upgrade: upgrade dependencies github.com/prometheus/common to the newest version

Signed-off-by: jwcesign <jwcesign@gmail.com>

vendor/github.com/prometheus/client_golang/prometheus/collectors/expvar_collector.go

@@ -22,7 +22,7 @@ import "github.com/prometheus/client_golang/prometheus"
 // Prometheus metrics. Note that the data models of expvar and Prometheus are
 // fundamentally different, and that the expvar Collector is inherently slower
 // than native Prometheus metrics. Thus, the expvar Collector is probably great
-// for experiments and prototying, but you should seriously consider a more
+// for experiments and prototyping, but you should seriously consider a more
 // direct implementation of Prometheus metrics for monitoring production
 // systems.
 //

vendor/github.com/prometheus/client_golang/prometheus/collectors/go_collector_latest.go

@@ -132,16 +132,19 @@ type GoCollectionOption uint32
 
 const (
 	// GoRuntimeMemStatsCollection represents the metrics represented by runtime.MemStats structure.
-	// Deprecated. Use WithGoCollectorMemStatsMetricsDisabled() function to disable those metrics in the collector.
+	//
+	// Deprecated: Use WithGoCollectorMemStatsMetricsDisabled() function to disable those metrics in the collector.
 	GoRuntimeMemStatsCollection GoCollectionOption = 1 << iota
 	// GoRuntimeMetricsCollection is the new set of metrics represented by runtime/metrics package.
-	// Deprecated. Use WithGoCollectorRuntimeMetrics(GoRuntimeMetricsRule{Matcher: regexp.MustCompile("/.*")})
+	//
+	// Deprecated: Use WithGoCollectorRuntimeMetrics(GoRuntimeMetricsRule{Matcher: regexp.MustCompile("/.*")})
 	// function to enable those metrics in the collector.
 	GoRuntimeMetricsCollection
 )
 
 // WithGoCollections allows enabling different collections for Go collector on top of base metrics.
-// Deprecated. Use WithGoCollectorRuntimeMetrics() and WithGoCollectorMemStatsMetricsDisabled() instead to control metrics.
+//
+// Deprecated: Use WithGoCollectorRuntimeMetrics() and WithGoCollectorMemStatsMetricsDisabled() instead to control metrics.
 func WithGoCollections(flags GoCollectionOption) func(options *internal.GoCollectorOptions) {
 	return func(options *internal.GoCollectorOptions) {
 		if flags&GoRuntimeMemStatsCollection == 0 {

vendor/github.com/prometheus/client_golang/prometheus/counter.go

@@ -20,6 +20,7 @@ import (
 	"time"
 
 	dto "github.com/prometheus/client_model/go"
+	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
 // Counter is a Metric that represents a single numerical value that only ever
@@ -66,7 +67,7 @@ type CounterVecOpts struct {
 	CounterOpts
 
 	// VariableLabels are used to partition the metric vector by the given set
-	// of labels. Each label value will be constrained with the optional Contraint
+	// of labels. Each label value will be constrained with the optional Constraint
 	// function, if provided.
 	VariableLabels ConstrainableLabels
 }
@@ -90,8 +91,12 @@ func NewCounter(opts CounterOpts) Counter {
 		nil,
 		opts.ConstLabels,
 	)
-	result := &counter{desc: desc, labelPairs: desc.constLabelPairs, now: time.Now}
+	if opts.now == nil {
+		opts.now = time.Now
+	}
+	result := &counter{desc: desc, labelPairs: desc.constLabelPairs, now: opts.now}
 	result.init(result) // Init self-collection.
+	result.createdTs = timestamppb.New(opts.now())
 	return result
 }
 
@@ -106,10 +111,12 @@ type counter struct {
 	selfCollector
 	desc *Desc
 
+	createdTs  *timestamppb.Timestamp
 	labelPairs []*dto.LabelPair
 	exemplar   atomic.Value // Containing nil or a *dto.Exemplar.
 
-	now func() time.Time // To mock out time.Now() for testing.
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
 }
 
 func (c *counter) Desc() *Desc {
@@ -159,8 +166,7 @@ func (c *counter) Write(out *dto.Metric) error {
 		exemplar = e.(*dto.Exemplar)
 	}
 	val := c.get()
-
-	return populateMetric(CounterValue, val, c.labelPairs, exemplar, out)
+	return populateMetric(CounterValue, val, c.labelPairs, exemplar, out, c.createdTs)
 }
 
 func (c *counter) updateExemplar(v float64, l Labels) {
@@ -200,13 +206,17 @@ func (v2) NewCounterVec(opts CounterVecOpts) *CounterVec {
 		opts.VariableLabels,
 		opts.ConstLabels,
 	)
+	if opts.now == nil {
+		opts.now = time.Now
+	}
 	return &CounterVec{
 		MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
-			if len(lvs) != len(desc.variableLabels) {
-				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.labelNames(), lvs))
+			if len(lvs) != len(desc.variableLabels.names) {
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, lvs))
 			}
-			result := &counter{desc: desc, labelPairs: MakeLabelPairs(desc, lvs), now: time.Now}
+			result := &counter{desc: desc, labelPairs: MakeLabelPairs(desc, lvs), now: opts.now}
 			result.init(result) // Init self-collection.
+			result.createdTs = timestamppb.New(opts.now())
 			return result
 		}),
 	}

vendor/github.com/prometheus/client_golang/prometheus/desc.go

@@ -52,7 +52,7 @@ type Desc struct {
 	constLabelPairs []*dto.LabelPair
 	// variableLabels contains names of labels and normalization function for
 	// which the metric maintains variable values.
-	variableLabels ConstrainedLabels
+	variableLabels *compiledLabels
 	// id is a hash of the values of the ConstLabels and fqName. This
 	// must be unique among all registered descriptors and can therefore be
 	// used as an identifier of the descriptor.
@@ -93,7 +93,7 @@ func (v2) NewDesc(fqName, help string, variableLabels ConstrainableLabels, const
 	d := &Desc{
 		fqName:         fqName,
 		help:           help,
-		variableLabels: variableLabels.constrainedLabels(),
+		variableLabels: variableLabels.compile(),
 	}
 	if !model.IsValidMetricName(model.LabelValue(fqName)) {
 		d.err = fmt.Errorf("%q is not a valid metric name", fqName)
@@ -103,7 +103,7 @@ func (v2) NewDesc(fqName, help string, variableLabels ConstrainableLabels, const
 	// their sorted label names) plus the fqName (at position 0).
 	labelValues := make([]string, 1, len(constLabels)+1)
 	labelValues[0] = fqName
-	labelNames := make([]string, 0, len(constLabels)+len(d.variableLabels))
+	labelNames := make([]string, 0, len(constLabels)+len(d.variableLabels.names))
 	labelNameSet := map[string]struct{}{}
 	// First add only the const label names and sort them...
 	for labelName := range constLabels {
@@ -128,13 +128,13 @@ func (v2) NewDesc(fqName, help string, variableLabels ConstrainableLabels, const
 	// Now add the variable label names, but prefix them with something that
 	// cannot be in a regular label name. That prevents matching the label
 	// dimension with a different mix between preset and variable labels.
-	for _, label := range d.variableLabels {
-		if !checkLabelName(label.Name) {
-			d.err = fmt.Errorf("%q is not a valid label name for metric %q", label.Name, fqName)
+	for _, label := range d.variableLabels.names {
+		if !checkLabelName(label) {
+			d.err = fmt.Errorf("%q is not a valid label name for metric %q", label, fqName)
 			return d
 		}
-		labelNames = append(labelNames, "$"+label.Name)
-		labelNameSet[label.Name] = struct{}{}
+		labelNames = append(labelNames, "$"+label)
+		labelNameSet[label] = struct{}{}
 	}
 	if len(labelNames) != len(labelNameSet) {
 		d.err = fmt.Errorf("duplicate label names in constant and variable labels for metric %q", fqName)
@@ -189,11 +189,19 @@ func (d *Desc) String() string {
 			fmt.Sprintf("%s=%q", lp.GetName(), lp.GetValue()),
 		)
 	}
+	vlStrings := make([]string, 0, len(d.variableLabels.names))
+	for _, vl := range d.variableLabels.names {
+		if fn, ok := d.variableLabels.labelConstraints[vl]; ok && fn != nil {
+			vlStrings = append(vlStrings, fmt.Sprintf("c(%s)", vl))
+		} else {
+			vlStrings = append(vlStrings, vl)
+		}
+	}
 	return fmt.Sprintf(
-		"Desc{fqName: %q, help: %q, constLabels: {%s}, variableLabels: %v}",
+		"Desc{fqName: %q, help: %q, constLabels: {%s}, variableLabels: {%s}}",
 		d.fqName,
 		d.help,
 		strings.Join(lpStrings, ","),
-		d.variableLabels,
+		strings.Join(vlStrings, ","),
 	)
 }

vendor/github.com/prometheus/client_golang/prometheus/expvar_collector.go

@@ -48,7 +48,7 @@ func (e *expvarCollector) Collect(ch chan<- Metric) {
 			continue
 		}
 		var v interface{}
-		labels := make([]string, len(desc.variableLabels))
+		labels := make([]string, len(desc.variableLabels.names))
 		if err := json.Unmarshal([]byte(expVar.String()), &v); err != nil {
 			ch <- NewInvalidMetric(desc, err)
 			continue

vendor/github.com/prometheus/client_golang/prometheus/gauge.go

@@ -62,7 +62,7 @@ type GaugeVecOpts struct {
 	GaugeOpts
 
 	// VariableLabels are used to partition the metric vector by the given set
-	// of labels. Each label value will be constrained with the optional Contraint
+	// of labels. Each label value will be constrained with the optional Constraint
 	// function, if provided.
 	VariableLabels ConstrainableLabels
 }
@@ -135,7 +135,7 @@ func (g *gauge) Sub(val float64) {
 
 func (g *gauge) Write(out *dto.Metric) error {
 	val := math.Float64frombits(atomic.LoadUint64(&g.valBits))
-	return populateMetric(GaugeValue, val, g.labelPairs, nil, out)
+	return populateMetric(GaugeValue, val, g.labelPairs, nil, out, nil)
 }
 
