Dualstack example

examples/build.gradle

@@ -31,13 +31,12 @@ dependencies {
     implementation "io.grpc:grpc-protobuf:${grpcVersion}"
     implementation "io.grpc:grpc-services:${grpcVersion}"
     implementation "io.grpc:grpc-stub:${grpcVersion}"
+    implementation "io.grpc:grpc-netty-shaded:${grpcVersion}"
     compileOnly "org.apache.tomcat:annotations-api:6.0.53"
 
     // examples/advanced need this for JsonFormat
     implementation "com.google.protobuf:protobuf-java-util:${protobufVersion}"
 
-    runtimeOnly "io.grpc:grpc-netty-shaded:${grpcVersion}"
-
     testImplementation "io.grpc:grpc-testing:${grpcVersion}"
     testImplementation "io.grpc:grpc-inprocess:${grpcVersion}"
     testImplementation "junit:junit:4.13.2"
@@ -71,8 +70,8 @@ startScripts.enabled = false
 // the class io.grpc.examples.helloworld.HelloWorldClient, it creates the task
 // helloWorldClient with script name hello-world-client.
 def createStartScripts(String mainClassName) {
-    String bareName = mainClassName.substring(mainClassName.lastIndexOf('.') + 1);
-    String taskName = bareName.uncapitalize();
+    String bareName = mainClassName.substring(mainClassName.lastIndexOf('.') + 1)
+    String taskName = bareName.uncapitalize()
     def newTask = tasks.register(taskName, CreateStartScripts) {
         mainClass = mainClassName
         applicationName = taskName.replaceAll('([A-Z])') { '-' + it[0].uncapitalize() }
@@ -96,6 +95,8 @@ createStartScripts('io.grpc.examples.cancellation.CancellationServer')
 createStartScripts('io.grpc.examples.customloadbalance.CustomLoadBalanceClient')
 createStartScripts('io.grpc.examples.deadline.DeadlineClient')
 createStartScripts('io.grpc.examples.deadline.DeadlineServer')
+createStartScripts('io.grpc.examples.dualstack.DualStackClient')
+createStartScripts('io.grpc.examples.dualstack.DualStackServer')
 createStartScripts('io.grpc.examples.errordetails.ErrorDetailsExample')
 createStartScripts('io.grpc.examples.experimental.CompressingHelloWorldClient')
 createStartScripts('io.grpc.examples.grpcproxy.GrpcProxy')

examples/src/main/java/io/grpc/examples/dualstack/DualStackClient.java

@@ -0,0 +1,87 @@
+/*
+ * 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.examples.dualstack;
+
+import io.grpc.Channel;
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.NameResolverRegistry;
+import io.grpc.StatusRuntimeException;
+import io.grpc.examples.helloworld.GreeterGrpc;
+import io.grpc.examples.helloworld.HelloReply;
+import io.grpc.examples.helloworld.HelloRequest;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class DualStackClient {
+    public static final String channelTarget = "example:///lb.example.grpc.io";
+    private static final Logger logger = Logger.getLogger(DualStackClient.class.getName());
+    private final GreeterGrpc.GreeterBlockingStub blockingStub;
+
+    public DualStackClient(Channel channel) {
+        blockingStub = GreeterGrpc.newBlockingStub(channel);
+    }
+
+    public static void main(String[] args) throws Exception {
+        NameResolverRegistry.getDefaultRegistry()
+            .register(new ExampleDualStackNameResolverProvider());
+
+        logger.info("\n **** Use default DNS resolver ****");
+        ManagedChannel channel = ManagedChannelBuilder.forTarget("localhost:50051")
+                .usePlaintext()
+                .build();
+        try {
+            DualStackClient client = new DualStackClient(channel);
+            for (int i = 0; i < 5; i++) {
+                client.greet("request" + i);
+            }
+        } finally {
+            channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
+        }
+
+        logger.info("\n  **** Change to use example name resolver ****");
+        /*
+          Dial to "example:///resolver.example.grpc.io", use {@link ExampleNameResolver} to create connection
+          "resolver.example.grpc.io" is converted to {@link java.net.URI.path}
+         */
+        channel = ManagedChannelBuilder.forTarget(channelTarget)
+            .defaultLoadBalancingPolicy("round_robin")
+            .usePlaintext()
+            .build();
+        try {
+            DualStackClient client = new DualStackClient(channel);
+            for (int i = 0; i < 5; i++) {
+                client.greet("request" + i);
+            }
+        } finally {
+            channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
+        }
+    }
+
+    public void greet(String name) {
+        HelloRequest request = HelloRequest.newBuilder().setName(name).build();
+        HelloReply response;
+        try {
+            response = blockingStub.sayHello(request);
+        } catch (StatusRuntimeException e) {
+            logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
+            return;
+        }
+        logger.info("Greeting: " + response.getMessage());
+    }
+}

