[TrueCloudLab#26] Add billing metrics to separate registry

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

metrics/gate.go

@@ -0,0 +1,51 @@
+package metrics
+
+import (
+	"net/http"
+
+	"github.com/TrueCloudLab/frostfs-sdk-go/pool"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+const namespace = "frostfs_s3_gw"
+
+type StatisticScraper interface {
+	Statistic() pool.Statistic
+}
+
+type GateMetrics struct {
+	State   stateMetrics
+	Pool    poolMetricsCollector
+	Billing *billingMetrics
+}
+
+func NewGateMetrics(scraper StatisticScraper) *GateMetrics {
+	stateMetric := newStateMetrics()
+	stateMetric.register()
+
+	poolMetric := newPoolMetricsCollector(scraper)
+	poolMetric.register()
+
+	billingMetric := newBillingMetrics()
+	billingMetric.register()
+
+	return &GateMetrics{
+		State:   *stateMetric,
+		Pool:    *poolMetric,
+		Billing: billingMetric,
+	}
+}
+
+func (g *GateMetrics) Unregister() {
+	g.State.unregister()
+	prometheus.Unregister(&g.Pool)
+	g.Billing.unregister()
+}
+
+func (g *GateMetrics) Handler() http.Handler {
+	handler := http.NewServeMux()
+	handler.Handle("/", promhttp.Handler())
+	handler.Handle("/metrics/billing", promhttp.HandlerFor(g.Billing.registry, promhttp.HandlerOpts{}))
+	return handler
+}