 // GaugeVec is a Collector that bundles a set of Gauges that all share the same
@@ -166,8 +166,8 @@ func (v2) NewGaugeVec(opts GaugeVecOpts) *GaugeVec {
 	)
 	return &GaugeVec{
 		MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
-			if len(lvs) != len(desc.variableLabels) {
-				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.labelNames(), lvs))
+			if len(lvs) != len(desc.variableLabels.names) {
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, lvs))
 			}
 			result := &gauge{desc: desc, labelPairs: MakeLabelPairs(desc, lvs)}
 			result.init(result) // Init self-collection.

vendor/github.com/prometheus/client_golang/prometheus/histogram.go

@@ -25,6 +25,7 @@ import (
 	dto "github.com/prometheus/client_model/go"
 
 	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
 // nativeHistogramBounds for the frac of observed values. Only relevant for
@@ -391,7 +392,7 @@ type HistogramOpts struct {
 	// zero, it is replaced by default buckets. The default buckets are
 	// DefBuckets if no buckets for a native histogram (see below) are used,
 	// otherwise the default is no buckets. (In other words, if you want to
-	// use both reguler buckets and buckets for a native histogram, you have
+	// use both regular buckets and buckets for a native histogram, you have
 	// to define the regular buckets here explicitly.)
 	Buckets []float64
 
@@ -413,8 +414,8 @@ type HistogramOpts struct {
 	// and 2, same as between 2 and 4, and 4 and 8, etc.).
 	//
 	// Details about the actually used factor: The factor is calculated as
-	// 2^(2^n), where n is an integer number between (and including) -8 and
-	// 4. n is chosen so that the resulting factor is the largest that is
+	// 2^(2^-n), where n is an integer number between (and including) -4 and
+	// 8. n is chosen so that the resulting factor is the largest that is
 	// still smaller or equal to NativeHistogramBucketFactor. Note that the
 	// smallest possible factor is therefore approx. 1.00271 (i.e. 2^(2^-8)
 	// ). If NativeHistogramBucketFactor is greater than 1 but smaller than
@@ -428,12 +429,12 @@ type HistogramOpts struct {
 	// a major version bump.
 	NativeHistogramBucketFactor float64
 	// All observations with an absolute value of less or equal
-	// NativeHistogramZeroThreshold are accumulated into a “zero”
-	// bucket. For best results, this should be close to a bucket
-	// boundary. This is usually the case if picking a power of two. If
+	// NativeHistogramZeroThreshold are accumulated into a “zero” bucket.
+	// For best results, this should be close to a bucket boundary. This is
+	// usually the case if picking a power of two. If
 	// NativeHistogramZeroThreshold is left at zero,
-	// DefNativeHistogramZeroThreshold is used as the threshold. To configure
-	// a zero bucket with an actual threshold of zero (i.e. only
+	// DefNativeHistogramZeroThreshold is used as the threshold. To
+	// configure a zero bucket with an actual threshold of zero (i.e. only
 	// observations of precisely zero will go into the zero bucket), set
 	// NativeHistogramZeroThreshold to the NativeHistogramZeroThresholdZero
 	// constant (or any negative float value).
@@ -446,26 +447,37 @@ type HistogramOpts struct {
 	// Histogram are sufficiently wide-spread. In particular, this could be
 	// used as a DoS attack vector. Where the observed values depend on
 	// external inputs, it is highly recommended to set a
-	// NativeHistogramMaxBucketNumber.)  Once the set
+	// NativeHistogramMaxBucketNumber.) Once the set
 	// NativeHistogramMaxBucketNumber is exceeded, the following strategy is
-	// enacted: First, if the last reset (or the creation) of the histogram
-	// is at least NativeHistogramMinResetDuration ago, then the whole
-	// histogram is reset to its initial state (including regular
-	// buckets). If less time has passed, or if
-	// NativeHistogramMinResetDuration is zero, no reset is
-	// performed. Instead, the zero threshold is increased sufficiently to
-	// reduce the number of buckets to or below
-	// NativeHistogramMaxBucketNumber, but not to more than
-	// NativeHistogramMaxZeroThreshold. Thus, if
-	// NativeHistogramMaxZeroThreshold is already at or below the current
-	// zero threshold, nothing happens at this step. After that, if the
-	// number of buckets still exceeds NativeHistogramMaxBucketNumber, the
-	// resolution of the histogram is reduced by doubling the width of the
-	// sparse buckets (up to a growth factor between one bucket to the next
-	// of 2^(2^4) = 65536, see above).
+	// enacted:
+	//  - First, if the last reset (or the creation) of the histogram is at
+	//    least NativeHistogramMinResetDuration ago, then the whole
+	//    histogram is reset to its initial state (including regular
+	//    buckets).
+	//  - If less time has passed, or if NativeHistogramMinResetDuration is
+	//    zero, no reset is performed. Instead, the zero threshold is
+	//    increased sufficiently to reduce the number of buckets to or below
+	//    NativeHistogramMaxBucketNumber, but not to more than
+	//    NativeHistogramMaxZeroThreshold. Thus, if
+	//    NativeHistogramMaxZeroThreshold is already at or below the current
+	//    zero threshold, nothing happens at this step.
+	//  - After that, if the number of buckets still exceeds
+	//    NativeHistogramMaxBucketNumber, the resolution of the histogram is
+	//    reduced by doubling the width of the sparse buckets (up to a
+	//    growth factor between one bucket to the next of 2^(2^4) = 65536,
+	//    see above).
+	//  - Any increased zero threshold or reduced resolution is reset back
+	//    to their original values once NativeHistogramMinResetDuration has
+	//    passed (since the last reset or the creation of the histogram).
 	NativeHistogramMaxBucketNumber  uint32
 	NativeHistogramMinResetDuration time.Duration
 	NativeHistogramMaxZeroThreshold float64
+
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
+
+	// afterFunc is for testing purposes, by default it's time.AfterFunc.
+	afterFunc func(time.Duration, func()) *time.Timer
 }
 
 // HistogramVecOpts bundles the options to create a HistogramVec metric.
@@ -475,7 +487,7 @@ type HistogramVecOpts struct {
 	HistogramOpts
 
 	// VariableLabels are used to partition the metric vector by the given set
-	// of labels. Each label value will be constrained with the optional Contraint
+	// of labels. Each label value will be constrained with the optional Constraint
 	// function, if provided.
 	VariableLabels ConstrainableLabels
 }
@@ -499,12 +511,12 @@ func NewHistogram(opts HistogramOpts) Histogram {
 }
 
 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
-	if len(desc.variableLabels) != len(labelValues) {
-		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.labelNames(), labelValues))
+	if len(desc.variableLabels.names) != len(labelValues) {
+		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, labelValues))
 	}
 
-	for _, n := range desc.variableLabels {
-		if n.Name == bucketLabel {
+	for _, n := range desc.variableLabels.names {
+		if n == bucketLabel {
 			panic(errBucketLabelNotAllowed)
 		}
 	}
@@ -514,6 +526,12 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 		}
 	}
 
+	if opts.now == nil {
+		opts.now = time.Now
+	}
+	if opts.afterFunc == nil {
+		opts.afterFunc = time.AfterFunc
+	}
 	h := &histogram{
 		desc:                            desc,
 		upperBounds:                     opts.Buckets,
@@ -521,8 +539,9 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 		nativeHistogramMaxBuckets:       opts.NativeHistogramMaxBucketNumber,
 		nativeHistogramMaxZeroThreshold: opts.NativeHistogramMaxZeroThreshold,
 		nativeHistogramMinResetDuration: opts.NativeHistogramMinResetDuration,
-		lastResetTime:                   time.Now(),
-		now:                             time.Now,
+		lastResetTime:                   opts.now(),
+		now:                             opts.now,
+		afterFunc:                       opts.afterFunc,
 	}
 	if len(h.upperBounds) == 0 && opts.NativeHistogramBucketFactor <= 1 {
 		h.upperBounds = DefBuckets
@@ -701,9 +720,18 @@ type histogram struct {
 	nativeHistogramMaxZeroThreshold float64
 	nativeHistogramMaxBuckets       uint32
 	nativeHistogramMinResetDuration time.Duration
-	lastResetTime                   time.Time // Protected by mtx.
+	// lastResetTime is protected by mtx. It is also used as created timestamp.
+	lastResetTime time.Time
+	// resetScheduled is protected by mtx. It is true if a reset is
+	// scheduled for a later time (when nativeHistogramMinResetDuration has
+	// passed).
+	resetScheduled bool
 
