io.grpc.LoadBalancer.PickResult Java Examples

@Test
public void subchannelPickerInterceptedWithLoadRecording() {
  List<EquivalentAddressGroup> backendAddrs = createResolvedBackendAddresses(2);
  deliverResolvedAddresses(backendAddrs, "round_robin");
  FakeLoadBalancer childBalancer = (FakeLoadBalancer) childBalancers.poll();
  NoopSubchannel subchannel = childBalancer.subchannels.values().iterator().next();
  deliverSubchannelState(subchannel, ConnectivityState.READY);
  assertThat(loadRecorder.recording).isTrue();
  ArgumentCaptor<SubchannelPicker> pickerCaptor = ArgumentCaptor.forClass(null);
  verify(helper).updateBalancingState(eq(ConnectivityState.READY), pickerCaptor.capture());
  SubchannelPicker picker = pickerCaptor.getValue();
  assertThat(picker).isInstanceOf(LoadRecordingSubchannelPicker.class);
  PickResult result = picker.pickSubchannel(mock(PickSubchannelArgs.class));
  ClientStreamTracer.Factory tracerFactory = result.getStreamTracerFactory();
  assertThat(((LoadRecordingStreamTracerFactory) tracerFactory).getCounter())
      .isSameInstanceAs(counter);
  loadBalancer.shutdown();
  assertThat(childBalancer.shutdown).isTrue();
  assertThat(loadRecorder.recording).isFalse();
}
 

@Test
public void clusterWatcher_resourceNotExist() {
  ResolvedAddresses resolvedAddresses = ResolvedAddresses.newBuilder()
      .setAddresses(ImmutableList.<EquivalentAddressGroup>of())
      .setAttributes(Attributes.newBuilder()
          .set(XdsAttributes.XDS_CLIENT_POOL, xdsClientPool)
          .build())
      .setLoadBalancingPolicyConfig(new CdsConfig("foo.googleapis.com"))
      .build();
  cdsLoadBalancer.handleResolvedAddresses(resolvedAddresses);

  ArgumentCaptor<ClusterWatcher> clusterWatcherCaptor = ArgumentCaptor.forClass(null);
  verify(xdsClient).watchClusterData(eq("foo.googleapis.com"), clusterWatcherCaptor.capture());

  ClusterWatcher clusterWatcher = clusterWatcherCaptor.getValue();
  ArgumentCaptor<SubchannelPicker> pickerCaptor = ArgumentCaptor.forClass(null);
  clusterWatcher.onResourceDoesNotExist("foo.googleapis.com");
  assertThat(edsLoadBalancers).isEmpty();
  verify(helper).updateBalancingState(eq(TRANSIENT_FAILURE), pickerCaptor.capture());
  PickResult result = pickerCaptor.getValue().pickSubchannel(mock(PickSubchannelArgs.class));
  assertThat(result.getStatus().getCode()).isEqualTo(Code.UNAVAILABLE);
  assertThat(result.getStatus().getDescription())
      .isEqualTo("Resource foo.googleapis.com is unavailable");
}
 

@Test
public void reprocess_NoPendingStream() {
  SubchannelPicker picker = mock(SubchannelPicker.class);
  AbstractSubchannel subchannel = mock(AbstractSubchannel.class);
  when(subchannel.obtainActiveTransport()).thenReturn(mockRealTransport);
  when(picker.pickSubchannel(any(PickSubchannelArgs.class))).thenReturn(
      PickResult.withSubchannel(subchannel));
  when(mockRealTransport.newStream(any(MethodDescriptor.class), any(Metadata.class),
          any(CallOptions.class))).thenReturn(mockRealStream);
  delayedTransport.reprocess(picker);
  verifyNoMoreInteractions(picker);
  verifyNoMoreInteractions(transportListener);

  // Though picker was not originally used, it will be saved and serve future streams.
  ClientStream stream = delayedTransport.newStream(method, headers, CallOptions.DEFAULT);
  verify(picker).pickSubchannel(new PickSubchannelArgsImpl(method, headers, CallOptions.DEFAULT));
  verify(subchannel).obtainActiveTransport();
  assertSame(mockRealStream, stream);
}
 

