Add internal channel builder API to get target

This will be used for gRFC A66's OTel per-RPC metric label:

> `grpc.target` : Canonicalized target URI used when creating gRPC
> Channel, e.g. "dns:///pubsub.googleapis.com:443",
> "xds:///helloworld-gke:8000". Canonicalized target URI is the form
> with the scheme included if the user didn't mention the scheme
> (`scheme://[authority]/path`).

The majority of the changes are to move target computation from
ManagedChannelImpl into the builder. A small hack API was added to
ManagedChannelBuilder to get the target to create an interceptor.

api/src/main/java/io/grpc/ForwardingChannelBuilder2.java

@@ -94,6 +94,12 @@ public abstract class ForwardingChannelBuilder2<T extends ManagedChannelBuilder<
     return thisT();
   }
 
+  @Override
+  protected T interceptWithTarget(InterceptorFactory factory) {
+    delegate().interceptWithTarget(factory);
+    return thisT();
+  }
+
   @Override
   public T addTransportFilter(ClientTransportFilter transportFilter) {
     delegate().addTransportFilter(transportFilter);

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

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2024 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;
+
+/**
+ * Internal accessors for {@link ManagedChannelBuilder}.
+ */
+public final class InternalManagedChannelBuilder {
+  private InternalManagedChannelBuilder() {}
+
+  public static <T extends ManagedChannelBuilder<T>> T interceptWithTarget(
+      ManagedChannelBuilder<T> builder, InternalInterceptorFactory factory) {
+    return builder.interceptWithTarget(factory);
+  }
+
+  public interface InternalInterceptorFactory extends ManagedChannelBuilder.InterceptorFactory {}
+}

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

@@ -159,6 +159,21 @@ public abstract class ManagedChannelBuilder<T extends ManagedChannelBuilder<T>>
    */
   public abstract T intercept(ClientInterceptor... interceptors);
 
+  /**
+   * Internal-only: Adds a factory that will construct an interceptor based on the channel's target.
+   * This can be used to work around nameResolverFactory() changing the target string.
+   */
+  @Internal
+  protected T interceptWithTarget(InterceptorFactory factory) {
+    throw new UnsupportedOperationException();
+  }
+
+  /** Internal-only. */
+  @Internal
+  protected interface InterceptorFactory {
+    ClientInterceptor newInterceptor(String target);
+  }
+
   /**
    * Adds a {@link ClientTransportFilter}. The order of filters being added is the order they will
    * be executed

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

@@ -93,9 +93,7 @@ import io.grpc.internal.ManagedChannelServiceConfig.ServiceConfigConvertedSelect
 import io.grpc.internal.RetriableStream.ChannelBufferMeter;
 import io.grpc.internal.RetriableStream.Throttle;
 import io.grpc.internal.RetryingNameResolver.ResolutionResultListener;
-import java.net.SocketAddress;
 import java.net.URI;
-import java.net.URISyntaxException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -117,7 +115,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.logging.Level;
 import java.util.logging.Logger;
-import java.util.regex.Pattern;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
@@ -129,12 +126,6 @@ final class ManagedChannelImpl extends ManagedChannel implements
   @VisibleForTesting
   static final Logger logger = Logger.getLogger(ManagedChannelImpl.class.getName());
 
-  // Matching this pattern means the target string is a URI target or at least intended to be one.
-  // A URI target must be an absolute hierarchical URI.
-  // From RFC 2396: scheme = alpha *( alpha | digit | "+" | "-" | "." )
-  @VisibleForTesting
-  static final Pattern URI_PATTERN = Pattern.compile("[a-zA-Z][a-zA-Z0-9+.-]*:/.*");
-
   static final long IDLE_TIMEOUT_MILLIS_DISABLE = -1;
 
