xds: Do RLS fallback policy eagar start

rls/src/main/java/io/grpc/rls/CachingRlsLbClient.java

@@ -132,6 +132,7 @@ final class CachingRlsLbClient {
   @GuardedBy("lock")
   private final RefCountedChildPolicyWrapperFactory refCountedChildPolicyWrapperFactory;
   private final ChannelLogger logger;
+  private final ChildPolicyWrapper fallbackChildPolicyWrapper;
 
   static {
     MetricInstrumentRegistry metricInstrumentRegistry
@@ -226,6 +227,13 @@ private CachingRlsLbClient(Builder builder) {
             lbPolicyConfig.getLoadBalancingPolicy(), childLbResolvedAddressFactory,
             childLbHelperProvider,
             new BackoffRefreshListener());
+    // TODO(creamsoup) wait until lb is ready
+    String defaultTarget = lbPolicyConfig.getRouteLookupConfig().defaultTarget();
+    if (defaultTarget != null && !defaultTarget.isEmpty()) {
+      fallbackChildPolicyWrapper = refCountedChildPolicyWrapperFactory.createOrGet(defaultTarget);
+    } else {
+      fallbackChildPolicyWrapper = null;
+    }
 
     gaugeRegistration = helper.getMetricRecorder()
         .registerBatchCallback(new BatchCallback() {
@@ -1022,12 +1030,8 @@ public PickResult pickSubchannel(PickSubchannelArgs args) {
       }
     }
 
-    private ChildPolicyWrapper fallbackChildPolicyWrapper;
-
     /** Uses Subchannel connected to default target. */
     private PickResult useFallback(PickSubchannelArgs args) {
-      // TODO(creamsoup) wait until lb is ready
-      startFallbackChildPolicy();
       SubchannelPicker picker = fallbackChildPolicyWrapper.getPicker();
       if (picker == null) {
         return PickResult.withNoResult();
@@ -1052,17 +1056,6 @@ private String determineMetricsPickResult(PickResult pickResult) {
       }
     }
 
-    private void startFallbackChildPolicy() {
-      String defaultTarget = lbPolicyConfig.getRouteLookupConfig().defaultTarget();
-      synchronized (lock) {
-        if (fallbackChildPolicyWrapper != null) {
-          return;
-        }
-        logger.log(ChannelLogLevel.DEBUG, "starting fallback to {0}", defaultTarget);
-        fallbackChildPolicyWrapper = refCountedChildPolicyWrapperFactory.createOrGet(defaultTarget);
-      }
-    }
-
     // GuardedBy CachingRlsLbClient.lock
     void close() {
       synchronized (lock) { // Lock is already held, but ErrorProne can't tell

rls/src/test/java/io/grpc/rls/CachingRlsLbClientTest.java

@@ -191,7 +191,9 @@ public void setUpMockMetricRecorder() {
 
   @After
   public void tearDown() throws Exception {
-    rlsLbClient.close();
+    if (rlsLbClient != null) {
+      rlsLbClient.close();
+    }
     assertWithMessage(
             "On client shut down, RlsLoadBalancer must shut down with all its child loadbalancers.")
         .that(lbProvider.loadBalancers).isEmpty();
@@ -372,12 +374,14 @@ public void get_updatesLbState() throws Exception {
     ArgumentCaptor<SubchannelPicker> pickerCaptor = ArgumentCaptor.forClass(SubchannelPicker.class);
     ArgumentCaptor<ConnectivityState> stateCaptor =
         ArgumentCaptor.forClass(ConnectivityState.class);
-    inOrder.verify(helper, times(2))
+    inOrder.verify(helper, times(3))
         .updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());
 
     assertThat(new HashSet<>(pickerCaptor.getAllValues())).hasSize(1);
+    // TRANSIENT_FAILURE is because the test setup pretends fallback is not available.
     assertThat(stateCaptor.getAllValues())
-        .containsExactly(ConnectivityState.CONNECTING, ConnectivityState.READY);
+        .containsExactly(ConnectivityState.TRANSIENT_FAILURE, ConnectivityState.CONNECTING,
+            ConnectivityState.READY);
     Metadata headers = new Metadata();
     PickResult pickResult = getPickResultForCreate(pickerCaptor, headers);
     assertThat(pickResult.getStatus().isOk()).isTrue();
@@ -439,7 +443,7 @@ public void timeout_not_changing_picked_subchannel() throws Exception {
     ArgumentCaptor<SubchannelPicker> pickerCaptor = ArgumentCaptor.forClass(SubchannelPicker.class);
     ArgumentCaptor<ConnectivityState> stateCaptor =
         ArgumentCaptor.forClass(ConnectivityState.class);
-    verify(helper, times(4)).updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());
+    verify(helper, times(5)).updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());
 