examples/src/main/java/io/grpc/examples/dualstack/DualStackServer.java

@@ -0,0 +1,125 @@
+/*
+ * 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.examples.dualstack;
+
+import io.grpc.Server;
+import io.grpc.ServerBuilder;
+import io.grpc.examples.helloworld.GreeterGrpc;
+import io.grpc.examples.helloworld.HelloReply;
+import io.grpc.examples.helloworld.HelloRequest;
+import io.grpc.examples.loadbalance.LoadBalanceServer;
+import io.grpc.netty.shaded.io.grpc.netty.NettyServerBuilder;
+import io.grpc.stub.StreamObserver;
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Logger;
+
+public class DualStackServer {
+    private static final Logger logger = Logger.getLogger(DualStackServer.class.getName());
+    private List<Server> servers;
+
+    public static void main(String[] args) throws IOException, InterruptedException {
+        final DualStackServer server = new DualStackServer();
+        server.start();
+        server.blockUntilShutdown();
+    }
+
+    private void start() throws IOException {
+        InetSocketAddress inetSocketAddress;
+
+        servers = new ArrayList<>();
+        for (int i = 0; i < LoadBalanceServer.SERVER_PORTS.length; i++ ) {
+            String addressType;
+            int port = LoadBalanceServer.SERVER_PORTS[i];
+            ServerBuilder<?> serverBuilder;
+            switch (i) {
+                case 0:
+                    serverBuilder = ServerBuilder.forPort(port); // bind to both IPv4 and IPv6
+                    addressType = "both IPv4 and IPv6";
+                    break;
+                case 1:
+                    // bind to IPv4 only
+                    inetSocketAddress = new InetSocketAddress("127.0.0.1", port);
+                    serverBuilder = NettyServerBuilder.forAddress(inetSocketAddress);
+                    addressType = "IPv4 only";
+                    break;
+                case 2:
+                    // bind to IPv6 only
+                    inetSocketAddress = new InetSocketAddress("::1", port);
+                    serverBuilder = NettyServerBuilder.forAddress(inetSocketAddress);
+                    addressType = "IPv6 only";
+                    break;
+                default:
+                    throw new IllegalStateException("Unexpected value: " + i);
+            }
+
+            servers.add(serverBuilder
+                .addService(new GreeterImpl(port, addressType))
+                .build()
+                .start());
+            logger.info("Server started, listening on " + port);
+        }
+        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+            System.err.println("*** shutting down gRPC server since JVM is shutting down");
+            try {
+                DualStackServer.this.stop();
+            } catch (InterruptedException e) {
+                e.printStackTrace(System.err);
+            }
+            System.err.println("*** server shut down");
+        }));
+    }
+
+    private void stop() throws InterruptedException {
+        for (Server server : servers) {
+            if (server != null) {
+                server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
+            }
+        }
+    }
+
+    private void blockUntilShutdown() throws InterruptedException {
+        for (Server server : servers) {
+            if (server != null) {
+                server.awaitTermination();
+            }
+        }
+    }
+
+    static class GreeterImpl extends GreeterGrpc.GreeterImplBase {
+
+        int port;
+        String addressType;
+
+        public GreeterImpl(int port, String addressType) {
+            this.port = port;
+            this.addressType = addressType;
+        }
+
+        @Override
+        public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+            String msg = String.format("Hello %s from server<%d> type: %s",
+                req.getName(), this.port, addressType);
+            HelloReply reply = HelloReply.newBuilder().setMessage(msg).build();
+            responseObserver.onNext(reply);
+            responseObserver.onCompleted();
+        }
+    }
+}

examples/src/main/java/io/grpc/examples/dualstack/ExampleDualStackNameResolver.java