   static final long SUBCHANNEL_SHUTDOWN_DELAY_SECONDS = 5;
@@ -595,6 +586,8 @@ final class ManagedChannelImpl extends ManagedChannel implements
   ManagedChannelImpl(
       ManagedChannelImplBuilder builder,
       ClientTransportFactory clientTransportFactory,
+      URI targetUri,
+      NameResolverProvider nameResolverProvider,
       BackoffPolicy.Provider backoffPolicyProvider,
       ObjectPool<? extends Executor> balancerRpcExecutorPool,
       Supplier<Stopwatch> stopwatchSupplier,
@@ -625,10 +618,8 @@ final class ManagedChannelImpl extends ManagedChannel implements
     this.retryEnabled = builder.retryEnabled;
     this.loadBalancerFactory = new AutoConfiguredLoadBalancerFactory(builder.defaultLbPolicy);
     this.nameResolverRegistry = builder.nameResolverRegistry;
-    ResolvedNameResolver resolvedResolver = getNameResolverProvider(
-        target, nameResolverRegistry, transportFactory.getSupportedSocketAddressTypes());
-    this.targetUri = resolvedResolver.targetUri;
-    this.nameResolverProvider = resolvedResolver.provider;
+    this.targetUri = checkNotNull(targetUri, "targetUri");
+    this.nameResolverProvider = checkNotNull(nameResolverProvider, "nameResolverProvider");
     ScParser serviceConfigParser =
         new ScParser(
             retryEnabled,
@@ -722,69 +713,6 @@ final class ManagedChannelImpl extends ManagedChannel implements
         MetricInstrumentRegistry.getDefaultRegistry());
   }
 
-  @VisibleForTesting
-  static class ResolvedNameResolver {
-    public final URI targetUri;
-    public final NameResolverProvider provider;
-
-    public ResolvedNameResolver(URI targetUri, NameResolverProvider provider) {
-      this.targetUri = checkNotNull(targetUri, "targetUri");
-      this.provider = checkNotNull(provider, "provider");
-    }
-  }
-
-  @VisibleForTesting
-  static ResolvedNameResolver getNameResolverProvider(
-      String target, NameResolverRegistry nameResolverRegistry,
-      Collection<Class<? extends SocketAddress>> channelTransportSocketAddressTypes) {
-    // Finding a NameResolver. Try using the target string as the URI. If that fails, try prepending
-    // "dns:///".
-    NameResolverProvider provider = null;
-    URI targetUri = null;
-    StringBuilder uriSyntaxErrors = new StringBuilder();
-    try {
-      targetUri = new URI(target);
-    } catch (URISyntaxException e) {
-      // Can happen with ip addresses like "[::1]:1234" or 127.0.0.1:1234.
-      uriSyntaxErrors.append(e.getMessage());
-    }
-    if (targetUri != null) {
-      // For "localhost:8080" this would likely cause provider to be null, because "localhost" is
-      // parsed as the scheme. Will hit the next case and try "dns:///localhost:8080".
-      provider = nameResolverRegistry.getProviderForScheme(targetUri.getScheme());
-    }
-
-    if (provider == null && !URI_PATTERN.matcher(target).matches()) {
-      // It doesn't look like a URI target. Maybe it's an authority string. Try with the default
-      // scheme from the registry.
-      try {
-        targetUri = new URI(nameResolverRegistry.getDefaultScheme(), "", "/" + target, null);
-      } catch (URISyntaxException e) {
-        // Should not be possible.
-        throw new IllegalArgumentException(e);
-      }
-      provider = nameResolverRegistry.getProviderForScheme(targetUri.getScheme());
-    }
-
-    if (provider == null) {
-      throw new IllegalArgumentException(String.format(
-          "Could not find a NameResolverProvider for %s%s",
-          target, uriSyntaxErrors.length() > 0 ? " (" + uriSyntaxErrors + ")" : ""));
-    }
-
-    if (channelTransportSocketAddressTypes != null) {
-      Collection<Class<? extends SocketAddress>> nameResolverSocketAddressTypes
-          = provider.getProducedSocketAddressTypes();
-      if (!channelTransportSocketAddressTypes.containsAll(nameResolverSocketAddressTypes)) {
-        throw new IllegalArgumentException(String.format(
-            "Address types of NameResolver '%s' for '%s' not supported by transport",
-            targetUri.getScheme(), target));
-      }
-    }
-
-    return new ResolvedNameResolver(targetUri, provider);
-  }
-
   @VisibleForTesting
   static NameResolver getNameResolver(
       URI targetUri, @Nullable final String overrideAuthority,

