func parseTime(s string) (model.Time, error) {
	if t, err := strconv.ParseFloat(s, 64); err == nil {
		ts := int64(t * float64(time.Second))
		return model.TimeFromUnixNano(ts), nil
	}
	if t, err := time.Parse(time.RFC3339Nano, s); err == nil {
		return model.TimeFromUnixNano(t.UnixNano()), nil
	}
	return 0, fmt.Errorf("cannot parse %q to a valid timestamp", s)
}

func TestTargetScraperScrapeOK(t *testing.T) {
	server := httptest.NewServer(
		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			w.Header().Set("Content-Type", `text/plain; version=0.0.4`)
			w.Write([]byte("metric_a 1\nmetric_b 2\n"))
		}),
	)
	defer server.Close()

	serverURL, err := url.Parse(server.URL)
	if err != nil {
		panic(err)
	}

	ts := &targetScraper{
		Target: &Target{
			labels: model.LabelSet{
				model.SchemeLabel:  model.LabelValue(serverURL.Scheme),
				model.AddressLabel: model.LabelValue(serverURL.Host),
			},
		},
		client: http.DefaultClient,
	}
	now := time.Now()

	samples, err := ts.scrape(context.Background(), now)
	if err != nil {
		t.Fatalf("Unexpected scrape error: %s", err)
	}

	expectedSamples := model.Samples{
		{
			Metric:    model.Metric{"__name__": "metric_a"},
			Timestamp: model.TimeFromUnixNano(now.UnixNano()),
			Value:     1,
		},
		{
			Metric:    model.Metric{"__name__": "metric_b"},
			Timestamp: model.TimeFromUnixNano(now.UnixNano()),
			Value:     2,
		},
	}
	sort.Sort(expectedSamples)
	sort.Sort(samples)

	if !reflect.DeepEqual(samples, expectedSamples) {
		t.Errorf("Scraped samples did not match served metrics")
		t.Errorf("Expected: %v", expectedSamples)
		t.Fatalf("Got: %v", samples)
	}
}

func extractSummary(o *DecodeOptions, f *dto.MetricFamily) model.Vector {
	samples := make(model.Vector, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Summary == nil {
			continue
		}

		timestamp := o.Timestamp
		if m.TimestampMs != nil {
			timestamp = model.TimeFromUnixNano(*m.TimestampMs * 1000000)
		}

		for _, q := range m.Summary.Quantile {
			lset := make(model.LabelSet, len(m.Label)+2)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			// BUG(matt): Update other names to "quantile".
			lset[model.LabelName(model.QuantileLabel)] = model.LabelValue(fmt.Sprint(q.GetQuantile()))
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName())

			samples = append(samples, &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(q.GetValue()),
				Timestamp: timestamp,
			})
		}

		if m.Summary.SampleSum != nil {
			lset := make(model.LabelSet, len(m.Label)+1)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_sum")

			samples = append(samples, &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(m.Summary.GetSampleSum()),
				Timestamp: timestamp,
			})
		}

		if m.Summary.SampleCount != nil {
			lset := make(model.LabelSet, len(m.Label)+1)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_count")

			samples = append(samples, &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(m.Summary.GetSampleCount()),
				Timestamp: timestamp,
			})
		}
	}

	return samples
}

func extractUntyped(o *DecodeOptions, f *dto.MetricFamily) model.Vector {
	samples := make(model.Vector, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Untyped == nil {
			continue
		}

		lset := make(model.LabelSet, len(m.Label)+1)
		for _, p := range m.Label {
			lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
		}
		lset[model.MetricNameLabel] = model.LabelValue(f.GetName())

		smpl := &model.Sample{
			Metric: model.Metric(lset),
			Value:  model.SampleValue(m.Untyped.GetValue()),
		}

		if m.TimestampMs != nil {
			smpl.Timestamp = model.TimeFromUnixNano(*m.TimestampMs * 1000000)
		} else {
			smpl.Timestamp = o.Timestamp
		}

		samples = append(samples, smpl)
	}

	return samples
}

func recordScrapeHealth(
	sampleAppender storage.SampleAppender,
	timestamp time.Time,
	baseLabels model.LabelSet,
	health TargetHealth,
	scrapeDuration time.Duration,
) {
	healthMetric := make(model.Metric, len(baseLabels)+1)
	durationMetric := make(model.Metric, len(baseLabels)+1)