@@ -0,0 +1,100 @@
+/*
+ * 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.examples.dualstack;
+
+import static io.grpc.examples.loadbalance.LoadBalanceClient.exampleServiceName;
+
+import com.google.common.collect.ImmutableMap;
+import io.grpc.EquivalentAddressGroup;
+import io.grpc.NameResolver;
+import io.grpc.Status;
+import io.grpc.examples.loadbalance.LoadBalanceServer;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class ExampleDualStackNameResolver extends NameResolver {
+
+    // This is a fake name resolver, so we just hard code the address here.
+    private static final ImmutableMap<String, List<List<SocketAddress>>> addrStore =
+        ImmutableMap.<String, List<List<SocketAddress>>>builder()
+        .put(exampleServiceName,
+            Arrays.stream(LoadBalanceServer.SERVER_PORTS)
+                .mapToObj(port -> getLocalAddrs(port))
+                .collect(Collectors.toList())
+        )
+        .build();
+
+    private Listener2 listener;
+
+    private final URI uri;
+
+    public ExampleDualStackNameResolver(URI targetUri) {
+        this.uri = targetUri;
+    }
+
+    private static List<SocketAddress> getLocalAddrs(int port) {
+        return Arrays.asList(
+            new InetSocketAddress("127.0.0.1", port),
+            new InetSocketAddress("::1", port));
+    }
+
+    @Override
+    public String getServiceAuthority() {
+        // Be consistent with behavior in grpc-go, authority is saved in Host field of URI.
+        if (uri.getHost() != null) {
+            return uri.getHost();
+        }
+        return "no host";
+    }
+
+    @Override
+    public void shutdown() {
+    }
+
+    @Override
+    public void start(Listener2 listener) {
+        this.listener = listener;
+        this.resolve();
+    }
+
+    @Override
+    public void refresh() {
+        this.resolve();
+    }
+
+    private void resolve() {
+        List<List<SocketAddress>> addresses = addrStore.get(uri.getPath().substring(1));
+        try {
+            List<EquivalentAddressGroup> eagList = new ArrayList<>();
+            for (List<SocketAddress> endpoint : addresses) {
+                // every server is an EquivalentAddressGroup, so they can be accessed randomly
+                eagList.add(new EquivalentAddressGroup(endpoint));
+            }
+
+            this.listener.onResult(ResolutionResult.newBuilder().setAddresses(eagList).build());
+        } catch (Exception e){
+            // when error occurs, notify listener
+            this.listener.onError(Status.UNAVAILABLE.withDescription("Unable to resolve host ").withCause(e));
+        }
+    }
+
+}

examples/src/main/java/io/grpc/examples/dualstack/ExampleDualStackNameResolverProvider.java

@@ -0,0 +1,47 @@
+/*
+ * 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.examples.dualstack;
+
+import io.grpc.NameResolver;
+import io.grpc.NameResolverProvider;
+
+import java.net.URI;
+
+import static io.grpc.examples.loadbalance.LoadBalanceClient.exampleScheme;
+
+public class ExampleDualStackNameResolverProvider extends NameResolverProvider {
+    @Override
+    public NameResolver newNameResolver(URI targetUri, NameResolver.Args args) {
+        return new ExampleDualStackNameResolver(targetUri);
+    }
+
+    @Override
+    protected boolean isAvailable() {
+        return true;
+    }
+
+    @Override
+    protected int priority() {
+        return 5;
+    }
+
+    @Override
+    // gRPC choose the first NameResolverProvider that supports the target URI scheme.
+    public String getDefaultScheme() {
+        return exampleScheme;
+    }
+}