[#44] Expose metrics

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

metrics/service.go

@@ -0,0 +1,44 @@
+package metrics
+
+import (
+	"context"
+	"net/http"
+
+	"go.uber.org/zap"
+)
+
+// Service serves metrics.
+type Service struct {
+	*http.Server
+	enabled     bool
+	log         *zap.Logger
+	serviceType string
+}
+
+// Config is a params to configure service.
+type Config struct {
+	Address string
+	Enabled bool
+}
+
+// Start runs http service with the exposed endpoint on the configured port.
+func (ms *Service) Start() {
+	if ms.enabled {
+		ms.log.Info("service is running", zap.String("endpoint", ms.Addr))
+		err := ms.ListenAndServe()
+		if err != nil && err != http.ErrServerClosed {
+			ms.log.Warn("service couldn't start on configured port")
+		}
+	} else {
+		ms.log.Info("service hasn't started since it's disabled")
+	}
+}
+
+// ShutDown stops the service.
+func (ms *Service) ShutDown(ctx context.Context) {
+	ms.log.Info("shutting down service", zap.String("endpoint", ms.Addr))
+	err := ms.Shutdown(ctx)
+	if err != nil {
+		ms.log.Panic("can't shut down service", zap.Error(err))
+	}
+}