vendor/github.com/openzipkin/zipkin-go/model/doc.go

+// Copyright 2022 The OpenZipkin 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 contains the Zipkin V2 model which is used by the Zipkin Go
+tracer implementation.
+
+Third party instrumentation libraries can use the model and transport packages
+found in this Zipkin Go library to directly interface with the Zipkin Server or
+Zipkin Collectors without the need to use the tracer implementation itself.
+*/
+package model

vendor/github.com/openzipkin/zipkin-go/model/endpoint.go

+// Copyright 2022 The OpenZipkin 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"
+	"net"
+	"strings"
+)
+
+// Endpoint holds the network context of a node in the service graph.
+type Endpoint struct {
+	ServiceName string
+	IPv4        net.IP
+	IPv6        net.IP
+	Port        uint16
+}
+
+// MarshalJSON exports our Endpoint into the correct format for the Zipkin V2 API.
+func (e Endpoint) MarshalJSON() ([]byte, error) {
+	return json.Marshal(&struct {
+		ServiceName string `json:"serviceName,omitempty"`
+		IPv4        net.IP `json:"ipv4,omitempty"`
+		IPv6        net.IP `json:"ipv6,omitempty"`
+		Port        uint16 `json:"port,omitempty"`
+	}{
+		strings.ToLower(e.ServiceName),
+		e.IPv4,
+		e.IPv6,
+		e.Port,
+	})
+}
+
+// Empty returns if all Endpoint properties are empty / unspecified.
+func (e *Endpoint) Empty() bool {
+	return e == nil ||
+		(e.ServiceName == "" && e.Port == 0 && len(e.IPv4) == 0 && len(e.IPv6) == 0)
+}

vendor/github.com/openzipkin/zipkin-go/model/kind.go

+// Copyright 2022 The OpenZipkin 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
+
+// Kind clarifies context of timestamp, duration and remoteEndpoint in a span.
+type Kind string
+
+// Available Kind values
+const (
+	Undetermined Kind = ""
+	Client       Kind = "CLIENT"
+	Server       Kind = "SERVER"
+	Producer     Kind = "PRODUCER"
+	Consumer     Kind = "CONSUMER"
+)

vendor/github.com/openzipkin/zipkin-go/model/span.go

+// Copyright 2022 The OpenZipkin 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"
+	"errors"
+	"strings"
+	"time"
+)
+
+// unmarshal errors
+var (
+	ErrValidTraceIDRequired  = errors.New("valid traceId required")
+	ErrValidIDRequired       = errors.New("valid span id required")
+	ErrValidDurationRequired = errors.New("valid duration required")
+)
+
+// BaggageFields holds the interface for consumers needing to interact with
+// the fields in application logic.
+type BaggageFields interface {
+	// Get returns the values for a field identified by its key.
+	Get(key string) []string
+	// Add adds the provided values to a header designated by key. If not
+	// accepted by the baggage implementation, it will return false.
+	Add(key string, value ...string) bool
+	// Set sets the provided values to a header designated by key. If not
+	// accepted by the baggage implementation, it will return false.
+	Set(key string, value ...string) bool
+	// Delete removes the field data designated by key. If not accepted by the
+	// baggage implementation, it will return false.
+	Delete(key string) bool
+	// Iterate will iterate over the available fields and for each one it will
+	// trigger the callback function.
+	Iterate(f func(key string, values []string))
+}
+
+// SpanContext holds the context of a Span.
+type SpanContext struct {
+	TraceID  TraceID       `json:"traceId"`
+	ID       ID            `json:"id"`
+	ParentID *ID           `json:"parentId,omitempty"`
+	Debug    bool          `json:"debug,omitempty"`
+	Sampled  *bool         `json:"-"`
+	Err      error         `json:"-"`
+	Baggage  BaggageFields `json:"-"`
+}
+
+// SpanModel structure.
+//
+// If using this library to instrument your application you will not need to
+// directly access or modify this representation. The SpanModel is exported for
+// use cases involving 3rd party Go instrumentation libraries desiring to
+// export data to a Zipkin server using the Zipkin V2 Span model.
+type SpanModel struct {
+	SpanContext
+	Name           string            `json:"name,omitempty"`
+	Kind           Kind              `json:"kind,omitempty"`
+	Timestamp      time.Time         `json:"-"`
+	Duration       time.Duration     `json:"-"`
+	Shared         bool              `json:"shared,omitempty"`
+	LocalEndpoint  *Endpoint         `json:"localEndpoint,omitempty"`
+	RemoteEndpoint *Endpoint         `json:"remoteEndpoint,omitempty"`
+	Annotations    []Annotation      `json:"annotations,omitempty"`
+	Tags           map[string]string `json:"tags,omitempty"`
+}
+
+// MarshalJSON exports our Model into the correct format for the Zipkin V2 API.
+func (s SpanModel) MarshalJSON() ([]byte, error) {
+	type Alias SpanModel
+
+	var timestamp int64
+	if !s.Timestamp.IsZero() {
+		if s.Timestamp.Unix() < 1 {
+			// Zipkin does not allow Timestamps before Unix epoch
+			return nil, ErrValidTimestampRequired
+		}
+		timestamp = s.Timestamp.Round(time.Microsecond).UnixNano() / 1e3
+	}
+
+	if s.Duration < time.Microsecond {
+		if s.Duration < 0 {
+			// negative duration is not allowed and signals a timing logic error
+			return nil, ErrValidDurationRequired
+		} else if s.Duration > 0 {
+			// sub microsecond durations are reported as 1 microsecond
+			s.Duration = 1 * time.Microsecond
+		}
+	} else {
+		// Duration will be rounded to nearest microsecond representation.
+		//
+		// NOTE: Duration.Round() is not available in Go 1.8 which we still support.
+		// To handle microsecond resolution rounding we'll add 500 nanoseconds to
+		// the duration. When truncated to microseconds in the call to marshal, it
+		// will be naturally rounded. See TestSpanDurationRounding in span_test.go
+		s.Duration += 500 * time.Nanosecond
+	}
+
+	s.Name = strings.ToLower(s.Name)
+
+	if s.LocalEndpoint.Empty() {
+		s.LocalEndpoint = nil
+	}
+
+	if s.RemoteEndpoint.Empty() {
+		s.RemoteEndpoint = nil
+	}
+
+	return json.Marshal(&struct {
+		T int64 `json:"timestamp,omitempty"`
+		D int64 `json:"duration,omitempty"`
+		Alias
+	}{
+		T:     timestamp,
+		D:     s.Duration.Nanoseconds() / 1e3,
+		Alias: (Alias)(s),
+	})
+}
+
+// UnmarshalJSON imports our Model from a Zipkin V2 API compatible span
+// representation.
+func (s *SpanModel) UnmarshalJSON(b []byte) error {
+	type Alias SpanModel
+	span := &struct {
+		T uint64 `json:"timestamp,omitempty"`
+		D uint64 `json:"duration,omitempty"`
+		*Alias
+	}{
+		Alias: (*Alias)(s),
+	}
+	if err := json.Unmarshal(b, &span); err != nil {
+		return err
+	}
+	if s.ID < 1 {
+		return ErrValidIDRequired
+	}
+	if span.T > 0 {
+		s.Timestamp = time.Unix(0, int64(span.T)*1e3)
+	}
+	s.Duration = time.Duration(span.D*1e3) * time.Nanosecond
+	if s.LocalEndpoint.Empty() {
+		s.LocalEndpoint = nil
+	}
+
+	if s.RemoteEndpoint.Empty() {
+		s.RemoteEndpoint = nil
+	}
+	return nil
+}

vendor/github.com/openzipkin/zipkin-go/model/span_id.go

+// Copyright 2022 The OpenZipkin 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 (
+	"fmt"
+	"strconv"
+)
+
+// ID type
+type ID uint64
+
+// String outputs the 64-bit ID as hex string.
+func (i ID) String() string {
+	return fmt.Sprintf("%016x", uint64(i))
+}
+
+// MarshalJSON serializes an ID type (SpanID, ParentSpanID) to HEX.
+func (i ID) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf("%q", i.String())), nil
+}
+
+// UnmarshalJSON deserializes an ID type (SpanID, ParentSpanID) from HEX.
+func (i *ID) UnmarshalJSON(b []byte) (err error) {
+	var id uint64
+	if len(b) < 3 {
+		return nil
+	}
+	id, err = strconv.ParseUint(string(b[1:len(b)-1]), 16, 64)
+	*i = ID(id)
+	return err
+}

vendor/github.com/openzipkin/zipkin-go/model/traceid.go

+// Copyright 2022 The OpenZipkin 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 (
+	"fmt"
+	"strconv"
+)
+
+// TraceID is a 128 bit number internally stored as 2x uint64 (high & low).
+// In case of 64 bit traceIDs, the value can be found in Low.
+type TraceID struct {
+	High uint64
+	Low  uint64
+}
+
+// Empty returns if TraceID has zero value.
+func (t TraceID) Empty() bool {
+	return t.Low == 0 && t.High == 0
+}
+
+// String outputs the 128-bit traceID as hex string.
+func (t TraceID) String() string {
+	if t.High == 0 {
+		return fmt.Sprintf("%016x", t.Low)
+	}
+	return fmt.Sprintf("%016x%016x", t.High, t.Low)
+}
+
+// TraceIDFromHex returns the TraceID from a hex string.
+func TraceIDFromHex(h string) (t TraceID, err error) {
+	if len(h) > 16 {
+		if t.High, err = strconv.ParseUint(h[0:len(h)-16], 16, 64); err != nil {
+			return
+		}
+		t.Low, err = strconv.ParseUint(h[len(h)-16:], 16, 64)
+		return
+	}
+	t.Low, err = strconv.ParseUint(h, 16, 64)
+	return
+}
+
+// MarshalJSON custom JSON serializer to export the TraceID in the required
+// zero padded hex representation.
+func (t TraceID) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf("%q", t.String())), nil
+}
+
+// UnmarshalJSON custom JSON deserializer to retrieve the traceID from the hex
+// encoded representation.
+func (t *TraceID) UnmarshalJSON(traceID []byte) error {
+	if len(traceID) < 3 {
+		return ErrValidTraceIDRequired
+	}
+	// A valid JSON string is encoded wrapped in double quotes. We need to trim
+	// these before converting the hex payload.
+	tID, err := TraceIDFromHex(string(traceID[1 : len(traceID)-1]))
+	if err != nil {
+		return err
+	}
+	*t = tID
+	return nil
+}

vendor/github.com/prometheus/client_golang/prometheus/.gitignore

+command-line-arguments.test

vendor/github.com/prometheus/client_golang/prometheus/README.md

-See [![go-doc](https://godoc.org/github.com/prometheus/client_golang/prometheus?status.svg)](https://godoc.org/github.com/prometheus/client_golang/prometheus).
+See [![Go Reference](https://pkg.go.dev/badge/github.com/prometheus/client_golang/prometheus.svg)](https://pkg.go.dev/github.com/prometheus/client_golang/prometheus).

