use sync.Once - Events should return the same event channel

Signed-off-by: Davanum Srinivas <[email protected]>

Author: dims

store-client/pkg/client/mongodb_client.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"log/slog"
 	"strings"
+	"sync"
 
 	"github.com/nvidia/nvsentinel/data-models/pkg/model"
 	"github.com/nvidia/nvsentinel/store-client/pkg/config"
@@ -887,26 +888,33 @@ type mongoSessionContext struct {
 }
 
 type mongoChangeStreamWatcher struct {
-	watcher *mongoWatcher.ChangeStreamWatcher
+	watcher   *mongoWatcher.ChangeStreamWatcher
+	eventChan chan Event
+	initOnce  sync.Once
 }
 
 func (w *mongoChangeStreamWatcher) Start(ctx context.Context) {
 	w.watcher.Start(ctx)
 }
 
+// Events returns the event channel for this watcher.
+// The returned channel is initialized once and cached, so multiple calls
+// return the same channel. Safe for concurrent use.
 func (w *mongoChangeStreamWatcher) Events() <-chan Event {
-	bsonChan := w.watcher.Events()
-	eventChan := make(chan Event)
+	w.initOnce.Do(func() {
+		w.eventChan = make(chan Event)
+		bsonChan := w.watcher.Events()
 
-	go func() {
-		defer close(eventChan)
+		go func() {
+			defer close(w.eventChan)
 
-		for rawEvent := range bsonChan {
-			eventChan <- &mongoEvent{rawEvent: rawEvent}
-		}
-	}()
+			for rawEvent := range bsonChan {
+				w.eventChan <- &mongoEvent{rawEvent: rawEvent}
+			}
+		}()
+	})
 
-	return eventChan
+	return w.eventChan
 }
 
 func (w *mongoChangeStreamWatcher) MarkProcessed(ctx context.Context, token []byte) error {