	healthMetric[model.MetricNameLabel] = scrapeHealthMetricName
	durationMetric[model.MetricNameLabel] = scrapeDurationMetricName

	for ln, lv := range baseLabels {
		healthMetric[ln] = lv
		durationMetric[ln] = lv
	}

	ts := model.TimeFromUnixNano(timestamp.UnixNano())

	healthSample := &model.Sample{
		Metric:    healthMetric,
		Timestamp: ts,
		Value:     health.value(),
	}
	durationSample := &model.Sample{
		Metric:    durationMetric,
		Timestamp: ts,
		Value:     model.SampleValue(float64(scrapeDuration) / float64(time.Second)),
	}

	sampleAppender.Append(healthSample)
	sampleAppender.Append(durationSample)
}

func (sl *scrapeLoop) report(start time.Time, duration time.Duration, err error) {
	sl.scraper.report(start, duration, err)

	ts := model.TimeFromUnixNano(start.UnixNano())

	var health model.SampleValue
	if err == nil {
		health = 1
	}

	healthSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeHealthMetricName,
		},
		Timestamp: ts,
		Value:     health,
	}
	durationSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeDurationMetricName,
		},
		Timestamp: ts,
		Value:     model.SampleValue(float64(duration) / float64(time.Second)),
	}

	sl.reportAppender.Append(healthSample)
	sl.reportAppender.Append(durationSample)
}

func (t *Target) report(app storage.SampleAppender, start time.Time, duration time.Duration, err error) {
	t.status.setLastScrape(start)
	t.status.setLastError(err)

	ts := model.TimeFromUnixNano(start.UnixNano())

	var health model.SampleValue
	if err == nil {
		health = 1
	}

	healthSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeHealthMetricName,
		},
		Timestamp: ts,
		Value:     health,
	}
	durationSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeDurationMetricName,
		},
		Timestamp: ts,
		Value:     model.SampleValue(float64(duration) / float64(time.Second)),
	}

	app = t.wrapReportingAppender(app)

	app.Append(healthSample)
	app.Append(durationSample)
}

func (sl *scrapeLoop) report(start time.Time, duration time.Duration, err error) {
	sl.scraper.report(start, duration, err)

	ts := model.TimeFromUnixNano(start.UnixNano())

	var health model.SampleValue
	if err == nil {
		health = 1
	}

	healthSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeHealthMetricName,
		},
		Timestamp: ts,
		Value:     health,
	}
	durationSample := &model.Sample{
		Metric: model.Metric{
			model.MetricNameLabel: scrapeDurationMetricName,
		},
		Timestamp: ts,
		Value:     model.SampleValue(float64(duration) / float64(time.Second)),
	}

	if err := sl.reportAppender.Append(healthSample); err != nil {
		log.With("sample", healthSample).With("error", err).Warn("Scrape health sample discarded")
	}
	if err := sl.reportAppender.Append(durationSample); err != nil {
		log.With("sample", durationSample).With("error", err).Warn("Scrape duration sample discarded")
	}
}

func parseTimestampOrNow(t string, now model.Time) (model.Time, error) {
	if t == "" {
		return now, nil
	}

	tFloat, err := strconv.ParseFloat(t, 64)
	if err != nil {
		return 0, err
	}
	return model.TimeFromUnixNano(int64(tFloat * float64(time.Second/time.Nanosecond))), nil
}

func TestParseTime(t *testing.T) {
	ts, err := time.Parse(time.RFC3339Nano, "2015-06-03T13:21:58.555Z")
	if err != nil {
		panic(err)
	}

	var tests = []struct {
		input  string
		fail   bool
		result time.Time
	}{
		{
			input: "",
			fail:  true,
		}, {
			input: "abc",
			fail:  true,
		}, {
			input: "30s",
			fail:  true,
		}, {
			input:  "123",
			result: time.Unix(123, 0),
		}, {
			input:  "123.123",
			result: time.Unix(123, 123000000),
		}, {
			input:  "123.123",
			result: time.Unix(123, 123000000),
		}, {
			input:  "2015-06-03T13:21:58.555Z",
			result: ts,
		}, {
			input:  "2015-06-03T14:21:58.555+01:00",
			result: ts,
		},
	}

