Support BinderChannelBuilder.forTarget. (#8633)

Allows this class to be used with custom name resolvers.

binder/src/androidTest/java/io/grpc/binder/BinderChannelSmokeTest.java

@@ -36,11 +36,13 @@ import io.grpc.CallOptions;
 import io.grpc.ManagedChannel;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
+import io.grpc.NameResolverRegistry;
 import io.grpc.Server;
 import io.grpc.ServerCallHandler;
 import io.grpc.ServerInterceptors;
 import io.grpc.ServerServiceDefinition;
 import io.grpc.internal.GrpcUtil;
+import io.grpc.internal.testing.FakeNameResolverProvider;
 import io.grpc.stub.ClientCalls;
 import io.grpc.stub.ServerCalls;
 import io.grpc.stub.StreamObserver;
@@ -66,6 +68,7 @@ public final class BinderChannelSmokeTest {
 
   private static final int SLIGHTLY_MORE_THAN_ONE_BLOCK = 16 * 1024 + 100;
   private static final String MSG = "Some text which will be repeated many many times";
+  private static final String SERVER_TARGET_URI = "fake://server";
 
   final MethodDescriptor<String, String> method =
       MethodDescriptor.newBuilder(StringMarshaller.INSTANCE, StringMarshaller.INSTANCE)
@@ -85,7 +88,7 @@ public final class BinderChannelSmokeTest {
           .setType(MethodDescriptor.MethodType.BIDI_STREAMING)
           .build();
 
-  AndroidComponentAddress serverAddress;
+  FakeNameResolverProvider fakeNameResolverProvider;
   ManagedChannel channel;
   AtomicReference<Metadata> headersCapture = new AtomicReference<>();
 
@@ -118,6 +121,8 @@ public final class BinderChannelSmokeTest {
             TestUtils.recordRequestHeadersInterceptor(headersCapture));
 
     AndroidComponentAddress serverAddress = HostServices.allocateService(appContext);
+    fakeNameResolverProvider = new FakeNameResolverProvider(SERVER_TARGET_URI, serverAddress);
+    NameResolverRegistry.getDefaultRegistry().register(fakeNameResolverProvider);
     HostServices.configureService(serverAddress,
         HostServices.serviceParamsBuilder()
           .setServerFactory((service, receiver) ->
@@ -132,6 +137,7 @@ public final class BinderChannelSmokeTest {
   @After
   public void tearDown() throws Exception {
     channel.shutdownNow();
+    NameResolverRegistry.getDefaultRegistry().deregister(fakeNameResolverProvider);
     HostServices.awaitServiceShutdown();
   }
 
@@ -192,6 +198,12 @@ public final class BinderChannelSmokeTest {
     assertThat(headersCapture.get().get(GrpcUtil.TIMEOUT_KEY)).isGreaterThan(0);
   }
 
+  @Test
+  public void testConnectViaTargetUri() throws Exception {
+    channel = BinderChannelBuilder.forTarget(SERVER_TARGET_URI, appContext).build();
+    assertThat(doCall("Hello").get()).isEqualTo("Hello");
+  }
+
   private static String createLargeString(int size) {
     StringBuilder sb = new StringBuilder();
     while (sb.length() < size) {

binder/src/main/java/io/grpc/binder/BinderChannelBuilder.java

@@ -67,13 +67,35 @@ public final class BinderChannelBuilder
    * <p>You the caller are responsible for managing the lifecycle of any channels built by the
    * resulting builder. They will not be shut down automatically.
    *
-   * @param targetAddress the {@link AndroidComponentAddress} referencing the service to bind to.
+   * @param directAddress the {@link AndroidComponentAddress} referencing the service to bind to.
    * @param sourceContext the context to bind from (e.g. The current Activity or Application).
    * @return a new builder
    */
   public static BinderChannelBuilder forAddress(
-      AndroidComponentAddress targetAddress, Context sourceContext) {
-    return new BinderChannelBuilder(targetAddress, sourceContext);
+      AndroidComponentAddress directAddress, Context sourceContext) {
+    return new BinderChannelBuilder(
+        checkNotNull(directAddress, "directAddress"), null, sourceContext);
+  }
+
+  /**
+   * Creates a channel builder that will bind to a remote Android service, via a string
+   * target name which will be resolved.
+   *
+   * <p>The underlying Android binding will be torn down when the channel becomes idle. This happens
+   * after 30 minutes without use by default but can be configured via {@link
+   * ManagedChannelBuilder#idleTimeout(long, TimeUnit)} or triggered manually with {@link
+   * ManagedChannel#enterIdle()}.
+   *
+   * <p>You the caller are responsible for managing the lifecycle of any channels built by the
+   * resulting builder. They will not be shut down automatically.
+   *
+   * @param target A target uri which should resolve into an {@link AndroidComponentAddress}
+   * referencing the service to bind to.
+   * @param sourceContext the context to bind from (e.g. The current Activity or Application).
+   * @return a new builder
+   */
+  public static BinderChannelBuilder forTarget(String target, Context sourceContext) {
+    return new BinderChannelBuilder(null, checkNotNull(target, "target"), sourceContext);
   }
 
