func init() {
	prometheus.MustRegister(readCounter)
	prometheus.MustRegister(writeCounter)
	prometheus.MustRegister(expireCounter)
	prometheus.MustRegister(watchRequests)
	prometheus.MustRegister(watcherCount)
}

func ExampleCollector_clustermanager() {
	workerDB := NewClusterManager("db")
	workerCA := NewClusterManager("ca")
	prometheus.MustRegister(workerDB)
	prometheus.MustRegister(workerCA)

	// Since we are dealing with custom Collector implementations, it might
	// be a good idea to enable the collect checks in the registry.
	prometheus.EnableCollectChecks(true)
}

func ExampleCounterVec() {
	binaryVersion := flag.String("environment", "test", "Execution environment: test, staging, production.")
	flag.Parse()

	httpReqs := prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name:        "http_requests_total",
			Help:        "How many HTTP requests processed, partitioned by status code and HTTP method.",
			ConstLabels: prometheus.Labels{"env": *binaryVersion},
		},
		[]string{"code", "method"},
	)
	prometheus.MustRegister(httpReqs)

	httpReqs.WithLabelValues("404", "POST").Add(42)

	// If you have to access the same set of labels very frequently, it
	// might be good to retrieve the metric only once and keep a handle to
	// it. But beware of deletion of that metric, see below!
	m := httpReqs.WithLabelValues("200", "GET")
	for i := 0; i < 1000000; i++ {
		m.Inc()
	}
	// Delete a metric from the vector. If you have previously kept a handle
	// to that metric (as above), future updates via that handle will go
	// unseen (even if you re-create a metric with the same label set
	// later).
	httpReqs.DeleteLabelValues("200", "GET")
	// Same thing with the more verbose Labels syntax.
	httpReqs.Delete(prometheus.Labels{"method": "GET", "code": "200"})
}

func ExampleGaugeVec() {
	binaryVersion := flag.String("binary_version", "debug", "Version of the binary: debug, canary, production.")
	flag.Parse()

	opsQueued := prometheus.NewGaugeVec(
		prometheus.GaugeOpts{
			Namespace:   "our_company",
			Subsystem:   "blob_storage",
			Name:        "ops_queued",
			Help:        "Number of blob storage operations waiting to be processed, partitioned by user and type.",
			ConstLabels: prometheus.Labels{"binary_version": *binaryVersion},
		},
		[]string{
			// Which user has requested the operation?
			"user",
			// Of what type is the operation?
			"type",
		},
	)
	prometheus.MustRegister(opsQueued)

	// Increase a value using compact (but order-sensitive!) WithLabelValues().
	opsQueued.WithLabelValues("bob", "put").Add(4)
	// Increase a value with a map using WithLabels. More verbose, but order
	// doesn't matter anymore.
	opsQueued.With(prometheus.Labels{"type": "delete", "user": "alice"}).Inc()
}

func init() {
	prometheus.MustRegister(rangeCounter)
	prometheus.MustRegister(putCounter)
	prometheus.MustRegister(deleteCounter)
	prometheus.MustRegister(txnCounter)
	prometheus.MustRegister(keysGauge)
	prometheus.MustRegister(indexCompactionPauseDurations)
	prometheus.MustRegister(dbCompactionPauseDurations)
	prometheus.MustRegister(dbCompactionTotalDurations)
}

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 ExampleGauge() {
	opsQueued := prometheus.NewGauge(prometheus.GaugeOpts{
		Namespace: "our_company",
		Subsystem: "blob_storage",
		Name:      "ops_queued",
		Help:      "Number of blob storage operations waiting to be processed.",
	})
	prometheus.MustRegister(opsQueued)

	// 10 operations queued by the goroutine managing incoming requests.
	opsQueued.Add(10)
	// A worker goroutine has picked up a waiting operation.
	opsQueued.Dec()
	// And once more...
	opsQueued.Dec()
}

func init() {
	prometheus.MustRegister(rangeCounter)
	prometheus.MustRegister(putCounter)
	prometheus.MustRegister(deleteCounter)
	prometheus.MustRegister(txnCounter)
	prometheus.MustRegister(keysGauge)
	prometheus.MustRegister(watchStreamGauge)
	prometheus.MustRegister(watcherGauge)
	prometheus.MustRegister(slowWatcherGauge)
	prometheus.MustRegister(totalEventsCounter)
	prometheus.MustRegister(pendingEventsGauge)
	prometheus.MustRegister(indexCompactionPauseDurations)
	prometheus.MustRegister(dbCompactionPauseDurations)
	prometheus.MustRegister(dbCompactionTotalDurations)
	prometheus.MustRegister(dbTotalSize)
}

func init() {
	prometheus.MustRegister(saveDurations)
}

func init() {
	prometheus.MustRegister(saveDurations)
	prometheus.MustRegister(marshallingDurations)
}

func init() {
	prometheus.MustRegister(proposeDurations)
	prometheus.MustRegister(proposePending)
	prometheus.MustRegister(proposeFailed)
	prometheus.MustRegister(fileDescriptorUsed)
}

func init() {
	prometheus.MustRegister(caseTotalCounter)
	prometheus.MustRegister(caseFailedTotalCounter)
	prometheus.MustRegister(roundTotalCounter)
	prometheus.MustRegister(roundFailedTotalCounter)
}

func init() {
	prometheus.MustRegister(incomingEvents)
	prometheus.MustRegister(failedEvents)
	prometheus.MustRegister(successfulEventsHandlingTime)
}

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 >
}

func ExampleCollector_memstats() {
	prometheus.MustRegister(&MemStatsCollector{})
	// Since we are dealing with custom Collector implementations, it might
	// be a good idea to enable the collect checks in the registry.
	prometheus.EnableCollectChecks(true)
}