func()

in collector/prometheus_collector.go [216:286]
57 lines of code
13 McCabe index (conditional complexity)

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)
			labels := prometheusLabelSetToCadvisorLabels(sample.Metric)

			metric := v1.MetricVal{
				FloatValue: float64(sample.Value),
				Timestamp:  sample.Timestamp.Time(),
				Label:      label,
				Labels:     labels,
			}
			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
}