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

+// Copyright 2021 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 prometheus
+
+import "runtime/debug"
+
+// NewBuildInfoCollector is the obsolete version of collectors.NewBuildInfoCollector.
+// See there for documentation.
+//
+// Deprecated: Use collectors.NewBuildInfoCollector instead.
+func NewBuildInfoCollector() Collector {
+	path, version, sum := "unknown", "unknown", "unknown"
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		path = bi.Main.Path
+		version = bi.Main.Version
+		sum = bi.Main.Sum
+	}
+	c := &selfCollector{MustNewConstMetric(
+		NewDesc(
+			"go_build_info",
+			"Build information about the main Go module.",
+			nil, Labels{"path": path, "version": version, "checksum": sum},
+		),
+		GaugeValue, 1)}
+	c.init(c.self)
+	return c
+}

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

@@ -29,27 +29,72 @@ type Collector interface {
 	// collected by this Collector to the provided channel and returns once
 	// the last descriptor has been sent. The sent descriptors fulfill the
 	// consistency and uniqueness requirements described in the Desc
-	// documentation. (It is valid if one and the same Collector sends
-	// duplicate descriptors. Those duplicates are simply ignored. However,
-	// two different Collectors must not send duplicate descriptors.) This
-	// method idempotently sends the same descriptors throughout the
-	// lifetime of the Collector. If a Collector encounters an error while
-	// executing this method, it must send an invalid descriptor (created
-	// with NewInvalidDesc) to signal the error to the registry.
+	// documentation.
+	//
+	// It is valid if one and the same Collector sends duplicate
+	// descriptors. Those duplicates are simply ignored. However, two
+	// different Collectors must not send duplicate descriptors.
+	//
+	// Sending no descriptor at all marks the Collector as “unchecked”,
+	// i.e. no checks will be performed at registration time, and the
+	// Collector may yield any Metric it sees fit in its Collect method.
+	//
+	// This method idempotently sends the same descriptors throughout the
+	// lifetime of the Collector. It may be called concurrently and
+	// therefore must be implemented in a concurrency safe way.
+	//
+	// If a Collector encounters an error while executing this method, it
+	// must send an invalid descriptor (created with NewInvalidDesc) to
+	// signal the error to the registry.
 	Describe(chan<- *Desc)
 	// Collect is called by the Prometheus registry when collecting
 	// metrics. The implementation sends each collected metric via the
 	// provided channel and returns once the last metric has been sent. The
-	// descriptor of each sent metric is one of those returned by
-	// Describe. Returned metrics that share the same descriptor must differ
-	// in their variable label values. This method may be called
-	// concurrently and must therefore be implemented in a concurrency safe
-	// way. Blocking occurs at the expense of total performance of rendering
-	// all registered metrics. Ideally, Collector implementations support
-	// concurrent readers.
+	// descriptor of each sent metric is one of those returned by Describe
+	// (unless the Collector is unchecked, see above). Returned metrics that
+	// share the same descriptor must differ in their variable label
+	// values.
+	//
+	// This method may be called concurrently and must therefore be
+	// implemented in a concurrency safe way. Blocking occurs at the expense
+	// of total performance of rendering all registered metrics. Ideally,
+	// Collector implementations support concurrent readers.
 	Collect(chan<- Metric)
 }
 
+// DescribeByCollect is a helper to implement the Describe method of a custom
+// Collector. It collects the metrics from the provided Collector and sends
+// their descriptors to the provided channel.
+//
+// If a Collector collects the same metrics throughout its lifetime, its
+// Describe method can simply be implemented as:
+//
+//   func (c customCollector) Describe(ch chan<- *Desc) {
+//   	DescribeByCollect(c, ch)
+//   }
+//
+// However, this will not work if the metrics collected change dynamically over
+// the lifetime of the Collector in a way that their combined set of descriptors
+// changes as well. The shortcut implementation will then violate the contract
+// of the Describe method. If a Collector sometimes collects no metrics at all
+// (for example vectors like CounterVec, GaugeVec, etc., which only collect
+// metrics after a metric with a fully specified label set has been accessed),
+// it might even get registered as an unchecked Collector (cf. the Register
+// method of the Registerer interface). Hence, only use this shortcut
+// implementation of Describe if you are certain to fulfill the contract.
+//
+// The Collector example demonstrates a use of DescribeByCollect.
+func DescribeByCollect(c Collector, descs chan<- *Desc) {
+	metrics := make(chan Metric)
+	go func() {
+		c.Collect(metrics)
+		close(metrics)
+	}()
+	for m := range metrics {
+		descs <- m.Desc()
+	}
+}
+
 // selfCollector implements Collector for a single Metric so that the Metric
 // collects itself. Add it as an anonymous field to a struct that implements
 // Metric, and call init with the Metric itself as an argument.
@@ -73,3 +118,11 @@ func (c *selfCollector) Describe(ch chan<- *Desc) {
 func (c *selfCollector) Collect(ch chan<- Metric) {
 	ch <- c.self
 }
+
+// collectorMetric is a metric that is also a collector.
+// Because of selfCollector, most (if not all) Metrics in
+// this package are also collectors.
+type collectorMetric interface {
+	Metric
+	Collector
+}

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

@@ -15,6 +15,11 @@ package prometheus
 
 import (
 	"errors"
+	"math"
+	"sync/atomic"
+	"time"
+
+	dto "github.com/prometheus/client_model/go"
 )
 
 // Counter is a Metric that represents a single numerical value that only ever
@@ -38,10 +43,34 @@ type Counter interface {
 	Add(float64)
 }
 
+// ExemplarAdder is implemented by Counters that offer the option of adding a
+// value to the Counter together with an exemplar. Its AddWithExemplar method
+// works like the Add method of the Counter interface but also replaces the
+// currently saved exemplar (if any) with a new one, created from the provided
+// value, the current time as timestamp, and the provided labels. Empty Labels
+// will lead to a valid (label-less) exemplar. But if Labels is nil, the current
+// exemplar is left in place. AddWithExemplar panics if the value is < 0, if any
+// of the provided labels are invalid, or if the provided labels contain more
+// than 64 runes in total.
+type ExemplarAdder interface {
+	AddWithExemplar(value float64, exemplar Labels)
+}
+
 // CounterOpts is an alias for Opts. See there for doc comments.
 type CounterOpts Opts
 
 // NewCounter creates a new Counter based on the provided CounterOpts.
+//
+// The returned implementation also implements ExemplarAdder. It is safe to
+// perform the corresponding type assertion.
+//
+// The returned implementation tracks the counter value in two separate
+// variables, a float64 and a uint64. The latter is used to track calls of the
+// Inc method and calls of the Add method with a value that can be represented
+// as a uint64. This allows atomic increments of the counter with optimal
+// performance. (It is common to have an Inc call in very hot execution paths.)
+// Both internal tracking values are added up in the Write method. This has to
+// be taken into account when it comes to precision and overflow behavior.
 func NewCounter(opts CounterOpts) Counter {
 	desc := NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
@@ -49,20 +78,87 @@ func NewCounter(opts CounterOpts) Counter {
 		nil,
 		opts.ConstLabels,
 	)
-	result := &counter{value: value{desc: desc, valType: CounterValue, labelPairs: desc.constLabelPairs}}
+	result := &counter{desc: desc, labelPairs: desc.constLabelPairs, now: time.Now}
 	result.init(result) // Init self-collection.
 	return result
 }
 
 type counter struct {
-	value
+	// valBits contains the bits of the represented float64 value, while
+	// valInt stores values that are exact integers. Both have to go first
+	// in the struct to guarantee alignment for atomic operations.
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	valBits uint64
+	valInt  uint64
+
+	selfCollector
+	desc *Desc
+
+	labelPairs []*dto.LabelPair
+	exemplar   atomic.Value // Containing nil or a *dto.Exemplar.
+
+	now func() time.Time // To mock out time.Now() for testing.
+}
+
+func (c *counter) Desc() *Desc {
+	return c.desc
 }
 
 func (c *counter) Add(v float64) {
 	if v < 0 {
 		panic(errors.New("counter cannot decrease in value"))
 	}
-	c.value.Add(v)
+
+	ival := uint64(v)
+	if float64(ival) == v {
+		atomic.AddUint64(&c.valInt, ival)
+		return
+	}
+
+	for {
+		oldBits := atomic.LoadUint64(&c.valBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
+		if atomic.CompareAndSwapUint64(&c.valBits, oldBits, newBits) {
+			return
+		}
+	}
+}
+
+func (c *counter) AddWithExemplar(v float64, e Labels) {
+	c.Add(v)
+	c.updateExemplar(v, e)
+}
+
+func (c *counter) Inc() {
+	atomic.AddUint64(&c.valInt, 1)
+}
+
+func (c *counter) get() float64 {
+	fval := math.Float64frombits(atomic.LoadUint64(&c.valBits))
+	ival := atomic.LoadUint64(&c.valInt)
+	return fval + float64(ival)
+}
+
+func (c *counter) Write(out *dto.Metric) error {
+	val := c.get()
+
+	var exemplar *dto.Exemplar
+	if e := c.exemplar.Load(); e != nil {
+		exemplar = e.(*dto.Exemplar)
+	}
+
+	return populateMetric(CounterValue, val, c.labelPairs, exemplar, out)
+}
+
+func (c *counter) updateExemplar(v float64, l Labels) {
+	if l == nil {
+		return
+	}
+	e, err := newExemplar(v, c.now(), l)
+	if err != nil {
+		panic(err)
+	}
+	c.exemplar.Store(e)
 }
 
 // CounterVec is a Collector that bundles a set of Counters that all share the
@@ -71,7 +167,7 @@ func (c *counter) Add(v float64) {
 // (e.g. number of HTTP requests, partitioned by response code and
 // method). Create instances with NewCounterVec.
 type CounterVec struct {
-	*metricVec
+	*MetricVec
 }
 
 // NewCounterVec creates a new CounterVec based on the provided CounterOpts and
@@ -84,12 +180,11 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 		opts.ConstLabels,
 	)
 	return &CounterVec{
-		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
-			result := &counter{value: value{
-				desc:       desc,
-				valType:    CounterValue,
-				labelPairs: makeLabelPairs(desc, lvs),
-			}}
+		MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
+			if len(lvs) != len(desc.variableLabels) {
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
+			}
+			result := &counter{desc: desc, labelPairs: MakeLabelPairs(desc, lvs), now: time.Now}
 			result.init(result) // Init self-collection.
 			return result
 		}),
@@ -97,7 +192,7 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 }
 
 // GetMetricWithLabelValues returns the Counter for the given slice of label
-// values (same order as the VariableLabels in Desc). If that combination of
+// values (same order as the variable labels in Desc). If that combination of
 // label values is accessed for the first time, a new Counter is created.
 //
 // It is possible to call this method without using the returned Counter to only
@@ -111,7 +206,7 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 // Counter with the same label values is created later.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of variable labels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
@@ -119,8 +214,8 @@ func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec {
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
 // See also the GaugeVec example.
-func (m *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
+	metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Counter), err
 	}
@@ -128,19 +223,19 @@ func (m *CounterVec) GetMetricWithLabelValues(lvs ...string) (Counter, error) {
 }
 
 // GetMetricWith returns the Counter for the given Labels map (the label names
-// must match those of the VariableLabels in Desc). If that label map is
+// must match those of the variable labels in Desc). If that label map is
 // accessed for the first time, a new Counter is created. Implications of
 // creating a Counter without using it and keeping the Counter for later use are
 // the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the variable labels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
+	metric, err := v.MetricVec.GetMetricWith(labels)
 	if metric != nil {
 		return metric.(Counter), err
 	}
@@ -148,18 +243,57 @@ func (m *CounterVec) GetMetricWith(labels Labels) (Counter, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Add(42)
-func (m *CounterVec) WithLabelValues(lvs ...string) Counter {
-	return m.metricVec.withLabelValues(lvs...).(Counter)
+func (v *CounterVec) WithLabelValues(lvs ...string) Counter {
+	c, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return c
 }
 
