rebase: bump github.com/prometheus/client_golang from 1.14.0 to 1.15.1

Bumps [github.com/prometheus/client_golang](https://github.com/prometheus/client_golang) from 1.14.0 to 1.15.1.
- [Release notes](https://github.com/prometheus/client_golang/releases)
- [Changelog](https://github.com/prometheus/client_golang/blob/main/CHANGELOG.md)
- [Commits](https://github.com/prometheus/client_golang/compare/v1.14.0...v1.15.1)

---
updated-dependencies:
- dependency-name: github.com/prometheus/client_golang
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/github.com/prometheus/common/model/time.go

@@ -18,7 +18,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -183,54 +182,78 @@ func (d *Duration) Type() string {
 	return "duration"
 }
 
-var durationRE = regexp.MustCompile("^(([0-9]+)y)?(([0-9]+)w)?(([0-9]+)d)?(([0-9]+)h)?(([0-9]+)m)?(([0-9]+)s)?(([0-9]+)ms)?$")
+func isdigit(c byte) bool { return c >= '0' && c <= '9' }
+
+// Units are required to go in order from biggest to smallest.
+// This guards against confusion from "1m1d" being 1 minute + 1 day, not 1 month + 1 day.
+var unitMap = map[string]struct {
+	pos  int
+	mult uint64
+}{
+	"ms": {7, uint64(time.Millisecond)},
+	"s":  {6, uint64(time.Second)},
+	"m":  {5, uint64(time.Minute)},
+	"h":  {4, uint64(time.Hour)},
+	"d":  {3, uint64(24 * time.Hour)},
+	"w":  {2, uint64(7 * 24 * time.Hour)},
+	"y":  {1, uint64(365 * 24 * time.Hour)},
+}
 
 // ParseDuration parses a string into a time.Duration, assuming that a year
 // always has 365d, a week always has 7d, and a day always has 24h.
-func ParseDuration(durationStr string) (Duration, error) {
-	switch durationStr {
+func ParseDuration(s string) (Duration, error) {
+	switch s {
 	case "0":
 		// Allow 0 without a unit.
 		return 0, nil
 	case "":
 		return 0, errors.New("empty duration string")
 	}
-	matches := durationRE.FindStringSubmatch(durationStr)
-	if matches == nil {
-		return 0, fmt.Errorf("not a valid duration string: %q", durationStr)
-	}
-	var dur time.Duration
 
-	// Parse the match at pos `pos` in the regex and use `mult` to turn that
-	// into ms, then add that value to the total parsed duration.
-	var overflowErr error
-	m := func(pos int, mult time.Duration) {
-		if matches[pos] == "" {
-			return
+	orig := s
+	var dur uint64
+	lastUnitPos := 0
+
+	for s != "" {
+		if !isdigit(s[0]) {
+			return 0, fmt.Errorf("not a valid duration string: %q", orig)
 		}
-		n, _ := strconv.Atoi(matches[pos])
+		// Consume [0-9]*
+		i := 0
+		for ; i < len(s) && isdigit(s[i]); i++ {
+		}
+		v, err := strconv.ParseUint(s[:i], 10, 0)
+		if err != nil {
+			return 0, fmt.Errorf("not a valid duration string: %q", orig)
+		}
+		s = s[i:]
 
+		// Consume unit.
+		for i = 0; i < len(s) && !isdigit(s[i]); i++ {
+		}
+		if i == 0 {
+			return 0, fmt.Errorf("not a valid duration string: %q", orig)
+		}
+		u := s[:i]
+		s = s[i:]
+		unit, ok := unitMap[u]
+		if !ok {
+			return 0, fmt.Errorf("unknown unit %q in duration %q", u, orig)
+		}
+		if unit.pos <= lastUnitPos { // Units must go in order from biggest to smallest.
+			return 0, fmt.Errorf("not a valid duration string: %q", orig)
+		}
+		lastUnitPos = unit.pos
 		// Check if the provided duration overflows time.Duration (> ~ 290years).
-		if n > int((1<<63-1)/mult/time.Millisecond) {
-			overflowErr = errors.New("duration out of range")
+		if v > 1<<63/unit.mult {
+			return 0, errors.New("duration out of range")
 		}
-		d := time.Duration(n) * time.Millisecond
-		dur += d * mult
-
-		if dur < 0 {
-			overflowErr = errors.New("duration out of range")
+		dur += v * unit.mult
+		if dur > 1<<63-1 {
+			return 0, errors.New("duration out of range")
 		}
 	}
-
-	m(2, 1000*60*60*24*365) // y
-	m(4, 1000*60*60*24*7)   // w
-	m(6, 1000*60*60*24)     // d
-	m(8, 1000*60*60)        // h
-	m(10, 1000*60)          // m
-	m(12, 1000)             // s
-	m(14, 1)                // ms
-
-	return Duration(dur), overflowErr
+	return Duration(dur), nil
 }
 
