[management] Store connected proxies in DB (#5472)

Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>

management/internals/modules/reverseproxy/proxy/manager/metrics.go

@@ -0,0 +1,74 @@
+package manager
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/metric"
+)
+
+type metrics struct {
+	proxyConnectionCount   metric.Int64UpDownCounter
+	serviceUpdateSendCount metric.Int64Counter
+	proxyHeartbeatCount    metric.Int64Counter
+}
+
+func newMetrics(meter metric.Meter) (*metrics, error) {
+	proxyConnectionCount, err := meter.Int64UpDownCounter(
+		"management_proxy_connection_count",
+		metric.WithDescription("Number of active proxy connections"),
+		metric.WithUnit("{connection}"),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	serviceUpdateSendCount, err := meter.Int64Counter(
+		"management_proxy_service_update_send_count",
+		metric.WithDescription("Total number of service updates sent to proxies"),
+		metric.WithUnit("{update}"),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	proxyHeartbeatCount, err := meter.Int64Counter(
+		"management_proxy_heartbeat_count",
+		metric.WithDescription("Total number of proxy heartbeats received"),
+		metric.WithUnit("{heartbeat}"),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return &metrics{
+		proxyConnectionCount:   proxyConnectionCount,
+		serviceUpdateSendCount: serviceUpdateSendCount,
+		proxyHeartbeatCount:    proxyHeartbeatCount,
+	}, nil
+}
+
+func (m *metrics) IncrementProxyConnectionCount(clusterAddr string) {
+	m.proxyConnectionCount.Add(context.Background(), 1,
+		metric.WithAttributes(
+			attribute.String("cluster", clusterAddr),
+		))
+}
+
+func (m *metrics) DecrementProxyConnectionCount(clusterAddr string) {
+	m.proxyConnectionCount.Add(context.Background(), -1,
+		metric.WithAttributes(
+			attribute.String("cluster", clusterAddr),
+		))
+}
+
+func (m *metrics) IncrementServiceUpdateSendCount(clusterAddr string) {
+	m.serviceUpdateSendCount.Add(context.Background(), 1,
+		metric.WithAttributes(
+			attribute.String("cluster", clusterAddr),
+		))
+}
+
+func (m *metrics) IncrementProxyHeartbeatCount() {
+	m.proxyHeartbeatCount.Add(context.Background(), 1)
+}