@Test
public void roundRobinPickerWithIdleEntry_andDrop() {
  GrpclbClientLoadRecorder loadRecorder =
      new GrpclbClientLoadRecorder(fakeClock.getTimeProvider());
  // 1 out of 2 requests are to be dropped
  DropEntry d = new DropEntry(loadRecorder, "LBTOKEN0003");
  List<DropEntry> dropList = Arrays.asList(null, d);

  Subchannel subchannel = mock(Subchannel.class);
  IdleSubchannelEntry entry = new IdleSubchannelEntry(subchannel, syncContext);

  RoundRobinPicker picker = new RoundRobinPicker(dropList, Collections.singletonList(entry));
  PickSubchannelArgs args = mock(PickSubchannelArgs.class);

  verify(subchannel, never()).requestConnection();
  assertThat(picker.pickSubchannel(args)).isSameInstanceAs(PickResult.withNoResult());
  verify(subchannel).requestConnection();

  assertThat(picker.pickSubchannel(args)).isSameInstanceAs(DROP_PICK_RESULT);

  verify(subchannel).requestConnection();
  assertThat(picker.pickSubchannel(args)).isSameInstanceAs(PickResult.withNoResult());
  // Only the first pick triggers requestConnection()
  verify(subchannel).requestConnection();
}
 

@SuppressWarnings("unchecked")
@Test
public void nameResolutionErrorWithActiveChannels() throws Exception {
  final Subchannel readySubchannel = subchannels.values().iterator().next();
  loadBalancer.handleResolvedAddressGroups(servers, affinity);
  loadBalancer.handleSubchannelState(readySubchannel, ConnectivityStateInfo.forNonError(READY));
  loadBalancer.handleNameResolutionError(Status.NOT_FOUND.withDescription("nameResolutionError"));

  verify(mockHelper, times(3)).createSubchannel(any(List.class), any(Attributes.class));
  verify(mockHelper, times(3))
      .updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());

  Iterator<ConnectivityState> stateIterator = stateCaptor.getAllValues().iterator();
  assertEquals(CONNECTING, stateIterator.next());
  assertEquals(READY, stateIterator.next());
  assertEquals(TRANSIENT_FAILURE, stateIterator.next());

  LoadBalancer.PickResult pickResult = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(readySubchannel, pickResult.getSubchannel());
  assertEquals(Status.OK.getCode(), pickResult.getStatus().getCode());

  LoadBalancer.PickResult pickResult2 = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(readySubchannel, pickResult2.getSubchannel());
  verifyNoMoreInteractions(mockHelper);
}
 

@Test
public void roundRobinPickerWithIdleEntry_noDrop() {
  Subchannel subchannel = mock(Subchannel.class);
  IdleSubchannelEntry entry = new IdleSubchannelEntry(subchannel, syncContext);

  RoundRobinPicker picker =
      new RoundRobinPicker(Collections.<DropEntry>emptyList(), Collections.singletonList(entry));
  PickSubchannelArgs args = mock(PickSubchannelArgs.class);

  verify(subchannel, never()).requestConnection();
  assertThat(picker.pickSubchannel(args)).isSameInstanceAs(PickResult.withNoResult());
  verify(subchannel).requestConnection();
  assertThat(picker.pickSubchannel(args)).isSameInstanceAs(PickResult.withNoResult());
  // Only the first pick triggers requestConnection()
  verify(subchannel).requestConnection();
}
 

@VisibleForTesting
void panic(final Throwable t) {
  if (panicMode) {
    // Preserve the first panic information
    return;
  }
  panicMode = true;
  cancelIdleTimer(/* permanent= */ true);
  shutdownNameResolverAndLoadBalancer(false);
  final class PanicSubchannelPicker extends SubchannelPicker {
    private final PickResult panicPickResult =
        PickResult.withDrop(
            Status.INTERNAL.withDescription("Panic! This is a bug!").withCause(t));

    @Override
    public PickResult pickSubchannel(PickSubchannelArgs args) {
      return panicPickResult;
    }
  }

  updateSubchannelPicker(new PanicSubchannelPicker());
  channelLogger.log(ChannelLogLevel.ERROR, "PANIC! Entering TRANSIENT_FAILURE");
  channelStateManager.gotoState(TRANSIENT_FAILURE);
}
 