	for _, test := range tests {
		ts, err := parseTime(test.input)
		if err != nil && !test.fail {
			t.Errorf("Unexpected error for %q: %s", test.input, err)
			continue
		}
		if err == nil && test.fail {
			t.Errorf("Expected error for %q but got none", test.input)
			continue
		}
		res := model.TimeFromUnixNano(test.result.UnixNano())
		if !test.fail && ts != res {
			t.Errorf("Expected time %v for input %q but got %v", res, test.input, ts)
		}
	}
}

func (s *targetScraper) scrape(ctx context.Context, ts time.Time) (model.Samples, error) {
	req, err := http.NewRequest("GET", s.URL().String(), nil)
	if err != nil {
		return nil, err
	}
	req.Header.Add("Accept", acceptHeader)

	resp, err := ctxhttp.Do(ctx, s.client, req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("server returned HTTP status %s", resp.Status)
	}

	var (
		allSamples = make(model.Samples, 0, 200)
		decSamples = make(model.Vector, 0, 50)
	)
	sdec := expfmt.SampleDecoder{
		Dec: expfmt.NewDecoder(resp.Body, expfmt.ResponseFormat(resp.Header)),
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(ts.UnixNano()),
		},
	}

	for {
		if err = sdec.Decode(&decSamples); err != nil {
			break
		}
		allSamples = append(allSamples, decSamples...)
		decSamples = decSamples[:0]
	}

	if err == io.EOF {
		// Set err to nil since it is used in the scrape health recording.
		err = nil
	}
	return allSamples, err
}

func TestParseTimestampOrNow(t *testing.T) {
	ts, err := parseTimestampOrNow("", testNow())
	if err != nil {
		t.Fatalf("err = %s; want nil", err)
	}
	if !testNow().Equal(ts) {
		t.Fatalf("ts = %v; want ts = %v", ts, testNow)
	}

	ts, err = parseTimestampOrNow("1426956073.12345", testNow())
	if err != nil {
		t.Fatalf("err = %s; want nil", err)
	}
	expTS := model.TimeFromUnixNano(1426956073123000000)
	if !ts.Equal(expTS) {
		t.Fatalf("ts = %v; want %v", ts, expTS)
	}

	_, err = parseTimestampOrNow("123.45foo", testNow())
	if err == nil {
		t.Fatalf("err = nil; want %s", err)
	}
}

func verifyStorage(t testing.TB, s *memorySeriesStorage, samples model.Samples, maxAge time.Duration) bool {
	s.WaitForIndexing()
	result := true
	for _, i := range rand.Perm(len(samples)) {
		sample := samples[i]
		if sample.Timestamp.Before(model.TimeFromUnixNano(time.Now().Add(-maxAge).UnixNano())) {
			continue
			// TODO: Once we have a guaranteed cutoff at the
			// retention period, we can verify here that no results
			// are returned.
		}
		fp, err := s.mapper.mapFP(sample.Metric.FastFingerprint(), sample.Metric)
		if err != nil {
			t.Fatal(err)
		}
		p := s.NewPreloader()
		p.PreloadRange(fp, sample.Timestamp, sample.Timestamp, time.Hour)
		found := s.NewIterator(fp).ValueAtTime(sample.Timestamp)
		if len(found) != 1 {
			t.Errorf("Sample %#v: Expected exactly one value, found %d.", sample, len(found))
			result = false
			p.Close()
			continue
		}
		want := sample.Value
		got := found[0].Value
		if want != got || sample.Timestamp != found[0].Timestamp {
			t.Errorf(
				"Value (or timestamp) mismatch, want %f (at time %v), got %f (at time %v).",
				want, sample.Timestamp, got, found[0].Timestamp,
			)
			result = false
		}
		p.Close()
	}
	return result
}

func (t *Target) scrape(appender storage.SampleAppender) (err error) {
	start := time.Now()
	baseLabels := t.BaseLabels()

	defer func(appender storage.SampleAppender) {
		t.status.setLastError(err)
		recordScrapeHealth(appender, start, baseLabels, t.status.Health(), time.Since(start))
	}(appender)

	t.RLock()

