expose APIs similar to internalConfigurator

AgraVator · AgraVator · commit d8398f516737 · 2026-03-16T12:31:10.000+05:30
diff --git a/api/src/main/java/io/grpc/ChildChannelConfigurer.java b/api/src/main/java/io/grpc/ChildChannelConfigurer.java
@@ -16,7 +16,7 @@
 
 package io.grpc;
 
-import java.util.function.Consumer;
+
 
 /**
  * A configurer for child channels created by gRPC's internal infrastructure.
@@ -44,27 +44,31 @@
  *     .build();
  * }</pre>
  *
- * <p>Implementations must be thread-safe as {@link #accept} may be invoked concurrently
+ * <p>Implementations must be thread-safe as the configure methods may be invoked concurrently
  * by multiple internal components.
  *
  * @since 1.79.0
  */
 @ExperimentalApi("https://github.com/grpc/grpc-java/issues/12574")
-@FunctionalInterface
-public interface ChildChannelConfigurer extends Consumer<ManagedChannelBuilder<?>> {
+public interface ChildChannelConfigurer {
 
   /**
    * Configures a builder for a new child channel.
    *
    * <p>This method is invoked synchronously during the creation of the child channel,
    * before {@link ManagedChannelBuilder#build()} is called.
    *
-   * <p>Note: The provided {@code builder} is generic (`?`). Implementations should use
-   * universal configuration methods (like {@code intercept()}, {@code userAgent()}) on the
-   * builder rather than casting it to specific implementation types.
-   *
    * @param builder the mutable channel builder for the new child channel
    */
-  @Override
-  void accept(ManagedChannelBuilder<?> builder);
+  default void configureChannelBuilder(ManagedChannelBuilder<?> builder) {}
+
+  /**
+   * Configures a builder for a new child server.
+   *
+   * <p>This method is invoked synchronously during the creation of the child server,
+   * before {@link ServerBuilder#build()} is called.
+   *
+   * @param builder the mutable server builder for the new child server
+   */
+  default void configureServerBuilder(ServerBuilder<?> builder) {}
 }
diff --git a/api/src/test/java/io/grpc/ChildChannelConfigurerTest.java b/api/src/test/java/io/grpc/ChildChannelConfigurerTest.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2026 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class ChildChannelConfigurerTest {
+
+  @Test
+  public void defaultMethods_doNothing() {
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {};
+    
+    ManagedChannelBuilder<?> mockChannelBuilder = mock(ManagedChannelBuilder.class);
+    configurer.configureChannelBuilder(mockChannelBuilder);
+    verifyNoInteractions(mockChannelBuilder);
+
+    ServerBuilder<?> mockServerBuilder = mock(ServerBuilder.class);
+    configurer.configureServerBuilder(mockServerBuilder);
+    verifyNoInteractions(mockServerBuilder);
+  }
+}
diff --git a/api/src/test/java/io/grpc/NameResolverTest.java b/api/src/test/java/io/grpc/NameResolverTest.java
@@ -147,8 +147,8 @@ public void uncaughtException(Thread t, Throwable e) {
     
     // Validate configurer accepts builders
     ManagedChannelBuilder<?> mockBuilder = mock(ManagedChannelBuilder.class);
-    args.getChildChannelConfigurer().accept(mockBuilder);
-    verify(childChannelConfigurer).accept(mockBuilder);
+    args.getChildChannelConfigurer().configureChannelBuilder(mockBuilder);
+    verify(childChannelConfigurer).configureChannelBuilder(mockBuilder);
   }
 
   @Test
diff --git a/core/src/main/java/io/grpc/internal/ManagedChannelImpl.java b/core/src/main/java/io/grpc/internal/ManagedChannelImpl.java
@@ -155,7 +155,7 @@ public Result selectConfig(PickSubchannelArgs args) {
   private static final LoadBalancer.PickDetailsConsumer NOOP_PICK_DETAILS_CONSUMER =
       new LoadBalancer.PickDetailsConsumer() {};
 