 func (d Duration) String() string {

vendor/github.com/prometheus/common/model/value.go

@@ -16,20 +16,12 @@ package model
 import (
 	"encoding/json"
 	"fmt"
-	"math"
 	"sort"
 	"strconv"
 	"strings"
 )
 
 var (
-	// ZeroSamplePair is the pseudo zero-value of SamplePair used to signal a
-	// non-existing sample pair. It is a SamplePair with timestamp Earliest and
-	// value 0.0. Note that the natural zero value of SamplePair has a timestamp
-	// of 0, which is possible to appear in a real SamplePair and thus not
-	// suitable to signal a non-existing SamplePair.
-	ZeroSamplePair = SamplePair{Timestamp: Earliest}
-
 	// ZeroSample is the pseudo zero-value of Sample used to signal a
 	// non-existing sample. It is a Sample with timestamp Earliest, value 0.0,
 	// and metric nil. Note that the natural zero value of Sample has a timestamp
@@ -38,82 +30,14 @@ var (
 	ZeroSample = Sample{Timestamp: Earliest}
 )
 
-// A SampleValue is a representation of a value for a given sample at a given
-// time.
-type SampleValue float64
-
-// MarshalJSON implements json.Marshaler.
-func (v SampleValue) MarshalJSON() ([]byte, error) {
-	return json.Marshal(v.String())
-}
-
-// UnmarshalJSON implements json.Unmarshaler.
-func (v *SampleValue) UnmarshalJSON(b []byte) error {
-	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
-		return fmt.Errorf("sample value must be a quoted string")
-	}
-	f, err := strconv.ParseFloat(string(b[1:len(b)-1]), 64)
-	if err != nil {
-		return err
-	}
-	*v = SampleValue(f)
-	return nil
-}
-
-// Equal returns true if the value of v and o is equal or if both are NaN. Note
-// that v==o is false if both are NaN. If you want the conventional float
-// behavior, use == to compare two SampleValues.
-func (v SampleValue) Equal(o SampleValue) bool {
-	if v == o {
-		return true
-	}
-	return math.IsNaN(float64(v)) && math.IsNaN(float64(o))
-}
-
-func (v SampleValue) String() string {
-	return strconv.FormatFloat(float64(v), 'f', -1, 64)
-}
-
-// SamplePair pairs a SampleValue with a Timestamp.
-type SamplePair struct {
-	Timestamp Time
-	Value     SampleValue
-}
-
-// MarshalJSON implements json.Marshaler.
-func (s SamplePair) MarshalJSON() ([]byte, error) {
-	t, err := json.Marshal(s.Timestamp)
-	if err != nil {
-		return nil, err
-	}
-	v, err := json.Marshal(s.Value)
-	if err != nil {
-		return nil, err
-	}
-	return []byte(fmt.Sprintf("[%s,%s]", t, v)), nil
-}
-
-// UnmarshalJSON implements json.Unmarshaler.
-func (s *SamplePair) UnmarshalJSON(b []byte) error {
-	v := [...]json.Unmarshaler{&s.Timestamp, &s.Value}
-	return json.Unmarshal(b, &v)
-}
-
-// Equal returns true if this SamplePair and o have equal Values and equal
-// Timestamps. The semantics of Value equality is defined by SampleValue.Equal.
-func (s *SamplePair) Equal(o *SamplePair) bool {
-	return s == o || (s.Value.Equal(o.Value) && s.Timestamp.Equal(o.Timestamp))
-}
-
-func (s SamplePair) String() string {
-	return fmt.Sprintf("%s @[%s]", s.Value, s.Timestamp)
-}
-
-// Sample is a sample pair associated with a metric.
+// Sample is a sample pair associated with a metric. A single sample must either
+// define Value or Histogram but not both. Histogram == nil implies the Value
+// field is used, otherwise it should be ignored.
 type Sample struct {
-	Metric    Metric      `json:"metric"`
-	Value     SampleValue `json:"value"`
-	Timestamp Time        `json:"timestamp"`
+	Metric    Metric           `json:"metric"`
+	Value     SampleValue      `json:"value"`
+	Timestamp Time             `json:"timestamp"`
+	Histogram *SampleHistogram `json:"histogram"`
 }
 
