Merge pull request prometheus#488 from peterj/master

Add more info to the inconsistent cardinality errors

prometheus/counter.go

@@ -136,7 +136,7 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
  return &CounterVec{
  metricVec: newMetricVec(desc, func(lvs ...string) Metric {
  if len(lvs) != len(desc.variableLabels) {
- panic(errInconsistentCardinality)
+ panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
  }
  result := &counter{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
  result.init(result) // Init self-collection.

prometheus/examples_test.go

@@ -282,7 +282,7 @@ func ExampleRegister() {
  // taskCounter unregistered.
  // taskCounterVec not registered: a previously registered descriptor with the same fully-qualified name as Desc{fqName: "worker_pool_completed_tasks_total", help: "Total number of tasks completed.", constLabels: {}, variableLabels: [worker_id]} has different label names or a different help string
  // taskCounterVec registered.
- // Worker initialization failed: inconsistent label cardinality
+ // Worker initialization failed: inconsistent label cardinality: expected 1 label values but got 2 in []string{"42", "spurious arg"}
  // notMyCounter is nil.
  // taskCounterForWorker42 registered.
  // taskCounterForWorker2001 registered.

prometheus/gauge.go

@@ -147,7 +147,7 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
  return &GaugeVec{
  metricVec: newMetricVec(desc, func(lvs ...string) Metric {
  if len(lvs) != len(desc.variableLabels) {
- panic(errInconsistentCardinality)
+ panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
  }
  result := &gauge{desc: desc, labelPairs: makeLabelPairs(desc, lvs)}
  result.init(result) // Init self-collection.

prometheus/histogram.go

@@ -165,7 +165,7 @@ func NewHistogram(opts HistogramOpts) Histogram {
 
 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
  if len(desc.variableLabels) != len(labelValues) {
- panic(errInconsistentCardinality)
+ panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, labelValues))
  }
 
  for _, n := range desc.variableLabels {

prometheus/labels.go

@@ -37,9 +37,22 @@ const reservedLabelPrefix = "__"
 
 var errInconsistentCardinality = errors.New("inconsistent label cardinality")
 
+func makeInconsistentCardinalityError(fqName string, labels, labelValues []string) error {
+ return fmt.Errorf(
+ "%s: %q has %d variable labels named %q but %d values %q were provided",
+ errInconsistentCardinality, fqName,
+ len(labels), labels,
+ len(labelValues), labelValues,
+ )
+}
+
 func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
  if len(labels) != expectedNumberOfValues {
- return errInconsistentCardinality
+ return fmt.Errorf(
+ "%s: expected %d label values but got %d in %#v",
+ errInconsistentCardinality, expectedNumberOfValues,
+ len(labels), labels,
+ )
  }
 
  for name, val := range labels {
@@ -53,7 +66,11 @@ func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
 
 func validateLabelValues(vals []string, expectedNumberOfValues int) error {
  if len(vals) != expectedNumberOfValues {
- return errInconsistentCardinality
+ return fmt.Errorf(
+ "%s: expected %d label values but got %d in %#v",
+ errInconsistentCardinality, expectedNumberOfValues,
+ len(vals), vals,
+ )
  }
 
  for _, val := range vals {

prometheus/summary.go

@@ -181,7 +181,7 @@ func NewSummary(opts SummaryOpts) Summary {
 
 func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
  if len(desc.variableLabels) != len(labelValues) {
- panic(errInconsistentCardinality)
+ panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, labelValues))
  }
 
  for _, n := range desc.variableLabels {