Function processMetric

prometheus/registry.go:620–725

processMetric is an internal helper method only used by the Gather method.

(
	metric Metric,
	metricFamiliesByName map[string]*dto.MetricFamily,
	metricHashes map[uint64]struct{},
	registeredDescIDs map[uint64]struct{},
)

// processMetric is an internal helper method only used by the Gather method.
func processMetric(
	metric Metric,
	metricFamiliesByName map[string]*dto.MetricFamily,
	metricHashes map[uint64]struct{},
	registeredDescIDs map[uint64]struct{},
) error {
	desc := metric.Desc()
	// Wrapped metrics collected by an unchecked Collector can have an
	// invalid Desc.
	if desc.err != nil {
		return desc.err
	}
	dtoMetric := &dto.Metric{}
	if err := metric.Write(dtoMetric); err != nil {
		return fmt.Errorf("error collecting metric %v: %w", desc, err)
	}
	metricFamily, ok := metricFamiliesByName[desc.fqName]
	if ok { // Existing name.
		if metricFamily.GetHelp() != desc.help {
			return fmt.Errorf(
				"collected metric %s %s has help %q but should have %q",
				desc.fqName, dtoMetric, desc.help, metricFamily.GetHelp(),
			)
		}
		// TODO(beorn7): Simplify switch once Desc has type.
		switch metricFamily.GetType() {
		case dto.MetricType_COUNTER:
			if dtoMetric.Counter == nil {
				return fmt.Errorf(
					"collected metric %s %s should be a Counter",
					desc.fqName, dtoMetric,
				)
			}
		case dto.MetricType_GAUGE:
			if dtoMetric.Gauge == nil {
				return fmt.Errorf(
					"collected metric %s %s should be a Gauge",
					desc.fqName, dtoMetric,
				)
			}
		case dto.MetricType_SUMMARY:
			if dtoMetric.Summary == nil {
				return fmt.Errorf(
					"collected metric %s %s should be a Summary",
					desc.fqName, dtoMetric,
				)
			}
		case dto.MetricType_UNTYPED:
			if dtoMetric.Untyped == nil {
				return fmt.Errorf(
					"collected metric %s %s should be Untyped",
					desc.fqName, dtoMetric,
				)
			}
		case dto.MetricType_HISTOGRAM:
			if dtoMetric.Histogram == nil {
				return fmt.Errorf(
					"collected metric %s %s should be a Histogram",