 // Equal compares first the metrics, then the timestamp, then the value. The
@@ -129,11 +53,19 @@ func (s *Sample) Equal(o *Sample) bool {
 	if !s.Timestamp.Equal(o.Timestamp) {
 		return false
 	}
-
+	if s.Histogram != nil {
+		return s.Histogram.Equal(o.Histogram)
+	}
 	return s.Value.Equal(o.Value)
 }
 
 func (s Sample) String() string {
+	if s.Histogram != nil {
+		return fmt.Sprintf("%s => %s", s.Metric, SampleHistogramPair{
+			Timestamp: s.Timestamp,
+			Histogram: s.Histogram,
+		})
+	}
 	return fmt.Sprintf("%s => %s", s.Metric, SamplePair{
 		Timestamp: s.Timestamp,
 		Value:     s.Value,
@@ -142,6 +74,19 @@ func (s Sample) String() string {
 
 // MarshalJSON implements json.Marshaler.
 func (s Sample) MarshalJSON() ([]byte, error) {
+	if s.Histogram != nil {
+		v := struct {
+			Metric    Metric              `json:"metric"`
+			Histogram SampleHistogramPair `json:"histogram"`
+		}{
+			Metric: s.Metric,
+			Histogram: SampleHistogramPair{
+				Timestamp: s.Timestamp,
+				Histogram: s.Histogram,
+			},
+		}
+		return json.Marshal(&v)
+	}
 	v := struct {
 		Metric Metric     `json:"metric"`
 		Value  SamplePair `json:"value"`
@@ -152,21 +97,25 @@ func (s Sample) MarshalJSON() ([]byte, error) {
 			Value:     s.Value,
 		},
 	}
-
 	return json.Marshal(&v)
 }
 
 // UnmarshalJSON implements json.Unmarshaler.
 func (s *Sample) UnmarshalJSON(b []byte) error {
 	v := struct {
-		Metric Metric     `json:"metric"`
-		Value  SamplePair `json:"value"`
+		Metric    Metric              `json:"metric"`
+		Value     SamplePair          `json:"value"`
+		Histogram SampleHistogramPair `json:"histogram"`
 	}{
 		Metric: s.Metric,
 		Value: SamplePair{
 			Timestamp: s.Timestamp,
 			Value:     s.Value,
 		},
+		Histogram: SampleHistogramPair{
+			Timestamp: s.Timestamp,
+			Histogram: s.Histogram,
+		},
 	}
 
 	if err := json.Unmarshal(b, &v); err != nil {
@@ -174,8 +123,13 @@ func (s *Sample) UnmarshalJSON(b []byte) error {
 	}
 
 	s.Metric = v.Metric
-	s.Timestamp = v.Value.Timestamp
-	s.Value = v.Value.Value
+	if v.Histogram.Histogram != nil {
+		s.Timestamp = v.Histogram.Timestamp
+		s.Histogram = v.Histogram.Histogram
+	} else {
+		s.Timestamp = v.Value.Timestamp
+		s.Value = v.Value.Value
+	}
 
 	return nil
 }
@@ -221,80 +175,76 @@ func (s Samples) Equal(o Samples) bool {
 
 // SampleStream is a stream of Values belonging to an attached COWMetric.
 type SampleStream struct {
-	Metric Metric       `json:"metric"`
-	Values []SamplePair `json:"values"`
+	Metric     Metric                `json:"metric"`
+	Values     []SamplePair          `json:"values"`
+	Histograms []SampleHistogramPair `json:"histograms"`
 }
 
 func (ss SampleStream) String() string {
-	vals := make([]string, len(ss.Values))
+	valuesLength := len(ss.Values)
+	vals := make([]string, valuesLength+len(ss.Histograms))
 	for i, v := range ss.Values {
 		vals[i] = v.String()
 	}
+	for i, v := range ss.Histograms {
+		vals[i+valuesLength] = v.String()
+	}
 	return fmt.Sprintf("%s =>\n%s", ss.Metric, strings.Join(vals, "\n"))
 }
 
