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MetricVec was already exported in early versions of this library, but nobody really used it to implement vectors of custom Metric implementations. Now #796 has shown up with a fairly special use case for which I'd prefer a custom implementation of a special "auto-sampling histogram" outside of this library. Therefore, I'd like to reinstate support for creating vectors of custom Metric implementations. I played around for quite some while with the option of a separate package providing the tools one would need to create vectors of custom Metric implementations. However, with the current structure of the prometheus/client_golang/prometheus package, this leads to a lot of complications with circular dependencies. (The new package would need the primitives from the prometheus package, while the existing metric vectors like GaugeVec need to import the new vector package to not duplicate the implementation. Separating vector types from the main prometheus package is out of the question at this point because that would be a breaking change.) Signed-off-by: beorn7 <beorn@grafana.com>
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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. | ||
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| package prometheus_test | ||
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| import ( | ||
| //lint:ignore SA1019 Need to keep deprecated package for compatibility. | ||
| "fmt" | ||
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| "github.com/golang/protobuf/proto" | ||
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| dto "github.com/prometheus/client_model/go" | ||
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| "github.com/prometheus/client_golang/prometheus" | ||
| ) | ||
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| // 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 | ||
| } | ||
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| func (i Info) Desc() *prometheus.Desc { | ||
| return i.desc | ||
| } | ||
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| func (i Info) Write(out *dto.Metric) error { | ||
| out.Label = i.labelPairs | ||
| out.Gauge = &dto.Gauge{Value: proto.Float64(1)} | ||
| return nil | ||
| } | ||
|
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| // 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 | ||
| } | ||
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| 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)} | ||
| }), | ||
| } | ||
| } | ||
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| func (v *InfoVec) GetMetricWithLabelValues(lvs ...string) (Info, error) { | ||
| metric, err := v.MetricVec.GetMetricWithLabelValues(lvs...) | ||
| return metric.(Info), err | ||
| } | ||
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| func (v *InfoVec) GetMetricWith(labels prometheus.Labels) (Info, error) { | ||
| metric, err := v.MetricVec.GetMetricWith(labels) | ||
| return metric.(Info), err | ||
| } | ||
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| func (v *InfoVec) WithLabelValues(lvs ...string) Info { | ||
| i, err := v.GetMetricWithLabelValues(lvs...) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return i | ||
| } | ||
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| func (v *InfoVec) With(labels prometheus.Labels) Info { | ||
| i, err := v.GetMetricWith(labels) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return i | ||
| } | ||
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| 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 | ||
| } | ||
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| func (v *InfoVec) MustCurryWith(labels prometheus.Labels) *InfoVec { | ||
| vec, err := v.CurryWith(labels) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return vec | ||
| } | ||
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| func ExampleMetricVec() { | ||
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| infoVec := NewInfoVec( | ||
| "library_version_info", | ||
| "Versions of the libraries used in this binary.", | ||
| []string{"library", "version"}, | ||
| ) | ||
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| infoVec.WithLabelValues("prometheus/client_golang", "1.7.1") | ||
| infoVec.WithLabelValues("k8s.io/client-go", "0.18.8") | ||
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| // 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) | ||
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| metricFamilies, err := reg.Gather() | ||
| if err != nil || len(metricFamilies) != 1 { | ||
| panic("unexpected behavior of custom test registry") | ||
| } | ||
| fmt.Println(proto.MarshalTextString(metricFamilies[0])) | ||
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| // 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" | ||
| // > | ||
| // label: < | ||
| // name: "version" | ||
| // value: "0.18.8" | ||
| // > | ||
| // gauge: < | ||
| // value: 1 | ||
| // > | ||
| // > | ||
| // metric: < | ||
| // label: < | ||
| // name: "library" | ||
| // value: "prometheus/client_golang" | ||
| // > | ||
| // label: < | ||
| // name: "version" | ||
| // value: "1.7.1" | ||
| // > | ||
| // gauge: < | ||
| // value: 1 | ||
| // > | ||
| // > | ||
| } |
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