api: deprecate Helper.updateSubchannelAddresses() and add equivalent on Subchannel

api/src/main/java/io/grpc/LoadBalancer.java

@@ -963,7 +963,9 @@ public Subchannel createSubchannel(CreateSubchannelArgs args) {
      * href="https://github.com/grpc/grpc-java/issues/5015">#5015</a> for the background.
      *
      * @since 1.4.0
+     * @deprecated use {@link Subchannel#updateAddresses} instead
      */
+    @Deprecated
     public final void updateSubchannelAddresses(
         Subchannel subchannel, EquivalentAddressGroup addrs) {
       checkNotNull(addrs, "addrs");
@@ -982,7 +984,9 @@ public final void updateSubchannelAddresses(
      * @throws IllegalArgumentException if {@code subchannel} was not returned from {@link
      *     #createSubchannel} or {@code addrs} is empty
      * @since 1.14.0
+     * @deprecated use {@link Subchannel#updateAddresses} instead
      */
+    @Deprecated
     public void updateSubchannelAddresses(
         Subchannel subchannel, List<EquivalentAddressGroup> addrs) {
       throw new UnsupportedOperationException();
@@ -1301,6 +1305,19 @@ public ChannelLogger getChannelLogger() {
       throw new UnsupportedOperationException();
     }
 
+    /**
+     * Replaces the existing addresses used with this {@code Subchannel}. If the new and old
+     * addresses overlap, the Subchannel can continue using an existing connection.
+     *
+     * <p>It must be called from the Synchronization Context or will throw.
+     *
+     * @throws IllegalArgumentException if {@code addrs} is empty
+     * @since 1.22.0
+     */
+    public void updateAddresses(List<EquivalentAddressGroup> addrs) {
+      throw new UnsupportedOperationException();
+    }
+
     /**
      * (Internal use only) returns an object that represents the underlying subchannel that is used
      * by the Channel for sending RPCs when this {@link Subchannel} is picked.  This is an opaque

api/src/test/java/io/grpc/LoadBalancerTest.java

@@ -170,6 +170,7 @@ public void helper_createSubchannelList_throws() {
     }
   }
 
+  @Deprecated
   @Test
   public void helper_updateSubchannelAddresses_delegates() {
     class OverrideUpdateSubchannel extends NoopHelper {
@@ -190,6 +191,7 @@ public void updateSubchannelAddresses(
     assertThat(helper.ran).isTrue();
   }
 
+  @Deprecated
   @Test(expected = UnsupportedOperationException.class)
   public void helper_updateSubchannelAddressesList_throws() {
     new NoopHelper().updateSubchannelAddresses(null, Arrays.asList(eag));

core/src/main/java/io/grpc/internal/ManagedChannelImpl.java

@@ -1132,6 +1132,7 @@ public void run() {
       syncContext.execute(new LoadBalancerRefreshNameResolution());
     }
 
+    @Deprecated
     @Override
     public void updateSubchannelAddresses(
         LoadBalancer.Subchannel subchannel, List<EquivalentAddressGroup> addrs) {
@@ -1606,6 +1607,12 @@ public Object getInternalSubchannel() {
     public ChannelLogger getChannelLogger() {
       return subchannel.getChannelLogger();
     }
+
+    @Override
+    public void updateAddresses(List<EquivalentAddressGroup> addrs) {
+      syncContext.throwIfNotInThisSynchronizationContext();
+      subchannel.updateAddresses(addrs);
+    }
   }
 
   @Override

core/src/main/java/io/grpc/internal/PickFirstLoadBalancer.java

@@ -64,7 +64,7 @@ public void onSubchannelState(ConnectivityStateInfo stateInfo) {
       helper.updateBalancingState(CONNECTING, new Picker(PickResult.withSubchannel(subchannel)));
       subchannel.requestConnection();
     } else {
-      helper.updateSubchannelAddresses(subchannel, servers);
+      subchannel.updateAddresses(servers);
     }
   }
 

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

@@ -51,6 +51,7 @@ public Subchannel createSubchannel(CreateSubchannelArgs args) {
     return delegate().createSubchannel(args);
   }
 
+  @Deprecated
   @Override
   public void updateSubchannelAddresses(
       Subchannel subchannel, List<EquivalentAddressGroup> addrs) {

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

@@ -74,6 +74,11 @@ public Object getInternalSubchannel() {
     return delegate().getInternalSubchannel();
   }
 
+  @Override
+  public void updateAddresses(List<EquivalentAddressGroup> addrs) {
+    delegate().updateAddresses(addrs);
+  }
+
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this).add("delegate", delegate()).toString();

core/src/test/java/io/grpc/internal/ManagedChannelImplIdlenessTest.java

@@ -549,7 +549,7 @@ private static void updateSubchannelAddressesSafely(
         new Runnable() {
           @Override
           public void run() {
-            helper.updateSubchannelAddresses(subchannel, addrs);
+            subchannel.updateAddresses(Collections.singletonList(addrs));
           }
         });
   }

core/src/test/java/io/grpc/internal/ManagedChannelImplTest.java

@@ -183,7 +183,16 @@ public String toString() {
           return "test-addr";
         }
       };
+  private final SocketAddress socketAddress2 =
+      new SocketAddress() {
+        @Override
+        public String toString() {
+          return "test-addr";
+        }
+      };
   private final EquivalentAddressGroup addressGroup = new EquivalentAddressGroup(socketAddress);
+  private final EquivalentAddressGroup addressGroup2 =
+      new EquivalentAddressGroup(Arrays.asList(socketAddress, socketAddress2));
   private final FakeClock timer = new FakeClock();
   private final FakeClock executor = new FakeClock();
   private final FakeClock balancerRpcExecutor = new FakeClock();
@@ -1301,6 +1310,11 @@ public void run() {
         .newClientTransport(
             eq(socketAddress), eq(clientTransportOptions), isA(TransportLogger.class));
 
