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- // 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"
- "github.com/golang/protobuf/proto"
- dto "github.com/prometheus/client_model/go"
- )
- // ValueType is an enumeration of metric types that represent a simple value.
- type ValueType int
- // Possible values for the ValueType enum.
- const (
- _ ValueType = iota
- CounterValue
- GaugeValue
- UntypedValue
- )
- // 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, 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.
- func NewConstMetric(desc *Desc, valueType ValueType, value float64, labelValues ...string) (Metric, error) {
- if err := validateLabelValues(labelValues, len(desc.variableLabels)); err != nil {
- return nil, err
- }
- return &constMetric{
- desc: desc,
- valType: valueType,
- val: value,
- labelPairs: makeLabelPairs(desc, labelValues),
- }, 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
- valType ValueType
- val float64
- labelPairs []*dto.LabelPair
- }
- func (m *constMetric) Desc() *Desc {
- return m.desc
- }
- func (m *constMetric) Write(out *dto.Metric) error {
- return populateMetric(m.valType, m.val, m.labelPairs, out)
- }
- func populateMetric(
- t ValueType,
- v float64,
- labelPairs []*dto.LabelPair,
- m *dto.Metric,
- ) error {
- m.Label = labelPairs
- switch t {
- case CounterValue:
- m.Counter = &dto.Counter{Value: proto.Float64(v)}
- 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
- }
- 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, n := range desc.variableLabels {
- labelPairs = append(labelPairs, &dto.LabelPair{
- Name: proto.String(n),
- Value: proto.String(labelValues[i]),
- })
- }
- labelPairs = append(labelPairs, desc.constLabelPairs...)
- sort.Sort(labelPairSorter(labelPairs))
- return labelPairs
- }
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