   /**
@@ -88,7 +110,7 @@ public final class BinderChannelBuilder
   /**
    * Always fails. Call {@link #forAddress(AndroidComponentAddress, Context)} instead.
    */
-  @DoNotCall("Unsupported. Use forAddress(AndroidComponentAddress, Context) instead")
+  @DoNotCall("Unsupported. Use forTarget(String, Context) instead")
   public static BinderChannelBuilder forTarget(String target) {
     throw new UnsupportedOperationException(
         "call forAddress(AndroidComponentAddress, Context) instead");
@@ -104,9 +126,11 @@ public final class BinderChannelBuilder
   private BindServiceFlags bindServiceFlags;
 
   private BinderChannelBuilder(
-      AndroidComponentAddress targetAddress,
+      @Nullable AndroidComponentAddress directAddress,
+      @Nullable String target,
       Context sourceContext) {
-    mainThreadExecutor = ContextCompat.getMainExecutor(sourceContext);
+    mainThreadExecutor =
+        ContextCompat.getMainExecutor(checkNotNull(sourceContext, "sourceContext"));
     securityPolicy = SecurityPolicies.internalOnly();
     inboundParcelablePolicy = InboundParcelablePolicy.DEFAULT;
     bindServiceFlags = BindServiceFlags.DEFAULTS;
@@ -126,12 +150,20 @@ public final class BinderChannelBuilder
       }
     }
 
-    managedChannelImplBuilder =
-        new ManagedChannelImplBuilder(
-            targetAddress,
-            targetAddress.getAuthority(),
-            new BinderChannelTransportFactoryBuilder(),
-            null);
+    if (directAddress != null) {
+      managedChannelImplBuilder =
+          new ManagedChannelImplBuilder(
+              directAddress,
+              directAddress.getAuthority(),
+              new BinderChannelTransportFactoryBuilder(),
+              null);
+    } else {
+      managedChannelImplBuilder =
+          new ManagedChannelImplBuilder(
+              target,
+              new BinderChannelTransportFactoryBuilder(),
+              null);
+    }
   }
 
   @Override

testing/src/main/java/io/grpc/internal/testing/FakeNameResolverProvider.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2021 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.testing;
+
+import com.google.common.collect.ImmutableList;
+import io.grpc.EquivalentAddressGroup;
+import io.grpc.NameResolver;
+import io.grpc.NameResolverProvider;
+import io.grpc.Status;
+import java.net.SocketAddress;
+import java.net.URI;
+
+/** A name resolver to always resolve the given URI into the given address. */
+public final class FakeNameResolverProvider extends NameResolverProvider {
+
+  private final URI targetUri;
+  private final SocketAddress address;
+
+  public FakeNameResolverProvider(String targetUri, SocketAddress address) {
+    this.targetUri = URI.create(targetUri);
+    this.address = address;
+  }
+
+  @Override
+  public NameResolver newNameResolver(URI targetUri, NameResolver.Args args) {
+    if (targetUri.equals(this.targetUri)) {
+      return new FakeNameResolver(address);
+    }
+    return null;
+  }
+
+  @Override
+  protected boolean isAvailable() {
+    return true;
+  }
+
+  @Override
+  protected int priority() {
+    return 5; // Default
+  }
+
+  @Override
+  public String getDefaultScheme() {
+    return targetUri.getScheme();
+  }
+
+  /** A single name resolver. */
+  private static final class FakeNameResolver extends NameResolver {
+    private static final String AUTHORITY = "fake-authority";
+
+    private final SocketAddress address;
+    private volatile boolean shutdown;
+
+    private FakeNameResolver(SocketAddress address) {
+      this.address = address;
+    }
+
+    @Override
+    public void start(Listener2 listener) {
+      if (shutdown) {
+        listener.onError(Status.FAILED_PRECONDITION.withDescription("Resolver is shutdown"));
+      } else {
+        listener.onResult(
+            ResolutionResult.newBuilder()
+                .setAddresses(ImmutableList.of(new EquivalentAddressGroup(address)))
+                .build());
+      }
+    }
+
+    @Override
+    public String getServiceAuthority() {
+      return AUTHORITY;
+    }
+
+    @Override
+    public void shutdown() {
+      shutdown = true;
+    }
+  }
+}