nil {
		fmt.Println(err)
	}

	out := &bytes.Buffer{}
	for _, mf := range gathering {
		if _, err := expfmt.MetricFamilyToText(out, mf); err != nil {
			panic(err)
		}
	}
	fmt.Print(out.String())
	fmt.Println("----------")

	// Note how the temperature_kelvin metric family has been merged from
	// different sources. Now try
	text = `
# TYPE humidity_percent gauge
# HELP humidity_percent Humidity in %.
humidity_percent{location="outside"} 45.4
humidity_percent{location="inside"} 33.2
# TYPE temperature_kelvin gauge
# HELP temperature_kelvin Temperature in Kelvin.
# Duplicate metric:
temperature_kelvin{location="outside"} 265.3
 # Wrong labels:
temperature_kelvin 4.5
`

	gathering, err = gatherers.Gather()
	if err != nil {
		fmt.Println(err)
	}
	// Note that still as many metrics as possible are returned:
	out.Reset()
	for _, mf := range gathering {
		if _, err := expfmt.MetricFamilyToText(out, mf); err != nil {
			panic(err)
		}
	}
	fmt.Print(out.String())

	// Output:
	// # HELP humidity_percent Humidity in %.
	// # TYPE humidity_percent gauge
	// humidity_percent{location="inside"} 33.2
	// humidity_percent{location="outside"} 45.4
	// # HELP temperature_kelvin Temperature in Kelvin.
	// # TYPE temperature_kelvin gauge
	// temperature_kelvin{location="inside"} 298.44
	// temperature_kelvin{location="outside"} 273.14
	// temperature_kelvin{location="somewhere else"} 4.5
	// ----------
	// 2 error(s) occurred:
	// * collected metric temperature_kelvin label:<name:"location" value:"outside" > gauge:<value:265.3 >  was collected before with the same name and label values
	// * collected metric temperature_kelvin gauge:<value:4.5 >  has label dimensions inconsistent with previously collected metrics in the same metric family
	// # HELP humidity_percent Humidity in %.
	// # TYPE humidity_percent gauge
//.........这里部分代码省略.........