@Test
public void reprocess_NoPendingStream() {
  SubchannelPicker picker = mock(SubchannelPicker.class);
  AbstractSubchannel subchannel = mock(AbstractSubchannel.class);
  when(subchannel.getInternalSubchannel()).thenReturn(mockInternalSubchannel);
  when(picker.pickSubchannel(any(PickSubchannelArgs.class))).thenReturn(
      PickResult.withSubchannel(subchannel));
  when(mockRealTransport.newStream(any(MethodDescriptor.class), any(Metadata.class),
          any(CallOptions.class))).thenReturn(mockRealStream);
  delayedTransport.reprocess(picker);
  verifyNoMoreInteractions(picker);
  verifyNoMoreInteractions(transportListener);

  // Though picker was not originally used, it will be saved and serve future streams.
  ClientStream stream = delayedTransport.newStream(method, headers, CallOptions.DEFAULT);
  verify(picker).pickSubchannel(new PickSubchannelArgsImpl(method, headers, CallOptions.DEFAULT));
  verify(mockInternalSubchannel).obtainActiveTransport();
  assertSame(mockRealStream, stream);
}
 

@Test
public void newStream_racesWithReprocessIdleMode() throws Exception {
  SubchannelPicker picker = new SubchannelPicker() {
    @Override public PickResult pickSubchannel(PickSubchannelArgs args) {
      // Assume entering idle mode raced with the pick
      delayedTransport.reprocess(null);
      // Act like IDLE LB
      return PickResult.withNoResult();
    }
  };

  // Because there is no pending stream yet, it will do nothing but save the picker.
  delayedTransport.reprocess(picker);

  ClientStream stream = delayedTransport.newStream(method, headers, callOptions);
  stream.start(streamListener);
  assertTrue(delayedTransport.hasPendingStreams());
  verify(transportListener).transportInUse(true);
}
 

@Test
public void nameResolutionErrorWithActiveChannels() throws Exception {
  final Subchannel readySubchannel = subchannels.values().iterator().next();
  loadBalancer.handleResolvedAddresses(
      ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(affinity).build());
  deliverSubchannelState(readySubchannel, ConnectivityStateInfo.forNonError(READY));
  loadBalancer.handleNameResolutionError(Status.NOT_FOUND.withDescription("nameResolutionError"));

  verify(mockHelper, times(3)).createSubchannel(any(CreateSubchannelArgs.class));
  verify(mockHelper, times(3))
      .updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());

  Iterator<ConnectivityState> stateIterator = stateCaptor.getAllValues().iterator();
  assertEquals(CONNECTING, stateIterator.next());
  assertEquals(READY, stateIterator.next());
  assertEquals(TRANSIENT_FAILURE, stateIterator.next());

  LoadBalancer.PickResult pickResult = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(readySubchannel, pickResult.getSubchannel());
  assertEquals(Status.OK.getCode(), pickResult.getStatus().getCode());

  LoadBalancer.PickResult pickResult2 = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(readySubchannel, pickResult2.getSubchannel());
  verifyNoMoreInteractions(mockHelper);
}
 

void handleSubchannelStateChange(final ConnectivityStateInfo newState) {
  channelTracer.reportEvent(
      new ChannelTrace.Event.Builder()
          .setDescription("Entering " + newState.getState() + " state")
          .setSeverity(ChannelTrace.Event.Severity.CT_INFO)
          .setTimestampNanos(timeProvider.currentTimeNanos())
          .build());
  switch (newState.getState()) {
    case READY:
    case IDLE:
      delayedTransport.reprocess(subchannelPicker);
      break;
    case TRANSIENT_FAILURE:
      delayedTransport.reprocess(new SubchannelPicker() {
          final PickResult errorResult = PickResult.withError(newState.getStatus());

          @Override
          public PickResult pickSubchannel(PickSubchannelArgs args) {
            return errorResult;
          }
        });
      break;
    default:
      // Do nothing
  }
}
 

/**
 * For PICK_FIRST: creates a BackendEntry that includes all addresses.
 */
BackendEntry(Subchannel subchannel, TokenAttachingTracerFactory tracerFactory) {
  this.subchannel = checkNotNull(subchannel, "subchannel");
  this.result =
      PickResult.withSubchannel(subchannel, checkNotNull(tracerFactory, "tracerFactory"));
  this.token = null;
}
 