+    // updateAddresses()
+    updateAddressesSafely(helper, sub1, Collections.singletonList(addressGroup2));
+    assertThat(((InternalSubchannel) sub1.getInternalSubchannel()).getAddressGroups())
+        .isEqualTo(Collections.singletonList(addressGroup2));
+
     // shutdown() has a delay
     shutdownSafely(helper, sub1);
     timer.forwardTime(ManagedChannelImpl.SUBCHANNEL_SHUTDOWN_DELAY_SECONDS - 1, TimeUnit.SECONDS);
@@ -4030,6 +4044,17 @@ public void run() {
         });
   }
 
+  private static void updateAddressesSafely(
+      Helper helper, final Subchannel subchannel, final List<EquivalentAddressGroup> addrs) {
+    helper.getSynchronizationContext().execute(
+        new Runnable() {
+          @Override
+          public void run() {
+            subchannel.updateAddresses(addrs);
+          }
+        });
+  }
+
   private static void shutdownSafely(
       final Helper helper, final Subchannel subchannel) {
     helper.getSynchronizationContext().execute(

core/src/test/java/io/grpc/internal/PickFirstLoadBalancerTest.java

@@ -172,15 +172,15 @@ public void pickAfterResolvedAndUnchanged() throws Exception {
     verify(mockSubchannel).requestConnection();
     loadBalancer.handleResolvedAddresses(
         ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(affinity).build());
+    verify(mockSubchannel).updateAddresses(eq(servers));
     verifyNoMoreInteractions(mockSubchannel);
 
     verify(mockHelper).createSubchannel(createArgsCaptor.capture());
     assertThat(createArgsCaptor.getValue()).isNotNull();
     verify(mockHelper)
         .updateBalancingState(isA(ConnectivityState.class), isA(SubchannelPicker.class));
     // Updating the subchannel addresses is unnecessary, but doesn't hurt anything
-    verify(mockHelper).updateSubchannelAddresses(
-        eq(mockSubchannel), ArgumentMatchers.<EquivalentAddressGroup>anyList());
+    verify(mockSubchannel).updateAddresses(ArgumentMatchers.<EquivalentAddressGroup>anyList());
 
     verifyNoMoreInteractions(mockHelper);
   }
@@ -191,7 +191,7 @@ public void pickAfterResolvedAndChanged() throws Exception {
     List<EquivalentAddressGroup> newServers =
         Lists.newArrayList(new EquivalentAddressGroup(socketAddr));
 
-    InOrder inOrder = inOrder(mockHelper);
+    InOrder inOrder = inOrder(mockHelper, mockSubchannel);
 
     loadBalancer.handleResolvedAddresses(
         ResolvedAddresses.newBuilder().setAddresses(servers).setAttributes(affinity).build());
@@ -205,7 +205,7 @@ public void pickAfterResolvedAndChanged() throws Exception {
 
     loadBalancer.handleResolvedAddresses(
         ResolvedAddresses.newBuilder().setAddresses(newServers).setAttributes(affinity).build());
-    inOrder.verify(mockHelper).updateSubchannelAddresses(eq(mockSubchannel), eq(newServers));
+    inOrder.verify(mockSubchannel).updateAddresses(eq(newServers));
 
     verifyNoMoreInteractions(mockSubchannel);
     verifyNoMoreInteractions(mockHelper);

grpclb/src/main/java/io/grpc/grpclb/GrpclbState.java

@@ -438,7 +438,7 @@ private void useRoundRobinLists(
         } else {
           checkState(subchannels.size() == 1, "Unexpected Subchannel count: %s", subchannels);
           subchannel = subchannels.values().iterator().next();
-          helper.updateSubchannelAddresses(subchannel, eagList);
+          subchannel.updateAddresses(eagList);
         }
         subchannels = Collections.singletonMap(eagList, subchannel);
         newBackendList.add(

grpclb/src/test/java/io/grpc/grpclb/GrpclbLoadBalancerTest.java

@@ -1776,8 +1776,7 @@ public void grpclbWorking_pickFirstMode() throws Exception {
     // createSubchannel() has ever been called only once
     verify(helper, times(1)).createSubchannel(any(List.class), any(Attributes.class));
     assertThat(mockSubchannels).isEmpty();
-    inOrder.verify(helper).updateSubchannelAddresses(
-        same(subchannel),
+    verify(subchannel).updateAddresses(
         eq(Arrays.asList(
                 new EquivalentAddressGroup(backends2.get(0).addr, eagAttrsWithToken("token0001")),
                 new EquivalentAddressGroup(backends2.get(2).addr,
@@ -1874,8 +1873,7 @@ public void pickFirstMode_fallback() throws Exception {
     // createSubchannel() has ever been called only once
     verify(helper, times(1)).createSubchannel(any(List.class), any(Attributes.class));
     assertThat(mockSubchannels).isEmpty();
-    inOrder.verify(helper).updateSubchannelAddresses(
-        same(subchannel),
+    verify(subchannel).updateAddresses(
         eq(Arrays.asList(
                 new EquivalentAddressGroup(backends1.get(0).addr, eagAttrsWithToken("token0001")),
                 new EquivalentAddressGroup(backends1.get(1).addr,