-  private ChildChannelConfigurer childChannelConfigurer = builder -> {};
+  private ChildChannelConfigurer childChannelConfigurer = new ChildChannelConfigurer() {};
 
   private final InternalLogId logId;
   private final String target;
@@ -1580,7 +1580,9 @@ protected ManagedChannelBuilder<?> delegate() {
 
       // Note that we follow the global configurator pattern and try to fuse the configurations as
       // soon as the builder gets created
-      builder.childChannelConfigurer(childChannelConfigurer);
+      if (childChannelConfigurer != null) {
+        childChannelConfigurer.configureChannelBuilder(builder);
+      }
 
       return builder
           // TODO(zdapeng): executors should not outlive the parent channel.
diff --git a/core/src/main/java/io/grpc/internal/ManagedChannelImplBuilder.java b/core/src/main/java/io/grpc/internal/ManagedChannelImplBuilder.java
@@ -125,7 +125,7 @@ public static ManagedChannelBuilder<?> forTarget(String target) {
 
   private static final Method GET_CLIENT_INTERCEPTOR_METHOD;
 
-  ChildChannelConfigurer childChannelConfigurer = builder -> {};
+  ChildChannelConfigurer childChannelConfigurer = new ChildChannelConfigurer() {};
 
   @Override
   public ManagedChannelImplBuilder childChannelConfigurer(
diff --git a/core/src/test/java/io/grpc/internal/ManagedChannelImplBuilderTest.java b/core/src/test/java/io/grpc/internal/ManagedChannelImplBuilderTest.java
@@ -786,11 +786,14 @@ public void childChannelConfigurer_propagatesMetricsAndInterceptors_xdsTarget()
     ClientInterceptor mockInterceptor = mock(ClientInterceptor.class);
 
     // Define the Configurer
-    ChildChannelConfigurer configurer = (builder) -> {
-      builder.addMetricSink(mockMetricSink);
-
-      // Assuming InternalInterceptorFactory is also accessible
-      builder.interceptWithTarget(target -> mockInterceptor);
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        builder.addMetricSink(mockMetricSink);
+
+        // Assuming InternalInterceptorFactory is also accessible
+        builder.interceptWithTarget(target -> mockInterceptor);
+      }
     };
 
     // Mock NameResolver.Factory to capture Args
@@ -833,7 +836,7 @@ public void childChannelConfigurer_propagatesMetricsAndInterceptors_xdsTarget()
     // Stub addMetricSink to return the builder to avoid generic return type issues
     doReturn(mockChildBuilder).when(mockChildBuilder).addMetricSink(any());
 
-    configurer.accept(mockChildBuilder);
+    configurer.configureChannelBuilder(mockChildBuilder);
     verify(mockChildBuilder).addMetricSink(mockMetricSink);
     verify(mockChildBuilder).interceptWithTarget(any());
   }
diff --git a/core/src/test/java/io/grpc/internal/ManagedChannelImplTest.java b/core/src/test/java/io/grpc/internal/ManagedChannelImplTest.java
@@ -69,7 +69,6 @@
 import io.grpc.Channel;
 import io.grpc.ChannelCredentials;
 import io.grpc.ChannelLogger;
-import io.grpc.ChildChannelConfigurer;
 import io.grpc.ClientCall;
 import io.grpc.ClientInterceptor;
 import io.grpc.ClientInterceptors;
@@ -102,7 +101,6 @@
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.LongCounterMetricInstrument;
 import io.grpc.ManagedChannel;
-import io.grpc.ManagedChannelBuilder;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
 import io.grpc.MethodDescriptor.MethodType;
@@ -306,8 +304,6 @@ public String getPolicyName() {
   private ArgumentCaptor<ResolvedAddresses> resolvedAddressCaptor;
   private ArgumentCaptor<ClientStreamListener> streamListenerCaptor =
       ArgumentCaptor.forClass(ClientStreamListener.class);
-  @Mock
-  private ChildChannelConfigurer mockChildChannelConfigurer;
 
