xds: ClusterResolverLoadBalancer handle update for both resolved addresses and errors via ResolutionResult (v1.71.x backport) (#12005)

Backport of #11997 to v1.71.x.
------------
Fixes #11995.

Author: kannanjgithub

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

@@ -32,6 +32,7 @@
 import io.grpc.NameResolver;
 import io.grpc.NameResolver.ResolutionResult;
 import io.grpc.Status;
+import io.grpc.StatusOr;
 import io.grpc.SynchronizationContext;
 import io.grpc.SynchronizationContext.ScheduledHandle;
 import io.grpc.internal.BackoffPolicy;
@@ -615,79 +616,84 @@ private class NameResolverListener extends NameResolver.Listener2 {
 
         @Override
         public void onResult(final ResolutionResult resolutionResult) {
-          class NameResolved implements Runnable {
-            @Override
-            public void run() {
-              if (shutdown) {
-                return;
-              }
-              backoffPolicy = null;  // reset backoff sequence if succeeded
-              // Arbitrary priority notation for all DNS-resolved endpoints.
-              String priorityName = priorityName(name, 0);  // value doesn't matter
-              List<EquivalentAddressGroup> addresses = new ArrayList<>();
-              for (EquivalentAddressGroup eag : resolutionResult.getAddresses()) {
-                // No weight attribute is attached, all endpoint-level LB policy should be able
-                // to handle such it.
-                String localityName = localityName(LOGICAL_DNS_CLUSTER_LOCALITY);
-                Attributes attr = eag.getAttributes().toBuilder()
-                    .set(XdsAttributes.ATTR_LOCALITY, LOGICAL_DNS_CLUSTER_LOCALITY)
-                    .set(XdsAttributes.ATTR_LOCALITY_NAME, localityName)
-                    .set(XdsAttributes.ATTR_ADDRESS_NAME, dnsHostName)
-                    .build();
-                eag = new EquivalentAddressGroup(eag.getAddresses(), attr);
-                eag = AddressFilter.setPathFilter(eag, Arrays.asList(priorityName, localityName));
-                addresses.add(eag);
-              }
-              PriorityChildConfig priorityChildConfig = generateDnsBasedPriorityChildConfig(
-                  name, lrsServerInfo, maxConcurrentRequests, tlsContext, filterMetadata,
-                  lbRegistry, Collections.<DropOverload>emptyList());
-              status = Status.OK;
-              resolved = true;
-              result = new ClusterResolutionResult(addresses, priorityName, priorityChildConfig);
-              handleEndpointResourceUpdate();
+          syncContext.execute(() -> onResult2(resolutionResult));
+        }
+
+        @Override
+        public Status onResult2(final ResolutionResult resolutionResult) {
+          if (shutdown) {
+            return Status.OK;
+          }
+          // Arbitrary priority notation for all DNS-resolved endpoints.
+          String priorityName = priorityName(name, 0);  // value doesn't matter
+          List<EquivalentAddressGroup> addresses = new ArrayList<>();
+          StatusOr<List<EquivalentAddressGroup>> addressesOrError =
+                  resolutionResult.getAddressesOrError();
+          if (addressesOrError.hasValue()) {
+            backoffPolicy = null;  // reset backoff sequence if succeeded
+            for (EquivalentAddressGroup eag : resolutionResult.getAddresses()) {
+              // No weight attribute is attached, all endpoint-level LB policy should be able
+              // to handle such it.
+              String localityName = localityName(LOGICAL_DNS_CLUSTER_LOCALITY);
+              Attributes attr = eag.getAttributes().toBuilder()
+                      .set(XdsAttributes.ATTR_LOCALITY, LOGICAL_DNS_CLUSTER_LOCALITY)
+                      .set(XdsAttributes.ATTR_LOCALITY_NAME, localityName)
+                      .set(XdsAttributes.ATTR_ADDRESS_NAME, dnsHostName)
+                      .build();
+              eag = new EquivalentAddressGroup(eag.getAddresses(), attr);
+              eag = AddressFilter.setPathFilter(eag, Arrays.asList(priorityName, localityName));
+              addresses.add(eag);
             }
+            PriorityChildConfig priorityChildConfig = generateDnsBasedPriorityChildConfig(
+                    name, lrsServerInfo, maxConcurrentRequests, tlsContext, filterMetadata,
+                    lbRegistry, Collections.<DropOverload>emptyList());
+            status = Status.OK;
+            resolved = true;
+            result = new ClusterResolutionResult(addresses, priorityName, priorityChildConfig);
+            handleEndpointResourceUpdate();
+            return Status.OK;
+          } else {
+            handleErrorInSyncContext(addressesOrError.getStatus());
+            return addressesOrError.getStatus();
           }
-
-          syncContext.execute(new NameResolved());
         }
 
