Function newExemplar

prometheus/value.go:245–274

newExemplar creates a new dto.Exemplar from the provided values. An error is returned if any of the label names or values are invalid or if the total number of runes in the label names and values exceeds ExemplarMaxRunes.

(value float64, ts time.Time, l Labels)

// returned if any of the label names or values are invalid or if the total
// number of runes in the label names and values exceeds ExemplarMaxRunes.
func newExemplar(value float64, ts time.Time, l Labels) (*dto.Exemplar, error) {
	e := &dto.Exemplar{}
	e.Value = proto.Float64(value)
	tsProto := timestamppb.New(ts)
	if err := tsProto.CheckValid(); err != nil {
		return nil, err
	}
	e.Timestamp = tsProto
	labelPairs := make([]*dto.LabelPair, 0, len(l))
	var runes int
	for name, value := range l {
		if !checkLabelName(name) {
			return nil, fmt.Errorf("exemplar label name %q is invalid", name)
		}
		runes += utf8.RuneCountInString(name)
		if !utf8.ValidString(value) {
			return nil, fmt.Errorf("exemplar label value %q is not valid UTF-8", value)
		}
		runes += utf8.RuneCountInString(value)
		labelPairs = append(labelPairs, &dto.LabelPair{
			Name:  proto.String(name),
			Value: proto.String(value),
		})
	}
	if runes > ExemplarMaxRunes {
		return nil, fmt.Errorf("exemplar labels have %d runes, exceeding the limit of %d", runes, ExemplarMaxRunes)
	}
	e.Label = labelPairs
	return e, nil
}