// Copyright 2014 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 ( "expvar" "fmt" "sort" "strings" dto "github.com/prometheus/client_model/go" "github.com/prometheus/client_golang/prometheus" ) func ExampleNewExpvarCollector() { expvarCollector := prometheus.NewExpvarCollector(map[string]*prometheus.Desc{ "memstats": prometheus.NewDesc( "expvar_memstats", "All numeric memstats as one metric family. Not a good role-model, actually... ;-)", []string{"type"}, nil, ), "lone-int": prometheus.NewDesc( "expvar_lone_int", "Just an expvar int as an example.", nil, nil, ), "http-request-map": prometheus.NewDesc( "expvar_http_request_total", "How many http requests processed, partitioned by status code and http method.", []string{"code", "method"}, nil, ), }) prometheus.MustRegister(expvarCollector) // The Prometheus part is done here. But to show that this example is // doing anything, we have to manually export something via expvar. In // real-life use-cases, some library would already have exported via // expvar what we want to re-export as Prometheus metrics. expvar.NewInt("lone-int").Set(42) expvarMap := expvar.NewMap("http-request-map") var ( expvarMap1, expvarMap2 expvar.Map expvarInt11, expvarInt12, expvarInt21, expvarInt22 expvar.Int ) expvarMap1.Init() expvarMap2.Init() expvarInt11.Set(3) expvarInt12.Set(13) expvarInt21.Set(11) expvarInt22.Set(212) expvarMap1.Set("POST", &expvarInt11) expvarMap1.Set("GET", &expvarInt12) expvarMap2.Set("POST", &expvarInt21) expvarMap2.Set("GET", &expvarInt22) expvarMap.Set("404", &expvarMap1) expvarMap.Set("200", &expvarMap2) // Results in the following expvar map: // "http-request-count": {"200": {"POST": 11, "GET": 212}, "404": {"POST": 3, "GET": 13}} // Let's see what the scrape would yield, but exclude the memstats metrics. metricStrings := []string{} metric := dto.Metric{} metricChan := make(chan prometheus.Metric) go func() { expvarCollector.Collect(metricChan) close(metricChan) }() for m := range metricChan { if !strings.Contains(m.Desc().String(), "expvar_memstats") { metric.Reset() m.Write(&metric) metricStrings = append(metricStrings, metric.String()) } } sort.Strings(metricStrings) for _, s := range metricStrings { fmt.Println(strings.TrimRight(s, " ")) } // Output: // label:<name:"code" value:"200" > label:<name:"method" value:"GET" > untyped:<value:212 > // label:<name:"code" value:"200" > label:<name:"method" value:"POST" > untyped:<value:11 > // label:<name:"code" value:"404" > label:<name:"method" value:"GET" > untyped:<value:13 > // label:<name:"code" value:"404" > label:<name:"method" value:"POST" > untyped:<value:3 > // untyped:<value:42 > }