 // With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
-func (m *CounterVec) With(labels Labels) Counter {
-	return m.metricVec.with(labels).(Counter)
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)
+func (v *CounterVec) With(labels Labels) Counter {
+	c, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return c
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the CounterVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *CounterVec) CurryWith(labels Labels) (*CounterVec, error) {
+	vec, err := v.MetricVec.CurryWith(labels)
+	if vec != nil {
+		return &CounterVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *CounterVec) MustCurryWith(labels Labels) *CounterVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 // CounterFunc is a Counter whose value is determined at collect time by calling a
@@ -179,6 +313,8 @@ type CounterFunc interface {
 // provided function must be concurrency-safe. The function should also honor
 // the contract for a Counter (values only go up, not down), but compliance will
 // not be checked.
+//
+// Check out the ExampleGaugeFunc examples for the similar GaugeFunc.
 func NewCounterFunc(opts CounterOpts, function func() float64) CounterFunc {
 	return newValueFunc(NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),

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

@@ -19,6 +19,8 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/cespare/xxhash/v2"
+	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/model"
 
@@ -49,7 +51,7 @@ type Desc struct {
 	// constLabelPairs contains precalculated DTO label pairs based on
 	// the constant labels.
 	constLabelPairs []*dto.LabelPair
-	// VariableLabels contains names of labels for which the metric
+	// variableLabels contains names of labels for which the metric
 	// maintains variable values.
 	variableLabels []string
 	// id is a hash of the values of the ConstLabels and fqName. This
@@ -67,24 +69,19 @@ type Desc struct {
 
 // NewDesc allocates and initializes a new Desc. Errors are recorded in the Desc
 // and will be reported on registration time. variableLabels and constLabels can
-// be nil if no such labels should be set. fqName and help must not be empty.
+// be nil if no such labels should be set. fqName must not be empty.
 //
 // variableLabels only contain the label names. Their label values are variable
 // and therefore not part of the Desc. (They are managed within the Metric.)
 //
 // For constLabels, the label values are constant. Therefore, they are fully
-// specified in the Desc. See the Opts documentation for the implications of
-// constant labels.
+// specified in the Desc. See the Collector example for a usage pattern.
 func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *Desc {
 	d := &Desc{
 		fqName:         fqName,
 		help:           help,
 		variableLabels: variableLabels,
 	}
-	if help == "" {
-		d.err = errors.New("empty help string")
-		return d
-	}
 	if !model.IsValidMetricName(model.LabelValue(fqName)) {
 		d.err = fmt.Errorf("%q is not a valid metric name", fqName)
 		return d
@@ -98,7 +95,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 	// First add only the const label names and sort them...
 	for labelName := range constLabels {
 		if !checkLabelName(labelName) {
-			d.err = fmt.Errorf("%q is not a valid label name", labelName)
+			d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName)
 			return d
 		}
 		labelNames = append(labelNames, labelName)
@@ -120,7 +117,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 	// dimension with a different mix between preset and variable labels.
 	for _, labelName := range variableLabels {
 		if !checkLabelName(labelName) {
-			d.err = fmt.Errorf("%q is not a valid label name", labelName)
+			d.err = fmt.Errorf("%q is not a valid label name for metric %q", labelName, fqName)
 			return d
 		}
 		labelNames = append(labelNames, "$"+labelName)
@@ -131,24 +128,24 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 		return d
 	}
 
-	vh := hashNew()
+	xxh := xxhash.New()
 	for _, val := range labelValues {
-		vh = hashAdd(vh, val)
-		vh = hashAddByte(vh, separatorByte)
+		xxh.WriteString(val)
+		xxh.Write(separatorByteSlice)
 	}
-	d.id = vh
+	d.id = xxh.Sum64()
 	// Sort labelNames so that order doesn't matter for the hash.
 	sort.Strings(labelNames)
 	// Now hash together (in this order) the help string and the sorted
 	// label names.
-	lh := hashNew()
-	lh = hashAdd(lh, help)
-	lh = hashAddByte(lh, separatorByte)
+	xxh.Reset()
+	xxh.WriteString(help)
+	xxh.Write(separatorByteSlice)
 	for _, labelName := range labelNames {
-		lh = hashAdd(lh, labelName)
-		lh = hashAddByte(lh, separatorByte)
+		xxh.WriteString(labelName)
+		xxh.Write(separatorByteSlice)
 	}
-	d.dimHash = lh
+	d.dimHash = xxh.Sum64()
 
 	d.constLabelPairs = make([]*dto.LabelPair, 0, len(constLabels))
 	for n, v := range constLabels {
@@ -157,7 +154,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 			Value: proto.String(v),
 		})
 	}
-	sort.Sort(LabelPairSorter(d.constLabelPairs))
+	sort.Sort(labelPairSorter(d.constLabelPairs))
 	return d
 }
 

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

@@ -11,10 +11,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package prometheus provides metrics primitives to instrument code for
-// monitoring. It also offers a registry for metrics. Sub-packages allow to
-// expose the registered metrics via HTTP (package promhttp) or push them to a
-// Pushgateway (package push).
+// Package prometheus is the core instrumentation package. It provides metrics
+// primitives to instrument code for monitoring. It also offers a registry for
+// metrics. Sub-packages allow to expose the registered metrics via HTTP
+// (package promhttp) or push them to a Pushgateway (package push). There is
+// also a sub-package promauto, which provides metrics constructors with
+// automatic registration.
 //
 // All exported functions and methods are safe to be used concurrently unless
 // specified otherwise.
@@ -72,32 +74,31 @@
 // The number of exported identifiers in this package might appear a bit
 // overwhelming. However, in addition to the basic plumbing shown in the example
 // above, you only need to understand the different metric types and their
-// vector versions for basic usage.
+// vector versions for basic usage. Furthermore, if you are not concerned with
+// fine-grained control of when and how to register metrics with the registry,
+// have a look at the promauto package, which will effectively allow you to
+// ignore registration altogether in simple cases.
 //
 // Above, you have already touched the Counter and the Gauge. There are two more
 // advanced metric types: the Summary and Histogram. A more thorough description
 // of those four metric types can be found in the Prometheus docs:
 // https://prometheus.io/docs/concepts/metric_types/
 //
-// A fifth "type" of metric is Untyped. It behaves like a Gauge, but signals the
-// Prometheus server not to assume anything about its type.
-//
-// In addition to the fundamental metric types Gauge, Counter, Summary,
-// Histogram, and Untyped, a very important part of the Prometheus data model is
-// the partitioning of samples along dimensions called labels, which results in
+// In addition to the fundamental metric types Gauge, Counter, Summary, and
+// Histogram, a very important part of the Prometheus data model is the
+// partitioning of samples along dimensions called labels, which results in
 // metric vectors. The fundamental types are GaugeVec, CounterVec, SummaryVec,
-// HistogramVec, and UntypedVec.
+// and HistogramVec.
 //
 // While only the fundamental metric types implement the Metric interface, both
 // the metrics and their vector versions implement the Collector interface. A
 // Collector manages the collection of a number of Metrics, but for convenience,
-// a Metric can also “collect itself”. Note that Gauge, Counter, Summary,
-// Histogram, and Untyped are interfaces themselves while GaugeVec, CounterVec,
-// SummaryVec, HistogramVec, and UntypedVec are not.
+// a Metric can also “collect itself”. Note that Gauge, Counter, Summary, and
+// Histogram are interfaces themselves while GaugeVec, CounterVec, SummaryVec,
+// and HistogramVec are not.
 //
 // To create instances of Metrics and their vector versions, you need a suitable
-// …Opts struct, i.e. GaugeOpts, CounterOpts, SummaryOpts, HistogramOpts, or
-// UntypedOpts.
+// …Opts struct, i.e. GaugeOpts, CounterOpts, SummaryOpts, or HistogramOpts.
 //
 // Custom Collectors and constant Metrics
 //
@@ -113,10 +114,23 @@
 // existing numbers into Prometheus Metrics during collection. An own
 // implementation of the Collector interface is perfect for that. You can create
 // Metric instances “on the fly” using NewConstMetric, NewConstHistogram, and
-// NewConstSummary (and their respective Must… versions). That will happen in
-// the Collect method. The Describe method has to return separate Desc
-// instances, representative of the “throw-away” metrics to be created later.
-// NewDesc comes in handy to create those Desc instances.
+// NewConstSummary (and their respective Must… versions). NewConstMetric is used
+// for all metric types with just a float64 as their value: Counter, Gauge, and
+// a special “type” called Untyped. Use the latter if you are not sure if the
+// mirrored metric is a Counter or a Gauge. Creation of the Metric instance
+// happens in the Collect method. The Describe method has to return separate
+// Desc instances, representative of the “throw-away” metrics to be created
+// later.  NewDesc comes in handy to create those Desc instances. Alternatively,
+// you could return no Desc at all, which will mark the Collector “unchecked”.
+// No checks are performed at registration time, but metric consistency will
+// still be ensured at scrape time, i.e. any inconsistencies will lead to scrape
+// errors. Thus, with unchecked Collectors, the responsibility to not collect
+// metrics that lead to inconsistencies in the total scrape result lies with the
+// implementer of the Collector. While this is not a desirable state, it is
+// sometimes necessary. The typical use case is a situation where the exact
+// metrics to be returned by a Collector cannot be predicted at registration
+// time, but the implementer has sufficient knowledge of the whole system to
+// guarantee metric consistency.
 //
 // The Collector example illustrates the use case. You can also look at the
 // source code of the processCollector (mirroring process metrics), the
@@ -168,7 +182,6 @@
 // method can then expose the gathered metrics in some way. Usually, the metrics
 // are served via HTTP on the /metrics endpoint. That's happening in the example
 // above. The tools to expose metrics via HTTP are in the promhttp sub-package.
-// (The top-level functions in the prometheus package are deprecated.)
 //
 // Pushing to the Pushgateway
 //

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

@@ -22,43 +22,10 @@ type expvarCollector struct {
 	exports map[string]*Desc
 }
 
-// NewExpvarCollector returns a newly allocated expvar Collector that still has
-// to be registered with a Prometheus registry.
+// NewExpvarCollector is the obsolete version of collectors.NewExpvarCollector.
+// See there for documentation.
 //
-// An expvar Collector collects metrics from the expvar interface. It provides a
-// quick way to expose numeric values that are already exported via expvar as
-// 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
-// direct implementation of Prometheus metrics for monitoring production
-// systems.
-//
-// The exports map has the following meaning:
-//
-// The keys in the map correspond to expvar keys, i.e. for every expvar key you
-// want to export as Prometheus metric, you need an entry in the exports
-// map. The descriptor mapped to each key describes how to export the expvar
-// value. It defines the name and the help string of the Prometheus metric
-// proxying the expvar value. The type will always be Untyped.
-//
-// For descriptors without variable labels, the expvar value must be a number or
-// a bool. The number is then directly exported as the Prometheus sample
-// value. (For a bool, 'false' translates to 0 and 'true' to 1). Expvar values
-// that are not numbers or bools are silently ignored.
-//
-// If the descriptor has one variable label, the expvar value must be an expvar
-// map. The keys in the expvar map become the various values of the one
-// Prometheus label. The values in the expvar map must be numbers or bools again
-// as above.
-//
-// For descriptors with more than one variable label, the expvar must be a
-// nested expvar map, i.e. where the values of the topmost map are maps again
-// etc. until a depth is reached that corresponds to the number of labels. The
-// leaves of that structure must be numbers or bools as above to serve as the
-// sample values.
-//
-// Anything that does not fit into the scheme above is silently ignored.
+// Deprecated: Use collectors.NewExpvarCollector instead.
 func NewExpvarCollector(exports map[string]*Desc) Collector {
 	return &expvarCollector{
 		exports: exports,

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

+// Copyright 2018 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 prometheus
 
 // Inline and byte-free variant of hash/fnv's fnv64a.

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

@@ -13,6 +13,14 @@
 
 package prometheus
 
+import (
+	"math"
+	"sync/atomic"
+	"time"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
 // Gauge is a Metric that represents a single numerical value that can
 // arbitrarily go up and down.
 //
@@ -48,13 +56,74 @@ type Gauge interface {
 type GaugeOpts Opts
 
 // NewGauge creates a new Gauge based on the provided GaugeOpts.
+//
+// The returned implementation is optimized for a fast Set method. If you have a
+// choice for managing the value of a Gauge via Set vs. Inc/Dec/Add/Sub, pick
+// the former. For example, the Inc method of the returned Gauge is slower than
+// the Inc method of a Counter returned by NewCounter. This matches the typical
+// scenarios for Gauges and Counters, where the former tends to be Set-heavy and
+// the latter Inc-heavy.
 func NewGauge(opts GaugeOpts) Gauge {
-	return newValue(NewDesc(
+	desc := NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
 		opts.Help,
 		nil,
 		opts.ConstLabels,
-	), GaugeValue, 0)
+	)
+	result := &gauge{desc: desc, labelPairs: desc.constLabelPairs}
+	result.init(result) // Init self-collection.
+	return result
+}
+
+type gauge struct {
+	// valBits contains the bits of the represented float64 value. It has
+	// to go first in the struct to guarantee alignment for atomic
+	// operations.  http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	valBits uint64
+
+	selfCollector
+
+	desc       *Desc
+	labelPairs []*dto.LabelPair
+}
+
+func (g *gauge) Desc() *Desc {
+	return g.desc
+}
+
+func (g *gauge) Set(val float64) {
+	atomic.StoreUint64(&g.valBits, math.Float64bits(val))
+}
+
+func (g *gauge) SetToCurrentTime() {
+	g.Set(float64(time.Now().UnixNano()) / 1e9)
+}
+
+func (g *gauge) Inc() {
+	g.Add(1)
+}
+
+func (g *gauge) Dec() {
+	g.Add(-1)
+}
+
+func (g *gauge) Add(val float64) {
+	for {
+		oldBits := atomic.LoadUint64(&g.valBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + val)
+		if atomic.CompareAndSwapUint64(&g.valBits, oldBits, newBits) {
+			return
+		}
+	}
+}
+
+func (g *gauge) Sub(val float64) {
+	g.Add(val * -1)
+}
+
+func (g *gauge) Write(out *dto.Metric) error {
+	val := math.Float64frombits(atomic.LoadUint64(&g.valBits))
+	return populateMetric(GaugeValue, val, g.labelPairs, nil, out)
 }
 
 // GaugeVec is a Collector that bundles a set of Gauges that all share the same
@@ -63,7 +132,7 @@ func NewGauge(opts GaugeOpts) Gauge {
 // (e.g. number of operations queued, partitioned by user and operation
 // type). Create instances with NewGaugeVec.
 type GaugeVec struct {
-	*metricVec
+	*MetricVec
 }
 
 // NewGaugeVec creates a new GaugeVec based on the provided GaugeOpts and
@@ -76,14 +145,19 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 		opts.ConstLabels,
 	)
 	return &GaugeVec{
-		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
-			return newValue(desc, GaugeValue, 0, lvs...)
+		MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
+			if len(lvs) != len(desc.variableLabels) {
+				panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, lvs))
+			}
+			result := &gauge{desc: desc, labelPairs: MakeLabelPairs(desc, lvs)}
+			result.init(result) // Init self-collection.
+			return result
 		}),
 	}
 }
 
 // GetMetricWithLabelValues returns the Gauge for the given slice of label
-// values (same order as the VariableLabels in Desc). If that combination of
+// values (same order as the variable labels in Desc). If that combination of
 // label values is accessed for the first time, a new Gauge is created.
 //
 // It is possible to call this method without using the returned Gauge to only
@@ -98,15 +172,15 @@ func NewGaugeVec(opts GaugeOpts, labelNames []string) *GaugeVec {
 // example.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of variable labels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
 // an alternative to avoid that type of mistake. For higher label numbers, the
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
-func (m *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
+	metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Gauge), err
 	}
@@ -114,19 +188,19 @@ func (m *GaugeVec) GetMetricWithLabelValues(lvs ...string) (Gauge, error) {
 }
 
 // GetMetricWith returns the Gauge for the given Labels map (the label names
-// must match those of the VariableLabels in Desc). If that label map is
+// must match those of the variable labels in Desc). If that label map is
 // accessed for the first time, a new Gauge is created. Implications of
 // creating a Gauge without using it and keeping the Gauge for later use are
 // the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the variable labels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
+	metric, err := v.MetricVec.GetMetricWith(labels)
 	if metric != nil {
 		return metric.(Gauge), err
 	}
@@ -134,18 +208,57 @@ func (m *GaugeVec) GetMetricWith(labels Labels) (Gauge, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Add(42)
-func (m *GaugeVec) WithLabelValues(lvs ...string) Gauge {
-	return m.metricVec.withLabelValues(lvs...).(Gauge)
+func (v *GaugeVec) WithLabelValues(lvs ...string) Gauge {
+	g, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return g
 }
 
 // With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
-func (m *GaugeVec) With(labels Labels) Gauge {
-	return m.metricVec.with(labels).(Gauge)
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Add(42)
+func (v *GaugeVec) With(labels Labels) Gauge {
+	g, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return g
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the GaugeVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *GaugeVec) CurryWith(labels Labels) (*GaugeVec, error) {
+	vec, err := v.MetricVec.CurryWith(labels)
+	if vec != nil {
+		return &GaugeVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *GaugeVec) MustCurryWith(labels Labels) *GaugeVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 // GaugeFunc is a Gauge whose value is determined at collect time by calling a
@@ -160,9 +273,12 @@ type GaugeFunc interface {
 // NewGaugeFunc creates a new GaugeFunc based on the provided GaugeOpts. The
 // value reported is determined by calling the given function from within the
 // Write method. Take into account that metric collection may happen
-// concurrently. If that results in concurrent calls to Write, like in the case
-// where a GaugeFunc is directly registered with Prometheus, the provided
-// function must be concurrency-safe.
+// concurrently. Therefore, it must be safe to call the provided function
+// concurrently.
+//
+// NewGaugeFunc is a good way to create an “info” style metric with a constant
+// value of 1. Example:
+// https://github.com/prometheus/common/blob/8558a5b7db3c84fa38b4766966059a7bd5bfa2ee/version/info.go#L36-L56
 func NewGaugeFunc(opts GaugeOpts, function func() float64) GaugeFunc {
 	return newValueFunc(NewDesc(
 		BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),

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

+// Copyright 2018 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 prometheus
 
 import (
-	"fmt"
 	"runtime"
 	"runtime/debug"
 	"time"
 )
 
-type goCollector struct {
-	goroutinesDesc *Desc
-	threadsDesc    *Desc
-	gcDesc         *Desc
-	goInfoDesc     *Desc
-
-	// metrics to describe and collect
-	metrics memStatsMetrics
-}
-
-// NewGoCollector returns a collector which exports metrics about the current
-// go process.
-func NewGoCollector() Collector {
-	return &goCollector{
-		goroutinesDesc: NewDesc(
-			"go_goroutines",
-			"Number of goroutines that currently exist.",
-			nil, nil),
-		threadsDesc: NewDesc(
-			"go_threads",
-			"Number of OS threads created.",
-			nil, nil),
-		gcDesc: NewDesc(
-			"go_gc_duration_seconds",
-			"A summary of the GC invocation durations.",
-			nil, nil),
-		goInfoDesc: NewDesc(
-			"go_info",
-			"Information about the Go environment.",
-			nil, Labels{"version": runtime.Version()}),
-		metrics: memStatsMetrics{
+func goRuntimeMemStats() memStatsMetrics {
+	return memStatsMetrics{
 		{
 			desc: NewDesc(
 				memstatNamespace("alloc_bytes"),
@@ -214,44 +197,54 @@ func NewGoCollector() Collector {
 			),
 			eval:    func(ms *runtime.MemStats) float64 { return float64(ms.NextGC) },
 			valType: GaugeValue,
-			}, {
-				desc: NewDesc(
-					memstatNamespace("last_gc_time_seconds"),
-					"Number of seconds since 1970 of last garbage collection.",
-					nil, nil,
-				),
-				eval:    func(ms *runtime.MemStats) float64 { return float64(ms.LastGC) / 1e9 },
-				valType: GaugeValue,
-			}, {
-				desc: NewDesc(
-					memstatNamespace("gc_cpu_fraction"),
-					"The fraction of this program's available CPU time used by the GC since the program started.",
-					nil, nil,
-				),
-				eval:    func(ms *runtime.MemStats) float64 { return ms.GCCPUFraction },
-				valType: GaugeValue,
-			},
 		},
 	}
 }
 
-func memstatNamespace(s string) string {
-	return fmt.Sprintf("go_memstats_%s", s)
+type baseGoCollector struct {
+	goroutinesDesc *Desc
+	threadsDesc    *Desc
+	gcDesc         *Desc
+	gcLastTimeDesc *Desc
+	goInfoDesc     *Desc
+}
+
+func newBaseGoCollector() baseGoCollector {
+	return baseGoCollector{
+		goroutinesDesc: NewDesc(
+			"go_goroutines",
+			"Number of goroutines that currently exist.",
+			nil, nil),
+		threadsDesc: NewDesc(
+			"go_threads",
+			"Number of OS threads created.",
+			nil, nil),
+		gcDesc: NewDesc(
+			"go_gc_duration_seconds",
+			"A summary of the pause duration of garbage collection cycles.",
+			nil, nil),
+		gcLastTimeDesc: NewDesc(
+			memstatNamespace("last_gc_time_seconds"),
+			"Number of seconds since 1970 of last garbage collection.",
+			nil, nil),
+		goInfoDesc: NewDesc(
+			"go_info",
+			"Information about the Go environment.",
+			nil, Labels{"version": runtime.Version()}),
+	}
 }
 
 // Describe returns all descriptions of the collector.
-func (c *goCollector) Describe(ch chan<- *Desc) {
+func (c *baseGoCollector) Describe(ch chan<- *Desc) {
 	ch <- c.goroutinesDesc
 	ch <- c.threadsDesc
 	ch <- c.gcDesc
+	ch <- c.gcLastTimeDesc
 	ch <- c.goInfoDesc
-	for _, i := range c.metrics {
-		ch <- i.desc
-	}
 }
 
 // Collect returns the current state of all metrics of the collector.
-func (c *goCollector) Collect(ch chan<- Metric) {
+func (c *baseGoCollector) Collect(ch chan<- Metric) {
 	ch <- MustNewConstMetric(c.goroutinesDesc, GaugeValue, float64(runtime.NumGoroutine()))
 	n, _ := runtime.ThreadCreateProfile(nil)
 	ch <- MustNewConstMetric(c.threadsDesc, GaugeValue, float64(n))
@@ -265,18 +258,18 @@ func (c *goCollector) Collect(ch chan<- Metric) {
 		quantiles[float64(idx+1)/float64(len(stats.PauseQuantiles)-1)] = pq.Seconds()
 	}
 	quantiles[0.0] = stats.PauseQuantiles[0].Seconds()
-	ch <- MustNewConstSummary(c.gcDesc, uint64(stats.NumGC), float64(stats.PauseTotal.Seconds()), quantiles)
-
+	ch <- MustNewConstSummary(c.gcDesc, uint64(stats.NumGC), stats.PauseTotal.Seconds(), quantiles)
+	ch <- MustNewConstMetric(c.gcLastTimeDesc, GaugeValue, float64(stats.LastGC.UnixNano())/1e9)
 	ch <- MustNewConstMetric(c.goInfoDesc, GaugeValue, 1)
-
-	ms := &runtime.MemStats{}
-	runtime.ReadMemStats(ms)
-	for _, i := range c.metrics {
-		ch <- MustNewConstMetric(i.desc, i.valType, i.eval(ms))
 }
+
+func memstatNamespace(s string) string {
+	return "go_memstats_" + s
 }
 
-// memStatsMetrics provide description, value, and value type for memstat metrics.
+// memStatsMetrics provide description, evaluator, runtime/metrics name, and
+// value type for memstat metrics.
+// TODO(bwplotka): Remove with end Go 1.16 EOL and replace with runtime/metrics.Description
 type memStatsMetrics []struct {
 	desc    *Desc
 	eval    func(*runtime.MemStats) float64

vendor/github.com/prometheus/client_golang/prometheus/go_collector_go116.go

+// Copyright 2021 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 !go1.17
+// +build !go1.17
+
+package prometheus
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+type goCollector struct {
+	base baseGoCollector
+
+	// ms... are memstats related.
+	msLast          *runtime.MemStats // Previously collected memstats.
+	msLastTimestamp time.Time
+	msMtx           sync.Mutex // Protects msLast and msLastTimestamp.
+	msMetrics       memStatsMetrics
+	msRead          func(*runtime.MemStats) // For mocking in tests.
+	msMaxWait       time.Duration           // Wait time for fresh memstats.
+	msMaxAge        time.Duration           // Maximum allowed age of old memstats.
+}
+
+// NewGoCollector is the obsolete version of collectors.NewGoCollector.
+// See there for documentation.
+//
+// Deprecated: Use collectors.NewGoCollector instead.
+func NewGoCollector() Collector {
+	msMetrics := goRuntimeMemStats()
+	msMetrics = append(msMetrics, struct {
+		desc    *Desc
+		eval    func(*runtime.MemStats) float64
+		valType ValueType
+	}{
+		// This metric is omitted in Go1.17+, see https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034
+		desc: NewDesc(
+			memstatNamespace("gc_cpu_fraction"),
+			"The fraction of this program's available CPU time used by the GC since the program started.",
+			nil, nil,
+		),
+		eval:    func(ms *runtime.MemStats) float64 { return ms.GCCPUFraction },
+		valType: GaugeValue,
+	})
+	return &goCollector{
+		base:      newBaseGoCollector(),
+		msLast:    &runtime.MemStats{},
+		msRead:    runtime.ReadMemStats,
+		msMaxWait: time.Second,
+		msMaxAge:  5 * time.Minute,
+		msMetrics: msMetrics,
+	}
+}
+
+// Describe returns all descriptions of the collector.
+func (c *goCollector) Describe(ch chan<- *Desc) {
+	c.base.Describe(ch)
+	for _, i := range c.msMetrics {
+		ch <- i.desc
+	}
+}
+
+// Collect returns the current state of all metrics of the collector.
+func (c *goCollector) Collect(ch chan<- Metric) {
+	var (
+		ms   = &runtime.MemStats{}
+		done = make(chan struct{})
+	)
+	// Start reading memstats first as it might take a while.
+	go func() {
+		c.msRead(ms)
+		c.msMtx.Lock()
+		c.msLast = ms
+		c.msLastTimestamp = time.Now()
+		c.msMtx.Unlock()
+		close(done)
+	}()
+
+	// Collect base non-memory metrics.
+	c.base.Collect(ch)
+
+	timer := time.NewTimer(c.msMaxWait)
+	select {
+	case <-done: // Our own ReadMemStats succeeded in time. Use it.
+		timer.Stop() // Important for high collection frequencies to not pile up timers.
+		c.msCollect(ch, ms)
+		return
+	case <-timer.C: // Time out, use last memstats if possible. Continue below.
+	}
+	c.msMtx.Lock()
+	if time.Since(c.msLastTimestamp) < c.msMaxAge {
+		// Last memstats are recent enough. Collect from them under the lock.
+		c.msCollect(ch, c.msLast)
+		c.msMtx.Unlock()
+		return
+	}
+	// If we are here, the last memstats are too old or don't exist. We have
+	// to wait until our own ReadMemStats finally completes. For that to
+	// happen, we have to release the lock.
+	c.msMtx.Unlock()
+	<-done
+	c.msCollect(ch, ms)
+}
+
+func (c *goCollector) msCollect(ch chan<- Metric, ms *runtime.MemStats) {
+	for _, i := range c.msMetrics {
+		ch <- MustNewConstMetric(i.desc, i.valType, i.eval(ms))
+	}
+}

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

+// Copyright 2021 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 go1.17
+// +build go1.17
+
+package prometheus
+
+import (
+	"math"
+	"runtime"
+	"runtime/metrics"
+	"strings"
+	"sync"
+
+	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
+	"github.com/golang/protobuf/proto"
+	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus/internal"
+)
+
+const (
+	goGCHeapTinyAllocsObjects               = "/gc/heap/tiny/allocs:objects"
+	goGCHeapAllocsObjects                   = "/gc/heap/allocs:objects"
+	goGCHeapFreesObjects                    = "/gc/heap/frees:objects"
+	goGCHeapAllocsBytes                     = "/gc/heap/allocs:bytes"
+	goGCHeapObjects                         = "/gc/heap/objects:objects"
+	goGCHeapGoalBytes                       = "/gc/heap/goal:bytes"
+	goMemoryClassesTotalBytes               = "/memory/classes/total:bytes"
+	goMemoryClassesHeapObjectsBytes         = "/memory/classes/heap/objects:bytes"
+	goMemoryClassesHeapUnusedBytes          = "/memory/classes/heap/unused:bytes"
+	goMemoryClassesHeapReleasedBytes        = "/memory/classes/heap/released:bytes"
+	goMemoryClassesHeapFreeBytes            = "/memory/classes/heap/free:bytes"
+	goMemoryClassesHeapStacksBytes          = "/memory/classes/heap/stacks:bytes"
+	goMemoryClassesOSStacksBytes            = "/memory/classes/os-stacks:bytes"
+	goMemoryClassesMetadataMSpanInuseBytes  = "/memory/classes/metadata/mspan/inuse:bytes"
+	goMemoryClassesMetadataMSPanFreeBytes   = "/memory/classes/metadata/mspan/free:bytes"
+	goMemoryClassesMetadataMCacheInuseBytes = "/memory/classes/metadata/mcache/inuse:bytes"
+	goMemoryClassesMetadataMCacheFreeBytes  = "/memory/classes/metadata/mcache/free:bytes"
+	goMemoryClassesProfilingBucketsBytes    = "/memory/classes/profiling/buckets:bytes"
+	goMemoryClassesMetadataOtherBytes       = "/memory/classes/metadata/other:bytes"
+	goMemoryClassesOtherBytes               = "/memory/classes/other:bytes"
+)
+
+// runtime/metrics names required for runtimeMemStats like logic.
+var rmForMemStats = []string{goGCHeapTinyAllocsObjects,
+	goGCHeapAllocsObjects,
+	goGCHeapFreesObjects,
+	goGCHeapAllocsBytes,
+	goGCHeapObjects,
+	goGCHeapGoalBytes,
+	goMemoryClassesTotalBytes,
+	goMemoryClassesHeapObjectsBytes,
+	goMemoryClassesHeapUnusedBytes,
+	goMemoryClassesHeapReleasedBytes,
+	goMemoryClassesHeapFreeBytes,
+	goMemoryClassesHeapStacksBytes,
+	goMemoryClassesOSStacksBytes,
+	goMemoryClassesMetadataMSpanInuseBytes,
+	goMemoryClassesMetadataMSPanFreeBytes,
+	goMemoryClassesMetadataMCacheInuseBytes,
+	goMemoryClassesMetadataMCacheFreeBytes,
+	goMemoryClassesProfilingBucketsBytes,
+	goMemoryClassesMetadataOtherBytes,
+	goMemoryClassesOtherBytes,
+}
+
+func bestEffortLookupRM(lookup []string) []metrics.Description {
+	ret := make([]metrics.Description, 0, len(lookup))
+	for _, rm := range metrics.All() {
+		for _, m := range lookup {
+			if m == rm.Name {
+				ret = append(ret, rm)
+			}
+		}
+	}
+	return ret
+}
+
+type goCollector struct {
+	opt  GoCollectorOptions
+	base baseGoCollector
+
+	// mu protects updates to all fields ensuring a consistent
+	// snapshot is always produced by Collect.
+	mu sync.Mutex
+
+	// rm... fields all pertain to the runtime/metrics package.
+	rmSampleBuf []metrics.Sample
+	rmSampleMap map[string]*metrics.Sample
+	rmMetrics   []collectorMetric
+
+	// With Go 1.17, the runtime/metrics package was introduced.
+	// From that point on, metric names produced by the runtime/metrics
+	// package could be generated from runtime/metrics names. However,
+	// these differ from the old names for the same values.
+	//
+	// This field exist to export the same values under the old names
+	// as well.
+	msMetrics memStatsMetrics
+}
+
+const (
+	// Those are not exposed due to need to move Go collector to another package in v2.
+	// See issue https://github.com/prometheus/client_golang/issues/1030.
+	goRuntimeMemStatsCollection uint32 = 1 << iota
+	goRuntimeMetricsCollection
+)
+
+// GoCollectorOptions should not be used be directly by anything, except `collectors` package.
+// Use it via collectors package instead. See issue
+// https://github.com/prometheus/client_golang/issues/1030.
+//
+// Deprecated: Use collectors.WithGoCollections
+type GoCollectorOptions struct {
+	// EnabledCollection sets what type of collections collector should expose on top of base collection.
+	// By default it's goMemStatsCollection | goRuntimeMetricsCollection.
+	EnabledCollections uint32
+}
+
+func (c GoCollectorOptions) isEnabled(flag uint32) bool {
+	return c.EnabledCollections&flag != 0
+}
+
+const defaultGoCollections = goRuntimeMemStatsCollection
+
+// NewGoCollector is the obsolete version of collectors.NewGoCollector.
+// See there for documentation.
+//
+// Deprecated: Use collectors.NewGoCollector instead.
+func NewGoCollector(opts ...func(o *GoCollectorOptions)) Collector {
+	opt := GoCollectorOptions{EnabledCollections: defaultGoCollections}
+	for _, o := range opts {
+		o(&opt)
+	}
+
+	var descriptions []metrics.Description
+	if opt.isEnabled(goRuntimeMetricsCollection) {
+		descriptions = metrics.All()
+	} else if opt.isEnabled(goRuntimeMemStatsCollection) {
+		descriptions = bestEffortLookupRM(rmForMemStats)
+	}
+
+	// Collect all histogram samples so that we can get their buckets.
+	// The API guarantees that the buckets are always fixed for the lifetime
+	// of the process.
+	var histograms []metrics.Sample
+	for _, d := range descriptions {
+		if d.Kind == metrics.KindFloat64Histogram {
+			histograms = append(histograms, metrics.Sample{Name: d.Name})
+		}
+	}
+
+	if len(histograms) > 0 {
+		metrics.Read(histograms)
+	}
+
+	bucketsMap := make(map[string][]float64)
+	for i := range histograms {
+		bucketsMap[histograms[i].Name] = histograms[i].Value.Float64Histogram().Buckets
+	}
+
+	// Generate a Desc and ValueType for each runtime/metrics metric.
+	metricSet := make([]collectorMetric, 0, len(descriptions))
+	sampleBuf := make([]metrics.Sample, 0, len(descriptions))
+	sampleMap := make(map[string]*metrics.Sample, len(descriptions))
+	for i := range descriptions {
+		d := &descriptions[i]
+		namespace, subsystem, name, ok := internal.RuntimeMetricsToProm(d)
+		if !ok {
+			// Just ignore this metric; we can't do anything with it here.
+			// If a user decides to use the latest version of Go, we don't want
+			// to fail here. This condition is tested in TestExpectedRuntimeMetrics.
+			continue
+		}
+
+		// Set up sample buffer for reading, and a map
+		// for quick lookup of sample values.
+		sampleBuf = append(sampleBuf, metrics.Sample{Name: d.Name})
+		sampleMap[d.Name] = &sampleBuf[len(sampleBuf)-1]
+
+		var m collectorMetric
+		if d.Kind == metrics.KindFloat64Histogram {
+			_, hasSum := rmExactSumMap[d.Name]
+			unit := d.Name[strings.IndexRune(d.Name, ':')+1:]
+			m = newBatchHistogram(
+				NewDesc(
+					BuildFQName(namespace, subsystem, name),
+					d.Description,
+					nil,
+					nil,
+				),
+				internal.RuntimeMetricsBucketsForUnit(bucketsMap[d.Name], unit),
+				hasSum,
+			)
+		} else if d.Cumulative {
+			m = NewCounter(CounterOpts{
+				Namespace: namespace,
+				Subsystem: subsystem,
+				Name:      name,
+				Help:      d.Description,
+			})
+		} else {
+			m = NewGauge(GaugeOpts{
+				Namespace: namespace,
+				Subsystem: subsystem,
+				Name:      name,
+				Help:      d.Description,
+			})
+		}
+		metricSet = append(metricSet, m)
+	}
+
+	var msMetrics memStatsMetrics
+	if opt.isEnabled(goRuntimeMemStatsCollection) {
+		msMetrics = goRuntimeMemStats()
+	}
+	return &goCollector{
+		opt:         opt,
+		base:        newBaseGoCollector(),
+		rmSampleBuf: sampleBuf,
+		rmSampleMap: sampleMap,
+		rmMetrics:   metricSet,
+		msMetrics:   msMetrics,
+	}
+}
+
+// Describe returns all descriptions of the collector.
+func (c *goCollector) Describe(ch chan<- *Desc) {
+	c.base.Describe(ch)
+	for _, i := range c.msMetrics {
+		ch <- i.desc
+	}
+	for _, m := range c.rmMetrics {
+		ch <- m.Desc()
+	}
+}
+
+// Collect returns the current state of all metrics of the collector.
+func (c *goCollector) Collect(ch chan<- Metric) {
+	// Collect base non-memory metrics.
+	c.base.Collect(ch)
+
+	// Collect must be thread-safe, so prevent concurrent use of
+	// rmSampleBuf. Just read into rmSampleBuf but write all the data
+	// we get into our Metrics or MemStats.
+	//
+	// This lock also ensures that the Metrics we send out are all from
+	// the same updates, ensuring their mutual consistency insofar as
+	// is guaranteed by the runtime/metrics package.
+	//
+	// N.B. This locking is heavy-handed, but Collect is expected to be called
+	// relatively infrequently. Also the core operation here, metrics.Read,
+	// is fast (O(tens of microseconds)) so contention should certainly be
+	// low, though channel operations and any allocations may add to that.
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if len(c.rmSampleBuf) > 0 {
+		// Populate runtime/metrics sample buffer.
+		metrics.Read(c.rmSampleBuf)
+	}
+
+	if c.opt.isEnabled(goRuntimeMetricsCollection) {
+		// Collect all our metrics from rmSampleBuf.
+		for i, sample := range c.rmSampleBuf {
+			// N.B. switch on concrete type because it's significantly more efficient
+			// than checking for the Counter and Gauge interface implementations. In
+			// this case, we control all the types here.
+			switch m := c.rmMetrics[i].(type) {
+			case *counter:
+				// Guard against decreases. This should never happen, but a failure
+				// to do so will result in a panic, which is a harsh consequence for
+				// a metrics collection bug.
+				v0, v1 := m.get(), unwrapScalarRMValue(sample.Value)
+				if v1 > v0 {
+					m.Add(unwrapScalarRMValue(sample.Value) - m.get())
+				}
+				m.Collect(ch)
+			case *gauge:
+				m.Set(unwrapScalarRMValue(sample.Value))
+				m.Collect(ch)
+			case *batchHistogram:
+				m.update(sample.Value.Float64Histogram(), c.exactSumFor(sample.Name))
+				m.Collect(ch)
+			default:
+				panic("unexpected metric type")
+			}
+		}
+	}
+
+	// ms is a dummy MemStats that we populate ourselves so that we can
+	// populate the old metrics from it if goMemStatsCollection is enabled.
+	if c.opt.isEnabled(goRuntimeMemStatsCollection) {
+		var ms runtime.MemStats
+		memStatsFromRM(&ms, c.rmSampleMap)
+		for _, i := range c.msMetrics {
+			ch <- MustNewConstMetric(i.desc, i.valType, i.eval(&ms))
+		}
+	}
+}
+
+// unwrapScalarRMValue unwraps a runtime/metrics value that is assumed
+// to be scalar and returns the equivalent float64 value. Panics if the
+// value is not scalar.
+func unwrapScalarRMValue(v metrics.Value) float64 {
+	switch v.Kind() {
+	case metrics.KindUint64:
+		return float64(v.Uint64())
+	case metrics.KindFloat64:
+		return v.Float64()
+	case metrics.KindBad:
+		// Unsupported metric.
+		//
+		// This should never happen because we always populate our metric
+		// set from the runtime/metrics package.
+		panic("unexpected unsupported metric")
+	default:
+		// Unsupported metric kind.
+		//
+		// This should never happen because we check for this during initialization
+		// and flag and filter metrics whose kinds we don't understand.
+		panic("unexpected unsupported metric kind")
+	}
+}
+
+var rmExactSumMap = map[string]string{
+	"/gc/heap/allocs-by-size:bytes": "/gc/heap/allocs:bytes",
+	"/gc/heap/frees-by-size:bytes":  "/gc/heap/frees:bytes",
+}
+
+// exactSumFor takes a runtime/metrics metric name (that is assumed to
+// be of kind KindFloat64Histogram) and returns its exact sum and whether
+// its exact sum exists.
+//
+// The runtime/metrics API for histograms doesn't currently expose exact
+// sums, but some of the other metrics are in fact exact sums of histograms.
+func (c *goCollector) exactSumFor(rmName string) float64 {
+	sumName, ok := rmExactSumMap[rmName]
+	if !ok {
+		return 0
+	}
+	s, ok := c.rmSampleMap[sumName]
+	if !ok {
+		return 0
+	}
+	return unwrapScalarRMValue(s.Value)
+}
+
+func memStatsFromRM(ms *runtime.MemStats, rm map[string]*metrics.Sample) {
+	lookupOrZero := func(name string) uint64 {
+		if s, ok := rm[name]; ok {
+			return s.Value.Uint64()
+		}
+		return 0
+	}
+
+	// Currently, MemStats adds tiny alloc count to both Mallocs AND Frees.
+	// The reason for this is because MemStats couldn't be extended at the time
+	// but there was a desire to have Mallocs at least be a little more representative,
+	// while having Mallocs - Frees still represent a live object count.
+	// Unfortunately, MemStats doesn't actually export a large allocation count,
+	// so it's impossible to pull this number out directly.
+	tinyAllocs := lookupOrZero(goGCHeapTinyAllocsObjects)
+	ms.Mallocs = lookupOrZero(goGCHeapAllocsObjects) + tinyAllocs
+	ms.Frees = lookupOrZero(goGCHeapFreesObjects) + tinyAllocs
+
+	ms.TotalAlloc = lookupOrZero(goGCHeapAllocsBytes)
+	ms.Sys = lookupOrZero(goMemoryClassesTotalBytes)
+	ms.Lookups = 0 // Already always zero.
+	ms.HeapAlloc = lookupOrZero(goMemoryClassesHeapObjectsBytes)
+	ms.Alloc = ms.HeapAlloc
+	ms.HeapInuse = ms.HeapAlloc + lookupOrZero(goMemoryClassesHeapUnusedBytes)
+	ms.HeapReleased = lookupOrZero(goMemoryClassesHeapReleasedBytes)
+	ms.HeapIdle = ms.HeapReleased + lookupOrZero(goMemoryClassesHeapFreeBytes)
+	ms.HeapSys = ms.HeapInuse + ms.HeapIdle
+	ms.HeapObjects = lookupOrZero(goGCHeapObjects)
+	ms.StackInuse = lookupOrZero(goMemoryClassesHeapStacksBytes)
+	ms.StackSys = ms.StackInuse + lookupOrZero(goMemoryClassesOSStacksBytes)
+	ms.MSpanInuse = lookupOrZero(goMemoryClassesMetadataMSpanInuseBytes)
+	ms.MSpanSys = ms.MSpanInuse + lookupOrZero(goMemoryClassesMetadataMSPanFreeBytes)
+	ms.MCacheInuse = lookupOrZero(goMemoryClassesMetadataMCacheInuseBytes)
+	ms.MCacheSys = ms.MCacheInuse + lookupOrZero(goMemoryClassesMetadataMCacheFreeBytes)
+	ms.BuckHashSys = lookupOrZero(goMemoryClassesProfilingBucketsBytes)
+	ms.GCSys = lookupOrZero(goMemoryClassesMetadataOtherBytes)
+	ms.OtherSys = lookupOrZero(goMemoryClassesOtherBytes)
+	ms.NextGC = lookupOrZero(goGCHeapGoalBytes)
+
+	// N.B. GCCPUFraction is intentionally omitted. This metric is not useful,
+	// and often misleading due to the fact that it's an average over the lifetime
+	// of the process.
+	// See https://github.com/prometheus/client_golang/issues/842#issuecomment-861812034
+	// for more details.
+	ms.GCCPUFraction = 0
+}
+
+// batchHistogram is a mutable histogram that is updated
+// in batches.
+type batchHistogram struct {
+	selfCollector
+
+	// Static fields updated only once.
+	desc   *Desc
+	hasSum bool
+
+	// Because this histogram operates in batches, it just uses a
+	// single mutex for everything. updates are always serialized
+	// but Write calls may operate concurrently with updates.
+	// Contention between these two sources should be rare.
+	mu      sync.Mutex
+	buckets []float64 // Inclusive lower bounds, like runtime/metrics.
+	counts  []uint64
+	sum     float64 // Used if hasSum is true.
+}
+
+// newBatchHistogram creates a new batch histogram value with the given
+// Desc, buckets, and whether or not it has an exact sum available.
+//
+// buckets must always be from the runtime/metrics package, following
+// the same conventions.
+func newBatchHistogram(desc *Desc, buckets []float64, hasSum bool) *batchHistogram {
+	// We need to remove -Inf values. runtime/metrics keeps them around.
+	// But -Inf bucket should not be allowed for prometheus histograms.
+	if buckets[0] == math.Inf(-1) {
+		buckets = buckets[1:]
+	}
+	h := &batchHistogram{
+		desc:    desc,
+		buckets: buckets,
+		// Because buckets follows runtime/metrics conventions, there's
+		// 1 more value in the buckets list than there are buckets represented,
+		// because in runtime/metrics, the bucket values represent *boundaries*,
+		// and non-Inf boundaries are inclusive lower bounds for that bucket.
+		counts: make([]uint64, len(buckets)-1),
+		hasSum: hasSum,
+	}
+	h.init(h)
+	return h
+}
+
+// update updates the batchHistogram from a runtime/metrics histogram.
+//
+// sum must be provided if the batchHistogram was created to have an exact sum.
+// h.buckets must be a strict subset of his.Buckets.
+func (h *batchHistogram) update(his *metrics.Float64Histogram, sum float64) {
+	counts, buckets := his.Counts, his.Buckets
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	// Clear buckets.
+	for i := range h.counts {
+		h.counts[i] = 0
+	}
+	// Copy and reduce buckets.
+	var j int
+	for i, count := range counts {
+		h.counts[j] += count
+		if buckets[i+1] == h.buckets[j+1] {
+			j++
+		}
+	}
+	if h.hasSum {
+		h.sum = sum
+	}
+}
+
+func (h *batchHistogram) Desc() *Desc {
+	return h.desc
+}
+
+func (h *batchHistogram) Write(out *dto.Metric) error {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	sum := float64(0)
+	if h.hasSum {
+		sum = h.sum
+	}
+	dtoBuckets := make([]*dto.Bucket, 0, len(h.counts))
+	totalCount := uint64(0)
+	for i, count := range h.counts {
+		totalCount += count
+		if !h.hasSum {
+			if count != 0 {
+				// N.B. This computed sum is an underestimate.
+				sum += h.buckets[i] * float64(count)
+			}
+		}
+
+		// Skip the +Inf bucket, but only for the bucket list.
+		// It must still count for sum and totalCount.
+		if math.IsInf(h.buckets[i+1], 1) {
+			break
+		}
+		// Float64Histogram's upper bound is exclusive, so make it inclusive
+		// by obtaining the next float64 value down, in order.
+		upperBound := math.Nextafter(h.buckets[i+1], h.buckets[i])
+		dtoBuckets = append(dtoBuckets, &dto.Bucket{
+			CumulativeCount: proto.Uint64(totalCount),
+			UpperBound:      proto.Float64(upperBound),
+		})
+	}
+	out.Histogram = &dto.Histogram{
+		Bucket:      dtoBuckets,
+		SampleCount: proto.Uint64(totalCount),
+		SampleSum:   proto.Float64(sum),
+	}
+	return nil
+}

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

@@ -16,9 +16,13 @@ package prometheus
 import (
 	"fmt"
 	"math"
+	"runtime"
 	"sort"
+	"sync"
 	"sync/atomic"
+	"time"
 
+	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
@@ -43,7 +47,12 @@ type Histogram interface {
 	Metric
 	Collector
 
-	// Observe adds a single observation to the histogram.
+	// Observe adds a single observation to the histogram. Observations are
+	// usually positive or zero. Negative observations are accepted but
+	// prevent current versions of Prometheus from properly detecting
+	// counter resets in the sum of observations. See
+	// https://prometheus.io/docs/practices/histograms/#count-and-sum-of-observations
+	// for details.
 	Observe(float64)
 }
 
@@ -107,9 +116,38 @@ func ExponentialBuckets(start, factor float64, count int) []float64 {
 	return buckets
 }
 
+// ExponentialBucketsRange creates 'count' buckets, where the lowest bucket is
+// 'min' and the highest bucket is 'max'. The final +Inf bucket is not counted
+// and not included in the returned slice. The returned slice is meant to be
+// used for the Buckets field of HistogramOpts.
+//
+// The function panics if 'count' is 0 or negative, if 'min' is 0 or negative.
+func ExponentialBucketsRange(min, max float64, count int) []float64 {
+	if count < 1 {
+		panic("ExponentialBucketsRange count needs a positive count")
+	}
+	if min <= 0 {
+		panic("ExponentialBucketsRange min needs to be greater than 0")
+	}
+
+	// Formula for exponential buckets.
+	// max = min*growthFactor^(bucketCount-1)
+
+	// We know max/min and highest bucket. Solve for growthFactor.
+	growthFactor := math.Pow(max/min, 1.0/float64(count-1))
+
+	// Now that we know growthFactor, solve for each bucket.
+	buckets := make([]float64, count)
+	for i := 1; i <= count; i++ {
+		buckets[i-1] = min * math.Pow(growthFactor, float64(i-1))
+	}
+	return buckets
+}
+
 // HistogramOpts bundles the options for creating a Histogram metric. It is
-// mandatory to set Name and Help to a non-empty string. All other fields are
-// optional and can safely be left at their zero value.
+// mandatory to set Name to a non-empty string. All other fields are optional
+// and can safely be left at their zero value, although it is strongly
+// encouraged to set a Help string.
 type HistogramOpts struct {
 	// Namespace, Subsystem, and Name are components of the fully-qualified
 	// name of the Histogram (created by joining these components with
@@ -120,29 +158,22 @@ type HistogramOpts struct {
 	Subsystem string
 	Name      string
 
-	// Help provides information about this Histogram. Mandatory!
+	// Help provides information about this Histogram.
 	//
 	// Metrics with the same fully-qualified name must have the same Help
 	// string.
 	Help string
 
-	// ConstLabels are used to attach fixed labels to this
-	// Histogram. Histograms with the same fully-qualified name must have the
-	// same label names in their ConstLabels.
+	// ConstLabels are used to attach fixed labels to this metric. Metrics
+	// with the same fully-qualified name must have the same label names in
+	// their ConstLabels.
 	//
-	// Note that in most cases, labels have a value that varies during the
-	// lifetime of a process. Those labels are usually managed with a
-	// HistogramVec. ConstLabels serve only special purposes. One is for the
-	// special case where the value of a label does not change during the
-	// lifetime of a process, e.g. if the revision of the running binary is
-	// put into a label. Another, more advanced purpose is if more than one
-	// Collector needs to collect Histograms with the same fully-qualified
-	// name. In that case, those Summaries must differ in the values of
-	// their ConstLabels. See the Collector examples.
-	//
-	// If the value of a label never changes (not even between binaries),
-	// that label most likely should not be a label at all (but part of the
-	// metric name).
+	// ConstLabels are only used rarely. In particular, do not use them to
+	// attach the same labels to all your metrics. Those use cases are
+	// better covered by target labels set by the scraping Prometheus
+	// server, or by one specific metric (e.g. a build_info or a
+	// machine_role metric). See also
+	// https://prometheus.io/docs/instrumenting/writing_exporters/#target-labels-not-static-scraped-labels
 	ConstLabels Labels
 
 	// Buckets defines the buckets into which observations are counted. Each
@@ -155,6 +186,10 @@ type HistogramOpts struct {
 
 // NewHistogram creates a new Histogram based on the provided HistogramOpts. It
 // panics if the buckets in HistogramOpts are not in strictly increasing order.
+//
+// The returned implementation also implements ExemplarObserver. It is safe to
+// perform the corresponding type assertion. Exemplars are tracked separately
+// for each bucket.
 func NewHistogram(opts HistogramOpts) Histogram {
 	return newHistogram(
 		NewDesc(
@@ -169,7 +204,7 @@ func NewHistogram(opts HistogramOpts) Histogram {
 
 func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
 	if len(desc.variableLabels) != len(labelValues) {
-		panic(errInconsistentCardinality)
+		panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels, labelValues))
 	}
 
 	for _, n := range desc.variableLabels {
@@ -190,7 +225,9 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 	h := &histogram{
 		desc:        desc,
 		upperBounds: opts.Buckets,
-		labelPairs:  makeLabelPairs(desc, labelValues),
+		labelPairs:  MakeLabelPairs(desc, labelValues),
+		counts:      [2]*histogramCounts{{}, {}},
+		now:         time.Now,
 	}
 	for i, upperBound := range h.upperBounds {
 		if i < len(h.upperBounds)-1 {
@@ -207,30 +244,60 @@ func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogr
 			}
 		}
 	}
-	// Finally we know the final length of h.upperBounds and can make counts.
-	h.counts = make([]uint64, len(h.upperBounds))
+	// Finally we know the final length of h.upperBounds and can make buckets
+	// for both counts as well as exemplars:
+	h.counts[0].buckets = make([]uint64, len(h.upperBounds))
+	h.counts[1].buckets = make([]uint64, len(h.upperBounds))
+	h.exemplars = make([]atomic.Value, len(h.upperBounds)+1)
 
 	h.init(h) // Init self-collection.
 	return h
 }
 
-type histogram struct {
+type histogramCounts struct {
 	// sumBits contains the bits of the float64 representing the sum of all
 	// observations. sumBits and count have to go first in the struct to
 	// guarantee alignment for atomic operations.
 	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
 	sumBits uint64
 	count   uint64
+	buckets []uint64
+}
 
-	selfCollector
-	// Note that there is no mutex required.
+type histogram struct {
+	// countAndHotIdx enables lock-free writes with use of atomic updates.
+	// The most significant bit is the hot index [0 or 1] of the count field
+	// below. Observe calls update the hot one. All remaining bits count the
+	// number of Observe calls. Observe starts by incrementing this counter,
+	// and finish by incrementing the count field in the respective
+	// histogramCounts, as a marker for completion.
+	//
+	// Calls of the Write method (which are non-mutating reads from the
+	// perspective of the histogram) swap the hot–cold under the writeMtx
+	// lock. A cooldown is awaited (while locked) by comparing the number of
+	// observations with the initiation count. Once they match, then the
+	// last observation on the now cool one has completed. All cool fields must
+	// be merged into the new hot before releasing writeMtx.
+	//
+	// Fields with atomic access first! See alignment constraint:
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG
+	countAndHotIdx uint64
 
+	selfCollector
 	desc     *Desc
+	writeMtx sync.Mutex // Only used in the Write method.
 
-	upperBounds []float64
-	counts      []uint64
+	// Two counts, one is "hot" for lock-free observations, the other is
+	// "cold" for writing out a dto.Metric. It has to be an array of
+	// pointers to guarantee 64bit alignment of the histogramCounts, see
+	// http://golang.org/pkg/sync/atomic/#pkg-note-BUG.
+	counts [2]*histogramCounts
 
+	upperBounds []float64
 	labelPairs  []*dto.LabelPair
+	exemplars   []atomic.Value // One more than buckets (to include +Inf), each a *dto.Exemplar.
+
+	now func() time.Time // To mock out time.Now() for testing.
 }
 
 func (h *histogram) Desc() *Desc {
@@ -238,6 +305,89 @@ func (h *histogram) Desc() *Desc {
 }
 
 func (h *histogram) Observe(v float64) {
+	h.observe(v, h.findBucket(v))
+}
+
+func (h *histogram) ObserveWithExemplar(v float64, e Labels) {
+	i := h.findBucket(v)
+	h.observe(v, i)
+	h.updateExemplar(v, i, e)
+}
+
+func (h *histogram) Write(out *dto.Metric) error {
+	// For simplicity, we protect this whole method by a mutex. It is not in
+	// the hot path, i.e. Observe is called much more often than Write. The
+	// complication of making Write lock-free isn't worth it, if possible at
+	// all.
+	h.writeMtx.Lock()
+	defer h.writeMtx.Unlock()
+
+	// Adding 1<<63 switches the hot index (from 0 to 1 or from 1 to 0)
+	// without touching the count bits. See the struct comments for a full
+	// description of the algorithm.
+	n := atomic.AddUint64(&h.countAndHotIdx, 1<<63)
+	// count is contained unchanged in the lower 63 bits.
+	count := n & ((1 << 63) - 1)
+	// The most significant bit tells us which counts is hot. The complement
+	// is thus the cold one.
+	hotCounts := h.counts[n>>63]
+	coldCounts := h.counts[(^n)>>63]
+
+	// Await cooldown.
+	for count != atomic.LoadUint64(&coldCounts.count) {
+		runtime.Gosched() // Let observations get work done.
+	}
+
+	his := &dto.Histogram{
+		Bucket:      make([]*dto.Bucket, len(h.upperBounds)),
+		SampleCount: proto.Uint64(count),
+		SampleSum:   proto.Float64(math.Float64frombits(atomic.LoadUint64(&coldCounts.sumBits))),
+	}
+	var cumCount uint64
+	for i, upperBound := range h.upperBounds {
+		cumCount += atomic.LoadUint64(&coldCounts.buckets[i])
+		his.Bucket[i] = &dto.Bucket{
+			CumulativeCount: proto.Uint64(cumCount),
+			UpperBound:      proto.Float64(upperBound),
+		}
+		if e := h.exemplars[i].Load(); e != nil {
+			his.Bucket[i].Exemplar = e.(*dto.Exemplar)
+		}
+	}
+	// If there is an exemplar for the +Inf bucket, we have to add that bucket explicitly.
+	if e := h.exemplars[len(h.upperBounds)].Load(); e != nil {
+		b := &dto.Bucket{
+			CumulativeCount: proto.Uint64(count),
+			UpperBound:      proto.Float64(math.Inf(1)),
+			Exemplar:        e.(*dto.Exemplar),
+		}
+		his.Bucket = append(his.Bucket, b)
+	}
+
+	out.Histogram = his
+	out.Label = h.labelPairs
+
+	// Finally add all the cold counts to the new hot counts and reset the cold counts.
+	atomic.AddUint64(&hotCounts.count, count)
+	atomic.StoreUint64(&coldCounts.count, 0)
+	for {
+		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
+		newBits := math.Float64bits(math.Float64frombits(oldBits) + his.GetSampleSum())
+		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
+			atomic.StoreUint64(&coldCounts.sumBits, 0)
+			break
+		}
+	}
+	for i := range h.upperBounds {
+		atomic.AddUint64(&hotCounts.buckets[i], atomic.LoadUint64(&coldCounts.buckets[i]))
+		atomic.StoreUint64(&coldCounts.buckets[i], 0)
+	}
+	return nil
+}
+
+// findBucket returns the index of the bucket for the provided value, or
+// len(h.upperBounds) for the +Inf bucket.
+func (h *histogram) findBucket(v float64) int {
 	// TODO(beorn7): For small numbers of buckets (<30), a linear search is
 	// slightly faster than the binary search. If we really care, we could
 	// switch from one search strategy to the other depending on the number
@@ -247,38 +397,43 @@ func (h *histogram) Observe(v float64) {
 	// 11 buckets: 38.3 ns/op linear - binary 48.7 ns/op
 	// 100 buckets: 78.1 ns/op linear - binary 54.9 ns/op
 	// 300 buckets: 154 ns/op linear - binary 61.6 ns/op
-	i := sort.SearchFloat64s(h.upperBounds, v)
-	if i < len(h.counts) {
-		atomic.AddUint64(&h.counts[i], 1)
+	return sort.SearchFloat64s(h.upperBounds, v)
+}
+
+// observe is the implementation for Observe without the findBucket part.
+func (h *histogram) observe(v float64, bucket int) {
+	// We increment h.countAndHotIdx so that the counter in the lower
+	// 63 bits gets incremented. At the same time, we get the new value
+	// back, which we can use to find the currently-hot counts.
+	n := atomic.AddUint64(&h.countAndHotIdx, 1)
+	hotCounts := h.counts[n>>63]
+
+	if bucket < len(h.upperBounds) {
+		atomic.AddUint64(&hotCounts.buckets[bucket], 1)
 	}
-	atomic.AddUint64(&h.count, 1)
 	for {
-		oldBits := atomic.LoadUint64(&h.sumBits)
+		oldBits := atomic.LoadUint64(&hotCounts.sumBits)
 		newBits := math.Float64bits(math.Float64frombits(oldBits) + v)
-		if atomic.CompareAndSwapUint64(&h.sumBits, oldBits, newBits) {
+		if atomic.CompareAndSwapUint64(&hotCounts.sumBits, oldBits, newBits) {
 			break
 		}
 	}
+	// Increment count last as we take it as a signal that the observation
+	// is complete.
+	atomic.AddUint64(&hotCounts.count, 1)
 }
 
-func (h *histogram) Write(out *dto.Metric) error {
-	his := &dto.Histogram{}
-	buckets := make([]*dto.Bucket, len(h.upperBounds))
-
-	his.SampleSum = proto.Float64(math.Float64frombits(atomic.LoadUint64(&h.sumBits)))
-	his.SampleCount = proto.Uint64(atomic.LoadUint64(&h.count))
-	var count uint64
-	for i, upperBound := range h.upperBounds {
-		count += atomic.LoadUint64(&h.counts[i])
-		buckets[i] = &dto.Bucket{
-			CumulativeCount: proto.Uint64(count),
-			UpperBound:      proto.Float64(upperBound),
+// updateExemplar replaces the exemplar for the provided bucket. With empty
+// labels, it's a no-op. It panics if any of the labels is invalid.
+func (h *histogram) updateExemplar(v float64, bucket int, l Labels) {
+	if l == nil {
+		return
 	}
+	e, err := newExemplar(v, h.now(), l)
+	if err != nil {
+		panic(err)
 	}
-	his.Bucket = buckets
-	out.Histogram = his
-	out.Label = h.labelPairs
-	return nil
+	h.exemplars[bucket].Store(e)
 }
 
 // HistogramVec is a Collector that bundles a set of Histograms that all share the
@@ -287,7 +442,7 @@ func (h *histogram) Write(out *dto.Metric) error {
 // (e.g. HTTP request latencies, partitioned by status code and method). Create
 // instances with NewHistogramVec.
 type HistogramVec struct {
-	*metricVec
+	*MetricVec
 }
 
 // NewHistogramVec creates a new HistogramVec based on the provided HistogramOpts and
@@ -300,14 +455,14 @@ func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec {
 		opts.ConstLabels,
 	)
 	return &HistogramVec{
-		metricVec: newMetricVec(desc, func(lvs ...string) Metric {
+		MetricVec: NewMetricVec(desc, func(lvs ...string) Metric {
 			return newHistogram(desc, opts, lvs...)
 		}),
 	}
 }
 
 // GetMetricWithLabelValues returns the Histogram for the given slice of label
-// values (same order as the VariableLabels in Desc). If that combination of
+// values (same order as the variable labels in Desc). If that combination of
 // label values is accessed for the first time, a new Histogram is created.
 //
 // It is possible to call this method without using the returned Histogram to only
@@ -322,7 +477,7 @@ func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec {
 // example.
 //
 // An error is returned if the number of label values is not the same as the
-// number of VariableLabels in Desc.
+// number of variable labels in Desc (minus any curried labels).
 //
 // Note that for more than one label value, this method is prone to mistakes
 // caused by an incorrect order of arguments. Consider GetMetricWith(Labels) as
@@ -330,8 +485,8 @@ func NewHistogramVec(opts HistogramOpts, labelNames []string) *HistogramVec {
 // latter has a much more readable (albeit more verbose) syntax, but it comes
 // with a performance overhead (for creating and processing the Labels map).
 // See also the GaugeVec example.
-func (m *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
-	metric, err := m.metricVec.getMetricWithLabelValues(lvs...)
+func (v *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error) {
+	metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -339,19 +494,19 @@ func (m *HistogramVec) GetMetricWithLabelValues(lvs ...string) (Observer, error)
 }
 
 // GetMetricWith returns the Histogram for the given Labels map (the label names
-// must match those of the VariableLabels in Desc). If that label map is
+// must match those of the variable labels in Desc). If that label map is
 // accessed for the first time, a new Histogram is created. Implications of
 // creating a Histogram without using it and keeping the Histogram for later use
 // are the same as for GetMetricWithLabelValues.
 //
 // An error is returned if the number and names of the Labels are inconsistent
-// with those of the VariableLabels in Desc.
+// with those of the variable labels in Desc (minus any curried labels).
 //
 // This method is used for the same purpose as
 // GetMetricWithLabelValues(...string). See there for pros and cons of the two
 // methods.
-func (m *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
-	metric, err := m.metricVec.getMetricWith(labels)
+func (v *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
+	metric, err := v.MetricVec.GetMetricWith(labels)
 	if metric != nil {
 		return metric.(Observer), err
 	}
@@ -359,18 +514,57 @@ func (m *HistogramVec) GetMetricWith(labels Labels) (Observer, error) {
 }
 
 // WithLabelValues works as GetMetricWithLabelValues, but panics where
-// GetMetricWithLabelValues would have returned an error. By not returning an
-// error, WithLabelValues allows shortcuts like
+// GetMetricWithLabelValues would have returned an error. Not returning an
+// error allows shortcuts like
 //     myVec.WithLabelValues("404", "GET").Observe(42.21)
-func (m *HistogramVec) WithLabelValues(lvs ...string) Observer {
-	return m.metricVec.withLabelValues(lvs...).(Observer)
+func (v *HistogramVec) WithLabelValues(lvs ...string) Observer {
+	h, err := v.GetMetricWithLabelValues(lvs...)
+	if err != nil {
+		panic(err)
+	}
+	return h
 }
 
-// With works as GetMetricWith, but panics where GetMetricWithLabels would have
-// returned an error. By not returning an error, With allows shortcuts like
-//     myVec.With(Labels{"code": "404", "method": "GET"}).Observe(42.21)
-func (m *HistogramVec) With(labels Labels) Observer {
-	return m.metricVec.with(labels).(Observer)
+// With works as GetMetricWith but panics where GetMetricWithLabels would have
+// returned an error. Not returning an error allows shortcuts like
+//     myVec.With(prometheus.Labels{"code": "404", "method": "GET"}).Observe(42.21)
+func (v *HistogramVec) With(labels Labels) Observer {
+	h, err := v.GetMetricWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return h
+}
+
+// CurryWith returns a vector curried with the provided labels, i.e. the
+// returned vector has those labels pre-set for all labeled operations performed
+// on it. The cardinality of the curried vector is reduced accordingly. The
+// order of the remaining labels stays the same (just with the curried labels
+// taken out of the sequence – which is relevant for the
+// (GetMetric)WithLabelValues methods). It is possible to curry a curried
+// vector, but only with labels not yet used for currying before.
+//
+// The metrics contained in the HistogramVec are shared between the curried and
+// uncurried vectors. They are just accessed differently. Curried and uncurried
+// vectors behave identically in terms of collection. Only one must be
+// registered with a given registry (usually the uncurried version). The Reset
+// method deletes all metrics, even if called on a curried vector.
+func (v *HistogramVec) CurryWith(labels Labels) (ObserverVec, error) {
+	vec, err := v.MetricVec.CurryWith(labels)
+	if vec != nil {
+		return &HistogramVec{vec}, err
+	}
+	return nil, err
+}
+
+// MustCurryWith works as CurryWith but panics where CurryWith would have
+// returned an error.
+func (v *HistogramVec) MustCurryWith(labels Labels) ObserverVec {
+	vec, err := v.CurryWith(labels)
+	if err != nil {
+		panic(err)
+	}
+	return vec
 }
 
 type constHistogram struct {
@@ -422,7 +616,7 @@ func (h *constHistogram) Write(out *dto.Metric) error {
 // bucket.
 //
 // NewConstHistogram returns an error if the length of labelValues is not
-// consistent with the variable labels in Desc.
+// consistent with the variable labels in Desc or if Desc is invalid.
 func NewConstHistogram(
 	desc *Desc,
 	count uint64,
@@ -430,6 +624,9 @@ func NewConstHistogram(
 	buckets map[float64]uint64,
 	labelValues ...string,
 ) (Metric, error) {
+	if desc.err != nil {
+		return nil, desc.err
+	}
 	if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
 		return nil, err
 	}
@@ -438,12 +635,12 @@ func NewConstHistogram(
 		count:      count,
 		sum:        sum,
 		buckets:    buckets,
-		labelPairs: makeLabelPairs(desc, labelValues),
+		labelPairs: MakeLabelPairs(desc, labelValues),
 	}, nil
 }
 
 // MustNewConstHistogram is a version of NewConstHistogram that panics where
-// NewConstMetric would have returned an error.
+// NewConstHistogram would have returned an error.
 func MustNewConstHistogram(
 	desc *Desc,
 	count uint64,