Turned "le" and "quantile" label names into constants.

extraction/metricfamilyprocessor.go

@@ -164,7 +164,7 @@ func extractSummary(out Ingester, o *ProcessOptions, f *dto.MetricFamily) error
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
 			// BUG(matt): Update other names to "quantile".
-			metric[model.LabelName("quantile")] = model.LabelValue(fmt.Sprint(q.GetQuantile()))
+			metric[model.LabelName(model.QuantileLabel)] = model.LabelValue(fmt.Sprint(q.GetQuantile()))
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName())
 		}
 
@@ -259,7 +259,7 @@ func extractHistogram(out Ingester, o *ProcessOptions, f *dto.MetricFamily) erro
 			for _, p := range m.Label {
 				metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 			}
-			metric[model.LabelName("le")] = model.LabelValue(fmt.Sprint(q.GetUpperBound()))
+			metric[model.LabelName(model.BucketLabel)] = model.LabelValue(fmt.Sprint(q.GetUpperBound()))
 			metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")
 
 			if math.IsInf(q.GetUpperBound(), +1) {
@@ -308,7 +308,7 @@ func extractHistogram(out Ingester, o *ProcessOptions, f *dto.MetricFamily) erro
 				for _, p := range m.Label {
 					metric[model.LabelName(p.GetName())] = model.LabelValue(p.GetValue())
 				}
-				metric[model.LabelName("le")] = model.LabelValue("+Inf")
+				metric[model.LabelName(model.BucketLabel)] = model.LabelValue("+Inf")
 				metric[model.MetricNameLabel] = model.LabelValue(f.GetName() + "_bucket")
 			}
 		}

model/labelname.go

@@ -33,6 +33,14 @@ const (
 	// JobLabel is the label name indicating the job from which a timeseries
 	// was scraped.
 	JobLabel LabelName = "job"
+
+	// BucketLabel is used for the label that defines the upper bound of a
+	// bucket of a histogram ("le" -> "less or equal").
+	BucketLabel = "le"
+
+	// QuantileLabel is used for the label that defines the quantile in a
+	// summary.
+	QuantileLabel = "quantile"
 )
 
 // A LabelName is a key for a LabelSet or Metric.  It has a value associated

prometheus/histogram.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/golang/protobuf/proto"
 
+	"github.com/prometheus/client_golang/model"
 	dto "github.com/prometheus/client_model/go"
 )
 
@@ -33,7 +34,7 @@ import (
 //
 // Note that Histograms, in contrast to Summaries, can be aggregated with the
 // Prometheus query language (see the documentation for detailed
-// procedures). However, Histograms requires the user to pre-define suitable
+// procedures). However, Histograms require the user to pre-define suitable
 // buckets, and they are in general less accurate. The Observe method of a
 // Histogram has a very low performance overhead in comparison with the Observe
 // method of a Summary.
@@ -47,12 +48,16 @@ type Histogram interface {
 	Observe(float64)
 }
 
+var (
 	// DefBuckets are the default Histogram buckets. The default buckets are
 	// tailored to broadly measure response time in seconds for a typical online
 	// serving system. Most likely, however, you will be required to define buckets
 	// customized to your use case.
-var (
 	DefBuckets = []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10}
+
+	errBucketLabelNotAllowed = fmt.Errorf(
+		"%q is not allowed as label name in histograms", model.BucketLabel,
+	)
 )
 
 // LinearBuckets creates 'count' buckets, each 'width' wide, where the lowest
@@ -165,13 +170,13 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 	}
 
 	for _, n := range desc.variableLabels {
-		if n == "le" {
+		if n == model.BucketLabel {
-			panic("'le' is not allowed as label name in histograms")
+			panic(errBucketLabelNotAllowed)
 		}
 	}
 	for _, lp := range desc.constLabelPairs {
-		if lp.GetName() == "le" {
+		if lp.GetName() == model.BucketLabel {
-			panic("'le' is not allowed as label name in histograms")
+			panic(errBucketLabelNotAllowed)
 		}
 	}
 

prometheus/summary.go

@@ -25,6 +25,7 @@ import (
 	dto "github.com/prometheus/client_model/go"
 
 	"github.com/prometheus/client_golang/_vendor/perks/quantile"
+	"github.com/prometheus/client_golang/model"
 )
 
 // A Summary captures individual observations from an event or sample stream and
@@ -50,9 +51,13 @@ type Summary interface {
 	Observe(float64)
 }
 
