Add a gRPC Hello World example. (#1044)

8 files changed, 590 insertions, 5 deletions

diff --git a/examples/BUILD.bazel b/examples/BUILD.bazel
index 82f322e7..6245c0a3 100644
--- a/examples/BUILD.bazel
+++ b/examples/BUILD.bazel
@@ -4,7 +4,8 @@ opencensus_java_libraries()
 java_library(
     name = "opencensus_examples",
     srcs = glob(
-        ["src/main/java/**/*.java"]
+        ["src/main/java/**/*.java"],
+        exclude = ["src/main/java/io/opencensus/examples/grpc/**/*.java"],
     ),
     deps = [
         "@io_opencensus_opencensus_api//jar",
diff --git a/examples/README.md b/examples/README.md
index e7a270c4..62324f20 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -78,3 +78,33 @@ $ ./target/appassembler/bin/QuickStart
 ```
 $ ./bazel-bin/QuickStart
 ```
+
+## To run "gRPC Hello World" example use
+
+Please note all the arguments are optional. If you do not specify these arguments, default values
+will be used:
+
+* host and serverPort will be "localhost:50051"
+* user will be "world"
+* cloudProjectId will be null (which means no stats/spans will be exported to Stackdriver)
+* server zPagePort will be 3000
+* client zPagePort will be 3001
+* Prometheus port will be 9090
+
+
+However, if you want to specify any of these arguements, please make sure they are in order.
+
+### Gradle
+```
+$ ./build/install/opencensus-examples/bin/HelloWorldServer serverPort cloudProjectId zPagePort prometheusPort
+$ ./build/install/opencensus-examples/bin/HelloWorldClient user host serverPort cloudProjectId zPagePort
+```
+
+### Maven
+```
+$ ./target/appassembler/bin/HelloWorldServer serverPort cloudProjectId zPagePort prometheusPort
+$ ./target/appassembler/bin/HelloWorldClient user host serverPort cloudProjectId zPagePort
+```
+
+### Bazel
+TODO
\ No newline at end of file
diff --git a/examples/build.gradle b/examples/build.gradle
index ab5de34a..163b0b80 100644
--- a/examples/build.gradle
+++ b/examples/build.gradle
@@ -10,12 +10,14 @@ buildscript {
     }
     dependencies {
         classpath "gradle.plugin.com.github.sherter.google-java-format:google-java-format-gradle-plugin:0.6"
+        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.3'
     }
 }
 
 apply plugin: 'checkstyle'
 apply plugin: 'idea'
 apply plugin: 'java'
+apply plugin: 'com.google.protobuf'
 // Plugins that require java8
 if (JavaVersion.current().isJava8Compatible()) {
     apply plugin: 'com.github.sherter.google-java-format'
@@ -30,6 +32,8 @@ group = "io.opencensus"
 version = "0.13.0-SNAPSHOT" // CURRENT_OPENCENSUS_VERSION
 
 def opencensusVersion = "0.12.2" // LATEST_OPENCENSUS_RELEASE_VERSION
+def grpcVersion = "1.9.0" // CURRENT_GRPC_VERSION
+def prometheusVersion = "0.3.0"
 
 checkstyle {
     configFile = file("$rootDir/../buildscripts/checkstyle.xml")
@@ -41,6 +45,11 @@ checkstyle {
     configProperties["rootDir"] = file("$rootDir/../")
 }
 
+checkstyleMain {
+    // This skips proto generated files beucasue they are in gen_gradle/src/main/**
+    source = fileTree(dir: "src/main", include: "**/*.java")
+}
+
 // Google formatter works only on java8.
 if (JavaVersion.current().isJava8Compatible()) {
     googleJavaFormat {
@@ -49,12 +58,14 @@ if (JavaVersion.current().isJava8Compatible()) {
 
     afterEvaluate {  // Allow subproject to add more source sets.
         tasks.googleJavaFormat {
-            source = sourceSets*.allJava
+            // This skips proto generated files beucasue they are in gen_gradle/src/main/**
+            source = "src/main"
             include '**/*.java'
         }
 
