examples: add keepalive example

examples/README.md

@@ -117,6 +117,8 @@ before trying out the examples.
 
 </details>
 
+- [Keep Alive](src/main/java/io/grpc/examples/keepalive)
+
 ### <a name="to-build-the-examples"></a> To build the examples
 
 1. **[Install gRPC Java library SNAPSHOT locally, including code generation plugin](../COMPILING.md) (Only need this step for non-released versions, e.g. master HEAD).**

examples/build.gradle

@@ -167,6 +167,20 @@ task nameResolveClient(type: CreateStartScripts) {
     classpath = startScripts.classpath
 }
 
+task keepAliveServer(type: CreateStartScripts) {
+    mainClass = 'io.grpc.examples.keepalive.KeepAliveServer'
+    applicationName = 'keep-alive-server'
+    outputDir = new File(project.buildDir, 'tmp/scripts/' + name)
+    classpath = startScripts.classpath
+}
+
+task keepAliveClient(type: CreateStartScripts) {
+    mainClass = 'io.grpc.examples.keepalive.KeepAliveClient'
+    applicationName = 'keep-alive-client'
+    outputDir = new File(project.buildDir, 'tmp/scripts/' + name)
+    classpath = startScripts.classpath
+}
+
 applicationDistribution.into('bin') {
     from(routeGuideServer)
     from(routeGuideClient)
@@ -183,5 +197,7 @@ applicationDistribution.into('bin') {
     from(loadBalanceClient)
     from(nameResolveServer)
     from(nameResolveClient)
+    from(keepAliveServer)
+    from(keepAliveClient)
     fileMode = 0755
 }

examples/logging.properties

@@ -0,0 +1,8 @@
+# Create a file called logging.properties with the following contents.
+handlers=java.util.logging.ConsoleHandler
+io.grpc.level=FINE
+java.util.logging.ConsoleHandler.level=ALL
+java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter
+
+# Pass the location of the file to JVM via this command-line flag
+JAVA_OPTS=-Djava.util.logging.config.file=logging.properties

examples/src/main/java/io/grpc/examples/keepalive/KeepAliveClient.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2023 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.keepalive;
+
+import io.grpc.Channel;
+import io.grpc.Grpc;
+import io.grpc.InsecureChannelCredentials;
+import io.grpc.ManagedChannel;
+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;
+
+/**
+ * A simple client that requests a greeting from the {@link KeepAliveServer}.
+ */
+public class KeepAliveClient {
+  private static final Logger logger = Logger.getLogger(KeepAliveClient.class.getName());
+
+  private final GreeterGrpc.GreeterBlockingStub blockingStub;
+
+  /** Construct client for accessing HelloWorld server using the existing channel. */
+  public KeepAliveClient(Channel channel) {
+    // 'channel' here is a Channel, not a ManagedChannel, so it is not this code's responsibility to
+    // shut it down.
+
+    // Passing Channels to code makes code easier to test and makes it easier to reuse Channels.
+    blockingStub = GreeterGrpc.newBlockingStub(channel);
+  }
+
+  /** Say hello to server. */
+  public void greet(String name) {
+    logger.info("Will try to greet " + 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());
+  }
+
+  /**
+   * Greet server.
+   */
+  public static void main(String[] args) throws Exception {
+    // Access a service running on the local machine on port 50051
+    String target = "localhost:50051";
+
+    // Create a channel with the following keep alive configurations (demo only, you should set
+    // more appropriate values based on your environment):
+    // keepAliveTime: Send pings every 10 seconds if there is no activity. Set to an appropriate
+    // value in reality, e.g. (5, TimeUnit.MINUTES).
+    // keepAliveTimeout: Wait 1 second for ping ack before considering the connection dead. Set to a
+    // larger value in reality, e.g. (10, TimeUnit.SECONDS). You should only set such a small value,
+    // e.g. (1, TimeUnit.SECONDS) in certain low latency environments.
+    // keepAliveWithoutCalls: Send pings even without active streams. Normally disable it.
+    // Use JAVA_OPTS=-Djava.util.logging.config.file=logging.properties to see the keep alive ping
+    // frames.
+    // More details see: https://github.com/grpc/proposal/blob/master/A8-client-side-keepalive.md
+    ManagedChannel channel = Grpc.newChannelBuilder(target, InsecureChannelCredentials.create())
+        .keepAliveTime(5, TimeUnit.MINUTES)
+        .keepAliveTime(10, TimeUnit.SECONDS) // Change to a larger value, e.g. 5min.
+        .keepAliveTimeout(1, TimeUnit.SECONDS) // Change to a larger value, e.g. 10s.
+        .keepAliveWithoutCalls(true)// You should normally avoid enabling this.
+        .build();
+
+    try {
+      KeepAliveClient client = new KeepAliveClient(channel);
+      client.greet("Keep-alive Demo");
+      Thread.sleep(30000);
+    } finally {
+      channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
+    }
+  }
+}

