xds: Disable LOGICAL_DNS in XdsDepMan until used

ClusterResolverLb is still doing DNS itself, so disable it in XdsDepMan
until that migration has finished. EDS is fine in XdsDepman, because
XdsClient will share the result with ClusterResolverLb.

Author: ejona86

xds/src/main/java/io/grpc/xds/XdsDependencyManager.java

@@ -82,6 +82,9 @@ private enum TrackedWatcherTypeEnum {
   private static final Locality LOGICAL_DNS_CLUSTER_LOCALITY = Locality.create("", "", "");
 
   private static final int MAX_CLUSTER_RECURSION_DEPTH = 16; // Specified by gRFC A37
+
+  static boolean enableLogicalDns = false;
+
   private final String listenerName;
   private final XdsClient xdsClient;
   private final SynchronizationContext syncContext;
@@ -363,9 +366,14 @@ private static void addConfigForCluster(
         }
         break;
       case LOGICAL_DNS:
-        TrackedWatcher<List<EquivalentAddressGroup>> dnsWatcher =
-            tracer.getWatcher(DNS_TYPE, cdsUpdate.dnsHostName());
-        child = new EndpointConfig(dnsToEdsUpdate(dnsWatcher.getData(), cdsUpdate.dnsHostName()));
+        if (enableLogicalDns) {
+          TrackedWatcher<List<EquivalentAddressGroup>> dnsWatcher =
+              tracer.getWatcher(DNS_TYPE, cdsUpdate.dnsHostName());
+          child = new EndpointConfig(dnsToEdsUpdate(dnsWatcher.getData(), cdsUpdate.dnsHostName()));
+        } else {
+          child = new EndpointConfig(StatusOr.fromStatus(
+              Status.INTERNAL.withDescription("Logical DNS in dependency manager unsupported")));
+        }
         break;
       default:
         child = new EndpointConfig(StatusOr.fromStatus(Status.UNAVAILABLE.withDescription(
@@ -806,7 +814,9 @@ public void subscribeToChildren(XdsClusterResource.CdsUpdate update) {
           addEdsWatcher(getEdsServiceName());
           break;
         case LOGICAL_DNS:
-          addDnsWatcher(update.dnsHostName());
+          if (enableLogicalDns) {
+            addDnsWatcher(update.dnsHostName());
+          }
           break;
         case AGGREGATE:
           update.prioritizedClusterNames()

xds/src/test/java/io/grpc/xds/XdsDependencyManagerTest.java

@@ -152,6 +152,7 @@ public class XdsDependencyManagerTest {
 
   private XdsDependencyManager xdsDependencyManager = new XdsDependencyManager(
       xdsClient, syncContext, serverName, serverName, nameResolverArgs);
+  private boolean savedEnableLogicalDns;
 
   @Before
   public void setUp() throws Exception {
@@ -168,6 +169,8 @@ public void setUp() throws Exception {
     testWatcher = new TestWatcher();
     xdsConfigWatcher = mock(TestWatcher.class, delegatesTo(testWatcher));
     defaultXdsConfig = XdsTestUtils.getDefaultXdsConfig(serverName);
+
+    savedEnableLogicalDns = XdsDependencyManager.enableLogicalDns;
   }
 
   @After
@@ -180,6 +183,8 @@ public void tearDown() throws InterruptedException {
     assertThat(adsEnded.get()).isTrue();
     assertThat(lrsEnded.get()).isTrue();
     assertThat(fakeClock.getPendingTasks()).isEmpty();
+
+    XdsDependencyManager.enableLogicalDns = savedEnableLogicalDns;
   }
 
   @Test
@@ -749,6 +754,7 @@ public void testChangeAggCluster() {
 
   @Test
   public void testLogicalDns_success() {
+    XdsDependencyManager.enableLogicalDns = true;
     FakeSocketAddress fakeAddress = new FakeSocketAddress();
     nameResolverRegistry.register(new FakeNameResolverProvider(
         "dns:///dns.example.com:1111", fakeAddress));
@@ -789,6 +795,7 @@ public void testLogicalDns_success() {
 
   @Test
   public void testLogicalDns_noDnsNr() {
+    XdsDependencyManager.enableLogicalDns = true;
     Cluster cluster = Cluster.newBuilder()
         .setName(CLUSTER_NAME)
         .setType(Cluster.DiscoveryType.LOGICAL_DNS)