-// DefObjectives are the default Summary quantile values.
 var (
+	// DefObjectives are the default Summary quantile values.
 	DefObjectives = map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001}
+
+	errQuantileLabelNotAllowed = fmt.Errorf(
+		"%q is not allowed as label name in summaries", model.QuantileLabel,
+	)
 )
 
 // Default values for SummaryOpts.
@@ -164,13 +169,13 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 	}
 
 	for _, n := range desc.variableLabels {
-		if n == "quantile" {
+		if n == model.QuantileLabel {
-			panic("'quantile' is not allowed as label name in summaries")
+			panic(errQuantileLabelNotAllowed)
 		}
 	}
 	for _, lp := range desc.constLabelPairs {
-		if lp.GetName() == "quantile" {
+		if lp.GetName() == model.QuantileLabel {
-			panic("'quantile' is not allowed as label name in summaries")
+			panic(errQuantileLabelNotAllowed)
 		}
 	}
 

text/create.go

@@ -27,6 +27,7 @@ import (
 	"math"
 	"strings"
 
+	"github.com/prometheus/client_golang/model"
 	dto "github.com/prometheus/client_model/go"
 )
 
@@ -117,7 +118,7 @@ func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
 			for _, q := range metric.Summary.Quantile {
 				n, err = writeSample(
 					name, metric,
-					"quantile", fmt.Sprint(q.GetQuantile()),
+					model.QuantileLabel, fmt.Sprint(q.GetQuantile()),
 					q.GetValue(),
 					out,
 				)
@@ -150,7 +151,7 @@ func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
 			for _, q := range metric.Histogram.Bucket {
 				n, err = writeSample(
 					name+"_bucket", metric,
-					"le", fmt.Sprint(q.GetUpperBound()),
+					model.BucketLabel, fmt.Sprint(q.GetUpperBound()),
 					float64(q.GetCumulativeCount()),
 					out,
 				)
@@ -165,7 +166,7 @@ func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
 			if !infSeen {
 				n, err = writeSample(
 					name+"_bucket", metric,
-					"le", "+Inf",
+					model.BucketLabel, "+Inf",
 					float64(metric.Histogram.GetSampleCount()),
 					out,
 				)

text/parse.go

@@ -274,8 +274,8 @@ func (p *Parser) startLabelName() stateFn {
 	}
 	// Special summary/histogram treatment. Don't add 'quantile' and 'le'
 	// labels to 'real' labels.
-	if !(p.currentMF.GetType() == dto.MetricType_SUMMARY && p.currentLabelPair.GetName() == "quantile") &&
+	if !(p.currentMF.GetType() == dto.MetricType_SUMMARY && p.currentLabelPair.GetName() == model.QuantileLabel) &&
-		!(p.currentMF.GetType() == dto.MetricType_HISTOGRAM && p.currentLabelPair.GetName() == "le") {
+		!(p.currentMF.GetType() == dto.MetricType_HISTOGRAM && p.currentLabelPair.GetName() == model.BucketLabel) {
 		p.currentMetric.Label = append(p.currentMetric.Label, p.currentLabelPair)
 	}
 	if p.skipBlankTabIfCurrentBlankTab(); p.err != nil {
@@ -306,7 +306,7 @@ func (p *Parser) startLabelValue() stateFn {
 	// - Quantile labels are special, will result in dto.Quantile later.
 	// - Other labels have to be added to currentLabels for signature calculation.
 	if p.currentMF.GetType() == dto.MetricType_SUMMARY {
-		if p.currentLabelPair.GetName() == "quantile" {
+		if p.currentLabelPair.GetName() == model.QuantileLabel {
 			if p.currentQuantile, p.err = strconv.ParseFloat(p.currentLabelPair.GetValue(), 64); p.err != nil {
 				// Create a more helpful error message.
 				p.parseError(fmt.Sprintf("expected float as value for 'quantile' label, got %q", p.currentLabelPair.GetValue()))
@@ -318,7 +318,7 @@ func (p *Parser) startLabelValue() stateFn {
 	}
 	// Similar special treatment of histograms.
 	if p.currentMF.GetType() == dto.MetricType_HISTOGRAM {
-		if p.currentLabelPair.GetName() == "le" {
+		if p.currentLabelPair.GetName() == model.BucketLabel {
 			if p.currentBucket, p.err = strconv.ParseFloat(p.currentLabelPair.GetValue(), 64); p.err != nil {
 				// Create a more helpful error message.
 				p.parseError(fmt.Sprintf("expected float as value for 'le' label, got %q", p.currentLabelPair.GetValue()))