@Test
public void pickResult_withSubchannelAndTracer() {
  PickResult result = PickResult.withSubchannel(subchannel, tracerFactory);
  assertThat(result.getSubchannel()).isSameAs(subchannel);
  assertThat(result.getStatus()).isSameAs(Status.OK);
  assertThat(result.getStreamTracerFactory()).isSameAs(tracerFactory);
  assertThat(result.isDrop()).isFalse();
}
 

@Test
public void pickerReturnsStreamTracer_delayed() {
  ClientStream mockStream = mock(ClientStream.class);
  ClientStreamTracer.Factory factory1 = mock(ClientStreamTracer.Factory.class);
  ClientStreamTracer.Factory factory2 = mock(ClientStreamTracer.Factory.class);
  createChannel();

  CallOptions callOptions = CallOptions.DEFAULT.withStreamTracerFactory(factory1);
  ClientCall<String, Integer> call = channel.newCall(method, callOptions);
  call.start(mockCallListener, new Metadata());

  Subchannel subchannel =
      createSubchannelSafely(helper, addressGroup, Attributes.EMPTY, subchannelStateListener);
  requestConnectionSafely(helper, subchannel);
  MockClientTransportInfo transportInfo = transports.poll();
  transportInfo.listener.transportReady();
  ClientTransport mockTransport = transportInfo.transport;
  when(mockTransport.newStream(
          any(MethodDescriptor.class), any(Metadata.class), any(CallOptions.class)))
      .thenReturn(mockStream);
  when(mockPicker.pickSubchannel(any(PickSubchannelArgs.class))).thenReturn(
      PickResult.withSubchannel(subchannel, factory2));

  updateBalancingStateSafely(helper, READY, mockPicker);
  assertEquals(1, executor.runDueTasks());

  verify(mockPicker).pickSubchannel(any(PickSubchannelArgs.class));
  verify(mockTransport).newStream(same(method), any(Metadata.class), callOptionsCaptor.capture());
  assertEquals(
      Arrays.asList(factory1, factory2),
      callOptionsCaptor.getValue().getStreamTracerFactories());
  // The factories are safely not stubbed because we do not expect any usage of them.
  verifyZeroInteractions(factory1);
  verifyZeroInteractions(factory2);
}
 

/**
 * For ROUND_ROBIN: creates a BackendEntry whose usage will be reported to load recorder.
 */
BackendEntry(Subchannel subchannel, GrpclbClientLoadRecorder loadRecorder, String token) {
  this.subchannel = checkNotNull(subchannel, "subchannel");
  this.result =
      PickResult.withSubchannel(subchannel, checkNotNull(loadRecorder, "loadRecorder"));
  this.token = checkNotNull(token, "token");
}
 

@Before public void setUp() {
  when(mockPicker.pickSubchannel(any(PickSubchannelArgs.class)))
      .thenReturn(PickResult.withSubchannel(mockSubchannel));
  when(mockSubchannel.getInternalSubchannel()).thenReturn(mockInternalSubchannel);
  when(mockInternalSubchannel.obtainActiveTransport()).thenReturn(mockRealTransport);
  when(mockRealTransport.newStream(same(method), same(headers), same(callOptions)))
      .thenReturn(mockRealStream);
  when(mockRealTransport2.newStream(same(method2), same(headers2), same(callOptions2)))
      .thenReturn(mockRealStream2);
  delayedTransport.start(transportListener);
}
 

@Override
public PickResult picked(Metadata headers) {
  if (connectionRequested.compareAndSet(false, true)) {
    syncContext.execute(new Runnable() {
        @Override
        public void run() {
          subchannel.requestConnection();
        }
      });
  }
  return PickResult.withNoResult();
}
 

@Test
public void pickResult_withDrop() {
  PickResult result = PickResult.withDrop(status);
  assertThat(result.getSubchannel()).isNull();
  assertThat(result.getStatus()).isSameAs(status);
  assertThat(result.getStreamTracerFactory()).isNull();
  assertThat(result.isDrop()).isTrue();
}
 