-// Value is a generic interface for values resulting from a query evaluation.
-type Value interface {
-	Type() ValueType
-	String() string
+func (ss SampleStream) MarshalJSON() ([]byte, error) {
+	if len(ss.Histograms) > 0 && len(ss.Values) > 0 {
+		v := struct {
+			Metric     Metric                `json:"metric"`
+			Values     []SamplePair          `json:"values"`
+			Histograms []SampleHistogramPair `json:"histograms"`
+		}{
+			Metric:     ss.Metric,
+			Values:     ss.Values,
+			Histograms: ss.Histograms,
+		}
+		return json.Marshal(&v)
+	} else if len(ss.Histograms) > 0 {
+		v := struct {
+			Metric     Metric                `json:"metric"`
+			Histograms []SampleHistogramPair `json:"histograms"`
+		}{
+			Metric:     ss.Metric,
+			Histograms: ss.Histograms,
+		}
+		return json.Marshal(&v)
+	} else {
+		v := struct {
+			Metric Metric       `json:"metric"`
+			Values []SamplePair `json:"values"`
+		}{
+			Metric: ss.Metric,
+			Values: ss.Values,
+		}
+		return json.Marshal(&v)
+	}
 }
 
-func (Matrix) Type() ValueType  { return ValMatrix }
-func (Vector) Type() ValueType  { return ValVector }
-func (*Scalar) Type() ValueType { return ValScalar }
-func (*String) Type() ValueType { return ValString }
+func (ss *SampleStream) UnmarshalJSON(b []byte) error {
+	v := struct {
+		Metric     Metric                `json:"metric"`
+		Values     []SamplePair          `json:"values"`
+		Histograms []SampleHistogramPair `json:"histograms"`
+	}{
+		Metric:     ss.Metric,
+		Values:     ss.Values,
+		Histograms: ss.Histograms,
+	}
 
-type ValueType int
-
-const (
-	ValNone ValueType = iota
-	ValScalar
-	ValVector
-	ValMatrix
-	ValString
-)
-
-// MarshalJSON implements json.Marshaler.
-func (et ValueType) MarshalJSON() ([]byte, error) {
-	return json.Marshal(et.String())
-}
-
-func (et *ValueType) UnmarshalJSON(b []byte) error {
-	var s string
-	if err := json.Unmarshal(b, &s); err != nil {
+	if err := json.Unmarshal(b, &v); err != nil {
 		return err
 	}
-	switch s {
-	case "<ValNone>":
-		*et = ValNone
-	case "scalar":
-		*et = ValScalar
-	case "vector":
-		*et = ValVector
-	case "matrix":
-		*et = ValMatrix
-	case "string":
-		*et = ValString
-	default:
-		return fmt.Errorf("unknown value type %q", s)
-	}
-	return nil
-}
 
-func (e ValueType) String() string {
-	switch e {
-	case ValNone:
-		return "<ValNone>"
-	case ValScalar:
-		return "scalar"
-	case ValVector:
-		return "vector"
-	case ValMatrix:
-		return "matrix"
-	case ValString:
-		return "string"
-	}
-	panic("ValueType.String: unhandled value type")
+	ss.Metric = v.Metric
+	ss.Values = v.Values
+	ss.Histograms = v.Histograms
+
+	return nil
 }
 
 // Scalar is a scalar value evaluated at the set timestamp.