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

@@ -26,7 +26,10 @@ import com.google.errorprone.annotations.DoNotCall;
 import io.grpc.Attributes;
 import io.grpc.BinaryLog;
 import io.grpc.CallCredentials;
+import io.grpc.CallOptions;
+import io.grpc.Channel;
 import io.grpc.ChannelCredentials;
+import io.grpc.ClientCall;
 import io.grpc.ClientInterceptor;
 import io.grpc.ClientTransportFilter;
 import io.grpc.CompressorRegistry;
@@ -36,6 +39,7 @@ import io.grpc.InternalChannelz;
 import io.grpc.InternalConfiguratorRegistry;
 import io.grpc.ManagedChannel;
 import io.grpc.ManagedChannelBuilder;
+import io.grpc.MethodDescriptor;
 import io.grpc.MetricSink;
 import io.grpc.NameResolver;
 import io.grpc.NameResolverProvider;
@@ -57,6 +61,7 @@ import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.regex.Pattern;
 import javax.annotation.Nullable;
 
 /**
@@ -109,6 +114,12 @@ public final class ManagedChannelImplBuilder
   private static final long DEFAULT_RETRY_BUFFER_SIZE_IN_BYTES = 1L << 24;  // 16M
   private static final long DEFAULT_PER_RPC_BUFFER_LIMIT_IN_BYTES = 1L << 20; // 1M
 
+  // Matching this pattern means the target string is a URI target or at least intended to be one.
+  // A URI target must be an absolute hierarchical URI.
+  // From RFC 2396: scheme = alpha *( alpha | digit | "+" | "-" | "." )
+  @VisibleForTesting
+  static final Pattern URI_PATTERN = Pattern.compile("[a-zA-Z][a-zA-Z0-9+.-]*:/.*");
+
   private static final Method GET_CLIENT_INTERCEPTOR_METHOD;
 
   static {
@@ -384,6 +395,14 @@ public final class ManagedChannelImplBuilder
     return intercept(Arrays.asList(interceptors));
   }
 
+  @Override
+  protected ManagedChannelImplBuilder interceptWithTarget(InterceptorFactory factory) {
+    // Add a placeholder instance to the interceptor list, and replace it with a real instance
+    // during build().
+    this.interceptors.add(new InterceptorFactoryWrapper(factory));
+    return this;
+  }
+
   @Override
   public ManagedChannelImplBuilder addTransportFilter(ClientTransportFilter hook) {
     transportFilters.add(checkNotNull(hook, "transport filter"));
@@ -675,13 +694,19 @@ public final class ManagedChannelImplBuilder
 
   @Override
   public ManagedChannel build() {
+    ClientTransportFactory clientTransportFactory =
+        clientTransportFactoryBuilder.buildClientTransportFactory();
+    ResolvedNameResolver resolvedResolver = getNameResolverProvider(
+        target, nameResolverRegistry, clientTransportFactory.getSupportedSocketAddressTypes());
     return new ManagedChannelOrphanWrapper(new ManagedChannelImpl(
         this,
-        clientTransportFactoryBuilder.buildClientTransportFactory(),
+        clientTransportFactory,
+        resolvedResolver.targetUri,
+        resolvedResolver.provider,
         new ExponentialBackoffPolicy.Provider(),
         SharedResourcePool.forResource(GrpcUtil.SHARED_CHANNEL_EXECUTOR),
         GrpcUtil.STOPWATCH_SUPPLIER,
-        getEffectiveInterceptors(),
+        getEffectiveInterceptors(resolvedResolver.targetUri.toString()),
         TimeProvider.SYSTEM_TIME_PROVIDER));
   }
 
