Add more info to the inconsistent cardinality errors

Signed-off-by: Peter Jausovec <[email protected]>

Author: Peter Jausovec

prometheus/counter.go

@@ -136,7 +136,8 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 	return &CounterVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
 			if len(lvs) != len(desc.variableLabels) {
-				panic(errInconsistentCardinality)
+				err := fmt.Errorf("%s: labels and values for '%s' don't match: labels %v, values %v", errInconsistentCardinality, desc.fqName, desc.variableLabels, lvs)
+				panic(err)
 			}
 			result := &counter{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.

prometheus/gauge.go

@@ -147,7 +147,8 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 	return &GaugeVec{
 		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
 			if len(lvs) != len(desc.variableLabels) {
-				panic(errInconsistentCardinality)
+				err := fmt.Errorf("%s: labels and values for '%s' don't match: labels %v, values %v", errInconsistentCardinality, desc.fqName, desc.variableLabels, labelValues)
+				panic(err)
 			}
 			result := &gauge{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.

prometheus/histogram.go

@@ -165,7 +165,8 @@ func NewHistogram(opts HistogramOpts) Histogram {
 
 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
 	if len(desc.variableLabels) != len(labelValues) {
-		panic(errInconsistentCardinality)
+		err := fmt.Errorf("%s: labels and values for '%s' don't match: labels %v, values %v", errInconsistentCardinality, desc.fqName, desc.variableLabels, labelValues)
+		panic(err)
 	}
 
 	for _, n := range desc.variableLabels {

prometheus/labels.go

@@ -39,7 +39,7 @@ var errInconsistentCardinality = errors.New("inconsistent label cardinality")
 
 func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
 	if len(labels) != expectedNumberOfValues {
-		return errInconsistentCardinality
+		return fmt.Errorf("%s: number of labels and values don't match: expected %d, actual %d, labels %v", errInconsistentCardinality, expectedNumberOfValues, len(labels), labels)
 	}
 
 	for name, val := range labels {

prometheus/summary.go

@@ -181,7 +181,8 @@ func NewSummary(opts SummaryOpts) Summary {
 
 func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 	if len(desc.variableLabels) != len(labelValues) {
-		panic(errInconsistentCardinality)
+		err := fmt.Errorf("%s: labels and values for '%s' don't match: labels %v, values %v", errInconsistentCardinality, desc.fqName, desc.variableLabels, labelValues)
+		panic(err)
 	}
 
 	for _, n := range desc.variableLabels {