	// The relabelAppender has to be inside the label-modifying appenders
	// so the relabeling rules are applied to the correct label set.
	if len(t.metricRelabelConfigs) > 0 {
		appender = relabelAppender{
			app:         appender,
			relabelings: t.metricRelabelConfigs,
		}
	}

	if t.honorLabels {
		appender = honorLabelsAppender{
			app:    appender,
			labels: baseLabels,
		}
	} else {
		appender = ruleLabelsAppender{
			app:    appender,
			labels: baseLabels,
		}
	}

	httpClient := t.httpClient

	t.RUnlock()

	req, err := http.NewRequest("GET", t.URL().String(), nil)
	if err != nil {
		return err
	}
	req.Header.Add("Accept", acceptHeader)

	resp, err := httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("server returned HTTP status %s", resp.Status)
	}

	dec := expfmt.NewDecoder(resp.Body, expfmt.ResponseFormat(resp.Header))

	sdec := expfmt.SampleDecoder{
		Dec: dec,
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(start.UnixNano()),
		},
	}

	t.ingestedSamples = make(chan model.Vector, ingestedSamplesCap)

	go func() {
		for {
			// TODO(fabxc): Change the SampleAppender interface to return an error
			// so we can proceed based on the status and don't leak goroutines trying
			// to append a single sample after dropping all the other ones.
			//
			// This will also allow use to reuse this vector and save allocations.
			var samples model.Vector
			if err = sdec.Decode(&samples); err != nil {
				break
			}
			if err = t.ingest(samples); err != nil {
				break
			}
		}
		close(t.ingestedSamples)
	}()

	for samples := range t.ingestedSamples {
		for _, s := range samples {
			appender.Append(s)
		}
	}

	if err == io.EOF {
		return nil
	}
	return err
}

func (t *Target) scrape(sampleAppender storage.SampleAppender) (err error) {
	start := time.Now()
	baseLabels := t.BaseLabels()

	t.RLock()
	var (
		honorLabels          = t.honorLabels
		httpClient           = t.httpClient
		metricRelabelConfigs = t.metricRelabelConfigs
	)
	t.RUnlock()

	defer func() {
		t.status.setLastError(err)
		recordScrapeHealth(sampleAppender, start, baseLabels, t.status.Health(), time.Since(start))
	}()

	req, err := http.NewRequest("GET", t.URL().String(), nil)
	if err != nil {
		panic(err)
	}
	req.Header.Add("Accept", acceptHeader)

	resp, err := httpClient.Do(req)
	if err != nil {
		return err
	}
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("server returned HTTP status %s", resp.Status)
	}

	dec, err := expfmt.NewDecoder(resp.Body, resp.Header)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	sdec := expfmt.SampleDecoder{
		Dec: dec,
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(start.UnixNano()),
		},
	}

	t.ingestedSamples = make(chan model.Vector, ingestedSamplesCap)

	go func() {
		for {
			// TODO(fabxc): Changex the SampleAppender interface to return an error
			// so we can proceed based on the status and don't leak goroutines trying
			// to append a single sample after dropping all the other ones.
			//
			// This will also allow use to reuse this vector and save allocations.
			var samples model.Vector
			if err = sdec.Decode(&samples); err != nil {
				break
			}
			if err = t.ingest(samples); err != nil {
				break
			}
		}
		close(t.ingestedSamples)
	}()

