70 lines
2.0 KiB
Go
70 lines
2.0 KiB
Go
// Copyright 2014 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package prometheus_test
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import (
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"runtime"
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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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)
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func NewCallbackMetric(desc *prometheus.Desc, callback func() float64) *CallbackMetric {
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result := &CallbackMetric{desc: desc, callback: callback}
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result.Init(result) // Initialize the SelfCollector.
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return result
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}
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// TODO: Come up with a better example.
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// CallbackMetric is an example for a user-defined Metric that exports the
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// result of a function call as a metric of type "untyped" without any
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// labels. It uses SelfCollector to turn the Metric into a Collector so that it
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// can be registered with Prometheus.
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//
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// Note that this example is pretty much academic as the prometheus package
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// already provides an UntypedFunc type.
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type CallbackMetric struct {
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prometheus.SelfCollector
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desc *prometheus.Desc
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callback func() float64
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}
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func (cm *CallbackMetric) Desc() *prometheus.Desc {
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return cm.desc
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}
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func (cm *CallbackMetric) Write(m *dto.Metric) error {
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m.Untyped = &dto.Untyped{Value: proto.Float64(cm.callback())}
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return nil
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}
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func ExampleSelfCollector() {
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m := NewCallbackMetric(
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prometheus.NewDesc(
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"runtime_goroutines_count",
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"Total number of goroutines that currently exist.",
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nil, nil, // No labels, these must be nil.
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),
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func() float64 {
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return float64(runtime.NumGoroutine())
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},
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)
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prometheus.MustRegister(m)
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}
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