         tasks.verifyGoogleJavaFormat {
-            source = sourceSets*.allJava
+            // This skips proto generated files beucasue they are in gen_gradle/src/main/**
+            source = "src/main"
             include '**/*.java'
         }
     }
@@ -66,13 +77,50 @@ tasks.withType(JavaCompile) {
 }
 
 dependencies {
-    compile "io.opencensus:opencensus-api:${opencensusVersion}",
+    compile "com.google.api.grpc:proto-google-common-protos:1.0.5",
+            "io.opencensus:opencensus-api:${opencensusVersion}",
             "io.opencensus:opencensus-contrib-zpages:${opencensusVersion}",
-            "io.opencensus:opencensus-exporter-trace-logging:${opencensusVersion}"
+            "io.opencensus:opencensus-contrib-grpc-metrics:${opencensusVersion}",
+            "io.opencensus:opencensus-exporter-stats-prometheus:${opencensusVersion}",
+            "io.opencensus:opencensus-exporter-stats-stackdriver:${opencensusVersion}",
+            "io.opencensus:opencensus-exporter-trace-stackdriver:${opencensusVersion}",
+            "io.opencensus:opencensus-exporter-trace-logging:${opencensusVersion}",
+            "io.grpc:grpc-protobuf:${grpcVersion}",
+            "io.grpc:grpc-stub:${grpcVersion}",
+            "io.grpc:grpc-netty:${grpcVersion}",
+            "io.prometheus:simpleclient_httpserver:${prometheusVersion}"
 
     runtime "io.opencensus:opencensus-impl:${opencensusVersion}"
 }
 
+protobuf {
+    protoc {
+        artifact = 'com.google.protobuf:protoc:3.5.1-1'
+    }
+    plugins {
+        grpc {
+            artifact = "io.grpc:protoc-gen-grpc-java:${grpcVersion}"
+        }
+    }
+    generateProtoTasks {
+        all()*.plugins {
+            grpc {}
+        }
+        ofSourceSet('main')
+    }
+}
+
+// Inform IDEs like IntelliJ IDEA, Eclipse or NetBeans about the generated code.
+sourceSets {
+    main {
+        java {
+            srcDir 'src'
+            srcDirs 'build/generated/source/proto/main/grpc'
+            srcDirs 'build/generated/source/proto/main/java'
+        }
+    }
+}
+
 // Provide convenience executables for trying out the examples.
 apply plugin: 'application'
 
@@ -120,6 +168,20 @@ task quickStart(type: CreateStartScripts) {
     classpath = jar.outputs.files + project.configurations.runtime
 }
 