	for samples := range t.ingestedSamples {
		for _, s := range samples {
			if honorLabels {
				// Merge the metric with the baseLabels for labels not already set in the
				// metric. This also considers labels explicitly set to the empty string.
				for ln, lv := range baseLabels {
					if _, ok := s.Metric[ln]; !ok {
						s.Metric[ln] = lv
					}
				}
			} else {
				// Merge the ingested metric with the base label set. On a collision the
				// value of the label is stored in a label prefixed with the exported prefix.
				for ln, lv := range baseLabels {
					if v, ok := s.Metric[ln]; ok && v != "" {
						s.Metric[model.ExportedLabelPrefix+ln] = v
					}
					s.Metric[ln] = lv
				}
			}
			// Avoid the copy in Relabel if there are no configs.
			if len(metricRelabelConfigs) > 0 {
				labels, err := Relabel(model.LabelSet(s.Metric), metricRelabelConfigs...)
				if err != nil {
					log.Errorf("Error while relabeling metric %s of instance %s: %s", s.Metric, req.URL, err)
					continue
				}
				// Check if the timeseries was dropped.
				if labels == nil {
					continue
				}
				s.Metric = model.Metric(labels)
			}
			sampleAppender.Append(s)
		}
	}
//.........这里部分代码省略.........

//.........这里部分代码省略.........
			"title":     strings.Title,
			"graphLink": strutil.GraphLinkForExpression,
			"tableLink": strutil.TableLinkForExpression,
			"sortByLabel": func(label string, v queryResult) queryResult {
				sorter := queryResultByLabelSorter{v[:], label}
				sort.Stable(sorter)
				return v
			},
			"humanize": func(v float64) string {
				if v == 0 || math.IsNaN(v) || math.IsInf(v, 0) {
					return fmt.Sprintf("%.4g", v)
				}
				if math.Abs(v) >= 1 {
					prefix := ""
					for _, p := range []string{"k", "M", "G", "T", "P", "E", "Z", "Y"} {
						if math.Abs(v) < 1000 {
							break
						}
						prefix = p
						v /= 1000
					}
					return fmt.Sprintf("%.4g%s", v, prefix)
				}
				prefix := ""
				for _, p := range []string{"m", "u", "n", "p", "f", "a", "z", "y"} {
					if math.Abs(v) >= 1 {
						break
					}
					prefix = p
					v *= 1000
				}
				return fmt.Sprintf("%.4g%s", v, prefix)
			},
			"humanize1024": func(v float64) string {
				if math.Abs(v) <= 1 || math.IsNaN(v) || math.IsInf(v, 0) {
					return fmt.Sprintf("%.4g", v)
				}
				prefix := ""
				for _, p := range []string{"ki", "Mi", "Gi", "Ti", "Pi", "Ei", "Zi", "Yi"} {
					if math.Abs(v) < 1024 {
						break
					}
					prefix = p
					v /= 1024
				}
				return fmt.Sprintf("%.4g%s", v, prefix)
			},
			"humanizeDuration": func(v float64) string {
				if math.IsNaN(v) || math.IsInf(v, 0) {
					return fmt.Sprintf("%.4g", v)
				}
				if v == 0 {
					return fmt.Sprintf("%.4gs", v)
				}
				if math.Abs(v) >= 1 {
					sign := ""
					if v < 0 {
						sign = "-"
						v = -v
					}
					seconds := int64(v) % 60
					minutes := (int64(v) / 60) % 60
					hours := (int64(v) / 60 / 60) % 24
					days := (int64(v) / 60 / 60 / 24)
					// For days to minutes, we display seconds as an integer.
					if days != 0 {
						return fmt.Sprintf("%s%dd %dh %dm %ds", sign, days, hours, minutes, seconds)
					}
					if hours != 0 {
						return fmt.Sprintf("%s%dh %dm %ds", sign, hours, minutes, seconds)
					}
					if minutes != 0 {
						return fmt.Sprintf("%s%dm %ds", sign, minutes, seconds)
					}
					// For seconds, we display 4 significant digts.
					return fmt.Sprintf("%s%.4gs", sign, v)
				}
				prefix := ""
				for _, p := range []string{"m", "u", "n", "p", "f", "a", "z", "y"} {
					if math.Abs(v) >= 1 {
						break
					}
					prefix = p
					v *= 1000
				}
				return fmt.Sprintf("%.4g%ss", v, prefix)
			},
			"humanizeTimestamp": func(v float64) string {
				if math.IsNaN(v) || math.IsInf(v, 0) {
					return fmt.Sprintf("%.4g", v)
				}
				t := model.TimeFromUnixNano(int64(v * 1e9)).Time().UTC()
				return fmt.Sprint(t)
			},
			"pathPrefix": func() string {
				return pathPrefix
			},
		},
	}
}

func (t *Target) scrape(appender storage.SampleAppender) (err error) {
	start := time.Now()
	baseLabels := t.BaseLabels()

	defer func(appender storage.SampleAppender) {
		t.status.setLastError(err)
		recordScrapeHealth(appender, start, baseLabels, t.status.Health(), time.Since(start))
	}(appender)

	t.RLock()