-	now func() time.Time // To mock out time.Now() for testing.
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
+
+	// afterFunc is for testing purposes, by default it's time.AfterFunc.
+	afterFunc func(time.Duration, func()) *time.Timer
 }
 
 func (h *histogram) Desc() *Desc {
@@ -742,9 +770,10 @@ func (h *histogram) Write(out *dto.Metric) error {
 	waitForCooldown(count, coldCounts)
 
 	his := &dto.Histogram{
-		Bucket:      make([]*dto.Bucket, len(h.upperBounds)),
-		SampleCount: proto.Uint64(count),
-		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		Bucket:           make([]*dto.Bucket, len(h.upperBounds)),
+		SampleCount:      proto.Uint64(count),
+		SampleSum:        proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		CreatedTimestamp: timestamppb.New(h.lastResetTime),
 	}
 	out.Histogram = his
 	out.Label = h.labelPairs
@@ -782,6 +811,16 @@ func (h *histogram) Write(out *dto.Metric) error {
 		his.ZeroCount = proto.Uint64(zeroBucket)
 		his.NegativeSpan, his.NegativeDelta = makeBuckets(&coldCounts.nativeHistogramBucketsNegative)
 		his.PositiveSpan, his.PositiveDelta = makeBuckets(&coldCounts.nativeHistogramBucketsPositive)
+
+		// Add a no-op span to a histogram without observations and with
+		// a zero threshold of zero. Otherwise, a native histogram would
+		// look like a classic histogram to scrapers.
+		if *his.ZeroThreshold == 0 && *his.ZeroCount == 0 && len(his.PositiveSpan) == 0 && len(his.NegativeSpan) == 0 {
+			his.PositiveSpan = []*dto.BucketSpan{{
+				Offset: proto.Int32(0),
+				Length: proto.Uint32(0),
+			}}
+		}
 	}
 	addAndResetCounts(hotCounts, coldCounts)
 	return nil
@@ -848,26 +887,39 @@ func (h *histogram) limitBuckets(counts *histogramCounts, value float64, bucket
 	if h.maybeReset(hotCounts, coldCounts, coldIdx, value, bucket) {
 		return
 	}
+	// One of the other strategies will happen. To undo what they will do as
+	// soon as enough time has passed to satisfy
+	// h.nativeHistogramMinResetDuration, schedule a reset at the right time
+	// if we haven't done so already.
+	if h.nativeHistogramMinResetDuration > 0 && !h.resetScheduled {
+		h.resetScheduled = true
+		h.afterFunc(h.nativeHistogramMinResetDuration-h.now().Sub(h.lastResetTime), h.reset)
+	}
+
 	if h.maybeWidenZeroBucket(hotCounts, coldCounts) {
 		return
 	}
 	h.doubleBucketWidth(hotCounts, coldCounts)
 }
 
-// maybeReset resests the whole histogram if at least h.nativeHistogramMinResetDuration
-// has been passed. It returns true if the histogram has been reset. The caller
-// must have locked h.mtx.
-func (h *histogram) maybeReset(hot, cold *histogramCounts, coldIdx uint64, value float64, bucket int) bool {
+// maybeReset resets the whole histogram if at least
+// h.nativeHistogramMinResetDuration has been passed. It returns true if the
+// histogram has been reset. The caller must have locked h.mtx.
+func (h *histogram) maybeReset(
+	hot, cold *histogramCounts, coldIdx uint64, value float64, bucket int,
+) bool {
 	// We are using the possibly mocked h.now() rather than
 	// time.Since(h.lastResetTime) to enable testing.
-	if h.nativeHistogramMinResetDuration == 0 || h.now().Sub(h.lastResetTime) < h.nativeHistogramMinResetDuration {
+	if h.nativeHistogramMinResetDuration == 0 || // No reset configured.
+		h.resetScheduled || // Do not interefere if a reset is already scheduled.
+		h.now().Sub(h.lastResetTime) < h.nativeHistogramMinResetDuration {
 		return false
 	}
 	// Completely reset coldCounts.
 	h.resetCounts(cold)
 	// Repeat the latest observation to not lose it completely.
 	cold.observe(value, bucket, true)
-	// Make coldCounts the new hot counts while ressetting countAndHotIdx.
+	// Make coldCounts the new hot counts while resetting countAndHotIdx.
 	n := atomic.SwapUint64(&h.countAndHotIdx, (coldIdx<<63)+1)
 	count := n & ((1 << 63) - 1)
 	waitForCooldown(count, hot)
@@ -877,6 +929,29 @@ func (h *histogram) maybeReset(hot, cold *histogramCounts, coldIdx uint64, value
 	return true
 }
 
+// reset resets the whole histogram. It locks h.mtx itself, i.e. it has to be
+// called without having locked h.mtx.
+func (h *histogram) reset() {
+	h.mtx.Lock()
+	defer h.mtx.Unlock()
+
+	n := atomic.LoadUint64(&h.countAndHotIdx)
+	hotIdx := n >> 63
+	coldIdx := (^n) >> 63
+	hot := h.counts[hotIdx]
+	cold := h.counts[coldIdx]
+	// Completely reset coldCounts.
+	h.resetCounts(cold)
+	// Make coldCounts the new hot counts while resetting countAndHotIdx.
+	n = atomic.SwapUint64(&h.countAndHotIdx, coldIdx<<63)
+	count := n & ((1 << 63) - 1)
+	waitForCooldown(count, hot)
+	// Finally, reset the formerly hot counts, too.
+	h.resetCounts(hot)
+	h.lastResetTime = h.now()
+	h.resetScheduled = false
+}
+
 // maybeWidenZeroBucket widens the zero bucket until it includes the existing
 // buckets closest to the zero bucket (which could be two, if an equidistant
 // negative and a positive bucket exists, but usually it's only one bucket to be
@@ -1176,6 +1251,7 @@ type constHistogram struct {
 	sum        float64
 	buckets    map[float64]uint64
 	labelPairs []*dto.LabelPair
+	createdTs  *timestamppb.Timestamp
 }
 
 func (h *constHistogram) Desc() *Desc {
@@ -1183,7 +1259,9 @@ func (h *constHistogram) Desc() *Desc {
 }
 
 func (h *constHistogram) Write(out *dto.Metric) error {
-	his := &dto.Histogram{}
+	his := &dto.Histogram{
+		CreatedTimestamp: h.createdTs,
+	}
 
 	buckets := make([]*dto.Bucket, 0, len(h.buckets))
 
@@ -1230,7 +1308,7 @@ func NewConstHistogram(
 	if desc.err != nil {
 		return nil, desc.err
 	}
-	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
+	if err := validateLabelValues(labelValues, len(desc.variableLabels.names)); err != nil {
 		return nil, err
 	}
 	return &constHistogram{
@@ -1324,7 +1402,7 @@ func makeBuckets(buckets *sync.Map) ([]*dto.BucketSpan, []int64) {
 		// Multiple spans with only small gaps in between are probably
 		// encoded more efficiently as one larger span with a few empty
 		// buckets. Needs some research to find the sweet spot. For now,
-		// we assume that gaps of one ore two buckets should not create
+		// we assume that gaps of one or two buckets should not create
 		// a new span.
 		iDelta := int32(i - nextI)
 		if n == 0 || iDelta > 2 {

vendor/github.com/prometheus/client_golang/prometheus/internal/difflib.go

@@ -14,7 +14,7 @@
 // It provides tools to compare sequences of strings and generate textual diffs.
 //
 // Maintaining `GetUnifiedDiffString` here because original repository
-// (https://github.com/pmezard/go-difflib) is no loger maintained.
+// (https://github.com/pmezard/go-difflib) is no longer maintained.
 package internal
 
 import (

vendor/github.com/prometheus/client_golang/prometheus/labels.go

@@ -32,19 +32,15 @@ import (
 // create a Desc.
 type Labels map[string]string
 
+// LabelConstraint normalizes label values.
+type LabelConstraint func(string) string
+
 // ConstrainedLabels represents a label name and its constrain function
 // to normalize label values. This type is commonly used when constructing
 // metric vector Collectors.
 type ConstrainedLabel struct {
 	Name       string
-	Constraint func(string) string
-}
-
-func (cl ConstrainedLabel) Constrain(v string) string {
-	if cl.Constraint == nil {
-		return v
-	}
-	return cl.Constraint(v)
+	Constraint LabelConstraint
 }
 
 // ConstrainableLabels is an interface that allows creating of labels that can
@@ -58,7 +54,7 @@ func (cl ConstrainedLabel) Constrain(v string) string {
 //	  },
 //	})
 type ConstrainableLabels interface {
-	constrainedLabels() ConstrainedLabels
+	compile() *compiledLabels
 	labelNames() []string
 }
 
@@ -67,8 +63,20 @@ type ConstrainableLabels interface {
 // metric vector Collectors.
 type ConstrainedLabels []ConstrainedLabel
 
-func (cls ConstrainedLabels) constrainedLabels() ConstrainedLabels {
-	return cls
+func (cls ConstrainedLabels) compile() *compiledLabels {
+	compiled := &compiledLabels{
+		names:            make([]string, len(cls)),
+		labelConstraints: map[string]LabelConstraint{},
+	}
+
+	for i, label := range cls {
+		compiled.names[i] = label.Name
+		if label.Constraint != nil {
+			compiled.labelConstraints[label.Name] = label.Constraint
+		}
+	}
+
+	return compiled
 }
 
 func (cls ConstrainedLabels) labelNames() []string {
@@ -92,18 +100,36 @@ func (cls ConstrainedLabels) labelNames() []string {
 //	}
 type UnconstrainedLabels []string
 
