core: keep round_robin lb subchannel in TRANSIENT_FAILURE until becoming READY (#6657)

Make each subchannel created by RR stay in TRANSIENT_FAILURE state until READY. That is, each subchannel ignores consequent non-READY states after TRANSIENT_FAILURE.

Author: voidzcy

core/src/main/java/io/grpc/util/RoundRobinLoadBalancer.java

@@ -142,7 +142,13 @@ private void processSubchannelState(Subchannel subchannel, ConnectivityStateInfo
  if (stateInfo.getState() == IDLE) {
  subchannel.requestConnection();
  }
- getSubchannelStateInfoRef(subchannel).value = stateInfo;
+ Ref<ConnectivityStateInfo> subchannelStateRef = getSubchannelStateInfoRef(subchannel);
+ if (subchannelStateRef.value.getState().equals(TRANSIENT_FAILURE)) {
+ if (stateInfo.getState().equals(CONNECTING) || stateInfo.getState().equals(IDLE)) {
+ return;
+ }
+ }
+ subchannelStateRef.value = stateInfo;
  updateBalancingState();
  }
 

core/src/test/java/io/grpc/util/RoundRobinLoadBalancerTest.java

@@ -279,21 +279,61 @@ public void pickAfterStateChange() throws Exception {
  Status error = Status.UNKNOWN.withDescription("¯\\_(ツ)_//¯");
  deliverSubchannelState(subchannel,
  ConnectivityStateInfo.forTransientFailure(error));
- assertThat(subchannelStateInfo.value).isEqualTo(
-  ConnectivityStateInfo.forTransientFailure(error));
+ assertThat(subchannelStateInfo.value.getState()).isEqualTo(TRANSIENT_FAILURE);
+ assertThat(subchannelStateInfo.value.getStatus()).isEqualTo(error);
  inOrder.verify(mockHelper).updateBalancingState(eq(CONNECTING), pickerCaptor.capture());
  assertThat(pickerCaptor.getValue()).isInstanceOf(EmptyPicker.class);
 
  deliverSubchannelState(subchannel,
  ConnectivityStateInfo.forNonError(IDLE));
- assertThat(subchannelStateInfo.value).isEqualTo(
-  ConnectivityStateInfo.forNonError(IDLE));
+ assertThat(subchannelStateInfo.value.getState()).isEqualTo(TRANSIENT_FAILURE);
+ assertThat(subchannelStateInfo.value.getStatus()).isEqualTo(error);
 
  verify(subchannel, times(2)).requestConnection();
  verify(mockHelper, times(3)).createSubchannel(any(CreateSubchannelArgs.class));
  verifyNoMoreInteractions(mockHelper);
  }
 
+ @Test
+ public void stayTransientFailureUntilReady() {
+ InOrder inOrder = inOrder(mockHelper);
+ loadBalancer.handleResolvedAddresses(
+ ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(Attributes.EMPTY)
+ .build());
+
+ inOrder.verify(mockHelper).updateBalancingState(eq(CONNECTING), isA(EmptyPicker.class));
+
+ // Simulate state transitions for each subchannel individually.
+ for (Subchannel sc : loadBalancer.getSubchannels()) {
+ Status error = Status.UNKNOWN.withDescription("connection broken");
+ deliverSubchannelState(
+ sc,
+ ConnectivityStateInfo.forTransientFailure(error));
+ deliverSubchannelState(
+ sc,
+ ConnectivityStateInfo.forNonError(IDLE));
+ deliverSubchannelState(
+ sc,
+ ConnectivityStateInfo.forNonError(CONNECTING));
+ Ref<ConnectivityStateInfo> scStateInfo = sc.getAttributes().get(
+ STATE_INFO);
+ assertThat(scStateInfo.value.getState()).isEqualTo(TRANSIENT_FAILURE);
+ assertThat(scStateInfo.value.getStatus()).isEqualTo(error);
+ }
+ inOrder.verify(mockHelper).updateBalancingState(eq(TRANSIENT_FAILURE), isA(EmptyPicker.class));
+ inOrder.verifyNoMoreInteractions();
+
+ Subchannel subchannel = loadBalancer.getSubchannels().iterator().next();
+ deliverSubchannelState(subchannel, ConnectivityStateInfo.forNonError(READY));
+ Ref<ConnectivityStateInfo> subchannelStateInfo = subchannel.getAttributes().get(
+ STATE_INFO);
+ assertThat(subchannelStateInfo.value).isEqualTo(ConnectivityStateInfo.forNonError(READY));
+ inOrder.verify(mockHelper).updateBalancingState(eq(READY), isA(ReadyPicker.class));
+
+ verify(mockHelper, times(3)).createSubchannel(any(CreateSubchannelArgs.class));
+ verifyNoMoreInteractions(mockHelper);
+ }
+
  @Test
  public void pickerRoundRobin() throws Exception {
  Subchannel subchannel = mock(Subchannel.class);