+task helloWorldServer(type: CreateStartScripts) {
+    mainClassName = 'io.opencensus.examples.grpc.helloworld.HelloWorldServer'
+    applicationName = 'HelloWorldServer'
+    outputDir = new File(project.buildDir, 'tmp')
+    classpath = jar.outputs.files + project.configurations.runtime
+}
+
+task helloWorldClient(type: CreateStartScripts) {
+    mainClassName = 'io.opencensus.examples.grpc.helloworld.HelloWorldClient'
+    applicationName = 'HelloWorldClient'
+    outputDir = new File(project.buildDir, 'tmp')
+    classpath = jar.outputs.files + project.configurations.runtime
+}
+
 applicationDistribution.into('bin') {
     from(multiSpansTracing)
     from(multiSpansScopedTracing)
@@ -127,5 +189,7 @@ applicationDistribution.into('bin') {
     from(statsRunner)
     from(zPagesTester)
     from(quickStart)
+    from(helloWorldServer)
+    from(helloWorldClient)
     fileMode = 0755
 }
diff --git a/examples/pom.xml b/examples/pom.xml
index 468f9774..38c6d6d0 100644
--- a/examples/pom.xml
+++ b/examples/pom.xml
@@ -11,6 +11,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <!-- change to the version you want to use. -->
     <opencensus.version>0.12.2</opencensus.version><!-- LATEST_OPENCENSUS_RELEASE_VERSION -->
+    <grpc.version>1.9.0</grpc.version><!-- CURRENT_GRPC_VERSION -->
   </properties>
   <dependencies>
     <dependency>
@@ -20,15 +21,55 @@
     </dependency>
     <dependency>
       <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-contrib-grpc-metrics</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
       <artifactId>opencensus-contrib-zpages</artifactId>
       <version>${opencensus.version}</version>
     </dependency>
     <dependency>
       <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-exporter-stats-stackdriver</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-exporter-stats-prometheus</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
+      <artifactId>opencensus-exporter-trace-stackdriver</artifactId>
+      <version>${opencensus.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.opencensus</groupId>
       <artifactId>opencensus-exporter-trace-logging</artifactId>
       <version>${opencensus.version}</version>
     </dependency>
     <dependency>
+      <groupId>io.grpc</groupId>
+      <artifactId>grpc-netty</artifactId>
+      <version>${grpc.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.grpc</groupId>
+      <artifactId>grpc-protobuf</artifactId>
+      <version>${grpc.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.grpc</groupId>
+      <artifactId>grpc-stub</artifactId>
+      <version>${grpc.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>io.prometheus</groupId>
+      <artifactId>simpleclient_httpserver</artifactId>
+      <version>0.3.0</version>
+    </dependency>
+    <dependency>
       <groupId>io.opencensus</groupId>
       <artifactId>opencensus-impl</artifactId>
       <version>${opencensus.version}</version>
@@ -36,6 +77,13 @@
     </dependency>
   </dependencies>
   <build>
+    <extensions>
+      <extension>
+        <groupId>kr.motd.maven</groupId>
+        <artifactId>os-maven-plugin</artifactId>
+        <version>1.5.0.Final</version>
+      </extension>
+    </extensions>
     <pluginManagement>
       <plugins>
         <plugin>
@@ -80,9 +128,35 @@
               <id>QuickStart</id>
               <mainClass>io.opencensus.examples.helloworld.QuickStart</mainClass>
             </program>
+            <program>
+              <id>HelloWorldClient</id>
+              <mainClass>io.opencensus.examples.grpc.helloworld.HelloWorldClient</mainClass>
+            </program>
+            <program>
+              <id>HelloWorldServer</id>
+              <mainClass>io.opencensus.examples.grpc.helloworld.HelloWorldServer</mainClass>
+            </program>
           </programs>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.xolstice.maven.plugins</groupId>
+        <artifactId>protobuf-maven-plugin</artifactId>
+        <version>0.5.0</version>
+        <configuration>
+          <protocArtifact>com.google.protobuf:protoc:3.5.1-1:exe:${os.detected.classifier}</protocArtifact>
+          <pluginId>grpc-java</pluginId>
+          <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}</pluginArtifact>
+        </configuration>
+        <executions>
+          <execution>
+            <goals>
+              <goal>compile</goal>
