[#324] Add replicator metrics

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/metrics/replicator.go

@@ -0,0 +1,59 @@
+package metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+const replicatorSubsystem = "replicator"
+
+type replicatorMetrics struct {
+	inFlightRequests           metric[prometheus.Gauge]
+	processedObjects           metric[prometheus.Counter]
+	totalReplicatedPayloadSize metric[prometheus.Counter]
+}
+
+func (m replicatorMetrics) IncInFlightRequest() {
+	m.inFlightRequests.value.Inc()
+}
+
+func (m replicatorMetrics) DecInFlightRequest() {
+	m.inFlightRequests.value.Dec()
+}
+
+func (m replicatorMetrics) IncProcessedObjects() {
+	m.processedObjects.value.Inc()
+}
+
+func (m replicatorMetrics) AddPayloadSize(size int64) {
+	m.totalReplicatedPayloadSize.value.Add(float64(size))
+}
+
+func newReplicatorMetrics() replicatorMetrics {
+	return replicatorMetrics{
+		inFlightRequests:           newReplicatorGauge("in_flight_requests", "Number of in-flight requests"),
+		processedObjects:           newReplicatorCounter("processed_objects", "Number of objects processed since the node startup"),
+		totalReplicatedPayloadSize: newReplicatorCounter("total_replicated_payload_size", "Total size of payloads replicated"),
+	}
+}
+
+func (m replicatorMetrics) register() {
+	mustRegister(m.inFlightRequests)
+	mustRegister(m.processedObjects)
+	mustRegister(m.totalReplicatedPayloadSize)
+}
+
+func newReplicatorCounter(name, help string) metric[prometheus.Counter] {
+	return newCounter(prometheus.CounterOpts{
+		Namespace: namespace,
+		Subsystem: replicatorSubsystem,
+		Name:      name,
+		Help:      help,
+	})
+}
+
+func newReplicatorGauge(name, help string) metric[prometheus.Gauge] {
+	return newGauge(prometheus.GaugeOpts{
+		Namespace: namespace,
+		Subsystem: replicatorSubsystem,
+		Name:      name,
+		Help:      help,
+	})
+}