@@ -689,12 +714,25 @@ public final class ManagedChannelImplBuilder
   // what should be the desired behavior for retry + stats/tracing.
   // TODO(zdapeng): FIX IT
   @VisibleForTesting
-  List<ClientInterceptor> getEffectiveInterceptors() {
+  List<ClientInterceptor> getEffectiveInterceptors(String computedTarget) {
+    List<ClientInterceptor> effectiveInterceptors = new ArrayList<>(this.interceptors);
+    for (int i = 0; i < effectiveInterceptors.size(); i++) {
+      if (!(effectiveInterceptors.get(i) instanceof InterceptorFactoryWrapper)) {
+        continue;
+      }
+      InterceptorFactory factory =
+          ((InterceptorFactoryWrapper) effectiveInterceptors.get(i)).factory;
+      ClientInterceptor interceptor = factory.newInterceptor(computedTarget);
+      if (interceptor == null) {
+        throw new NullPointerException("Factory returned null interceptor: " + factory);
+      }
+      effectiveInterceptors.set(i, interceptor);
+    }
+
     boolean disableImplicitCensus = InternalConfiguratorRegistry.wasSetConfiguratorsCalled();
     if (disableImplicitCensus) {
-      return this.interceptors;
+      return effectiveInterceptors;
     }
-    List<ClientInterceptor> effectiveInterceptors = new ArrayList<>(this.interceptors);
     if (statsEnabled) {
       ClientInterceptor statsInterceptor = null;
 
@@ -754,6 +792,69 @@ public final class ManagedChannelImplBuilder
     return channelBuilderDefaultPortProvider.getDefaultPort();
   }
 
+  @VisibleForTesting
+  static class ResolvedNameResolver {
+    public final URI targetUri;
+    public final NameResolverProvider provider;
+
+    public ResolvedNameResolver(URI targetUri, NameResolverProvider provider) {
+      this.targetUri = checkNotNull(targetUri, "targetUri");
+      this.provider = checkNotNull(provider, "provider");
+    }
+  }
+
+  @VisibleForTesting
+  static ResolvedNameResolver getNameResolverProvider(
+      String target, NameResolverRegistry nameResolverRegistry,
+      Collection<Class<? extends SocketAddress>> channelTransportSocketAddressTypes) {
+    // Finding a NameResolver. Try using the target string as the URI. If that fails, try prepending
+    // "dns:///".
+    NameResolverProvider provider = null;
+    URI targetUri = null;
+    StringBuilder uriSyntaxErrors = new StringBuilder();
+    try {
+      targetUri = new URI(target);
+    } catch (URISyntaxException e) {
+      // Can happen with ip addresses like "[::1]:1234" or 127.0.0.1:1234.
+      uriSyntaxErrors.append(e.getMessage());
+    }
+    if (targetUri != null) {
+      // For "localhost:8080" this would likely cause provider to be null, because "localhost" is
+      // parsed as the scheme. Will hit the next case and try "dns:///localhost:8080".
+      provider = nameResolverRegistry.getProviderForScheme(targetUri.getScheme());
+    }
+
+    if (provider == null && !URI_PATTERN.matcher(target).matches()) {
+      // It doesn't look like a URI target. Maybe it's an authority string. Try with the default
+      // scheme from the registry.
+      try {
+        targetUri = new URI(nameResolverRegistry.getDefaultScheme(), "", "/" + target, null);
+      } catch (URISyntaxException e) {
+        // Should not be possible.
+        throw new IllegalArgumentException(e);
+      }
+      provider = nameResolverRegistry.getProviderForScheme(targetUri.getScheme());
+    }
+
+    if (provider == null) {
+      throw new IllegalArgumentException(String.format(
+          "Could not find a NameResolverProvider for %s%s",
+          target, uriSyntaxErrors.length() > 0 ? " (" + uriSyntaxErrors + ")" : ""));
+    }
+
+    if (channelTransportSocketAddressTypes != null) {
+      Collection<Class<? extends SocketAddress>> nameResolverSocketAddressTypes
+          = provider.getProducedSocketAddressTypes();
+      if (!channelTransportSocketAddressTypes.containsAll(nameResolverSocketAddressTypes)) {
+        throw new IllegalArgumentException(String.format(
+            "Address types of NameResolver '%s' for '%s' not supported by transport",
+            targetUri.getScheme(), target));
+      }
+    }
+
+    return new ResolvedNameResolver(targetUri, provider);
+  }
+
   private static class DirectAddressNameResolverProvider extends NameResolverProvider {
     final SocketAddress address;
     final String authority;
@@ -809,6 +910,20 @@ public final class ManagedChannelImplBuilder
     }
   }
 