+              <goal>compile-custom</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>
diff --git a/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldClient.java b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldClient.java
new file mode 100644
index 00000000..30e41633
--- /dev/null
+++ b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldClient.java
@@ -0,0 +1,151 @@
+/*
+ * Copyright 2018, OpenCensus 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.opencensus.examples.grpc.helloworld;
+
+import static io.opencensus.examples.grpc.helloworld.HelloWorldUtils.getPortOrDefaultFromArgs;
+import static io.opencensus.examples.grpc.helloworld.HelloWorldUtils.getStringOrDefaultFromArgs;
+
+import io.grpc.ManagedChannel;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.StatusRuntimeException;
+import io.opencensus.common.Duration;
+import io.opencensus.common.Scope;
+import io.opencensus.contrib.grpc.metrics.RpcViews;
+import io.opencensus.contrib.zpages.ZPageHandlers;
+import io.opencensus.exporter.stats.prometheus.PrometheusStatsCollector;
+import io.opencensus.exporter.stats.stackdriver.StackdriverStatsConfiguration;
+import io.opencensus.exporter.stats.stackdriver.StackdriverStatsExporter;
+import io.opencensus.exporter.trace.logging.LoggingTraceExporter;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceConfiguration;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceExporter;
+import io.opencensus.trace.SpanBuilder;
+import io.opencensus.trace.Status.CanonicalCode;
+import io.opencensus.trace.Tracer;
+import io.opencensus.trace.Tracing;
+import io.opencensus.trace.samplers.Samplers;
+import java.io.IOException;
+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 HelloWorldServer}. */
+public class HelloWorldClient {
+  private static final Logger logger = Logger.getLogger(HelloWorldClient.class.getName());
+
+  private static final Tracer tracer = Tracing.getTracer();
+
+  private final ManagedChannel channel;
+  private final GreeterGrpc.GreeterBlockingStub blockingStub;
+
+  /** Construct client connecting to HelloWorld server at {@code host:port}. */
+  public HelloWorldClient(String host, int port) {
+    this(
+        ManagedChannelBuilder.forAddress(host, port)
+            // Channels are secure by default (via SSL/TLS). For the example we disable TLS to avoid
+            // needing certificates.
+            .usePlaintext(true)
+            .build());
+  }
+
+  /** Construct client for accessing RouteGuide server using the existing channel. */
+  HelloWorldClient(ManagedChannel channel) {
+    this.channel = channel;
+    blockingStub = GreeterGrpc.newBlockingStub(channel);
+  }
+
+  public void shutdown() throws InterruptedException {
+    channel.shutdown().awaitTermination(5, TimeUnit.SECONDS);
+  }
+
+  /** 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;
+
+    SpanBuilder spanBuilder =
+        tracer.spanBuilder("client").setRecordEvents(true).setSampler(Samplers.alwaysSample());
+    try (Scope scope = spanBuilder.startScopedSpan()) {
+      tracer.getCurrentSpan().addAnnotation("Saying Hello to Server.");
+      response = blockingStub.sayHello(request);
+      tracer.getCurrentSpan().addAnnotation("Received response from Server.");
+    } catch (StatusRuntimeException e) {
+      tracer
+          .getCurrentSpan()
+          .setStatus(
+              CanonicalCode.valueOf(e.getStatus().getCode().name())
+                  .toStatus()
+                  .withDescription(e.getMessage()));
+      logger.log(Level.WARNING, "RPC failed: {0}", e.getStatus());
+      return;
+    }
+    logger.info("Greeting: " + response.getMessage());
+  }
+
+  /**
+   * Greet server. If provided, the first element of {@code args} is the name to use in the
+   * greeting.
+   */
+  public static void main(String[] args) throws IOException, InterruptedException {
+    // Add final keyword to pass checkStyle.
+    final String user = getStringOrDefaultFromArgs(args, 0, "world");
+    final String host = getStringOrDefaultFromArgs(args, 1, "localhost");
+    final int serverPort = getPortOrDefaultFromArgs(args, 2, 50051);
+    final String cloudProjectId = getStringOrDefaultFromArgs(args, 3, null);
+    final int zPagePort = getPortOrDefaultFromArgs(args, 4, 3001);
+
+    // Registers all RPC views.
+    RpcViews.registerAllViews();
+
+    // Starts a HTTP server and registers all Zpages to it.
+    ZPageHandlers.startHttpServerAndRegisterAll(zPagePort);
