88 lines
2.8 KiB
Go
88 lines
2.8 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/prometheus/client_golang/prometheus"
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)
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var (
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allocDesc = prometheus.NewDesc(
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prometheus.BuildFQName("", "memstats", "alloc_bytes"),
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"bytes allocated and still in use",
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nil, nil,
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)
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totalAllocDesc = prometheus.NewDesc(
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prometheus.BuildFQName("", "memstats", "total_alloc_bytes"),
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"bytes allocated (even if freed)",
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nil, nil,
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)
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numGCDesc = prometheus.NewDesc(
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prometheus.BuildFQName("", "memstats", "num_gc_total"),
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"number of GCs run",
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nil, nil,
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)
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)
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// MemStatsCollector is an example for a custom Collector that solves the
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// problem of feeding into multiple metrics at the same time. The
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// runtime.ReadMemStats should happen only once, and then the results need to be
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// fed into a number of separate Metrics. In this example, only a few of the
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// values reported by ReadMemStats are used. For each, there is a Desc provided
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// as a var, so the MemStatsCollector itself needs nothing else in the
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// struct. Only the methods need to be implemented.
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type MemStatsCollector struct{}
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// Describe just sends the three Desc objects for the Metrics we intend to
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// collect.
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func (_ MemStatsCollector) Describe(ch chan<- *prometheus.Desc) {
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ch <- allocDesc
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ch <- totalAllocDesc
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ch <- numGCDesc
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}
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// Collect does the trick by calling ReadMemStats once and then constructing
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// three different Metrics on the fly.
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func (_ MemStatsCollector) Collect(ch chan<- prometheus.Metric) {
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var ms runtime.MemStats
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runtime.ReadMemStats(&ms)
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ch <- prometheus.MustNewConstMetric(
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allocDesc,
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prometheus.GaugeValue,
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float64(ms.Alloc),
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)
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ch <- prometheus.MustNewConstMetric(
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totalAllocDesc,
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prometheus.GaugeValue,
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float64(ms.TotalAlloc),
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)
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ch <- prometheus.MustNewConstMetric(
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numGCDesc,
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prometheus.CounterValue,
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float64(ms.NumGC),
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)
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// To avoid new allocations on each collection, you could also keep
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// metric objects around and return the same objects each time, just
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// with new values set.
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}
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func ExampleCollector_memstats() {
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prometheus.MustRegister(&MemStatsCollector{})
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// Since we are dealing with custom Collector implementations, it might
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// be a good idea to enable the collect checks in the registry.
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prometheus.EnableCollectChecks(true)
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}
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