examples/src/main/java/io/grpc/examples/keepalive/KeepAliveServer.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2023 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.keepalive;
+
+import io.grpc.Grpc;
+import io.grpc.InsecureServerCredentials;
+import io.grpc.Server;
+import io.grpc.examples.helloworld.GreeterGrpc;
+import io.grpc.examples.helloworld.HelloReply;
+import io.grpc.examples.helloworld.HelloRequest;
+import io.grpc.stub.StreamObserver;
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Logger;
+
+/**
+ * Server that manages startup/shutdown of a keep alive server.
+ */
+public class KeepAliveServer {
+  private static final Logger logger = Logger.getLogger(KeepAliveServer.class.getName());
+
+  private Server server;
+
+  private void start() throws IOException {
+    /* The port on which the server should run */
+    int port = 50051;
+
+    // Start a server with the following configurations (demo only, you should set more appropriate
+    // values based on your real environment):
+    // keepAliveTime: Ping the client if it is idle for 5 seconds to ensure the connection is
+    // still active. Set to an appropriate value in reality, e.g. in minutes.
+    // keepAliveTimeout: Wait 1 second for the ping ack before assuming the connection is dead.
+    // Set to an appropriate value in reality, e.g. (10, TimeUnit.SECONDS).
+    // permitKeepAliveTime: If a client pings more than once every 5 seconds, terminate the
+    // connection.
+    // permitKeepAliveWithoutCalls: Allow pings even when there are no active streams.
+    // maxConnectionIdle: If a client is idle for 15 seconds, send a GOAWAY.
+    // maxConnectionAge: If any connection is alive for more than 30 seconds, send a GOAWAY.
+    // maxConnectionAgeGrace: Allow 5 seconds for pending RPCs to complete before forcibly closing
+    // connections.
+    // Use JAVA_OPTS=-Djava.util.logging.config.file=logging.properties to see keep alive ping
+    // frames.
+    // More details see: https://github.com/grpc/proposal/blob/master/A9-server-side-conn-mgt.md
+    server = Grpc.newServerBuilderForPort(port, InsecureServerCredentials.create())
+        .addService(new GreeterImpl())
+        .keepAliveTime(5, TimeUnit.SECONDS)
+        .keepAliveTimeout(1, TimeUnit.SECONDS)
+        .permitKeepAliveTime(5, TimeUnit.SECONDS)
+        .permitKeepAliveWithoutCalls(true)
+        .maxConnectionIdle(15, TimeUnit.SECONDS)
+        .maxConnectionAge(30, TimeUnit.SECONDS)
+        .maxConnectionAgeGrace(5, TimeUnit.SECONDS)
+        .build()
+        .start();
+    logger.info("Server started, listening on " + port);
+    Runtime.getRuntime().addShutdownHook(new Thread() {
+      @Override
+      public void run() {
+        // Use stderr here since the logger may have been reset by its JVM shutdown hook.
+        System.err.println("*** shutting down gRPC server since JVM is shutting down");
+        try {
+          KeepAliveServer.this.stop();
+        } catch (InterruptedException e) {
+          e.printStackTrace(System.err);
+        }
+        System.err.println("*** server shut down");
+      }
+    });
+  }
+
+  private void stop() throws InterruptedException {
+    if (server != null) {
+      server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
+    }
+  }
+
+  /**
+   * Await termination on the main thread since the grpc library uses daemon threads.
+   */
+  private void blockUntilShutdown() throws InterruptedException {
+    if (server != null) {
+      server.awaitTermination();
+    }
+  }
+
+  /**
+   * Main launches the server from the command line.
+   */
+  public static void main(String[] args) throws IOException, InterruptedException {
+    final KeepAliveServer server = new KeepAliveServer();
+    server.start();
+    server.blockUntilShutdown();
+  }
+
+  static class GreeterImpl extends GreeterGrpc.GreeterImplBase {
+
+    @Override
+    public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+      HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
+      responseObserver.onNext(reply);
+      responseObserver.onCompleted();
+    }
+  }
+}