+    logger.info("ZPages server starts at localhost:" + zPagePort);
+
+    // Registers logging trace exporter.
+    LoggingTraceExporter.register();
+
+    // Registers Stackdriver exporters.
+    if (cloudProjectId != null) {
+      StackdriverTraceExporter.createAndRegister(
+          StackdriverTraceConfiguration.builder().setProjectId(cloudProjectId).build());
+      StackdriverStatsExporter.createAndRegister(
+          StackdriverStatsConfiguration.builder()
+              .setProjectId(cloudProjectId)
+              .setExportInterval(Duration.create(15, 0))
+              .build());
+    }
+
+    // Register Prometheus exporters and export metrics to a Prometheus HTTPServer.
+    PrometheusStatsCollector.createAndRegister();
+
+    HelloWorldClient client = new HelloWorldClient(host, serverPort);
+    try {
+      client.greet(user);
+    } finally {
+      client.shutdown();
+    }
+
+    logger.info("Client sleeping, ^C to exit. Meanwhile you can view stats and spans on zpages.");
+    while (true) {
+      try {
+        Thread.sleep(10000);
+      } catch (InterruptedException e) {
+        logger.info("Exiting HelloWorldClient...");
+      }
+    }
+  }
+}
diff --git a/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldServer.java b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldServer.java
new file mode 100644
index 00000000..15a0a896
--- /dev/null
+++ b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldServer.java
@@ -0,0 +1,176 @@
+/*
+ * Copyright 2018, OpenCensus 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.opencensus.examples.grpc.helloworld;
+
+import static io.opencensus.examples.grpc.helloworld.HelloWorldUtils.getPortOrDefaultFromArgs;
+import static io.opencensus.examples.grpc.helloworld.HelloWorldUtils.getStringOrDefaultFromArgs;
+
+import com.google.common.collect.ImmutableMap;
+import io.grpc.Server;
+import io.grpc.ServerBuilder;
+import io.grpc.stub.StreamObserver;
+import io.opencensus.common.Duration;
+import io.opencensus.common.Scope;
+import io.opencensus.contrib.grpc.metrics.RpcViews;
+import io.opencensus.contrib.zpages.ZPageHandlers;
+import io.opencensus.exporter.stats.prometheus.PrometheusStatsCollector;
+import io.opencensus.exporter.stats.stackdriver.StackdriverStatsConfiguration;
+import io.opencensus.exporter.stats.stackdriver.StackdriverStatsExporter;
+import io.opencensus.exporter.trace.logging.LoggingTraceExporter;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceConfiguration;
+import io.opencensus.exporter.trace.stackdriver.StackdriverTraceExporter;
+import io.opencensus.trace.AttributeValue;
+import io.opencensus.trace.Span;
+import io.opencensus.trace.SpanBuilder;
+import io.opencensus.trace.Status;
+import io.opencensus.trace.Tracer;
+import io.opencensus.trace.Tracing;
+import io.opencensus.trace.samplers.Samplers;
+import io.prometheus.client.exporter.HTTPServer;
+import java.io.IOException;
+import java.util.logging.Logger;
+
+/** Server that manages startup/shutdown of a {@code Greeter} server. */
+public class HelloWorldServer {
+  private static final Logger logger = Logger.getLogger(HelloWorldServer.class.getName());
+
+  private static final Tracer tracer = Tracing.getTracer();
+
+  private final int serverPort;
+  private Server server;
+
+  private HelloWorldServer(int serverPort) {
+    this.serverPort = serverPort;
+  }
+
+  // A helper function that performs some work in its own Span.
+  private static void performWork(Span parent) {
+    SpanBuilder spanBuilder =
+        tracer
+            .spanBuilderWithExplicitParent("internal_work", parent)
+            .setRecordEvents(true)
+            .setSampler(Samplers.alwaysSample());
+    try (Scope scope = spanBuilder.startScopedSpan()) {
+      Span span = tracer.getCurrentSpan();
+      span.putAttribute("my_attribute", AttributeValue.stringAttributeValue("blue"));
+      span.addAnnotation("Performing work.");
+      sleepFor(20); // Working hard here.
+      span.addAnnotation("Done work.");
+    }
+  }
+
+  private static void sleepFor(int milliseconds) {
+    try {
+      Thread.sleep(milliseconds);
+    } catch (InterruptedException e) {
+      Span span = tracer.getCurrentSpan();
+      span.addAnnotation("Exception thrown when performing work " + e.getMessage());
+      span.setStatus(Status.UNKNOWN);
+    }
+  }
+
+  private void start() throws IOException {
+    server = ServerBuilder.forPort(serverPort).addService(new GreeterImpl()).build().start();