-func (uls UnconstrainedLabels) constrainedLabels() ConstrainedLabels {
-	constrainedLabels := make([]ConstrainedLabel, len(uls))
-	for i, l := range uls {
-		constrainedLabels[i] = ConstrainedLabel{Name: l}
+func (uls UnconstrainedLabels) compile() *compiledLabels {
+	return &compiledLabels{
+		names: uls,
 	}
-	return constrainedLabels
 }
 
 func (uls UnconstrainedLabels) labelNames() []string {
 	return uls
 }
 
+type compiledLabels struct {
+	names            []string
+	labelConstraints map[string]LabelConstraint
+}
+
+func (cls *compiledLabels) compile() *compiledLabels {
+	return cls
+}
+
+func (cls *compiledLabels) labelNames() []string {
+	return cls.names
+}
+
+func (cls *compiledLabels) constrain(labelName, value string) string {
+	if fn, ok := cls.labelConstraints[labelName]; ok && fn != nil {
+		return fn(value)
+	}
+	return value
+}
+
 // reservedLabelPrefix is a prefix which is not legal in user-supplied
 // label names.
 const reservedLabelPrefix = "__"
@@ -139,6 +165,8 @@ func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
 
 func validateLabelValues(vals []string, expectedNumberOfValues int) error {
 	if len(vals) != expectedNumberOfValues {
+		// The call below makes vals escape, copy them to avoid that.
+		vals := append([]string(nil), vals...)
 		return fmt.Errorf(
 			"%w: expected %d label values but got %d in %#v",
 			errInconsistentCardinality, expectedNumberOfValues,

vendor/github.com/prometheus/client_golang/prometheus/metric.go

@@ -92,6 +92,9 @@ type Opts struct {
 	// machine_role metric). See also
 	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels-not-static-scraped-labels
 	ConstLabels Labels
+
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
 }
 
 // BuildFQName joins the given three name components by "_". Empty name

vendor/github.com/prometheus/client_golang/prometheus/process_collector_other.go

@@ -11,8 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build !windows && !js
-// +build !windows,!js
+//go:build !windows && !js && !wasip1
+// +build !windows,!js,!wasip1
 
 package prometheus
 

vendor/github.com/prometheus/client_golang/prometheus/process_collector_wasip1.go

@@ -0,0 +1,26 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build wasip1
+// +build wasip1
+
+package prometheus
+
+func canCollectProcess() bool {
+	return false
+}
+
+func (*processCollector) processCollect(chan<- Metric) {
+	// noop on this platform
+	return
+}

vendor/github.com/prometheus/client_golang/prometheus/promhttp/instrument_server.go

@@ -389,16 +389,13 @@ func isLabelCurried(c prometheus.Collector, label string) bool {
 	return true
 }
 
-// emptyLabels is a one-time allocation for non-partitioned metrics to avoid
-// unnecessary allocations on each request.
-var emptyLabels = prometheus.Labels{}
-
 func labels(code, method bool, reqMethod string, status int, extraMethods ...string) prometheus.Labels {
-	if !(code || method) {
-		return emptyLabels
-	}
 	labels := prometheus.Labels{}
 
+	if !(code || method) {
+		return labels
+	}
+
 	if code {
 		labels["code"] = sanitizeCode(status)
 	}

vendor/github.com/prometheus/client_golang/prometheus/registry.go

@@ -548,7 +548,7 @@ func (r *Registry) Gather() ([]*dto.MetricFamily, error) {
 			goroutineBudget--
 			runtime.Gosched()
 		}
-		// Once both checkedMetricChan and uncheckdMetricChan are closed
+		// Once both checkedMetricChan and uncheckedMetricChan are closed
 		// and drained, the contraption above will nil out cmc and umc,
 		// and then we can leave the collect loop here.
 		if cmc == nil && umc == nil {
@@ -963,9 +963,9 @@ func checkDescConsistency(
 	// Is the desc consistent with the content of the metric?
 	lpsFromDesc := make([]*dto.LabelPair, len(desc.constLabelPairs), len(dtoMetric.Label))
 	copy(lpsFromDesc, desc.constLabelPairs)
-	for _, l := range desc.variableLabels {
+	for _, l := range desc.variableLabels.names {
 		lpsFromDesc = append(lpsFromDesc, &dto.LabelPair{
-			Name: proto.String(l.Name),
+			Name: proto.String(l),
 		})
 	}
 	if len(lpsFromDesc) != len(dtoMetric.Label) {

vendor/github.com/prometheus/client_golang/prometheus/summary.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/beorn7/perks/quantile"
 	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/timestamppb"
 )
 
 // quantileLabel is used for the label that defines the quantile in a
@@ -145,6 +146,9 @@ type SummaryOpts struct {
 	// is the internal buffer size of the underlying package
 	// "github.com/bmizerany/perks/quantile").
 	BufCap uint32
+
+	// now is for testing purposes, by default it's time.Now.
+	now func() time.Time
 }
 
 // SummaryVecOpts bundles the options to create a SummaryVec metric.
@@ -154,7 +158,7 @@ type SummaryVecOpts struct {
 	SummaryOpts
 
 	// VariableLabels are used to partition the metric vector by the given set
-	// of labels. Each label value will be constrained with the optional Contraint
+	// of labels. Each label value will be constrained with the optional Constraint
 	// function, if provided.
 	VariableLabels ConstrainableLabels
 }
@@ -188,12 +192,12 @@ func NewSummary(opts SummaryOpts) Summary {
 }
 
 func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
-	if len(desc.variableLabels) != len(labelValues) {
-		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.labelNames(), labelValues))
+	if len(desc.variableLabels.names) != len(labelValues) {
+		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, labelValues))
 	}
 
-	for _, n := range desc.variableLabels {
-		if n.Name == quantileLabel {
+	for _, n := range desc.variableLabels.names {
+		if n == quantileLabel {
 			panic(errQuantileLabelNotAllowed)
 		}
 	}
@@ -222,6 +226,9 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 		opts.BufCap = DefBufCap
 	}
 
+	if opts.now == nil {
+		opts.now = time.Now
+	}
 	if len(opts.Objectives) == 0 {
 		// Use the lock-free implementation of a Summary without objectives.
 		s := &noObjectivesSummary{
@@ -230,6 +237,7 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 			counts:     [2]*summaryCounts{{}, {}},
 		}
 		s.init(s) // Init self-collection.
+		s.createdTs = timestamppb.New(opts.now())
 		return s
 	}
 
@@ -245,7 +253,7 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 		coldBuf:        make([]float64, 0, opts.BufCap),
 		streamDuration: opts.MaxAge / time.Duration(opts.AgeBuckets),
 	}
-	s.headStreamExpTime = time.Now().Add(s.streamDuration)
+	s.headStreamExpTime = opts.now().Add(s.streamDuration)
 	s.hotBufExpTime = s.headStreamExpTime
 
 	for i := uint32(0); i < opts.AgeBuckets; i++ {
@@ -259,6 +267,7 @@ func newSummary(desc *Desc, opts SummaryOpts, labelValues ...string) Summary {
 	sort.Float64s(s.sortedObjectives)
 
 	s.init(s) // Init self-collection.
+	s.createdTs = timestamppb.New(opts.now())
 	return s
 }
 
@@ -286,6 +295,8 @@ type summary struct {
 	headStream                       *quantile.Stream
 	headStreamIdx                    int
 	headStreamExpTime, hotBufExpTime time.Time
+
+	createdTs *timestamppb.Timestamp
 }
 
 func (s *summary) Desc() *Desc {
@@ -307,7 +318,9 @@ func (s *summary) Observe(v float64) {
 }
 
 func (s *summary) Write(out *dto.Metric) error {
-	sum := &dto.Summary{}
+	sum := &dto.Summary{
+		CreatedTimestamp: s.createdTs,
+	}
 	qs := make([]*dto.Quantile, 0, len(s.objectives))
 
 	s.bufMtx.Lock()
@@ -440,6 +453,8 @@ type noObjectivesSummary struct {
 	counts [2]*summaryCounts
 
 	labelPairs []*dto.LabelPair
+
+	createdTs *timestamppb.Timestamp
 }
 
 func (s *noObjectivesSummary) Desc() *Desc {
@@ -490,8 +505,9 @@ func (s *noObjectivesSummary) Write(out *dto.Metric) error {
 	}
 
 	sum := &dto.Summary{
-		SampleCount: proto.Uint64(count),
-		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		SampleCount:      proto.Uint64(count),
+		SampleSum:        proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+		CreatedTimestamp: s.createdTs,
 	}
 
 	out.Summary = sum
@@ -681,6 +697,7 @@ type constSummary struct {
 	sum        float64
 	quantiles  map[float64]float64
 	labelPairs []*dto.LabelPair
+	createdTs  *timestamppb.Timestamp
 }
 
 func (s *constSummary) Desc() *Desc {
@@ -688,7 +705,9 @@ func (s *constSummary) Desc() *Desc {
 }
 
 func (s *constSummary) Write(out *dto.Metric) error {
-	sum := &dto.Summary{}
+	sum := &dto.Summary{
+		CreatedTimestamp: s.createdTs,
+	}
 	qs := make([]*dto.Quantile, 0, len(s.quantiles))
 
 	sum.SampleCount = proto.Uint64(s.count)
@@ -737,7 +756,7 @@ func NewConstSummary(
 	if desc.err != nil {
 		return nil, desc.err
 	}
-	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
+	if err := validateLabelValues(labelValues, len(desc.variableLabels.names)); err != nil {
 		return nil, err
 	}
 	return &constSummary{