 
   private void createChannel(ClientInterceptor... interceptors) {
@@ -3775,6 +3771,7 @@ public void channelsAndSubchannels_oob_instrumented_state() throws Exception {
     assertEquals(SHUTDOWN, getStats(channel).state);
     assertEquals(SHUTDOWN, getStats(oobChannel).state);
   }
+
   @Test
   public void binaryLogInstalled() throws Exception {
     final SettableFuture<Boolean> intercepted = SettableFuture.create();
diff --git a/xds/src/main/java/io/grpc/xds/GrpcXdsTransportFactory.java b/xds/src/main/java/io/grpc/xds/GrpcXdsTransportFactory.java
@@ -88,7 +88,7 @@ public GrpcXdsTransport(Bootstrapper.ServerInfo serverInfo, CallCredentials call
       ManagedChannelBuilder<?> channelBuilder = Grpc.newChannelBuilder(target, channelCredentials)
           .keepAliveTime(5, TimeUnit.MINUTES);
       if (childChannelConfigurer != null) {
-        childChannelConfigurer.accept(channelBuilder);
+        childChannelConfigurer.configureChannelBuilder(channelBuilder);
       }
       this.channel = channelBuilder.build();
       this.callCredentials = callCredentials;
diff --git a/xds/src/main/java/io/grpc/xds/XdsServerBuilder.java b/xds/src/main/java/io/grpc/xds/XdsServerBuilder.java
@@ -59,7 +59,7 @@ public final class XdsServerBuilder extends ForwardingServerBuilder<XdsServerBui
   private Map<String, ?> bootstrapOverride;
   private long drainGraceTime = 10;
   private TimeUnit drainGraceTimeUnit = TimeUnit.MINUTES;
-  private ChildChannelConfigurer childChannelConfigurer = builder -> { };
+  private ChildChannelConfigurer childChannelConfigurer = new ChildChannelConfigurer() {};
 
   private XdsServerBuilder(NettyServerBuilder nettyDelegate, int port) {
     this.delegate = nettyDelegate;
diff --git a/xds/src/main/java/io/grpc/xds/XdsServerWrapper.java b/xds/src/main/java/io/grpc/xds/XdsServerWrapper.java
@@ -129,7 +129,7 @@ public void uncaughtException(Thread t, Throwable e) {
   // NamedFilterConfig.filterStateKey -> filter_instance.
   private final HashMap<String, Filter> activeFiltersDefaultChain = new HashMap<>();
 
-  private ChildChannelConfigurer childChannelConfigurer = builder -> { };
+  private ChildChannelConfigurer childChannelConfigurer = new ChildChannelConfigurer() {};
 
   XdsServerWrapper(
       String listenerAddress,
diff --git a/xds/src/test/java/io/grpc/xds/FakeControlPlaneXdsIntegrationTest.java b/xds/src/test/java/io/grpc/xds/FakeControlPlaneXdsIntegrationTest.java
@@ -22,6 +22,13 @@
 import static io.grpc.xds.XdsTestControlPlaneService.ADS_TYPE_URL_CDS;
 import static io.grpc.xds.XdsTestControlPlaneService.ADS_TYPE_URL_EDS;
 import static org.junit.Assert.assertEquals;
+import static org.mockito.AdditionalAnswers.delegatesTo;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyList;
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.timeout;
+import static org.mockito.Mockito.verify;
 
