Add cluster notification metrics in metrics-v3 (#19533)

Signed-off-by: Bala.FA <bala@minio.io>

cmd/metrics-v3-cluster-notification.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2024 MinIO, Inc.
+//
+// # This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package cmd
+
+import (
+	"context"
+)
+
+const (
+	notificationCurrentSendInProgress = "current_send_in_progress"
+	notificationEventsErrorsTotal     = "events_errors_total"
+	notificationEventsSentTotal       = "events_sent_total"
+	notificationEventsSkippedTotal    = "events_skipped_total"
+)
+
+var (
+	notificationCurrentSendInProgressMD = NewCounterMD(notificationCurrentSendInProgress, "Number of concurrent async Send calls active to all targets")
+	notificationEventsErrorsTotalMD     = NewCounterMD(notificationEventsErrorsTotal, "Events that were failed to be sent to the targets")
+	notificationEventsSentTotalMD       = NewCounterMD(notificationEventsSentTotal, "Total number of events sent to the targets")
+	notificationEventsSkippedTotalMD    = NewCounterMD(notificationEventsSkippedTotal, "Events that were skipped to be sent to the targets due to the in-memory queue being full")
+)
+
+// loadClusterNotificationMetrics - `MetricsLoaderFn` for cluster notification metrics.
+func loadClusterNotificationMetrics(_ context.Context, m MetricValues, _ *metricsCache) error {
+	if globalEventNotifier == nil {
+		return nil
+	}
+
+	nstats := globalEventNotifier.targetList.Stats()
+	m.Set(notificationCurrentSendInProgress, float64(nstats.CurrentSendCalls))
+	m.Set(notificationEventsErrorsTotal, float64(nstats.EventsErrorsTotal))
+	m.Set(notificationEventsSentTotal, float64(nstats.TotalEvents))
+	m.Set(notificationEventsSkippedTotal, float64(nstats.EventsSkipped))
+
+	return nil
+}