vendor/github.com/prometheus/common/model/value_float.go

@@ -0,0 +1,100 @@
+// Copyright 2013 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 model
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"strconv"
+)
+
+var (
+	// ZeroSamplePair is the pseudo zero-value of SamplePair used to signal a
+	// non-existing sample pair. It is a SamplePair with timestamp Earliest and
+	// value 0.0. Note that the natural zero value of SamplePair has a timestamp
+	// of 0, which is possible to appear in a real SamplePair and thus not
+	// suitable to signal a non-existing SamplePair.
+	ZeroSamplePair = SamplePair{Timestamp: Earliest}
+)
+
+// A SampleValue is a representation of a value for a given sample at a given
+// time.
+type SampleValue float64
+
+// MarshalJSON implements json.Marshaler.
+func (v SampleValue) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.String())
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (v *SampleValue) UnmarshalJSON(b []byte) error {
+	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
+		return fmt.Errorf("sample value must be a quoted string")
+	}
+	f, err := strconv.ParseFloat(string(b[1:len(b)-1]), 64)
+	if err != nil {
+		return err
+	}
+	*v = SampleValue(f)
+	return nil
+}
+
+// Equal returns true if the value of v and o is equal or if both are NaN. Note
+// that v==o is false if both are NaN. If you want the conventional float
+// behavior, use == to compare two SampleValues.
+func (v SampleValue) Equal(o SampleValue) bool {
+	if v == o {
+		return true
+	}
+	return math.IsNaN(float64(v)) && math.IsNaN(float64(o))
+}
+
+func (v SampleValue) String() string {
+	return strconv.FormatFloat(float64(v), 'f', -1, 64)
+}
+
+// SamplePair pairs a SampleValue with a Timestamp.
+type SamplePair struct {
+	Timestamp Time
+	Value     SampleValue
+}
+
+func (s SamplePair) MarshalJSON() ([]byte, error) {
+	t, err := json.Marshal(s.Timestamp)
+	if err != nil {
+		return nil, err
+	}
+	v, err := json.Marshal(s.Value)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(fmt.Sprintf("[%s,%s]", t, v)), nil
+}
+
+// UnmarshalJSON implements json.Unmarshaler.
+func (s *SamplePair) UnmarshalJSON(b []byte) error {
+	v := [...]json.Unmarshaler{&s.Timestamp, &s.Value}
+	return json.Unmarshal(b, &v)
+}
+
+// Equal returns true if this SamplePair and o have equal Values and equal
+// Timestamps. The semantics of Value equality is defined by SampleValue.Equal.
+func (s *SamplePair) Equal(o *SamplePair) bool {
+	return s == o || (s.Value.Equal(o.Value) && s.Timestamp.Equal(o.Timestamp))
+}
+
+func (s SamplePair) String() string {
+	return fmt.Sprintf("%s @[%s]", s.Value, s.Timestamp)
+}