+  private static final class InterceptorFactoryWrapper implements ClientInterceptor {
+    final InterceptorFactory factory;
+
+    public InterceptorFactoryWrapper(InterceptorFactory factory) {
+      this.factory = checkNotNull(factory, "factory");
+    }
+
+    @Override
+    public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
+        MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, Channel next) {
+      throw new AssertionError("Should have been replaced with real instance");
+    }
+  }
+
   /**
    * Returns the internal offload executor pool for offloading tasks.
    */

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

@@ -38,6 +38,7 @@ import io.grpc.CompressorRegistry;
 import io.grpc.DecompressorRegistry;
 import io.grpc.InternalConfigurator;
 import io.grpc.InternalConfiguratorRegistry;
+import io.grpc.InternalManagedChannelBuilder.InternalInterceptorFactory;
 import io.grpc.ManagedChannel;
 import io.grpc.ManagedChannelBuilder;
 import io.grpc.MethodDescriptor;
@@ -473,7 +474,7 @@ public class ManagedChannelImplBuilderTest {
   @Test
   public void getEffectiveInterceptors_default() {
     builder.intercept(DUMMY_USER_INTERCEPTOR);
-    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors("unused:///");
     assertEquals(3, effectiveInterceptors.size());
     assertThat(effectiveInterceptors.get(0).getClass().getName())
         .isEqualTo("io.grpc.census.CensusTracingModule$TracingClientInterceptor");
@@ -486,7 +487,7 @@ public class ManagedChannelImplBuilderTest {
   public void getEffectiveInterceptors_disableStats() {
     builder.intercept(DUMMY_USER_INTERCEPTOR);
     builder.setStatsEnabled(false);
-    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors("unused:///");
     assertEquals(2, effectiveInterceptors.size());
     assertThat(effectiveInterceptors.get(0).getClass().getName())
         .isEqualTo("io.grpc.census.CensusTracingModule$TracingClientInterceptor");
@@ -497,7 +498,7 @@ public class ManagedChannelImplBuilderTest {
   public void getEffectiveInterceptors_disableTracing() {
     builder.intercept(DUMMY_USER_INTERCEPTOR);
     builder.setTracingEnabled(false);
-    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors("unused:///");
     assertEquals(2, effectiveInterceptors.size());
     assertThat(effectiveInterceptors.get(0).getClass().getName())
         .isEqualTo("io.grpc.census.CensusStatsModule$StatsClientInterceptor");
@@ -509,7 +510,7 @@ public class ManagedChannelImplBuilderTest {
     builder.intercept(DUMMY_USER_INTERCEPTOR);
     builder.setStatsEnabled(false);
     builder.setTracingEnabled(false);
-    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+    List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors("unused:///");
     assertThat(effectiveInterceptors).containsExactly(DUMMY_USER_INTERCEPTOR);
   }
 
@@ -529,7 +530,8 @@ public class ManagedChannelImplBuilderTest {
               DUMMY_TARGET,
               new UnsupportedClientTransportFactoryBuilder(),
               new FixedPortProvider(DUMMY_PORT));
-      List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+      List<ClientInterceptor> effectiveInterceptors =
+          builder.getEffectiveInterceptors("unused:///");
       assertThat(effectiveInterceptors).hasSize(2);
       try {
         InternalConfiguratorRegistry.setConfigurators(Collections.emptyList());
@@ -563,7 +565,8 @@ public class ManagedChannelImplBuilderTest {
               DUMMY_TARGET,
               new UnsupportedClientTransportFactoryBuilder(),
               new FixedPortProvider(DUMMY_PORT));
-      List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+      List<ClientInterceptor> effectiveInterceptors =
+          builder.getEffectiveInterceptors("unused:///");
       assertThat(effectiveInterceptors)
           .containsExactly(DUMMY_USER_INTERCEPTOR, DUMMY_USER_INTERCEPTOR1);
     }
@@ -587,11 +590,35 @@ public class ManagedChannelImplBuilderTest {
               DUMMY_TARGET,
               new UnsupportedClientTransportFactoryBuilder(),
               new FixedPortProvider(DUMMY_PORT));
-      List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
+      List<ClientInterceptor> effectiveInterceptors =
+          builder.getEffectiveInterceptors("unused:///");
       assertThat(effectiveInterceptors).isEmpty();
     }
   }
 