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/problem.go

@@ -0,0 +1,33 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package promlint
+
+import dto "github.com/prometheus/client_model/go"
+
+// A Problem is an issue detected by a linter.
+type Problem struct {
+	// The name of the metric indicated by this Problem.
+	Metric string
+
+	// A description of the issue for this Problem.
+	Text string
+}
+
+// newProblem is helper function to create a Problem.
+func newProblem(mf *dto.MetricFamily, text string) Problem {
+	return Problem{
+		Metric: mf.GetName(),
+		Text:   text,
+	}
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/promlint.go

@@ -16,15 +16,11 @@ package promlint
 
 import (
 	"errors"
-	"fmt"
 	"io"
-	"regexp"
 	"sort"
-	"strings"
-
-	"github.com/prometheus/common/expfmt"
 
 	dto "github.com/prometheus/client_model/go"
+	"github.com/prometheus/common/expfmt"
 )
 
 // A Linter is a Prometheus metrics linter.  It identifies issues with metric
@@ -37,23 +33,8 @@ type Linter struct {
 	// of them.
 	r   io.Reader
 	mfs []*dto.MetricFamily
-}
 
-// A Problem is an issue detected by a Linter.
-type Problem struct {
-	// The name of the metric indicated by this Problem.
-	Metric string
-
-	// A description of the issue for this Problem.
-	Text string
-}
-
-// newProblem is helper function to create a Problem.
-func newProblem(mf *dto.MetricFamily, text string) Problem {
-	return Problem{
-		Metric: mf.GetName(),
-		Text:   text,
-	}
+	customValidations []Validation
 }
 
 // New creates a new Linter that reads an input stream of Prometheus metrics in
@@ -72,6 +53,14 @@ func NewWithMetricFamilies(mfs []*dto.MetricFamily) *Linter {
 	}
 }
 
+// AddCustomValidations adds custom validations to the linter.
+func (l *Linter) AddCustomValidations(vs ...Validation) {
+	if l.customValidations == nil {
+		l.customValidations = make([]Validation, 0, len(vs))
+	}
+	l.customValidations = append(l.customValidations, vs...)
+}
+
 // Lint performs a linting pass, returning a slice of Problems indicating any
 // issues found in the metrics stream. The slice is sorted by metric name
 // and issue description.
@@ -79,7 +68,7 @@ func (l *Linter) Lint() ([]Problem, error) {
 	var problems []Problem
 
 	if l.r != nil {
-		d := expfmt.NewDecoder(l.r, expfmt.FmtText)
+		d := expfmt.NewDecoder(l.r, expfmt.NewFormat(expfmt.TypeTextPlain))
 
 		mf := &dto.MetricFamily{}
 		for {
@@ -91,11 +80,11 @@ func (l *Linter) Lint() ([]Problem, error) {
 				return nil, err
 			}
 
-			problems = append(problems, lint(mf)...)
+			problems = append(problems, l.lint(mf)...)
 		}
 	}
 	for _, mf := range l.mfs {
-		problems = append(problems, lint(mf)...)
+		problems = append(problems, l.lint(mf)...)
 	}
 
 	// Ensure deterministic output.
@@ -110,276 +99,25 @@ func (l *Linter) Lint() ([]Problem, error) {
 }
 
 // lint is the entry point for linting a single metric.
-func lint(mf *dto.MetricFamily) []Problem {
-	fns := []func(mf *dto.MetricFamily) []Problem{
-		lintHelp,
-		lintMetricUnits,
-		lintCounter,
-		lintHistogramSummaryReserved,
-		lintMetricTypeInName,
-		lintReservedChars,
-		lintCamelCase,
-		lintUnitAbbreviations,
+func (l *Linter) lint(mf *dto.MetricFamily) []Problem {
+	var problems []Problem
+
+	for _, fn := range defaultValidations {
+		errs := fn(mf)
+		for _, err := range errs {
+			problems = append(problems, newProblem(mf, err.Error()))
+		}
 	}
 
-	var problems []Problem
-	for _, fn := range fns {
-		problems = append(problems, fn(mf)...)
+	if l.customValidations != nil {
+		for _, fn := range l.customValidations {
+			errs := fn(mf)
+			for _, err := range errs {
+				problems = append(problems, newProblem(mf, err.Error()))
+			}
+		}
 	}
 
 	// TODO(mdlayher): lint rules for specific metrics types.
 	return problems
 }
-
-// lintHelp detects issues related to the help text for a metric.
-func lintHelp(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-
-	// Expect all metrics to have help text available.
-	if mf.Help == nil {
-		problems = append(problems, newProblem(mf, "no help text"))
-	}
-
-	return problems
-}
-
-// lintMetricUnits detects issues with metric unit names.
-func lintMetricUnits(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-
-	unit, base, ok := metricUnits(*mf.Name)
-	if !ok {
-		// No known units detected.
-		return nil
-	}
-
-	// Unit is already a base unit.
-	if unit == base {
-		return nil
-	}
-
-	problems = append(problems, newProblem(mf, fmt.Sprintf("use base unit %q instead of %q", base, unit)))
-
-	return problems
-}
-
-// lintCounter detects issues specific to counters, as well as patterns that should
-// only be used with counters.
-func lintCounter(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-
-	isCounter := mf.GetType() == dto.MetricType_COUNTER
-	isUntyped := mf.GetType() == dto.MetricType_UNTYPED
-	hasTotalSuffix := strings.HasSuffix(mf.GetName(), "_total")
-
-	switch {
-	case isCounter && !hasTotalSuffix:
-		problems = append(problems, newProblem(mf, `counter metrics should have "_total" suffix`))
-	case !isUntyped && !isCounter && hasTotalSuffix:
-		problems = append(problems, newProblem(mf, `non-counter metrics should not have "_total" suffix`))
-	}
-
-	return problems
-}
-
-// lintHistogramSummaryReserved detects when other types of metrics use names or labels
-// reserved for use by histograms and/or summaries.
-func lintHistogramSummaryReserved(mf *dto.MetricFamily) []Problem {
-	// These rules do not apply to untyped metrics.
-	t := mf.GetType()
-	if t == dto.MetricType_UNTYPED {
-		return nil
-	}
-
-	var problems []Problem
-
-	isHistogram := t == dto.MetricType_HISTOGRAM
-	isSummary := t == dto.MetricType_SUMMARY
-
-	n := mf.GetName()
-
-	if !isHistogram && strings.HasSuffix(n, "_bucket") {
-		problems = append(problems, newProblem(mf, `non-histogram metrics should not have "_bucket" suffix`))
-	}
-	if !isHistogram && !isSummary && strings.HasSuffix(n, "_count") {
-		problems = append(problems, newProblem(mf, `non-histogram and non-summary metrics should not have "_count" suffix`))
-	}
-	if !isHistogram && !isSummary && strings.HasSuffix(n, "_sum") {
-		problems = append(problems, newProblem(mf, `non-histogram and non-summary metrics should not have "_sum" suffix`))
-	}
-
-	for _, m := range mf.GetMetric() {
-		for _, l := range m.GetLabel() {
-			ln := l.GetName()
-
-			if !isHistogram && ln == "le" {
-				problems = append(problems, newProblem(mf, `non-histogram metrics should not have "le" label`))
-			}
-			if !isSummary && ln == "quantile" {
-				problems = append(problems, newProblem(mf, `non-summary metrics should not have "quantile" label`))
-			}
-		}
-	}
-
-	return problems
-}
-
-// lintMetricTypeInName detects when metric types are included in the metric name.
-func lintMetricTypeInName(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-	n := strings.ToLower(mf.GetName())
-
-	for i, t := range dto.MetricType_name {
-		if i == int32(dto.MetricType_UNTYPED) {
-			continue
-		}
-
-		typename := strings.ToLower(t)
-		if strings.Contains(n, "_"+typename+"_") || strings.HasSuffix(n, "_"+typename) {
-			problems = append(problems, newProblem(mf, fmt.Sprintf(`metric name should not include type '%s'`, typename)))
-		}
-	}
-	return problems
-}
-
-// lintReservedChars detects colons in metric names.
-func lintReservedChars(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-	if strings.Contains(mf.GetName(), ":") {
-		problems = append(problems, newProblem(mf, "metric names should not contain ':'"))
-	}
-	return problems
-}
-
-var camelCase = regexp.MustCompile(`[a-z][A-Z]`)
-
-// lintCamelCase detects metric names and label names written in camelCase.
-func lintCamelCase(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-	if camelCase.FindString(mf.GetName()) != "" {
-		problems = append(problems, newProblem(mf, "metric names should be written in 'snake_case' not 'camelCase'"))
-	}
-
-	for _, m := range mf.GetMetric() {
-		for _, l := range m.GetLabel() {
-			if camelCase.FindString(l.GetName()) != "" {
-				problems = append(problems, newProblem(mf, "label names should be written in 'snake_case' not 'camelCase'"))
-			}
-		}
-	}
-	return problems
-}
-
-// lintUnitAbbreviations detects abbreviated units in the metric name.
-func lintUnitAbbreviations(mf *dto.MetricFamily) []Problem {
-	var problems []Problem
-	n := strings.ToLower(mf.GetName())
-	for _, s := range unitAbbreviations {
-		if strings.Contains(n, "_"+s+"_") || strings.HasSuffix(n, "_"+s) {
-			problems = append(problems, newProblem(mf, "metric names should not contain abbreviated units"))
-		}
-	}
-	return problems
-}
-
-// metricUnits attempts to detect known unit types used as part of a metric name,
-// e.g. "foo_bytes_total" or "bar_baz_milligrams".
-func metricUnits(m string) (unit, base string, ok bool) {
-	ss := strings.Split(m, "_")
-
-	for _, s := range ss {
-		if base, found := units[s]; found {
-			return s, base, true
-		}
-
-		for _, p := range unitPrefixes {
-			if strings.HasPrefix(s, p) {
-				if base, found := units[s[len(p):]]; found {
-					return s, base, true
-				}
-			}
-		}
-	}
-
-	return "", "", false
-}
-
-// Units and their possible prefixes recognized by this library.  More can be
-// added over time as needed.
-var (
-	// map a unit to the appropriate base unit.
-	units = map[string]string{
-		// Base units.
-		"amperes": "amperes",
-		"bytes":   "bytes",
-		"celsius": "celsius", // Also allow Celsius because it is common in typical Prometheus use cases.
-		"grams":   "grams",
-		"joules":  "joules",
-		"kelvin":  "kelvin", // SI base unit, used in special cases (e.g. color temperature, scientific measurements).
-		"meters":  "meters", // Both American and international spelling permitted.
-		"metres":  "metres",
-		"seconds": "seconds",
-		"volts":   "volts",
-
-		// Non base units.
-		// Time.
-		"minutes": "seconds",
-		"hours":   "seconds",
-		"days":    "seconds",
-		"weeks":   "seconds",
-		// Temperature.
-		"kelvins":    "kelvin",
-		"fahrenheit": "celsius",
-		"rankine":    "celsius",
-		// Length.
-		"inches": "meters",
-		"yards":  "meters",
-		"miles":  "meters",
-		// Bytes.
-		"bits": "bytes",
-		// Energy.
-		"calories": "joules",
-		// Mass.
-		"pounds": "grams",
-		"ounces": "grams",
-	}
-
-	unitPrefixes = []string{
-		"pico",
-		"nano",
-		"micro",
-		"milli",
-		"centi",
-		"deci",
-		"deca",
-		"hecto",
-		"kilo",
-		"kibi",
-		"mega",
-		"mibi",
-		"giga",
-		"gibi",
-		"tera",
-		"tebi",
-		"peta",
-		"pebi",
-	}
-
-	// Common abbreviations that we'd like to discourage.
-	unitAbbreviations = []string{
-		"s",
-		"ms",
-		"us",
-		"ns",
-		"sec",
-		"b",
-		"kb",
-		"mb",
-		"gb",
-		"tb",
-		"pb",
-		"m",
-		"h",
-		"d",
-	}
-)