@Test
public void pickResult_withNoResult() {
  PickResult result = PickResult.withNoResult();
  assertThat(result.getSubchannel()).isNull();
  assertThat(result.getStatus()).isSameAs(Status.OK);
  assertThat(result.getStreamTracerFactory()).isNull();
  assertThat(result.isDrop()).isFalse();
}
 

@Test
public void getTransportFromPickResult_dropPickResult_waitForReady() {
  Status status = Status.UNAVAILABLE;
  PickResult pickResult = PickResult.withDrop(status);
  ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult, true);

  assertNotNull(transport);

  ClientStream stream = transport
      .newStream(TestMethodDescriptors.voidMethod(), new Metadata(), CallOptions.DEFAULT);
  ClientStreamListener listener = mock(ClientStreamListener.class);
  stream.start(listener);

  verify(listener).closed(eq(status), eq(RpcProgress.DROPPED), any(Metadata.class));
}
 

@Test
public void pickResult_withError() {
  PickResult result = PickResult.withError(status);
  assertThat(result.getSubchannel()).isNull();
  assertThat(result.getStatus()).isSameAs(status);
  assertThat(result.getStreamTracerFactory()).isNull();
  assertThat(result.isDrop()).isFalse();
}
 

@Override
public PickResult picked(Metadata headers) {
  headers.discardAll(GrpclbConstants.TOKEN_METADATA_KEY);
  if (token != null) {
    headers.put(GrpclbConstants.TOKEN_METADATA_KEY, token);
  }
  return result;
}
 

@Override
public PickResult pickSubchannel(PickSubchannelArgs args) {
  Map<String, Object> affinity =
      args.getCallOptions().getOption(GrpcCallOptions.CALLOPTIONS_CUSTOME_KEY);
  GrpcURL refUrl = (GrpcURL) affinity.get(GrpcCallOptions.GRPC_REF_URL);
  if (size > 0) {
    Subchannel subchannel = nextSubchannel(refUrl);
    affinity.put(GrpcCallOptions.GRPC_NAMERESOVER_ATTRIBUTES, nameResovleCache);
    return PickResult.withSubchannel(subchannel);
  }
  if (status != null) {
    return PickResult.withError(status);
  }
  return PickResult.withNoResult();
}
 

@Override
public PickResult pickSubchannel(PickSubchannelArgs args) {
  synchronized (pickList) {
    // Two-level round-robin.
    // First round-robin on dropList. If a drop entry is selected, request will be dropped.  If
    // a non-drop entry is selected, then round-robin on pickList.  This makes sure requests are
    // dropped at the same proportion as the drop entries appear on the round-robin list from
    // the balancer, while only backends from pickList are selected for the non-drop cases.
    if (!dropList.isEmpty()) {
      DropEntry drop = dropList.get(dropIndex);
      dropIndex++;
      if (dropIndex == dropList.size()) {
        dropIndex = 0;
      }
      if (drop != null) {
        return drop.picked();
      }
    }

    RoundRobinEntry pick = pickList.get(pickIndex);
    pickIndex++;
    if (pickIndex == pickList.size()) {
      pickIndex = 0;
    }
    return pick.picked(args.getHeaders());
  }
}
 

@Before public void setUp() {
  MockitoAnnotations.initMocks(this);
  when(mockPicker.pickSubchannel(any(PickSubchannelArgs.class)))
      .thenReturn(PickResult.withSubchannel(mockSubchannel));
  when(mockSubchannel.obtainActiveTransport()).thenReturn(mockRealTransport);
  when(mockRealTransport.newStream(same(method), same(headers), same(callOptions)))
      .thenReturn(mockRealStream);
  when(mockRealTransport2.newStream(same(method2), same(headers2), same(callOptions2)))
      .thenReturn(mockRealStream2);
  delayedTransport.start(transportListener);
}
 

@Test
public void getTransportFromPickResult_dropPickResult_failFast() {
  Status status = Status.UNAVAILABLE;
  PickResult pickResult = PickResult.withDrop(status);
  ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult, false);

  assertNotNull(transport);

  ClientStream stream = transport
      .newStream(TestMethodDescriptors.voidMethod(), new Metadata(), CallOptions.DEFAULT);
  ClientStreamListener listener = mock(ClientStreamListener.class);
  stream.start(listener);

  verify(listener).closed(eq(status), eq(RpcProgress.DROPPED), any(Metadata.class));
}
 

private void subtestFailRpcFromBalancer(boolean waitForReady, boolean drop, boolean shouldFail) {
  createChannel();