	// The relabelAppender has to be inside the label-modifying appenders
	// so the relabeling rules are applied to the correct label set.
	if len(t.metricRelabelConfigs) > 0 {
		appender = relabelAppender{
			SampleAppender: appender,
			relabelings:    t.metricRelabelConfigs,
		}
	}

	if t.honorLabels {
		appender = honorLabelsAppender{
			SampleAppender: appender,
			labels:         baseLabels,
		}
	} else {
		appender = ruleLabelsAppender{
			SampleAppender: appender,
			labels:         baseLabels,
		}
	}

	httpClient := t.httpClient

	t.RUnlock()

	req, err := http.NewRequest("GET", t.URL().String(), nil)
	if err != nil {
		return err
	}
	req.Header.Add("Accept", acceptHeader)

	resp, err := httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("server returned HTTP status %s", resp.Status)
	}

	dec := expfmt.NewDecoder(resp.Body, expfmt.ResponseFormat(resp.Header))

	sdec := expfmt.SampleDecoder{
		Dec: dec,
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(start.UnixNano()),
		},
	}

	var (
		samples       model.Vector
		numOutOfOrder int
		logger        = log.With("target", t.InstanceIdentifier())
	)
	for {
		if err = sdec.Decode(&samples); err != nil {
			break
		}
		for _, s := range samples {
			err := appender.Append(s)
			if err != nil {
				if err == local.ErrOutOfOrderSample {
					numOutOfOrder++
				} else {
					logger.With("sample", s).Warnf("Error inserting sample: %s", err)
				}
			}

		}
	}
	if numOutOfOrder > 0 {
		logger.With("numDropped", numOutOfOrder).Warn("Error on ingesting out-of-order samples")
	}

	if err == io.EOF {
		return nil
	}
	return err
}

func (t *Target) scrape(appender storage.SampleAppender) error {
	var (
		err   error
		start = time.Now()
	)
	defer func(appender storage.SampleAppender) {
		t.report(appender, start, time.Since(start), err)
	}(appender)

	t.RLock()

	appender = t.wrapAppender(appender)

	client := t.httpClient
	t.RUnlock()

	req, err := http.NewRequest("GET", t.URL().String(), nil)
	if err != nil {
		return err
	}
	req.Header.Add("Accept", acceptHeader)

	ctx, _ := context.WithTimeout(context.Background(), t.timeout())
	resp, err := ctxhttp.Do(ctx, client, req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("server returned HTTP status %s", resp.Status)
	}

	dec := expfmt.NewDecoder(resp.Body, expfmt.ResponseFormat(resp.Header))

	sdec := expfmt.SampleDecoder{
		Dec: dec,
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(start.UnixNano()),
		},
	}

	var (
		samples       model.Vector
		numOutOfOrder int
		logger        = log.With("target", t.InstanceIdentifier())
	)
	for {
		if err = sdec.Decode(&samples); err != nil {
			break
		}
		for _, s := range samples {
			err := appender.Append(s)
			if err != nil {
				if err == local.ErrOutOfOrderSample {
					numOutOfOrder++
				} else {
					logger.With("sample", s).Warnf("Error inserting sample: %s", err)
				}
			}

		}
	}
	if numOutOfOrder > 0 {
		logger.With("numDropped", numOutOfOrder).Warn("Error on ingesting out-of-order samples")
	}

	if err == io.EOF {
		// Set err to nil since it is used in the scrape health recording.
		err = nil
	}
	return err
}

func extractHistogram(o *DecodeOptions, f *dto.MetricFamily) model.Vector {
	samples := make(model.Vector, 0, len(f.Metric))

	for _, m := range f.Metric {
		if m.Histogram == nil {
			continue
		}

		timestamp := o.Timestamp
		if m.TimestampMs != nil {
			timestamp = model.TimeFromUnixNano(*m.TimestampMs * 1000000)
		}

