func ExampleSelfCollector() {
m := NewCallbackMetric(
prometheus.NewDesc(
"runtime_goroutines_count",
"Total number of goroutines that currently exist.",
nil, nil, // No labels, these must be nil.
),
func() float64 {
return float64(runtime.NumGoroutine())
},
)
prometheus.MustRegister(m)
}
func ExampleExpvarCollector() {
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.Index(m.Desc().String(), "expvar_memstats") == -1 {
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 >
}