NAS gateway: fix notification initialization (#8920)

Co-authored-by: Harshavardhana <harsha@minio.io>

cmd/gateway-main.go

@@ -243,12 +243,16 @@ func StartGateway(ctx *cli.Context, gw Gateway) {
 	// sub-systems, make sure that we do not move the above codeblock elsewhere.
 	if enableConfigOps {
 		logger.FatalIf(globalConfigSys.Init(newObject), "Unable to initialize config system")
+		buckets, err := newObject.ListBuckets(context.Background())
+		if err != nil {
+			logger.Fatal(err, "Unable to list buckets")
+		}
 
+		logger.FatalIf(globalNotificationSys.Init(buckets, newObject), "Unable to initialize notification system")
 		// Start watching disk for reloading config, this
 		// is only enabled for "NAS" gateway.
 		globalConfigSys.WatchConfigNASDisk(newObject)
 	}
-
 	// This is only to uniquely identify each gateway deployments.
 	globalDeploymentID = env.Get("MINIO_GATEWAY_DEPLOYMENT_ID", mustGetUUID())
 	logger.SetDeploymentID(globalDeploymentID)

cmd/notification.go

@@ -704,7 +704,7 @@ func (sys *NotificationSys) Init(buckets []BucketInfo, objAPI ObjectLayer) error
 	}
 
 	// In gateway mode, notifications are not supported.
-	if globalIsGateway {
+	if globalIsGateway && !objAPI.IsNotificationSupported() {
 		return nil
 	}