 import com.github.xds.type.v3.TypedStruct;
 import com.google.common.collect.ImmutableMap;
@@ -47,15 +54,23 @@
 import io.envoyproxy.envoy.extensions.load_balancing_policies.wrr_locality.v3.WrrLocality;
 import io.grpc.CallOptions;
 import io.grpc.Channel;
+import io.grpc.ChildChannelConfigurer;
 import io.grpc.ClientCall;
 import io.grpc.ClientInterceptor;
 import io.grpc.ClientStreamTracer;
 import io.grpc.ForwardingClientCall.SimpleForwardingClientCall;
 import io.grpc.ForwardingClientCallListener;
+import io.grpc.Grpc;
+import io.grpc.InsecureChannelCredentials;
+import io.grpc.InsecureServerCredentials;
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
+import io.grpc.MetricSink;
+import io.grpc.NoopMetricSink;
+import io.grpc.Server;
 import io.grpc.testing.protobuf.SimpleRequest;
 import io.grpc.testing.protobuf.SimpleResponse;
 import io.grpc.testing.protobuf.SimpleServiceGrpc;
@@ -339,4 +354,63 @@ public void pingPong_logicalDns_authorityOverride() {
       System.clearProperty("GRPC_EXPERIMENTAL_XDS_AUTHORITY_REWRITE");
     }
   }
+
+  @Test
+  public void childChannelConfigurer_passesMetricSinkToChannel_E2E() {
+    MetricSink mockSink = mock(MetricSink.class, delegatesTo(new NoopMetricSink()));
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        builder.addMetricSink(mockSink);
+      }
+    };
+
+    ManagedChannel channel = Grpc.newChannelBuilder("test-xds:///test-server",
+            InsecureChannelCredentials.create())
+        .childChannelConfigurer(configurer)
+        .build();
+
+    try {
+      SimpleServiceGrpc.SimpleServiceBlockingStub blockingStub = SimpleServiceGrpc.newBlockingStub(
+          channel);
+      blockingStub.unaryRpc(SimpleRequest.getDefaultInstance());
+
+      // The xDS client inside the channel configurer will have created an ADS stream.
+      // The metric sink should have received attempt or connection metrics.
+      verify(mockSink, timeout(5000).atLeastOnce())
+          .addLongCounter(any(), anyLong(), anyList(), anyList());
+    } finally {
+      channel.shutdownNow();
+    }
+  }
+
+  @Test
+  public void childChannelConfigurer_passesMetricSinkToServer_E2E() throws Exception {
+    MetricSink mockSink = mock(MetricSink.class, delegatesTo(new NoopMetricSink()));
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        // Child channels (xDS client connections) created by this server get the sink.
+        builder.addMetricSink(mockSink);
+      }
+    };
+
+    // We start an XdsServer manually.
+    // XdsServer needs RDS, LDS, etc. from control plane.
+    XdsServerBuilder serverBuilder = XdsServerBuilder.forPort(
+            0, InsecureServerCredentials.create())
+        .addService(new SimpleServiceGrpc.SimpleServiceImplBase() {})
+        .overrideBootstrapForTest(controlPlane.defaultBootstrapOverride())
+        .childChannelConfigurer(configurer);
+        
+    Server childServer = serverBuilder.build().start();
+
+    try {
+      // The server xDS client will connect to control plane to get LDS.
+      verify(mockSink, timeout(5000).atLeastOnce())
+          .addLongCounter(any(), anyLong(), anyList(), anyList());
+    } finally {
+      childServer.shutdownNow();
+    }
+  }
 }
diff --git a/xds/src/test/java/io/grpc/xds/GrpcXdsTransportFactoryTest.java b/xds/src/test/java/io/grpc/xds/GrpcXdsTransportFactoryTest.java
@@ -159,7 +159,12 @@ public void verifyConfigApplied_interceptor() {
         .thenReturn(new io.grpc.NoopClientCall<>());
 
     // Create Configurer that adds the interceptor
-    ChildChannelConfigurer configurer = (builder) -> builder.intercept(mockInterceptor);
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        builder.intercept(mockInterceptor);
+      }
+    };
 
