[FIXED] LeafNode: Don't report cluster name in varz/banner when none defined

server/leafnode_test.go

@@ -7968,3 +7968,38 @@ func TestLeafNodeServerKickClient(t *testing.T) {
 	require_True(t, lid != ln.Cid)
 	require_True(t, ln.Start.After(disconnectTime))
 }
+
+func TestLeafNodeBannerNoClusterNameIfNoCluster(t *testing.T) {
+	u, err := url.Parse("nats://127.0.0.1:1234")
+	require_NoError(t, err)
+
+	opts := DefaultOptions()
+	opts.ServerName = "LEAF_SERVER"
+	opts.Cluster.Name = _EMPTY_
+	opts.Cluster.Port = 0
+	opts.LeafNode.Remotes = []*RemoteLeafOpts{{URLs: []*url.URL{u}}}
+	opts.NoLog = false
+
+	s, err := NewServer(opts)
+	require_NoError(t, err)
+	defer func() {
+		s.Shutdown()
+		s.WaitForShutdown()
+	}()
+	l := &captureNoticeLogger{}
+	s.SetLogger(l, false, false)
+	s.Start()
+
+	if !s.ReadyForConnections(time.Second) {
+		t.Fatal("Server not ready!")
+	}
+
+	l.Lock()
+	for _, n := range l.notices {
+		if strings.Contains(n, "Cluster: ") {
+			l.Unlock()
+			t.Fatalf("Cluster name should not be displayed, got %q", n)
+		}
+	}
+	l.Unlock()
+}

server/monitor.go

@@ -1592,6 +1592,11 @@ func (s *Server) createVarz(pcpu float64, rss int64) *Varz {
 		TrustedOperatorsJwt:   opts.operatorJWT,
 		TrustedOperatorsClaim: opts.TrustedOperators,
 	}
+	// If this is a leaf without cluster, reset the cluster name (that is otherwise
+	// set to the server name).
+	if s.leafNoCluster {
+		varz.Cluster.Name = _EMPTY_
+	}
 	if len(opts.Routes) > 0 {
 		varz.Cluster.URLs = urlsToStrings(opts.Routes)
 	}

server/monitor_test.go

@@ -3138,6 +3138,14 @@ func TestMonitorLeafNode(t *testing.T) {
 	for mode := 0; mode < 2; mode++ {
 		check := func(t *testing.T, v *Varz) {
 			t.Helper()
+			// Issue 5913. When we have solicited leafnodes but no clustering
+			// and no clustername, we may need a stable clustername so we use
+			// the server name as cluster name. However, we should not expose
+			// it in /varz.
+			if v.Cluster.Name != _EMPTY_ {
+				t.Fatalf("mode=%v - unexpected cluster name: %s", mode, v.Cluster.Name)
+			}
+			// Check rest is as expected.
 			if !reflect.DeepEqual(v.LeafNode, expected) {
 				t.Fatalf("mode=%v - expected %+v, got %+v", mode, expected, v.LeafNode)
 			}

server/server.go

@@ -229,6 +229,7 @@ type Server struct {
 	leafRemoteAccounts sync.Map
 	leafNodeEnabled    bool
 	leafDisableConnect bool // Used in test only
+	leafNoCluster      bool // Indicate that this server has only remotes and no cluster defined
 
 	quitCh           chan struct{}
 	startupComplete  chan struct{}
@@ -750,6 +751,7 @@ func NewServer(opts *Options) (*Server, error) {
 	// If we have solicited leafnodes but no clustering and no clustername.
 	// However we may need a stable clustername so use the server name.
 	if len(opts.LeafNode.Remotes) > 0 && opts.Cluster.Port == 0 && opts.Cluster.Name == _EMPTY_ {
+		s.leafNoCluster = true
 		opts.Cluster.Name = opts.ServerName
 	}
 
@@ -2178,7 +2180,17 @@ func (s *Server) Start() {
 
 	// Snapshot server options.
 	opts := s.getOpts()
-	clusterName := s.ClusterName()
+
+	// Capture if this server is a leaf that has no cluster, so we don't
+	// display the cluster name if that is the case.
+	s.mu.RLock()
+	leafNoCluster := s.leafNoCluster
+	s.mu.RUnlock()
+
+	var clusterName string
+	if !leafNoCluster {
+		clusterName = s.ClusterName()
+	}
 
 	s.Noticef("  Version:  %s", VERSION)
 	s.Noticef("  Git:      [%s]", gc)