+  @Test
+  public void getEffectiveInterceptors_createsFromInterceptorFactories() throws Exception {
+    String target = "dns:///the-host";
+    builder.setStatsEnabled(false);
+    builder.setTracingEnabled(false);
+
+    builder.intercept(DUMMY_USER_INTERCEPTOR)
+        .interceptWithTarget(new InternalInterceptorFactory() {
+          @Override
+          public ClientInterceptor newInterceptor(String passedTarget) {
+            assertThat(passedTarget).isEqualTo(target);
+            return DUMMY_USER_INTERCEPTOR1;
+          }
+        })
+        .intercept(DUMMY_USER_INTERCEPTOR);
+
+    assertThat(builder.getEffectiveInterceptors(target))
+        .isEqualTo(Arrays.asList(
+            DUMMY_USER_INTERCEPTOR,
+            DUMMY_USER_INTERCEPTOR1,
+            DUMMY_USER_INTERCEPTOR));
+  }
+
   @Test
   public void idleTimeout() {
     assertEquals(ManagedChannelImplBuilder.IDLE_MODE_DEFAULT_TIMEOUT_MILLIS,
@@ -744,4 +771,15 @@ public class ManagedChannelImplBuilderTest {
 
     assertThat(builder.metricSinks).contains(mocksink);
   }
+
+  @Test
+  public void uriPattern() {
+    Pattern uriPattern = ManagedChannelImplBuilder.URI_PATTERN;
+    assertTrue(uriPattern.matcher("a:/").matches());
+    assertTrue(uriPattern.matcher("Z019+-.:/!@ #~ ").matches());
+    assertFalse(uriPattern.matcher("a/:").matches()); // "/:" not matched
+    assertFalse(uriPattern.matcher("0a:/").matches()); // '0' not matched
+    assertFalse(uriPattern.matcher("a,:/").matches()); // ',' not matched
+    assertFalse(uriPattern.matcher(" a:/").matches()); // space not matched
+  }
 }

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

@@ -30,7 +30,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-/** Unit tests for ManagedChannelImpl#getNameResolverProvider(). */
+/** Unit tests for ManagedChannelImplBuilder#getNameResolverProvider(). */
 @RunWith(JUnit4.class)
 public class ManagedChannelImplGetNameResolverTest {
   @Test
@@ -95,7 +95,7 @@ public class ManagedChannelImplGetNameResolverTest {
   public void validTargetNoProvider() {
     NameResolverRegistry nameResolverRegistry = new NameResolverRegistry();
     try {
-      ManagedChannelImpl.getNameResolverProvider(
+      ManagedChannelImplBuilder.getNameResolverProvider(
           "foo.googleapis.com:8080", nameResolverRegistry,
           Collections.singleton(InetSocketAddress.class));
       fail("Should fail");
@@ -108,7 +108,7 @@ public class ManagedChannelImplGetNameResolverTest {
   public void validTargetProviderAddrTypesNotSupported() {
     NameResolverRegistry nameResolverRegistry = getTestRegistry("testscheme");
     try {
-      ManagedChannelImpl.getNameResolverProvider(
+      ManagedChannelImplBuilder.getNameResolverProvider(
           "testscheme:///foo.googleapis.com:8080", nameResolverRegistry,
           Collections.singleton(InProcessSocketAddress.class));
       fail("Should fail");
@@ -121,7 +121,8 @@ public class ManagedChannelImplGetNameResolverTest {
 
