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// Copyright 2020 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package prometheus_test
import (
"fmt"
"google.golang.org/protobuf/proto"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/client_golang/prometheus"
)
// Info implements an info pseudo-metric, which is modeled as a Gauge that
// always has a value of 1. In practice, you would just use a Gauge directly,
// but for this example, we pretend it would be useful to have a “native”
// implementation.
type Info struct {
desc *prometheus.Desc
labelPairs []*dto.LabelPair
}
func (i Info) Desc() *prometheus.Desc {
return i.desc
}
func (i Info) Write(out *dto.Metric) error {
out.Label = i.labelPairs
out.Gauge = &dto.Gauge{Value: proto.Float64(1)}
return nil
}
// InfoVec is the vector version for Info. As an info metric never changes, we
// wouldn't really need to wrap GetMetricWithLabelValues and GetMetricWith
// because Info has no additional methods compared to the vanilla Metric that
// the unwrapped MetricVec methods return. However, to demonstrate all there is
// to do to fully implement a vector for a custom Metric implementation, we do
// it in this example anyway.
type InfoVec struct {
*prometheus.MetricVec
}
func NewInfoVec(name, help string, labelNames []string) *InfoVec {
desc := prometheus.NewDesc(name, help, labelNames, nil)
return &InfoVec{
MetricVec: prometheus.NewMetricVec(desc, func(lvs ...string) prometheus.Metric {
if len(lvs) != len(labelNames) {
panic("inconsistent label cardinality")
}
return Info{desc: desc, labelPairs: prometheus.MakeLabelPairs(desc, lvs)}
}),
}
}
func (v *InfoVec) GetMetricWithLabelValues(lvs ...string) (Info, error) {
metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...)
return metric.(Info), err
}
func (v *InfoVec) GetMetricWith(labels prometheus.Labels) (Info, error) {
metric, err := v.MetricVec.GetMetricWith(labels)
return metric.(Info), err
}
func (v *InfoVec) WithLabelValues(lvs ...string) Info {
i, err := v.GetMetricWithLabelValues(lvs...)
if err != nil {
panic(err)
}
return i
}
func (v *InfoVec) With(labels prometheus.Labels) Info {
i, err := v.GetMetricWith(labels)
if err != nil {
panic(err)
}
return i
}
func (v *InfoVec) CurryWith(labels prometheus.Labels) (*InfoVec, error) {
vec, err := v.MetricVec.CurryWith(labels)
if vec != nil {
return &InfoVec{vec}, err
}
return nil, err
}
func (v *InfoVec) MustCurryWith(labels prometheus.Labels) *InfoVec {
vec, err := v.CurryWith(labels)
if err != nil {
panic(err)
}
return vec
}
func ExampleMetricVec() {
infoVec := NewInfoVec(
"library_version_info",
"Versions of the libraries used in this binary.",
[]string{"library", "version"},
)
infoVec.WithLabelValues("prometheus/client_golang", "1.7.1")
infoVec.WithLabelValues("k8s.io/client-go", "0.18.8")
// Just for demonstration, let's check the state of the InfoVec by
// registering it with a custom registry and then let it collect the
// metrics.
reg := prometheus.NewRegistry()
reg.MustRegister(infoVec)
metricFamilies, err := reg.Gather()
if err != nil || len(metricFamilies) != 1 {
panic("unexpected behavior of custom test registry")
}
fmt.Println(toNormalizedJSON(metricFamilies[0]))
// Output:
// {"name":"library_version_info","help":"Versions of the libraries used in this binary.","type":"GAUGE","metric":[{"label":[{"name":"library","value":"k8s.io/client-go"},{"name":"version","value":"0.18.8"}],"gauge":{"value":1}},{"label":[{"name":"library","value":"prometheus/client_golang"},{"name":"version","value":"1.7.1"}],"gauge":{"value":1}}]}
}
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