         @Override
         public void onError(final Status error) {
-          syncContext.execute(new Runnable() {
-            @Override
-            public void run() {
-              if (shutdown) {
-                return;
-              }
-              status = error;
-              // NameResolver.Listener API cannot distinguish between address-not-found and
-              // transient errors. If the error occurs in the first resolution, treat it as
-              // address not found. Otherwise, either there is previously resolved addresses
-              // previously encountered error, propagate the error to downstream/upstream and
-              // let downstream/upstream handle it.
-              if (!resolved) {
-                resolved = true;
-                handleEndpointResourceUpdate();
-              } else {
-                handleEndpointResolutionError();
-              }
-              if (scheduledRefresh != null && scheduledRefresh.isPending()) {
-                return;
-              }
-              if (backoffPolicy == null) {
-                backoffPolicy = backoffPolicyProvider.get();
-              }
-              long delayNanos = backoffPolicy.nextBackoffNanos();
-              logger.log(XdsLogLevel.DEBUG,
+          syncContext.execute(() -> handleErrorInSyncContext(error));
+        }
+
+        private void handleErrorInSyncContext(final Status error) {
+          if (shutdown) {
+            return;
+          }
+          status = error;
+          // NameResolver.Listener API cannot distinguish between address-not-found and
+          // transient errors. If the error occurs in the first resolution, treat it as
+          // address not found. Otherwise, either there is previously resolved addresses
+          // previously encountered error, propagate the error to downstream/upstream and
+          // let downstream/upstream handle it.
+          if (!resolved) {
+            resolved = true;
+            handleEndpointResourceUpdate();
+          } else {
+            handleEndpointResolutionError();
+          }
+          if (scheduledRefresh != null && scheduledRefresh.isPending()) {
+            return;
+          }
+          if (backoffPolicy == null) {
+            backoffPolicy = backoffPolicyProvider.get();
+          }
+          long delayNanos = backoffPolicy.nextBackoffNanos();
+          logger.log(XdsLogLevel.DEBUG,
                   "Logical DNS resolver for cluster {0} encountered name resolution "
-                      + "error: {1}, scheduling DNS resolution backoff for {2} ns",
+                          + "error: {1}, scheduling DNS resolution backoff for {2} ns",
                   name, error, delayNanos);
-              scheduledRefresh =
+          scheduledRefresh =
                   syncContext.schedule(
-                      new DelayedNameResolverRefresh(), delayNanos, TimeUnit.NANOSECONDS,
-                      timeService);
-            }
-          });
+                          new DelayedNameResolverRefresh(), delayNanos, TimeUnit.NANOSECONDS,
+                          timeService);
         }
       }
     }

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

@@ -198,6 +198,7 @@ public XdsClient returnObject(Object object) {
   private ArgumentCaptor<SubchannelPicker> pickerCaptor;
   private int xdsClientRefs;
   private ClusterResolverLoadBalancer loadBalancer;
+  private NameResolverProvider fakeNameResolverProvider;
 
   @Before
   public void setUp() throws URISyntaxException {
@@ -214,7 +215,8 @@ public void setUp() throws URISyntaxException {
         .setServiceConfigParser(mock(ServiceConfigParser.class))
         .setChannelLogger(mock(ChannelLogger.class))
         .build();
-    nsRegistry.register(new FakeNameResolverProvider());
+    fakeNameResolverProvider = new FakeNameResolverProvider(false);
+    nsRegistry.register(fakeNameResolverProvider);
     when(helper.getNameResolverRegistry()).thenReturn(nsRegistry);
     when(helper.getNameResolverArgs()).thenReturn(args);
     when(helper.getSynchronizationContext()).thenReturn(syncContext);
@@ -715,6 +717,17 @@ public void handleEdsResource_noHealthyEndpoint() {
 