   private void testValidTarget(String target, String expectedUriString, URI expectedUri) {
     NameResolverRegistry nameResolverRegistry = getTestRegistry(expectedUri.getScheme());
-    ManagedChannelImpl.ResolvedNameResolver resolved = ManagedChannelImpl.getNameResolverProvider(
+    ManagedChannelImplBuilder.ResolvedNameResolver resolved =
+        ManagedChannelImplBuilder.getNameResolverProvider(
             target, nameResolverRegistry, Collections.singleton(InetSocketAddress.class));
     assertThat(resolved.provider).isInstanceOf(FakeNameResolverProvider.class);
     assertThat(resolved.targetUri).isEqualTo(expectedUri);
@@ -132,7 +133,8 @@ public class ManagedChannelImplGetNameResolverTest {
     NameResolverRegistry nameResolverRegistry = getTestRegistry("dns");
 
     try {
-      ManagedChannelImpl.ResolvedNameResolver resolved = ManagedChannelImpl.getNameResolverProvider(
+      ManagedChannelImplBuilder.ResolvedNameResolver resolved =
+          ManagedChannelImplBuilder.getNameResolverProvider(
               target, nameResolverRegistry, Collections.singleton(InetSocketAddress.class));
       FakeNameResolverProvider nameResolverProvider = (FakeNameResolverProvider) resolved.provider;
       fail("Should have failed, but got resolver provider " + nameResolverProvider);

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

@@ -61,6 +61,7 @@ import io.grpc.MethodDescriptor;
 import io.grpc.MethodDescriptor.MethodType;
 import io.grpc.NameResolver;
 import io.grpc.NameResolver.ResolutionResult;
+import io.grpc.NameResolverProvider;
 import io.grpc.Status;
 import io.grpc.StringMarshaller;
 import io.grpc.internal.FakeClock.ScheduledTask;
@@ -169,7 +170,9 @@ public class ManagedChannelImplIdlenessTest {
     when(mockTransportFactory.getSupportedSocketAddressTypes())
         .thenReturn(Collections.singleton(InetSocketAddress.class));
 
-    ManagedChannelImplBuilder builder = new ManagedChannelImplBuilder("mockscheme:///target",
+    String target = "mockscheme:///target";
+    URI targetUri = URI.create(target);
+    ManagedChannelImplBuilder builder = new ManagedChannelImplBuilder(target,
         new UnsupportedClientTransportFactoryBuilder(), null);
 
     builder
@@ -178,8 +181,11 @@ public class ManagedChannelImplIdlenessTest {
         .idleTimeout(IDLE_TIMEOUT_SECONDS, TimeUnit.SECONDS)
         .userAgent(USER_AGENT);
     builder.executorPool = executorPool;
+    NameResolverProvider nameResolverProvider =
+        builder.nameResolverRegistry.getProviderForScheme(targetUri.getScheme());
     channel = new ManagedChannelImpl(
-        builder, mockTransportFactory, new FakeBackoffPolicyProvider(),
+        builder, mockTransportFactory, targetUri, nameResolverProvider,
+        new FakeBackoffPolicyProvider(),
         oobExecutorPool, timer.getStopwatchSupplier(),
         Collections.<ClientInterceptor>emptyList(),
         TimeProvider.SYSTEM_TIME_PROVIDER);

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

@@ -310,8 +310,11 @@ public class ManagedChannelImplTest {
 
     when(mockTransportFactory.getSupportedSocketAddressTypes()).thenReturn(Collections.singleton(
         InetSocketAddress.class));
+    NameResolverProvider nameResolverProvider =
+        channelBuilder.nameResolverRegistry.getProviderForScheme(expectedUri.getScheme());
     channel = new ManagedChannelImpl(
-        channelBuilder, mockTransportFactory, new FakeBackoffPolicyProvider(),
+        channelBuilder, mockTransportFactory, expectedUri, nameResolverProvider,
+        new FakeBackoffPolicyProvider(),
         balancerRpcExecutorPool, timer.getStopwatchSupplier(), Arrays.asList(interceptors),
         timer.getTimeProvider());
 
