Yolo, add units.

Signed-off-by: bwplotka <[email protected]>

Author: bwplotka

prometheus/desc.go

@@ -47,6 +47,8 @@ type Desc struct {
 	fqName string
 	// help provides some helpful information about this metric.
 	help string
+	// unit is a OpenMetrics unit.
+	unit string
 	// constLabelPairs contains precalculated DTO label pairs based on
 	// the constant labels.
 	constLabelPairs []*dto.LabelPair
@@ -76,7 +78,7 @@ type Desc struct {
 // For constLabels, the label values are constant. Therefore, they are fully
 // specified in the Desc. See the Collector example for a usage pattern.
 func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc {
-	return V2.NewDesc(fqName, help, UnconstrainedLabels(variableLabels), constLabels)
+	return V2.NewDesc(fqName, help, "", UnconstrainedLabels(variableLabels), constLabels)
 }
 
 // NewDesc allocates and initializes a new Desc. Errors are recorded in the Desc
@@ -89,10 +91,11 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 //
 // For constLabels, the label values are constant. Therefore, they are fully
 // specified in the Desc. See the Collector example for a usage pattern.
-func (v2) NewDesc(fqName, help string, variableLabels ConstrainableLabels, constLabels Labels) *Desc {
+func (v2) NewDesc(fqName, help, unit string, variableLabels ConstrainableLabels, constLabels Labels) *Desc {
 	d := &Desc{
 		fqName:         fqName,
 		help:           help,
+		unit:           unit,
 		variableLabels: variableLabels.compile(),
 	}
 	if !model.IsValidMetricName(model.LabelValue(fqName)) {

prometheus/histogram.go

@@ -371,6 +371,7 @@ type HistogramOpts struct {
 	Namespace string
 	Subsystem string
 	Name      string
+	Unit      string
 
 	// Help provides information about this Histogram.
 	//
@@ -522,9 +523,10 @@ type HistogramVecOpts struct {
 // for each bucket.
 func NewHistogram(opts HistogramOpts) Histogram {
 	return newHistogram(
-		NewDesc(
+		V2.NewDesc(
 			BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
 			opts.Help,
+			opts.Unit,
 			nil,
 			opts.ConstLabels,
 		),

prometheus/registry.go

@@ -685,6 +685,10 @@ func processMetric(
 		metricFamily = &dto.MetricFamily{}
 		metricFamily.Name = proto.String(desc.fqName)
 		metricFamily.Help = proto.String(desc.help)
+		if desc.unit != "" {
+			metricFamily.Unit = proto.String(desc.unit)
+		}
+
 		// TODO(beorn7): Simplify switch once Desc has type.
 		switch {
 		case dtoMetric.Gauge != nil: