Viewing: value.go
// Copyright 2014 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"
"sort"
"time"
"unicode/utf8"
"github.com/prometheus/client_golang/prometheus/internal"
dto "github.com/prometheus/client_model/go"
"google.golang.org/protobuf/proto"
"google.golang.org/protobuf/types/known/timestamppb"
)
// ValueType is an enumeration of metric types that represent a simple value.
type ValueType int
// Possible values for the ValueType enum. Use UntypedValue to mark a metric
// with an unknown type.
const (
_ ValueType = iota
CounterValue
GaugeValue
UntypedValue
)
var (
CounterMetricTypePtr = func() *dto.MetricType { d := dto.MetricType_COUNTER; return &d }()
GaugeMetricTypePtr = func() *dto.MetricType { d := dto.MetricType_GAUGE; return &d }()
UntypedMetricTypePtr = func() *dto.MetricType { d := dto.MetricType_UNTYPED; return &d }()
)
func (v ValueType) ToDTO() *dto.MetricType {
switch v {
case CounterValue:
return CounterMetricTypePtr
case GaugeValue:
return GaugeMetricTypePtr
default:
return UntypedMetricTypePtr
}
}
// valueFunc is a generic metric for simple values retrieved on collect time
// from a function. It implements Metric and Collector. Its effective type is
// determined by ValueType. This is a low-level building block used by the
// library to back the implementations of CounterFunc, GaugeFunc, and
// UntypedFunc.
type valueFunc struct {
selfCollector
desc *Desc
valType ValueType
function func() float64
labelPairs []*dto.LabelPair
}
// newValueFunc returns a newly allocated valueFunc with the given Desc and
// ValueType. 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 valueFunc is directly registered with Prometheus, the
// provided function must be concurrency-safe.
func newValueFunc(desc *Desc, valueType ValueType, function func() float64) *valueFunc {
result := &valueFunc{
desc: desc,
valType: valueType,
function: function,
labelPairs: MakeLabelPairs(desc, nil),
}
result.init(result)
return result
}
func (v *valueFunc) Desc() *Desc {
return v.desc
}
func (v *valueFunc) Write(out *dto.Metric) error {
return populateMetric(v.valType, v.function(), v.labelPairs, nil, out)
}
// NewConstMetric returns a metric with one fixed value that cannot be
// changed. Users of this package will not have much use for it in regular
// operations. However, when implementing custom Collectors, it is useful as a
// throw-away metric that is generated on the fly to send it to Prometheus in
// the Collect method. NewConstMetric returns an error if the length of
// labelValues is not consistent with the variable labels in Desc or if Desc is
// invalid.
func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error) {
if desc.err != nil {
return nil, desc.err
}
if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
return nil, err
}
metric := &dto.Metric{}
if err := populateMetric(valueType, value, MakeLabelPairs(desc, labelValues), nil, metric); err != nil {
return nil, err
}
return &constMetric{
desc: desc,
metric: metric,
}, nil
}
// MustNewConstMetric is a version of NewConstMetric that panics where
// NewConstMetric would have returned an error.
func MustNewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) Metric {
m, err := NewConstMetric(desc, valueType, value, labelValues...)
if err != nil {
panic(err)
}
return m
}
type constMetric struct {
desc *Desc
metric *dto.Metric
}
func (m *constMetric) Desc() *Desc {
return m.desc
}
func (m *constMetric) Write(out *dto.Metric) error {
out.Label = m.metric.Label
out.Counter = m.metric.Counter
out.Gauge = m.metric.Gauge
out.Untyped = m.metric.Untyped
return nil
}
func populateMetric(
t ValueType,
v float64,
labelPairs []*dto.LabelPair,
e *dto.Exemplar,
m *dto.Metric,
) error {
m.Label = labelPairs
switch t {
case CounterValue:
m.Counter = &dto.Counter{Value: proto.Float64(v), Exemplar: e}
case GaugeValue:
m.Gauge = &dto.Gauge{Value: proto.Float64(v)}
case UntypedValue:
m.Untyped = &dto.Untyped{Value: proto.Float64(v)}
default:
return fmt.Errorf("encountered unknown type %v", t)
}
return nil
}
// MakeLabelPairs is a helper function to create protobuf LabelPairs from the
// variable and constant labels in the provided Desc. The values for the
// variable labels are defined by the labelValues slice, which must be in the
// same order as the corresponding variable labels in the Desc.
//
// This function is only needed for custom Metric implementations. See MetricVec
// example.
func MakeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
totalLen := len(desc.variableLabels) + len(desc.constLabelPairs)
if totalLen == 0 {
// Super fast path.
return nil
}
if len(desc.variableLabels) == 0 {
// Moderately fast path.
return desc.constLabelPairs
}
labelPairs := make([]*dto.LabelPair, 0, totalLen)
for i, l := range desc.variableLabels {
labelPairs = append(labelPairs, &dto.LabelPair{
Name: proto.String(l.Name),
Value: proto.String(labelValues[i]),
})
}
labelPairs = append(labelPairs, desc.constLabelPairs...)
sort.Sort(internal.LabelPairSorter(labelPairs))
return labelPairs
}
// ExemplarMaxRunes is the max total number of runes allowed in exemplar labels.
const ExemplarMaxRunes = 128
// newExemplar creates a new dto.Exemplar from the provided values. An error is
// returned if any of the label names or values are invalid or if the total
// number of runes in the label names and values exceeds ExemplarMaxRunes.
func newExemplar(value float64, ts time.Time, l Labels) (*dto.Exemplar, error) {
e := &dto.Exemplar{}
e.Value = proto.Float64(value)
tsProto := timestamppb.New(ts)
if err := tsProto.CheckValid(); err != nil {
return nil, err
}
e.Timestamp = tsProto
labelPairs := make([]*dto.LabelPair, 0, len(l))
var runes int
for name, value := range l {
if !checkLabelName(name) {
return nil, fmt.Errorf("exemplar label name %q is invalid", name)
}
runes += utf8.RuneCountInString(name)
if !utf8.ValidString(value) {
return nil, fmt.Errorf("exemplar label value %q is not valid UTF-8", value)
}
runes += utf8.RuneCountInString(value)
labelPairs = append(labelPairs, &dto.LabelPair{
Name: proto.String(name),
Value: proto.String(value),
})
}
if runes > ExemplarMaxRunes {
return nil, fmt.Errorf("exemplar labels have %d runes, exceeding the limit of %d", runes, ExemplarMaxRunes)
}
e.Label = labelPairs
return e, nil
}
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