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

…defined (#5931)

In situation where a Leaf server has no cluster specified, we internally
use the server name as the cluster name. We may need it in the protocol
so that the hub can suppress some messages to avoid duplicates.

We were however still reporting a cluster name in `/varz` and in the
banner on startup. This PR fixes both.

Resolves #5913

Signed-off-by: Ivan Kozlovic [email protected]

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)