		infSeen := false

		for _, q := range m.Histogram.Bucket {
			lset := make(model.LabelSet, len(m.Label)+2)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			lset[model.LabelName(model.BucketLabel)] = model.LabelValue(fmt.Sprint(q.GetUpperBound()))
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")

			if math.IsInf(q.GetUpperBound(), +1) {
				infSeen = true
			}

			samples = append(samples, &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(q.GetCumulativeCount()),
				Timestamp: timestamp,
			})
		}

		if m.Histogram.SampleSum != nil {
			lset := make(model.LabelSet, len(m.Label)+1)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_sum")

			samples = append(samples, &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(m.Histogram.GetSampleSum()),
				Timestamp: timestamp,
			})
		}

		if m.Histogram.SampleCount != nil {
			lset := make(model.LabelSet, len(m.Label)+1)
			for _, p := range m.Label {
				lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
			}
			lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_count")

			count := &model.Sample{
				Metric:    model.Metric(lset),
				Value:     model.SampleValue(m.Histogram.GetSampleCount()),
				Timestamp: timestamp,
			}
			samples = append(samples, count)

			if !infSeen {
				// Append a infinity bucket sample.
				lset := make(model.LabelSet, len(m.Label)+2)
				for _, p := range m.Label {
					lset[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
				}
				lset[model.LabelName(model.BucketLabel)] = model.LabelValue("+Inf")
				lset[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")

				samples = append(samples, &model.Sample{
					Metric:    model.Metric(lset),
					Value:     count.Value,
					Timestamp: timestamp,
				})
			}
		}
	}

	return samples
}

// Returns collected metrics and the next collection time of the collector
func (collector *PrometheusCollector) Collect(metrics map[string][]v1.MetricVal) (time.Time, map[string][]v1.MetricVal, error) {
	currentTime := time.Now()
	nextCollectionTime := currentTime.Add(time.Duration(collector.pollingFrequency))

	uri := collector.configFile.Endpoint.URL
	response, err := collector.httpClient.Get(uri)
	if err != nil {
		return nextCollectionTime, nil, err
	}
	defer response.Body.Close()

	if response.StatusCode != http.StatusOK {
		return nextCollectionTime, nil, fmt.Errorf("server returned HTTP status %s", response.Status)
	}

	sdec := expfmt.SampleDecoder{
		Dec: expfmt.NewDecoder(response.Body, expfmt.ResponseFormat(response.Header)),
		Opts: &expfmt.DecodeOptions{
			Timestamp: model.TimeFromUnixNano(currentTime.UnixNano()),
		},
	}

	var (
		// 50 is chosen as a reasonable guesstimate at a number of metrics we can
		// expect from virtually any endpoint to try to save allocations.
		decSamples = make(model.Vector, 0, 50)
		newMetrics = make(map[string][]v1.MetricVal)
	)
	for {
		if err = sdec.Decode(&decSamples); err != nil {
			break
		}

		for _, sample := range decSamples {
			metName := string(sample.Metric[model.MetricNameLabel])
			if len(metName) == 0 {
				continue
			}
			// If metrics to collect is specified, skip any metrics not in the list to collect.
			if _, ok := collector.metricsSet[metName]; collector.metricsSet != nil && !ok {
				continue
			}
			// TODO Handle multiple labels nicer. Prometheus metrics can have multiple
			// labels, cadvisor only accepts a single string for the metric label.
			label := prometheusLabelSetToCadvisorLabel(sample.Metric)

			metric := v1.MetricVal{
				FloatValue: float64(sample.Value),
				Timestamp:  sample.Timestamp.Time(),
				Label:      label,
			}
			newMetrics[metName] = append(newMetrics[metName], metric)
			if len(newMetrics) > collector.metricCountLimit {
				return nextCollectionTime, nil, fmt.Errorf("too many metrics to collect")
			}
		}
		decSamples = decSamples[:0]
	}

	if err != nil && err != io.EOF {
		return nextCollectionTime, nil, err
	}

	for key, val := range newMetrics {
		metrics[key] = append(metrics[key], val...)
	}

	return nextCollectionTime, metrics, nil
}