vendor/github.com/prometheus/common/model/value_histogram.go

@@ -0,0 +1,178 @@
+// Copyright 2013 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 model
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+type FloatString float64
+
+func (v FloatString) String() string {
+	return strconv.FormatFloat(float64(v), 'f', -1, 64)
+}
+
+func (v FloatString) MarshalJSON() ([]byte, error) {
+	return json.Marshal(v.String())
+}
+
+func (v *FloatString) UnmarshalJSON(b []byte) error {
+	if len(b) < 2 || b[0] != '"' || b[len(b)-1] != '"' {
+		return fmt.Errorf("float value must be a quoted string")
+	}
+	f, err := strconv.ParseFloat(string(b[1:len(b)-1]), 64)
+	if err != nil {
+		return err
+	}
+	*v = FloatString(f)
+	return nil
+}
+
+type HistogramBucket struct {
+	Boundaries int32
+	Lower      FloatString
+	Upper      FloatString
+	Count      FloatString
+}
+
+func (s HistogramBucket) MarshalJSON() ([]byte, error) {
+	b, err := json.Marshal(s.Boundaries)
+	if err != nil {
+		return nil, err
+	}
+	l, err := json.Marshal(s.Lower)
+	if err != nil {
+		return nil, err
+	}
+	u, err := json.Marshal(s.Upper)
+	if err != nil {
+		return nil, err
+	}
+	c, err := json.Marshal(s.Count)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(fmt.Sprintf("[%s,%s,%s,%s]", b, l, u, c)), nil
+}
+
+func (s *HistogramBucket) UnmarshalJSON(buf []byte) error {
+	tmp := []interface{}{&s.Boundaries, &s.Lower, &s.Upper, &s.Count}
+	wantLen := len(tmp)
+	if err := json.Unmarshal(buf, &tmp); err != nil {
+		return err
+	}
+	if gotLen := len(tmp); gotLen != wantLen {
+		return fmt.Errorf("wrong number of fields: %d != %d", gotLen, wantLen)
+	}
+	return nil
+}
+
+func (s *HistogramBucket) Equal(o *HistogramBucket) bool {
+	return s == o || (s.Boundaries == o.Boundaries && s.Lower == o.Lower && s.Upper == o.Upper && s.Count == o.Count)
+}
+
+func (b HistogramBucket) String() string {
+	var sb strings.Builder
+	lowerInclusive := b.Boundaries == 1 || b.Boundaries == 3
+	upperInclusive := b.Boundaries == 0 || b.Boundaries == 3
+	if lowerInclusive {
+		sb.WriteRune('[')
+	} else {
+		sb.WriteRune('(')
+	}
+	fmt.Fprintf(&sb, "%g,%g", b.Lower, b.Upper)
+	if upperInclusive {
+		sb.WriteRune(']')
+	} else {
+		sb.WriteRune(')')
+	}
+	fmt.Fprintf(&sb, ":%v", b.Count)
+	return sb.String()
+}
+
+type HistogramBuckets []*HistogramBucket
+
+func (s HistogramBuckets) Equal(o HistogramBuckets) bool {
+	if len(s) != len(o) {
+		return false
+	}
+
+	for i, bucket := range s {
+		if !bucket.Equal(o[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+type SampleHistogram struct {
+	Count   FloatString      `json:"count"`
+	Sum     FloatString      `json:"sum"`
+	Buckets HistogramBuckets `json:"buckets"`
+}
+
+func (s SampleHistogram) String() string {
+	return fmt.Sprintf("Count: %f, Sum: %f, Buckets: %v", s.Count, s.Sum, s.Buckets)
+}
+
+func (s *SampleHistogram) Equal(o *SampleHistogram) bool {
+	return s == o || (s.Count == o.Count && s.Sum == o.Sum && s.Buckets.Equal(o.Buckets))
+}
+
+type SampleHistogramPair struct {
+	Timestamp Time
+	// Histogram should never be nil, it's only stored as pointer for efficiency.
+	Histogram *SampleHistogram
+}
+
+func (s SampleHistogramPair) MarshalJSON() ([]byte, error) {
+	if s.Histogram == nil {
+		return nil, fmt.Errorf("histogram is nil")
+	}
+	t, err := json.Marshal(s.Timestamp)
+	if err != nil {
+		return nil, err
+	}
+	v, err := json.Marshal(s.Histogram)
+	if err != nil {
+		return nil, err
+	}
+	return []byte(fmt.Sprintf("[%s,%s]", t, v)), nil
+}
+
+func (s *SampleHistogramPair) UnmarshalJSON(buf []byte) error {
+	tmp := []interface{}{&s.Timestamp, &s.Histogram}
+	wantLen := len(tmp)
+	if err := json.Unmarshal(buf, &tmp); err != nil {
+		return err
+	}
+	if gotLen := len(tmp); gotLen != wantLen {
+		return fmt.Errorf("wrong number of fields: %d != %d", gotLen, wantLen)
+	}
+	if s.Histogram == nil {
+		return fmt.Errorf("histogram is null")
+	}
+	return nil
+}
+
+func (s SampleHistogramPair) String() string {
+	return fmt.Sprintf("%s @[%s]", s.Histogram, s.Timestamp)
+}
+
+func (s *SampleHistogramPair) Equal(o *SampleHistogramPair) bool {
+	return s == o || (s.Histogram.Equal(o.Histogram) && s.Timestamp.Equal(o.Timestamp))
+}

vendor/github.com/prometheus/common/model/value_type.go

@@ -0,0 +1,83 @@
+// Copyright 2013 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 model
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// Value is a generic interface for values resulting from a query evaluation.
+type Value interface {
+	Type() ValueType
+	String() string
+}
+
+func (Matrix) Type() ValueType  { return ValMatrix }
+func (Vector) Type() ValueType  { return ValVector }
+func (*Scalar) Type() ValueType { return ValScalar }
+func (*String) Type() ValueType { return ValString }
+
+type ValueType int
+
+const (
+	ValNone ValueType = iota
+	ValScalar
+	ValVector
+	ValMatrix
+	ValString
+)
+
+// MarshalJSON implements json.Marshaler.
+func (et ValueType) MarshalJSON() ([]byte, error) {
+	return json.Marshal(et.String())
+}
+
+func (et *ValueType) UnmarshalJSON(b []byte) error {
+	var s string
+	if err := json.Unmarshal(b, &s); err != nil {
+		return err
+	}
+	switch s {
+	case "<ValNone>":
+		*et = ValNone
+	case "scalar":
+		*et = ValScalar
+	case "vector":
+		*et = ValVector
+	case "matrix":
+		*et = ValMatrix
+	case "string":
+		*et = ValString
+	default:
+		return fmt.Errorf("unknown value type %q", s)
+	}
+	return nil
+}
+
+func (e ValueType) String() string {
+	switch e {
+	case ValNone:
+		return "<ValNone>"
+	case ValScalar:
+		return "scalar"
+	case ValVector:
+		return "vector"
+	case ValMatrix:
+		return "matrix"
+	case ValString:
+		return "string"
+	}
+	panic("ValueType.String: unhandled value type")
+}