1// Copyright 2014 The Prometheus Authors 2// Licensed under the Apache License, Version 2.0 (the "License"); 3// you may not use this file except in compliance with the License. 4// You may obtain a copy of the License at 5// 6// http://www.apache.org/licenses/LICENSE-2.0 7// 8// Unless required by applicable law or agreed to in writing, software 9// distributed under the License is distributed on an "AS IS" BASIS, 10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 11// See the License for the specific language governing permissions and 12// limitations under the License. 13 14package prometheus_test 15 16import ( 17 "runtime" 18 19 "github.com/coreos/etcd/Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus" 20) 21 22var ( 23 allocDesc = prometheus.NewDesc( 24 prometheus.BuildFQName("", "memstats", "alloc_bytes"), 25 "bytes allocated and still in use", 26 nil, nil, 27 ) 28 totalAllocDesc = prometheus.NewDesc( 29 prometheus.BuildFQName("", "memstats", "total_alloc_bytes"), 30 "bytes allocated (even if freed)", 31 nil, nil, 32 ) 33 numGCDesc = prometheus.NewDesc( 34 prometheus.BuildFQName("", "memstats", "num_gc_total"), 35 "number of GCs run", 36 nil, nil, 37 ) 38) 39 40// MemStatsCollector is an example for a custom Collector that solves the 41// problem of feeding into multiple metrics at the same time. The 42// runtime.ReadMemStats should happen only once, and then the results need to be 43// fed into a number of separate Metrics. In this example, only a few of the 44// values reported by ReadMemStats are used. For each, there is a Desc provided 45// as a var, so the MemStatsCollector itself needs nothing else in the 46// struct. Only the methods need to be implemented. 47type MemStatsCollector struct{} 48 49// Describe just sends the three Desc objects for the Metrics we intend to 50// collect. 51func (_ MemStatsCollector) Describe(ch chan<- *prometheus.Desc) { 52 ch <- allocDesc 53 ch <- totalAllocDesc 54 ch <- numGCDesc 55} 56 57// Collect does the trick by calling ReadMemStats once and then constructing 58// three different Metrics on the fly. 59func (_ MemStatsCollector) Collect(ch chan<- prometheus.Metric) { 60 var ms runtime.MemStats 61 runtime.ReadMemStats(&ms) 62 ch <- prometheus.MustNewConstMetric( 63 allocDesc, 64 prometheus.GaugeValue, 65 float64(ms.Alloc), 66 ) 67 ch <- prometheus.MustNewConstMetric( 68 totalAllocDesc, 69 prometheus.GaugeValue, 70 float64(ms.TotalAlloc), 71 ) 72 ch <- prometheus.MustNewConstMetric( 73 numGCDesc, 74 prometheus.CounterValue, 75 float64(ms.NumGC), 76 ) 77 // To avoid new allocations on each collection, you could also keep 78 // metric objects around and return the same objects each time, just 79 // with new values set. 80} 81 82func ExampleCollector_memstats() { 83 prometheus.MustRegister(&MemStatsCollector{}) 84 // Since we are dealing with custom Collector implementations, it might 85 // be a good idea to enable the collect checks in the registry. 86 prometheus.EnableCollectChecks(true) 87} 88