@@ -499,7 +502,8 @@ public class ManagedChannelImplTest {
     when(mockTransportFactory.getSupportedSocketAddressTypes()).thenReturn(Collections.singleton(
         InetSocketAddress.class));
     channel = new ManagedChannelImpl(
-        channelBuilder, mockTransportFactory, new FakeBackoffPolicyProvider(),
+        channelBuilder, mockTransportFactory, expectedUri, nameResolverFactory,
+        new FakeBackoffPolicyProvider(),
         balancerRpcExecutorPool, timer.getStopwatchSupplier(),
         Collections.<ClientInterceptor>emptyList(), timer.getTimeProvider());
     Map<String, Object> rawServiceConfig =
@@ -563,7 +567,8 @@ public class ManagedChannelImplTest {
     when(mockTransportFactory.getSupportedSocketAddressTypes()).thenReturn(Collections.singleton(
         InetSocketAddress.class));
     channel = new ManagedChannelImpl(
-        channelBuilder, mockTransportFactory, new FakeBackoffPolicyProvider(),
+        channelBuilder, mockTransportFactory, expectedUri, nameResolverFactory,
+        new FakeBackoffPolicyProvider(),
         balancerRpcExecutorPool, timer.getStopwatchSupplier(),
         Collections.<ClientInterceptor>emptyList(), timer.getTimeProvider());
     nameResolverFactory.nextConfigOrError.set(
@@ -2181,16 +2186,6 @@ public class ManagedChannelImplTest {
     assertEquals(expectedRefreshCount, resolver.refreshCalled);
   }
 
-  @Test
-  public void uriPattern() {
-    assertTrue(ManagedChannelImpl.URI_PATTERN.matcher("a:/").matches());
-    assertTrue(ManagedChannelImpl.URI_PATTERN.matcher("Z019+-.:/!@ #~ ").matches());
-    assertFalse(ManagedChannelImpl.URI_PATTERN.matcher("a/:").matches()); // "/:" not matched
-    assertFalse(ManagedChannelImpl.URI_PATTERN.matcher("0a:/").matches()); // '0' not matched
-    assertFalse(ManagedChannelImpl.URI_PATTERN.matcher("a,:/").matches()); // ',' not matched
-    assertFalse(ManagedChannelImpl.URI_PATTERN.matcher(" a:/").matches()); // space not matched
-  }
-
   /**
    * Test that information such as the Call's context, MethodDescriptor, authority, executor are
    * propagated to newStream() and applyRequestMetadata().
@@ -4429,7 +4424,7 @@ public class ManagedChannelImplTest {
     }
   }
 
-  private static final class FakeNameResolverFactory extends NameResolver.Factory {
+  private static final class FakeNameResolverFactory extends NameResolverProvider {
     final List<URI> expectedUris;
     final List<EquivalentAddressGroup> servers;
     final boolean resolvedAtStart;
@@ -4466,6 +4461,16 @@ public class ManagedChannelImplTest {
       return "fake";
     }
 
+    @Override
+    public int priority() {
+      return 9;
+    }
+
+    @Override
+    public boolean isAvailable() {
+      return true;
+    }
+
     void allResolved() {
       for (FakeNameResolverFactory.FakeNameResolver resolver : resolvers) {
         resolver.resolved();

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

@@ -45,6 +45,7 @@ import io.grpc.LoadBalancerProvider;
 import io.grpc.LoadBalancerRegistry;
 import io.grpc.NameResolver;
 import io.grpc.NameResolver.ConfigOrError;
+import io.grpc.NameResolverProvider;
 import io.grpc.Status;
 import io.grpc.internal.ManagedChannelImplBuilder.FixedPortProvider;
 import io.grpc.internal.ManagedChannelImplBuilder.UnsupportedClientTransportFactoryBuilder;
@@ -161,10 +162,14 @@ public class ServiceConfigErrorHandlingTest {
 
     when(mockTransportFactory.getSupportedSocketAddressTypes()).thenReturn(Collections.singleton(
         InetSocketAddress.class));
+    NameResolverProvider nameResolverProvider =
+        channelBuilder.nameResolverRegistry.getProviderForScheme(expectedUri.getScheme());
     channel =
         new ManagedChannelImpl(
             channelBuilder,
             mockTransportFactory,
+            expectedUri,
+            nameResolverProvider,
             new FakeBackoffPolicyProvider(),
             balancerRpcExecutorPool,
             timer.getStopwatchSupplier(),