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validation.go

@@ -0,0 +1,33 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package promlint
+
+import (
+	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus/testutil/promlint/validations"
+)
+
+type Validation = func(mf *dto.MetricFamily) []error
+
+var defaultValidations = []Validation{
+	validations.LintHelp,
+	validations.LintMetricUnits,
+	validations.LintCounter,
+	validations.LintHistogramSummaryReserved,
+	validations.LintMetricTypeInName,
+	validations.LintReservedChars,
+	validations.LintCamelCase,
+	validations.LintUnitAbbreviations,
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validations/counter_validations.go

@@ -0,0 +1,40 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validations
+
+import (
+	"errors"
+	"strings"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+// LintCounter detects issues specific to counters, as well as patterns that should
+// only be used with counters.
+func LintCounter(mf *dto.MetricFamily) []error {
+	var problems []error
+
+	isCounter := mf.GetType() == dto.MetricType_COUNTER
+	isUntyped := mf.GetType() == dto.MetricType_UNTYPED
+	hasTotalSuffix := strings.HasSuffix(mf.GetName(), "_total")
+
+	switch {
+	case isCounter && !hasTotalSuffix:
+		problems = append(problems, errors.New(`counter metrics should have "_total" suffix`))
+	case !isUntyped && !isCounter && hasTotalSuffix:
+		problems = append(problems, errors.New(`non-counter metrics should not have "_total" suffix`))
+	}
+
+	return problems
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validations/generic_name_validations.go

@@ -0,0 +1,101 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validations
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+var camelCase = regexp.MustCompile(`[a-z][A-Z]`)
+
+// LintMetricUnits detects issues with metric unit names.
+func LintMetricUnits(mf *dto.MetricFamily) []error {
+	var problems []error
+
+	unit, base, ok := metricUnits(*mf.Name)
+	if !ok {
+		// No known units detected.
+		return nil
+	}
+
+	// Unit is already a base unit.
+	if unit == base {
+		return nil
+	}
+
+	problems = append(problems, fmt.Errorf("use base unit %q instead of %q", base, unit))
+
+	return problems
+}
+
+// LintMetricTypeInName detects when metric types are included in the metric name.
+func LintMetricTypeInName(mf *dto.MetricFamily) []error {
+	var problems []error
+	n := strings.ToLower(mf.GetName())
+
+	for i, t := range dto.MetricType_name {
+		if i == int32(dto.MetricType_UNTYPED) {
+			continue
+		}
+
+		typename := strings.ToLower(t)
+		if strings.Contains(n, "_"+typename+"_") || strings.HasSuffix(n, "_"+typename) {
+			problems = append(problems, fmt.Errorf(`metric name should not include type '%s'`, typename))
+		}
+	}
+	return problems
+}
+
+// LintReservedChars detects colons in metric names.
+func LintReservedChars(mf *dto.MetricFamily) []error {
+	var problems []error
+	if strings.Contains(mf.GetName(), ":") {
+		problems = append(problems, errors.New("metric names should not contain ':'"))
+	}
+	return problems
+}
+
+// LintCamelCase detects metric names and label names written in camelCase.
+func LintCamelCase(mf *dto.MetricFamily) []error {
+	var problems []error
+	if camelCase.FindString(mf.GetName()) != "" {
+		problems = append(problems, errors.New("metric names should be written in 'snake_case' not 'camelCase'"))
+	}
+
+	for _, m := range mf.GetMetric() {
+		for _, l := range m.GetLabel() {
+			if camelCase.FindString(l.GetName()) != "" {
+				problems = append(problems, errors.New("label names should be written in 'snake_case' not 'camelCase'"))
+			}
+		}
+	}
+	return problems
+}
+
+// LintUnitAbbreviations detects abbreviated units in the metric name.
+func LintUnitAbbreviations(mf *dto.MetricFamily) []error {
+	var problems []error
+	n := strings.ToLower(mf.GetName())
+	for _, s := range unitAbbreviations {
+		if strings.Contains(n, "_"+s+"_") || strings.HasSuffix(n, "_"+s) {
+			problems = append(problems, errors.New("metric names should not contain abbreviated units"))
+		}
+	}
+	return problems
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validations/help_validations.go

@@ -0,0 +1,32 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validations
+
+import (
+	"errors"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+// LintHelp detects issues related to the help text for a metric.
+func LintHelp(mf *dto.MetricFamily) []error {
+	var problems []error
+
+	// Expect all metrics to have help text available.
+	if mf.Help == nil {
+		problems = append(problems, errors.New("no help text"))
+	}
+
+	return problems
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validations/histogram_validations.go

@@ -0,0 +1,63 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validations
+
+import (
+	"errors"
+	"strings"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+// LintHistogramSummaryReserved detects when other types of metrics use names or labels
+// reserved for use by histograms and/or summaries.
+func LintHistogramSummaryReserved(mf *dto.MetricFamily) []error {
+	// These rules do not apply to untyped metrics.
+	t := mf.GetType()
+	if t == dto.MetricType_UNTYPED {
+		return nil
+	}
+
+	var problems []error
+
+	isHistogram := t == dto.MetricType_HISTOGRAM
+	isSummary := t == dto.MetricType_SUMMARY
+
+	n := mf.GetName()
+
+	if !isHistogram && strings.HasSuffix(n, "_bucket") {
+		problems = append(problems, errors.New(`non-histogram metrics should not have "_bucket" suffix`))
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_count") {
+		problems = append(problems, errors.New(`non-histogram and non-summary metrics should not have "_count" suffix`))
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_sum") {
+		problems = append(problems, errors.New(`non-histogram and non-summary metrics should not have "_sum" suffix`))
+	}
+
+	for _, m := range mf.GetMetric() {
+		for _, l := range m.GetLabel() {
+			ln := l.GetName()
+
+			if !isHistogram && ln == "le" {
+				problems = append(problems, errors.New(`non-histogram metrics should not have "le" label`))
+			}
+			if !isSummary && ln == "quantile" {
+				problems = append(problems, errors.New(`non-summary metrics should not have "quantile" label`))
+			}
+		}
+	}
+
+	return problems
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/promlint/validations/units.go

