[#451] metrics: Move to internal

`metrics` don't look like something others want to import.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

internal/metrics/replicator.go

@@ -0,0 +1,61 @@
+package metrics
+
+import (
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/metrics"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type ReplicatorMetrics interface {
+	IncInFlightRequest()
+	DecInFlightRequest()
+	IncProcessedObjects()
+	AddPayloadSize(size int64)
+}
+
+type replicatorMetrics struct {
+	inFlightRequests           prometheus.Gauge
+	processedObjects           prometheus.Counter
+	totalReplicatedPayloadSize prometheus.Counter
+}
+
+func (m *replicatorMetrics) IncInFlightRequest() {
+	m.inFlightRequests.Inc()
+}
+
+func (m *replicatorMetrics) DecInFlightRequest() {
+	m.inFlightRequests.Dec()
+}
+
+func (m *replicatorMetrics) IncProcessedObjects() {
+	m.processedObjects.Inc()
+}
+
+func (m *replicatorMetrics) AddPayloadSize(size int64) {
+	m.totalReplicatedPayloadSize.Add(float64(size))
+}
+
+func newReplicatorMetrics() *replicatorMetrics {
+	return &replicatorMetrics{
+		inFlightRequests:           newReplicatorGauge("in_flight_requests_total", "Number of in-flight requests"),
+		processedObjects:           newReplicatorCounter("processed_objects_total", "Number of objects processed since the node startup"),
+		totalReplicatedPayloadSize: newReplicatorCounter("total_replicated_payload_size_bytes", "Total size of payloads replicated"),
+	}
+}
+
+func newReplicatorCounter(name, help string) prometheus.Counter {
+	return metrics.NewCounter(prometheus.CounterOpts{
+		Namespace: namespace,
+		Subsystem: replicatorSubsystem,
+		Name:      name,
+		Help:      help,
+	})
+}
+
+func newReplicatorGauge(name, help string) prometheus.Gauge {
+	return metrics.NewGauge(prometheus.GaugeOpts{
+		Namespace: namespace,
+		Subsystem: replicatorSubsystem,
+		Name:      name,
+		Help:      help,
+	})
+}