   @Test
   public void onlyLogicalDnsCluster_endpointsResolved() {
+    do_onlyLogicalDnsCluster_endpointsResolved();
+  }
+
+  @Test
+  public void oldListenerCallback_onlyLogicalDnsCluster_endpointsResolved() {
+    nsRegistry.deregister(fakeNameResolverProvider);
+    nsRegistry.register(new FakeNameResolverProvider(true));
+    do_onlyLogicalDnsCluster_endpointsResolved();
+  }
+
+  void do_onlyLogicalDnsCluster_endpointsResolved() {
     ClusterResolverConfig config = new ClusterResolverConfig(
         Collections.singletonList(logicalDnsDiscoveryMechanism), roundRobin);
     deliverLbConfig(config);
@@ -743,7 +756,6 @@ public void onlyLogicalDnsCluster_endpointsResolved() {
         .get(XdsAttributes.ATTR_ADDRESS_NAME)).isEqualTo(DNS_HOST_NAME);
     assertThat(childBalancer.addresses.get(1).getAttributes()
         .get(XdsAttributes.ATTR_ADDRESS_NAME)).isEqualTo(DNS_HOST_NAME);
-
   }
 
   @Test
@@ -763,37 +775,48 @@ public void onlyLogicalDnsCluster_handleRefreshNameResolution() {
   }
 
   @Test
-  public void onlyLogicalDnsCluster_resolutionError_backoffAndRefresh() {
+  public void resolutionError_backoffAndRefresh() {
+    do_onlyLogicalDnsCluster_resolutionError_backoffAndRefresh();
+  }
+
+  @Test
+  public void oldListenerCallback_resolutionError_backoffAndRefresh() {
+    nsRegistry.deregister(fakeNameResolverProvider);
+    nsRegistry.register(new FakeNameResolverProvider(true));
+    do_onlyLogicalDnsCluster_resolutionError_backoffAndRefresh();
+  }
+
+  void do_onlyLogicalDnsCluster_resolutionError_backoffAndRefresh() {
     InOrder inOrder = Mockito.inOrder(helper, backoffPolicyProvider,
-        backoffPolicy1, backoffPolicy2);
+            backoffPolicy1, backoffPolicy2);
     ClusterResolverConfig config = new ClusterResolverConfig(
-        Collections.singletonList(logicalDnsDiscoveryMechanism), roundRobin);
+            Collections.singletonList(logicalDnsDiscoveryMechanism), roundRobin);
     deliverLbConfig(config);
     FakeNameResolver resolver = assertResolverCreated("/" + DNS_HOST_NAME);
     assertThat(childBalancers).isEmpty();
     Status error = Status.UNAVAILABLE.withDescription("cannot reach DNS server");
     resolver.deliverError(error);
     inOrder.verify(helper).updateBalancingState(
-        eq(ConnectivityState.TRANSIENT_FAILURE), pickerCaptor.capture());
+            eq(ConnectivityState.TRANSIENT_FAILURE), pickerCaptor.capture());
     assertPicker(pickerCaptor.getValue(), error, null);
     assertThat(resolver.refreshCount).isEqualTo(0);
     inOrder.verify(backoffPolicyProvider).get();
     inOrder.verify(backoffPolicy1).nextBackoffNanos();
     assertThat(fakeClock.getPendingTasks()).hasSize(1);
     assertThat(Iterables.getOnlyElement(fakeClock.getPendingTasks()).getDelay(TimeUnit.SECONDS))
-        .isEqualTo(1L);
+            .isEqualTo(1L);
     fakeClock.forwardTime(1L, TimeUnit.SECONDS);
     assertThat(resolver.refreshCount).isEqualTo(1);
 