@@ -0,0 +1,118 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package validations
+
+import "strings"
+
+// Units and their possible prefixes recognized by this library.  More can be
+// added over time as needed.
+var (
+	// map a unit to the appropriate base unit.
+	units = map[string]string{
+		// Base units.
+		"amperes": "amperes",
+		"bytes":   "bytes",
+		"celsius": "celsius", // Also allow Celsius because it is common in typical Prometheus use cases.
+		"grams":   "grams",
+		"joules":  "joules",
+		"kelvin":  "kelvin", // SI base unit, used in special cases (e.g. color temperature, scientific measurements).
+		"meters":  "meters", // Both American and international spelling permitted.
+		"metres":  "metres",
+		"seconds": "seconds",
+		"volts":   "volts",
+
+		// Non base units.
+		// Time.
+		"minutes": "seconds",
+		"hours":   "seconds",
+		"days":    "seconds",
+		"weeks":   "seconds",
+		// Temperature.
+		"kelvins":    "kelvin",
+		"fahrenheit": "celsius",
+		"rankine":    "celsius",
+		// Length.
+		"inches": "meters",
+		"yards":  "meters",
+		"miles":  "meters",
+		// Bytes.
+		"bits": "bytes",
+		// Energy.
+		"calories": "joules",
+		// Mass.
+		"pounds": "grams",
+		"ounces": "grams",
+	}
+
+	unitPrefixes = []string{
+		"pico",
+		"nano",
+		"micro",
+		"milli",
+		"centi",
+		"deci",
+		"deca",
+		"hecto",
+		"kilo",
+		"kibi",
+		"mega",
+		"mibi",
+		"giga",
+		"gibi",
+		"tera",
+		"tebi",
+		"peta",
+		"pebi",
+	}
+
+	// Common abbreviations that we'd like to discourage.
+	unitAbbreviations = []string{
+		"s",
+		"ms",
+		"us",
+		"ns",
+		"sec",
+		"b",
+		"kb",
+		"mb",
+		"gb",
+		"tb",
+		"pb",
+		"m",
+		"h",
+		"d",
+	}
+)
+
+// metricUnits attempts to detect known unit types used as part of a metric name,
+// e.g. "foo_bytes_total" or "bar_baz_milligrams".
+func metricUnits(m string) (unit, base string, ok bool) {
+	ss := strings.Split(m, "_")
+
+	for _, s := range ss {
+		if base, found := units[s]; found {
+			return s, base, true
+		}
+
+		for _, p := range unitPrefixes {
+			if strings.HasPrefix(s, p) {
+				if base, found := units[s[len(p):]]; found {
+					return s, base, true
+				}
+			}
+		}
+	}
+
+	return "", "", false
+}

vendor/github.com/prometheus/client_golang/prometheus/testutil/testutil.go

@@ -47,6 +47,7 @@ import (
 	"github.com/davecgh/go-spew/spew"
 	dto "github.com/prometheus/client_model/go"
 	"github.com/prometheus/common/expfmt"
+	"google.golang.org/protobuf/proto"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/internal"
@@ -230,6 +231,20 @@ func convertReaderToMetricFamily(reader io.Reader) ([]*dto.MetricFamily, error)
 		return nil, fmt.Errorf("converting reader to metric families failed: %w", err)
 	}
 
+	// The text protocol handles empty help fields inconsistently. When
+	// encoding, any non-nil value, include the empty string, produces a
+	// "# HELP" line. But when decoding, the help field is only set to a
+	// non-nil value if the "# HELP" line contains a non-empty value.
+	//
+	// Because metrics in a registry always have non-nil help fields, populate
+	// any nil help fields in the parsed metrics with the empty string so that
+	// when we compare text encodings, the results are consistent.
+	for _, metric := range notNormalized {
+		if metric.Help == nil {
+			metric.Help = proto.String("")
+		}
+	}
+
 	return internal.NormalizeMetricFamilies(notNormalized), nil
 }
 
@@ -250,13 +265,13 @@ func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...str
 // result.
 func compare(got, want []*dto.MetricFamily) error {
 	var gotBuf, wantBuf bytes.Buffer
-	enc := expfmt.NewEncoder(&gotBuf, expfmt.FmtText)
+	enc := expfmt.NewEncoder(&gotBuf, expfmt.NewFormat(expfmt.TypeTextPlain))
 	for _, mf := range got {
 		if err := enc.Encode(mf); err != nil {
 			return fmt.Errorf("encoding gathered metrics failed: %w", err)
 		}
 	}
-	enc = expfmt.NewEncoder(&wantBuf, expfmt.FmtText)
+	enc = expfmt.NewEncoder(&wantBuf, expfmt.NewFormat(expfmt.TypeTextPlain))
 	for _, mf := range want {
 		if err := enc.Encode(mf); err != nil {
 			return fmt.Errorf("encoding expected metrics failed: %w", err)

vendor/github.com/prometheus/client_golang/prometheus/value.go

@@ -14,6 +14,7 @@
 package prometheus
 
 import (
+	"errors"
 	"fmt"
 	"sort"
 	"time"
@@ -91,7 +92,7 @@ func (v *valueFunc) Desc() *Desc {
 }
 
 func (v *valueFunc) Write(out *dto.Metric) error {
-	return populateMetric(v.valType, v.function(), v.labelPairs, nil, out)
+	return populateMetric(v.valType, v.function(), v.labelPairs, nil, out, nil)
 }
 
 // NewConstMetric returns a metric with one fixed value that cannot be
@@ -105,12 +106,12 @@ func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues
 	if desc.err != nil {
 		return nil, desc.err
 	}
-	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
+	if err := validateLabelValues(labelValues, len(desc.variableLabels.names)); err != nil {
 		return nil, err
 	}
 
 	metric := &dto.Metric{}
-	if err := populateMetric(valueType, value, MakeLabelPairs(desc, labelValues), nil, metric); err != nil {
+	if err := populateMetric(valueType, value, MakeLabelPairs(desc, labelValues), nil, metric, nil); err != nil {
 		return nil, err
 	}
 
@@ -130,6 +131,43 @@ func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelVal
 	return m
 }
 
+// NewConstMetricWithCreatedTimestamp does the same thing as NewConstMetric, but generates Counters
+// with created timestamp set and returns an error for other metric types.
+func NewConstMetricWithCreatedTimestamp(desc *Desc, valueType ValueType, value float64, ct time.Time, labelValues ...string) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
+	if err := validateLabelValues(labelValues, len(desc.variableLabels.names)); err != nil {
+		return nil, err
+	}
+	switch valueType {
+	case CounterValue:
+		break
+	default:
+		return nil, errors.New("created timestamps are only supported for counters")
+	}
+
+	metric := &dto.Metric{}
+	if err := populateMetric(valueType, value, MakeLabelPairs(desc, labelValues), nil, metric, timestamppb.New(ct)); err != nil {
+		return nil, err
+	}
+
+	return &constMetric{
+		desc:   desc,
+		metric: metric,
+	}, nil
+}
+
+// MustNewConstMetricWithCreatedTimestamp is a version of NewConstMetricWithCreatedTimestamp that panics where
+// NewConstMetricWithCreatedTimestamp would have returned an error.
+func MustNewConstMetricWithCreatedTimestamp(desc *Desc, valueType ValueType, value float64, ct time.Time, labelValues ...string) Metric {
+	m, err := NewConstMetricWithCreatedTimestamp(desc, valueType, value, ct, labelValues...)
+	if err != nil {
+		panic(err)
+	}
+	return m
+}
+
 type constMetric struct {
 	desc   *Desc
 	metric *dto.Metric
@@ -153,11 +191,12 @@ func populateMetric(
 	labelPairs []*dto.LabelPair,
 	e *dto.Exemplar,
 	m *dto.Metric,
+	ct *timestamppb.Timestamp,
 ) error {
 	m.Label = labelPairs
 	switch t {
 	case CounterValue:
-		m.Counter = &dto.Counter{Value: proto.Float64(v), Exemplar: e}
+		m.Counter = &dto.Counter{Value: proto.Float64(v), Exemplar: e, CreatedTimestamp: ct}
 	case GaugeValue:
 		m.Gauge = &dto.Gauge{Value: proto.Float64(v)}
 	case UntypedValue:
@@ -176,19 +215,19 @@ func populateMetric(
 // This function is only needed for custom Metric implementations. See MetricVec
 // example.
 func MakeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
-	totalLen := len(desc.variableLabels) + len(desc.constLabelPairs)
+	totalLen := len(desc.variableLabels.names) + len(desc.constLabelPairs)
 	if totalLen == 0 {
 		// Super fast path.
 		return nil
 	}
-	if len(desc.variableLabels) == 0 {
+	if len(desc.variableLabels.names) == 0 {
 		// Moderately fast path.
 		return desc.constLabelPairs
 	}
 	labelPairs := make([]*dto.LabelPair, 0, totalLen)
-	for i, l := range desc.variableLabels {
+	for i, l := range desc.variableLabels.names {
 		labelPairs = append(labelPairs, &dto.LabelPair{
-			Name:  proto.String(l.Name),
+			Name:  proto.String(l),
 			Value: proto.String(labelValues[i]),
 		})
 	}

vendor/github.com/prometheus/client_golang/prometheus/vec.go

@@ -20,24 +20,6 @@ import (
 	"github.com/prometheus/common/model"
 )
 