     // Create Factory
     GrpcXdsTransportFactory factory = new GrpcXdsTransportFactory(
@@ -204,7 +209,7 @@ public void useChildChannelConfigurer() {
         Bootstrapper.ServerInfo.create("localhost:8080", InsecureChannelCredentials.create()));
 
     // Verify Configurer was accessed and applied
-    verify(mockConfigurer).accept(any(ManagedChannelBuilder.class));
+    verify(mockConfigurer).configureChannelBuilder(any(ManagedChannelBuilder.class));
 
     transport.shutdown();
   }
@@ -215,10 +220,15 @@ public void verifyConfigApplied_maxInboundMessageSize() {
     ManagedChannelBuilder<?> mockBuilder = mock(ManagedChannelBuilder.class);
 
     // Create Configurer that modifies message size
-    ChildChannelConfigurer configurer = (builder) -> builder.maxInboundMessageSize(1024);
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        builder.maxInboundMessageSize(1024);
+      }
+    };
 
     // Apply configurer to builder
-    configurer.accept(mockBuilder);
+    configurer.configureChannelBuilder(mockBuilder);
 
     // Verify builder was modified
     verify(mockBuilder).maxInboundMessageSize(1024);
@@ -229,13 +239,16 @@ public void verifyConfigApplied_interceptors() {
     ClientInterceptor interceptor1 = mock(ClientInterceptor.class);
     ClientInterceptor interceptor2 = mock(ClientInterceptor.class);
 
-    ChildChannelConfigurer configurer = builder -> {
-      builder.intercept(interceptor1);
-      builder.intercept(interceptor2);
+    ChildChannelConfigurer configurer = new ChildChannelConfigurer() {
+      @Override
+      public void configureChannelBuilder(ManagedChannelBuilder<?> builder) {
+        builder.intercept(interceptor1);
+        builder.intercept(interceptor2);
+      }
     };
 
     ManagedChannelBuilder<?> mockBuilder = mock(ManagedChannelBuilder.class);
-    configurer.accept(mockBuilder);
+    configurer.configureChannelBuilder(mockBuilder);
 
     verify(mockBuilder).intercept(interceptor1);
     verify(mockBuilder).intercept(interceptor2);
diff --git a/xds/src/test/java/io/grpc/xds/SharedXdsClientPoolProviderTest.java b/xds/src/test/java/io/grpc/xds/SharedXdsClientPoolProviderTest.java

Original file line number	Diff line number	Diff line change
`@@ -147,8 +147,8 @@ public void uncaughtException(Thread t, Throwable e) {`
`147`	`147`
`148`	`148`	`// Validate configurer accepts builders`
`149`	`149`	`ManagedChannelBuilder<?> mockBuilder = mock(ManagedChannelBuilder.class);`
`150`		`- args.getChildChannelConfigurer().accept(mockBuilder);`
`151`		`- verify(childChannelConfigurer).accept(mockBuilder);`
	`150`	`+ args.getChildChannelConfigurer().configureChannelBuilder(mockBuilder);`
	`151`	`+ verify(childChannelConfigurer).configureChannelBuilder(mockBuilder);`
`152`	`152`	`}`
`153`	`153`
`154`	`154`	`@Test`
Original file line number	Diff line number	Diff line change
`@@ -88,7 +88,7 @@ public GrpcXdsTransport(Bootstrapper.ServerInfo serverInfo, CallCredentials call`
`88`	`88`	`ManagedChannelBuilder<?> channelBuilder = Grpc.newChannelBuilder(target, channelCredentials)`
`89`	`89`	`.keepAliveTime(5, TimeUnit.MINUTES);`
`90`	`90`	`if (childChannelConfigurer != null) {`
`91`		`- childChannelConfigurer.accept(channelBuilder);`
	`91`	`+ childChannelConfigurer.configureChannelBuilder(channelBuilder);`
`92`	`92`	`}`
`93`	`93`	`this.channel = channelBuilder.build();`
`94`	`94`	`this.callCredentials = callCredentials;`