  // This call will be buffered by the channel, thus involve delayed transport
  CallOptions callOptions = CallOptions.DEFAULT;
  if (waitForReady) {
    callOptions = callOptions.withWaitForReady();
  } else {
    callOptions = callOptions.withoutWaitForReady();
  }
  ClientCall<String, Integer> call1 = channel.newCall(method, callOptions);
  call1.start(mockCallListener, new Metadata());

  SubchannelPicker picker = mock(SubchannelPicker.class);
  Status status = Status.UNAVAILABLE.withDescription("for test");

  when(picker.pickSubchannel(any(PickSubchannelArgs.class)))
      .thenReturn(drop ? PickResult.withDrop(status) : PickResult.withError(status));
  updateBalancingStateSafely(helper, READY, picker);

  executor.runDueTasks();
  if (shouldFail) {
    verify(mockCallListener).onClose(same(status), any(Metadata.class));
  } else {
    verifyZeroInteractions(mockCallListener);
  }

  // This call doesn't involve delayed transport
  ClientCall<String, Integer> call2 = channel.newCall(method, callOptions);
  call2.start(mockCallListener2, new Metadata());

  executor.runDueTasks();
  if (shouldFail) {
    verify(mockCallListener2).onClose(same(status), any(Metadata.class));
  } else {
    verifyZeroInteractions(mockCallListener2);
  }
}
 

@Test
public void getTransportFromPickResult_errorPickResult_waitForReady() {
  Status status = Status.UNAVAILABLE;
  PickResult pickResult = PickResult.withError(status);
  ClientTransport transport = GrpcUtil.getTransportFromPickResult(pickResult, true);

  assertNull(transport);
}
 

@Test
public void nameResolutionErrorWithStateChanges() throws Exception {
  InOrder inOrder = inOrder(mockHelper);
  loadBalancer.handleResolvedAddresses(
      ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(affinity).build());
  inOrder.verify(mockHelper).createSubchannel(createArgsCaptor.capture());
  verify(mockSubchannel).start(stateListenerCaptor.capture());
  CreateSubchannelArgs args = createArgsCaptor.getValue();
  assertThat(args.getAddresses()).isEqualTo(servers);

  inOrder.verify(mockHelper).updateBalancingState(eq(CONNECTING), any(SubchannelPicker.class));

  SubchannelStateListener stateListener = stateListenerCaptor.getValue();

  stateListener.onSubchannelState(ConnectivityStateInfo.forTransientFailure(Status.UNAVAILABLE));
  inOrder.verify(mockHelper).updateBalancingState(
      eq(TRANSIENT_FAILURE), any(SubchannelPicker.class));

  Status error = Status.NOT_FOUND.withDescription("nameResolutionError");
  loadBalancer.handleNameResolutionError(error);
  inOrder.verify(mockHelper).updateBalancingState(eq(TRANSIENT_FAILURE), pickerCaptor.capture());

  PickResult pickResult = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(null, pickResult.getSubchannel());
  assertEquals(error, pickResult.getStatus());

  Status error2 = Status.NOT_FOUND.withDescription("nameResolutionError2");
  loadBalancer.handleNameResolutionError(error2);
  inOrder.verify(mockHelper).updateBalancingState(eq(TRANSIENT_FAILURE), pickerCaptor.capture());

  pickResult = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(null, pickResult.getSubchannel());
  assertEquals(error2, pickResult.getStatus());

  verifyNoMoreInteractions(mockHelper);
}
 

@Test
public void nameResolutionError() throws Exception {
  Status error = Status.NOT_FOUND.withDescription("nameResolutionError");
  loadBalancer.handleNameResolutionError(error);
  verify(mockHelper).updateBalancingState(eq(TRANSIENT_FAILURE), pickerCaptor.capture());
  PickResult pickResult = pickerCaptor.getValue().pickSubchannel(mockArgs);
  assertEquals(null, pickResult.getSubchannel());
  assertEquals(error, pickResult.getStatus());
  verify(mockSubchannel, never()).requestConnection();
  verifyNoMoreInteractions(mockHelper);
}