-var labelsPool = &sync.Pool{
-	New: func() interface{} {
-		return make(Labels)
-	},
-}
-
-func getLabelsFromPool() Labels {
-	return labelsPool.Get().(Labels)
-}
-
-func putLabelsToPool(labels Labels) {
-	for k := range labels {
-		delete(labels, k)
-	}
-
-	labelsPool.Put(labels)
-}
-
 // MetricVec is a Collector to bundle metrics of the same name that differ in
 // their label values. MetricVec is not used directly but as a building block
 // for implementations of vectors of a given metric type, like GaugeVec,
@@ -91,6 +73,7 @@ func NewMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *MetricVec {
 // See also the CounterVec example.
 func (m *MetricVec) DeleteLabelValues(lvs ...string) bool {
 	lvs = constrainLabelValues(m.desc, lvs, m.curry)
+
 	h, err := m.hashLabelValues(lvs)
 	if err != nil {
 		return false
@@ -110,8 +93,8 @@ func (m *MetricVec) DeleteLabelValues(lvs ...string) bool {
 // This method is used for the same purpose as DeleteLabelValues(...string). See
 // there for pros and cons of the two methods.
 func (m *MetricVec) Delete(labels Labels) bool {
-	labels = constrainLabels(m.desc, labels)
-	defer putLabelsToPool(labels)
+	labels, closer := constrainLabels(m.desc, labels)
+	defer closer()
 
 	h, err := m.hashLabels(labels)
 	if err != nil {
@@ -128,8 +111,8 @@ func (m *MetricVec) Delete(labels Labels) bool {
 // Note that curried labels will never be matched if deleting from the curried vector.
 // To match curried labels with DeletePartialMatch, it must be called on the base vector.
 func (m *MetricVec) DeletePartialMatch(labels Labels) int {
-	labels = constrainLabels(m.desc, labels)
-	defer putLabelsToPool(labels)
+	labels, closer := constrainLabels(m.desc, labels)
+	defer closer()
 
 	return m.metricMap.deleteByLabels(labels, m.curry)
 }
@@ -169,11 +152,11 @@ func (m *MetricVec) CurryWith(labels Labels) (*MetricVec, error) {
 		oldCurry = m.curry
 		iCurry   int
 	)
-	for i, label := range m.desc.variableLabels {
-		val, ok := labels[label.Name]
+	for i, labelName := range m.desc.variableLabels.names {
+		val, ok := labels[labelName]
 		if iCurry < len(oldCurry) && oldCurry[iCurry].index == i {
 			if ok {
-				return nil, fmt.Errorf("label name %q is already curried", label.Name)
+				return nil, fmt.Errorf("label name %q is already curried", labelName)
 			}
 			newCurry = append(newCurry, oldCurry[iCurry])
 			iCurry++
@@ -181,7 +164,10 @@ func (m *MetricVec) CurryWith(labels Labels) (*MetricVec, error) {
 			if !ok {
 				continue // Label stays uncurried.
 			}
-			newCurry = append(newCurry, curriedLabelValue{i, label.Constrain(val)})
+			newCurry = append(newCurry, curriedLabelValue{
+				i,
+				m.desc.variableLabels.constrain(labelName, val),
+			})
 		}
 	}
 	if l := len(oldCurry) + len(labels) - len(newCurry); l > 0 {
@@ -250,8 +236,8 @@ func (m *MetricVec) GetMetricWithLabelValues(lvs ...string) (Metric, error) {
 // around MetricVec, implementing a vector for a specific Metric implementation,
 // for example GaugeVec.
 func (m *MetricVec) GetMetricWith(labels Labels) (Metric, error) {
-	labels = constrainLabels(m.desc, labels)
-	defer putLabelsToPool(labels)
+	labels, closer := constrainLabels(m.desc, labels)
+	defer closer()
 
 	h, err := m.hashLabels(labels)
 	if err != nil {
@@ -262,7 +248,7 @@ func (m *MetricVec) GetMetricWith(labels Labels) (Metric, error) {
 }
 
 func (m *MetricVec) hashLabelValues(vals []string) (uint64, error) {
-	if err := validateLabelValues(vals, len(m.desc.variableLabels)-len(m.curry)); err != nil {
+	if err := validateLabelValues(vals, len(m.desc.variableLabels.names)-len(m.curry)); err != nil {
 		return 0, err
 	}
 
@@ -271,7 +257,7 @@ func (m *MetricVec) hashLabelValues(vals []string) (uint64, error) {
 		curry         = m.curry
 		iVals, iCurry int
 	)
-	for i := 0; i < len(m.desc.variableLabels); i++ {
+	for i := 0; i < len(m.desc.variableLabels.names); i++ {
 		if iCurry < len(curry) && curry[iCurry].index == i {
 			h = m.hashAdd(h, curry[iCurry].value)
 			iCurry++
@@ -285,7 +271,7 @@ func (m *MetricVec) hashLabelValues(vals []string) (uint64, error) {
 }
 
 func (m *MetricVec) hashLabels(labels Labels) (uint64, error) {
-	if err := validateValuesInLabels(labels, len(m.desc.variableLabels)-len(m.curry)); err != nil {
+	if err := validateValuesInLabels(labels, len(m.desc.variableLabels.names)-len(m.curry)); err != nil {
 		return 0, err
 	}
 
@@ -294,17 +280,17 @@ func (m *MetricVec) hashLabels(labels Labels) (uint64, error) {
 		curry  = m.curry
 		iCurry int
 	)
-	for i, label := range m.desc.variableLabels {
-		val, ok := labels[label.Name]
+	for i, labelName := range m.desc.variableLabels.names {
+		val, ok := labels[labelName]
 		if iCurry < len(curry) && curry[iCurry].index == i {
 			if ok {
-				return 0, fmt.Errorf("label name %q is already curried", label.Name)
+				return 0, fmt.Errorf("label name %q is already curried", labelName)
 			}
 			h = m.hashAdd(h, curry[iCurry].value)
 			iCurry++
 		} else {
 			if !ok {
-				return 0, fmt.Errorf("label name %q missing in label map", label.Name)
+				return 0, fmt.Errorf("label name %q missing in label map", labelName)
 			}
 			h = m.hashAdd(h, val)
 		}
@@ -482,7 +468,7 @@ func valueMatchesVariableOrCurriedValue(targetValue string, index int, values []
 func matchPartialLabels(desc *Desc, values []string, labels Labels, curry []curriedLabelValue) bool {
 	for l, v := range labels {
 		// Check if the target label exists in our metrics and get the index.
-		varLabelIndex, validLabel := indexOf(l, desc.variableLabels.labelNames())
+		varLabelIndex, validLabel := indexOf(l, desc.variableLabels.names)
 		if validLabel {
 			// Check the value of that label against the target value.
 			// We don't consider curried values in partial matches.
@@ -626,7 +612,7 @@ func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabe
 		return false
 	}
 	iCurry := 0
-	for i, k := range desc.variableLabels {
+	for i, k := range desc.variableLabels.names {
 		if iCurry < len(curry) && curry[iCurry].index == i {
 			if values[i] != curry[iCurry].value {
 				return false
@@ -634,7 +620,7 @@ func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabe
 			iCurry++
 			continue
 		}
-		if values[i] != labels[k.Name] {
+		if values[i] != labels[k] {
 			return false
 		}
 	}
@@ -644,13 +630,13 @@ func matchLabels(desc *Desc, values []string, labels Labels, curry []curriedLabe
 func extractLabelValues(desc *Desc, labels Labels, curry []curriedLabelValue) []string {
 	labelValues := make([]string, len(labels)+len(curry))
 	iCurry := 0
-	for i, k := range desc.variableLabels {
+	for i, k := range desc.variableLabels.names {
 		if iCurry < len(curry) && curry[iCurry].index == i {
 			labelValues[i] = curry[iCurry].value
 			iCurry++
 			continue
 		}
-		labelValues[i] = labels[k.Name]
+		labelValues[i] = labels[k]
 	}
 	return labelValues
 }
@@ -670,20 +656,37 @@ func inlineLabelValues(lvs []string, curry []curriedLabelValue) []string {
 	return labelValues
 }
 
-func constrainLabels(desc *Desc, labels Labels) Labels {
-	constrainedLabels := getLabelsFromPool()
-	for l, v := range labels {
-		if i, ok := indexOf(l, desc.variableLabels.labelNames()); ok {
-			v = desc.variableLabels[i].Constrain(v)
-		}
+var labelsPool = &sync.Pool{
+	New: func() interface{} {
+		return make(Labels)
+	},
+}
 
-		constrainedLabels[l] = v
+func constrainLabels(desc *Desc, labels Labels) (Labels, func()) {
+	if len(desc.variableLabels.labelConstraints) == 0 {
+		// Fast path when there's no constraints
+		return labels, func() {}
 	}
 
-	return constrainedLabels
+	constrainedLabels := labelsPool.Get().(Labels)
+	for l, v := range labels {
+		constrainedLabels[l] = desc.variableLabels.constrain(l, v)
+	}
+
+	return constrainedLabels, func() {
+		for k := range constrainedLabels {
+			delete(constrainedLabels, k)
+		}
+		labelsPool.Put(constrainedLabels)
+	}
 }
 
 func constrainLabelValues(desc *Desc, lvs []string, curry []curriedLabelValue) []string {
+	if len(desc.variableLabels.labelConstraints) == 0 {
+		// Fast path when there's no constraints
+		return lvs
+	}
+
 	constrainedValues := make([]string, len(lvs))
 	var iCurry, iLVs int
 	for i := 0; i < len(lvs)+len(curry); i++ {
@@ -692,8 +695,11 @@ func constrainLabelValues(desc *Desc, lvs []string, curry []curriedLabelValue) [
 			continue
 		}
 
-		if i < len(desc.variableLabels) {
-			constrainedValues[iLVs] = desc.variableLabels[i].Constrain(lvs[iLVs])
+		if i < len(desc.variableLabels.names) {
+			constrainedValues[iLVs] = desc.variableLabels.constrain(
+				desc.variableLabels.names[i],
+				lvs[iLVs],
+			)
 		} else {
 			constrainedValues[iLVs] = lvs[iLVs]
 		}