     Metadata headers = new Metadata();
     PickResult pickResult = getPickResultForCreate(pickerCaptor, headers);
@@ -509,7 +513,7 @@ public void get_withAdaptiveThrottler() throws Exception {
     ArgumentCaptor<SubchannelPicker> pickerCaptor = ArgumentCaptor.forClass(SubchannelPicker.class);
     ArgumentCaptor<ConnectivityState> stateCaptor =
         ArgumentCaptor.forClass(ConnectivityState.class);
-    inOrder.verify(helper, times(2))
+    inOrder.verify(helper, times(3))
         .updateBalancingState(stateCaptor.capture(), pickerCaptor.capture());
 
     Metadata headers = new Metadata();
@@ -699,6 +703,7 @@ public void metricGauges() throws ExecutionException, InterruptedException, Time
 
     // Shutdown
     rlsLbClient.close();
+    rlsLbClient = null;
     verify(mockGaugeRegistration).close();
   }
 

rls/src/test/java/io/grpc/rls/RlsLoadBalancerTest.java

@@ -201,7 +201,13 @@ public void tearDown() {
 
   @Test
   public void lb_serverStatusCodeConversion() throws Exception {
-    deliverResolvedAddresses();
+    helper.getSynchronizationContext().execute(() -> {
+      try {
+        deliverResolvedAddresses();
+      } catch (Exception e) {
+        throw new RuntimeException(e);
+      }
+    });
     InOrder inOrder = inOrder(helper);
     inOrder.verify(helper)
         .updateBalancingState(eq(ConnectivityState.CONNECTING), pickerCaptor.capture());
@@ -236,7 +242,13 @@ public void lb_serverStatusCodeConversion() throws Exception {
 
   @Test
   public void lb_working_withDefaultTarget_rlsResponding() throws Exception {
-    deliverResolvedAddresses();
+    helper.getSynchronizationContext().execute(() -> {
+      try {
+        deliverResolvedAddresses();
+      } catch (Exception e) {
+        throw new RuntimeException(e);
+      }
+    });
     InOrder inOrder = inOrder(helper);
     inOrder.verify(helper)
         .updateBalancingState(eq(ConnectivityState.CONNECTING), pickerCaptor.capture());
@@ -257,7 +269,7 @@ public void lb_working_withDefaultTarget_rlsResponding() throws Exception {
     inOrder.verifyNoMoreInteractions();
 
     assertThat(res.getStatus().isOk()).isTrue();
-    assertThat(subchannels).hasSize(1);
+    assertThat(subchannels).hasSize(2); // includes fallback sub-channel
     FakeSubchannel searchSubchannel = subchannels.getLast();
     assertThat(subchannelIsReady(searchSubchannel)).isFalse();
 
@@ -277,7 +289,7 @@ public void lb_working_withDefaultTarget_rlsResponding() throws Exception {
     // other rls picker itself is ready due to first channel.
     assertThat(res.getStatus().isOk()).isTrue();
     assertThat(subchannelIsReady(res.getSubchannel())).isFalse();
-    assertThat(subchannels).hasSize(2);
+    assertThat(subchannels).hasSize(3); // includes fallback sub-channel
     FakeSubchannel rescueSubchannel = subchannels.getLast();
 
     // search subchannel is down, rescue subchannel is connecting
@@ -393,7 +405,13 @@ public void lb_working_withoutDefaultTarget_noRlsResponse() throws Exception {
   public void lb_working_withDefaultTarget_noRlsResponse() throws Exception {
     fakeThrottler.nextResult = true;
 
-    deliverResolvedAddresses();
+    helper.getSynchronizationContext().execute(() -> {
+      try {
+        deliverResolvedAddresses();
+      } catch (Exception e) {
+        throw new RuntimeException(e);
+      }
+    });
     InOrder inOrder = inOrder(helper);
     inOrder.verify(helper)
         .updateBalancingState(eq(ConnectivityState.CONNECTING), pickerCaptor.capture());
@@ -535,7 +553,13 @@ public void lb_working_withoutDefaultTarget() throws Exception {
 
   @Test
   public void lb_nameResolutionFailed() throws Exception {
-    deliverResolvedAddresses();
+    helper.getSynchronizationContext().execute(() -> {
+      try {
+        deliverResolvedAddresses();
+      } catch (Exception e) {
+        throw new RuntimeException(e);
+      }
+    });
     InOrder inOrder = inOrder(helper);
     inOrder.verify(helper)
         .updateBalancingState(eq(ConnectivityState.CONNECTING), pickerCaptor.capture());
@@ -545,7 +569,7 @@ public void lb_nameResolutionFailed() throws Exception {
     assertThat(subchannelIsReady(res.getSubchannel())).isFalse();
 
     inOrder.verify(helper).createSubchannel(any(CreateSubchannelArgs.class));
-    assertThat(subchannels).hasSize(1);
+    assertThat(subchannels).hasSize(2); // includes fallback sub-channel
 
     FakeSubchannel searchSubchannel = subchannels.getLast();
     searchSubchannel.updateState(ConnectivityStateInfo.forNonError(ConnectivityState.READY));