[#1054] innerring: add epoch metric

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/innerring/innerring.go

@@ -28,6 +28,7 @@ import (
 	"github.com/nspcc-dev/neofs-node/pkg/innerring/processors/settlement"
 	auditSettlement "github.com/nspcc-dev/neofs-node/pkg/innerring/processors/settlement/audit"
 	timerEvent "github.com/nspcc-dev/neofs-node/pkg/innerring/timers"
+	"github.com/nspcc-dev/neofs-node/pkg/metrics"
 	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
 	auditWrapper "github.com/nspcc-dev/neofs-node/pkg/morph/client/audit/wrapper"
 	balanceWrapper "github.com/nspcc-dev/neofs-node/pkg/morph/client/balance/wrapper"
@@ -80,6 +81,9 @@ type (
 		netmapClient  *nmWrapper.Wrapper
 		persistate    *state.PersistentStorage
 
+		// metrics
+		metrics *metrics.InnerRingServiceMetrics
+
 		// notary configuration
 		feeConfig        *config.FeeConfig
 		mainNotaryConfig *notaryConfig
@@ -909,6 +913,11 @@ func New(ctx context.Context, log *zap.Logger, cfg *viper.Viper) (*Server, error
 		queueSize: cfg.GetUint32("workers.subnet"),
 	})
 
+	if cfg.GetString("metrics.address") != "" {
+		m := metrics.NewInnerRingMetrics()
+		server.metrics = &m
+	}
+
 	return server, nil
 }
 

pkg/innerring/state.go

@@ -30,6 +30,9 @@ func (s *Server) EpochCounter() uint64 {
 // epoch counter.
 func (s *Server) SetEpochCounter(val uint64) {
 	s.epochCounter.Store(val)
+	if s.metrics != nil {
+		s.metrics.SetEpoch(val)
+	}
 }
 
 // EpochDuration is a getter for a global epoch duration.

pkg/metrics/innerring.go

@@ -0,0 +1,33 @@
+package metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+const innerRingSubsystem = "object"
+
+// InnerRingServiceMetrics contains metrics collected by inner ring.
+type InnerRingServiceMetrics struct {
+	epoch prometheus.Gauge
+}
+
+// NewInnerRingMetrics returns new instance of metrics collectors for inner ring.
+func NewInnerRingMetrics() InnerRingServiceMetrics {
+	var (
+		epoch = prometheus.NewGauge(prometheus.GaugeOpts{
+			Namespace: namespace,
+			Subsystem: innerRingSubsystem,
+			Name:      "epoch",
+			Help:      "Current epoch as seen by inner-ring node.",
+		})
+	)
+
+	prometheus.MustRegister(epoch)
+
+	return InnerRingServiceMetrics{
+		epoch: epoch,
+	}
+}
+
+// SetEpoch updates epoch metrics.
+func (m InnerRingServiceMetrics) SetEpoch(epoch uint64) {
+	m.epoch.Set(float64(epoch))
+}