     error = Status.UNKNOWN.withDescription("I am lost");
     resolver.deliverError(error);
     inOrder.verify(helper).updateBalancingState(
-        eq(ConnectivityState.TRANSIENT_FAILURE), pickerCaptor.capture());
+            eq(ConnectivityState.TRANSIENT_FAILURE), pickerCaptor.capture());
     inOrder.verify(backoffPolicy1).nextBackoffNanos();
     assertPicker(pickerCaptor.getValue(), error, null);
     assertThat(fakeClock.getPendingTasks()).hasSize(1);
     assertThat(Iterables.getOnlyElement(fakeClock.getPendingTasks()).getDelay(TimeUnit.SECONDS))
-        .isEqualTo(10L);
+            .isEqualTo(10L);
     fakeClock.forwardTime(10L, TimeUnit.SECONDS);
     assertThat(resolver.refreshCount).isEqualTo(2);
 
@@ -803,7 +826,7 @@ public void onlyLogicalDnsCluster_resolutionError_backoffAndRefresh() {
     resolver.deliverEndpointAddresses(Arrays.asList(endpoint1, endpoint2));
     assertThat(childBalancers).hasSize(1);
     assertAddressesEqual(Arrays.asList(endpoint1, endpoint2),
-        Iterables.getOnlyElement(childBalancers).addresses);
+            Iterables.getOnlyElement(childBalancers).addresses);
 
     assertThat(fakeClock.getPendingTasks()).isEmpty();
     inOrder.verifyNoMoreInteractions();
@@ -1204,10 +1227,18 @@ void deliverError(Status error) {
   }
 
   private class FakeNameResolverProvider extends NameResolverProvider {
+    private final boolean useOldListenerCallback;
+
+    private FakeNameResolverProvider(boolean useOldListenerCallback) {
+      this.useOldListenerCallback = useOldListenerCallback;
+    }
+
     @Override
     public NameResolver newNameResolver(URI targetUri, NameResolver.Args args) {
       assertThat(targetUri.getScheme()).isEqualTo("dns");
-      FakeNameResolver resolver = new FakeNameResolver(targetUri);
+      FakeNameResolver resolver = useOldListenerCallback
+              ? new FakeNameResolverUsingOldListenerCallback(targetUri)
+              : new FakeNameResolver(targetUri);
       resolvers.add(resolver);
       return resolver;
     }
@@ -1228,9 +1259,10 @@ protected int priority() {
     }
   }
 
+
   private class FakeNameResolver extends NameResolver {
     private final URI targetUri;
-    private Listener2 listener;
+    protected Listener2 listener;
     private int refreshCount;
 
     private FakeNameResolver(URI targetUri) {
@@ -1257,12 +1289,33 @@ public void shutdown() {
       resolvers.remove(this);
     }
 
-    private void deliverEndpointAddresses(List<EquivalentAddressGroup> addresses) {
+    protected void deliverEndpointAddresses(List<EquivalentAddressGroup> addresses) {
+      syncContext.execute(() -> {
+        Status ret = listener.onResult2(ResolutionResult.newBuilder()
+                .setAddressesOrError(StatusOr.fromValue(addresses)).build());
+        assertThat(ret.getCode()).isEqualTo(Status.Code.OK);
+      });
+    }
+
+    protected void deliverError(Status error) {
+      syncContext.execute(() -> listener.onResult2(ResolutionResult.newBuilder()
+                      .setAddressesOrError(StatusOr.fromStatus(error)).build()));
+    }
+  }
+
+  private class FakeNameResolverUsingOldListenerCallback extends FakeNameResolver {
+    private FakeNameResolverUsingOldListenerCallback(URI targetUri) {
+      super(targetUri);
+    }
+
+    @Override
+    protected void deliverEndpointAddresses(List<EquivalentAddressGroup> addresses) {
       listener.onResult(ResolutionResult.newBuilder()
-          .setAddressesOrError(StatusOr.fromValue(addresses)).build());
+              .setAddressesOrError(StatusOr.fromValue(addresses)).build());
     }
 
-    private void deliverError(Status error) {
+    @Override
+    protected void deliverError(Status error) {
       listener.onError(error);
     }
   }