+    logger.info("Server started, listening on " + serverPort);
+    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");
+                HelloWorldServer.this.stop();
+                System.err.println("*** server shut down");
+              }
+            });
+  }
+
+  private void stop() {
+    if (server != null) {
+      server.shutdown();
+    }
+  }
+
+  /** 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 {
+    // Add final keyword to pass checkStyle.
+    final int serverPort = getPortOrDefaultFromArgs(args, 0, 50051);
+    final String cloudProjectId = getStringOrDefaultFromArgs(args, 1, null);
+    final int zPagePort = getPortOrDefaultFromArgs(args, 2, 3000);
+    final int prometheusPort = getPortOrDefaultFromArgs(args, 3, 9090);
+
+    // Registers all RPC views.
+    RpcViews.registerAllViews();
+
+    // Registers logging trace exporter.
+    LoggingTraceExporter.register();
+
+    // Starts a HTTP server and registers all Zpages to it.
+    ZPageHandlers.startHttpServerAndRegisterAll(zPagePort);
+    logger.info("ZPages server starts at localhost:" + zPagePort);
+
+    // Registers Stackdriver exporters.
+    if (cloudProjectId != null) {
+      StackdriverTraceExporter.createAndRegister(
+          StackdriverTraceConfiguration.builder().setProjectId(cloudProjectId).build());
+      StackdriverStatsExporter.createAndRegister(
+          StackdriverStatsConfiguration.builder()
+              .setProjectId(cloudProjectId)
+              .setExportInterval(Duration.create(15, 0))
+              .build());
+    }
+
+    // Register Prometheus exporters and export metrics to a Prometheus HTTPServer.
+    PrometheusStatsCollector.createAndRegister();
+    HTTPServer prometheusServer = new HTTPServer(prometheusPort, true);
+
+    // Start the RPC server. You shouldn't see any output from gRPC before this.
+    logger.info("gRPC starting.");
+    final HelloWorldServer server = new HelloWorldServer(serverPort);
+    server.start();
+    server.blockUntilShutdown();
+  }
+
+  static class GreeterImpl extends GreeterGrpc.GreeterImplBase {
+
+    @Override
+    public void sayHello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
+      Span span = tracer.getCurrentSpan();
+      span.putAttribute("my_attribute", AttributeValue.stringAttributeValue("red"));
+      span.addAnnotation(
+          "Constructing greeting.",
+          ImmutableMap.of(
+              "name", AttributeValue.stringAttributeValue(req.getName()),
+              "name length", AttributeValue.longAttributeValue(req.getName().length())));
+      sleepFor(10);
+      performWork(span);
+      span.addAnnotation("Sleeping.");
+      sleepFor(30);
+      HelloReply reply = HelloReply.newBuilder().setMessage("Hello " + req.getName()).build();
+      responseObserver.onNext(reply);
+      responseObserver.onCompleted();
+      logger.info("SayHello RPC handled.");
+    }
+  }
+}
diff --git a/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldUtils.java b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldUtils.java
new file mode 100644
index 00000000..f6dcdaab
--- /dev/null
+++ b/examples/src/main/java/io/opencensus/examples/grpc/helloworld/HelloWorldUtils.java
@@ -0,0 +1,50 @@
+/*
+ * Copyright 2018, OpenCensus 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.opencensus.examples.grpc.helloworld;
+
+import java.util.logging.Logger;
+import javax.annotation.Nullable;
+
+/** Util methods. */
+final class HelloWorldUtils {
+
+  private static Logger logger = Logger.getLogger(HelloWorldUtils.class.getName());
+
+  static int getPortOrDefaultFromArgs(String[] args, int index, int defaultPort) {
+    int portNumber = defaultPort;
+    if (index < args.length) {
+      try {
+        portNumber = Integer.parseInt(args[index]);
+      } catch (NumberFormatException e) {
+        logger.warning(
+            String.format("Port %s is invalid, use default port %d.", args[index], defaultPort));
+      }
+    }
+    return portNumber;
+  }
+
+  static String getStringOrDefaultFromArgs(
+      String[] args, int index, @Nullable String defaultString) {
+    String s = defaultString;
+    if (index < args.length) {
+      s = args[index];
+    }
+    return s;
+  }
+
+  private HelloWorldUtils() {}
+}
diff --git a/examples/src/main/proto/helloworld.proto b/examples/src/main/proto/helloworld.proto
new file mode 100644
index 00000000..1bd79300
--- /dev/null
+++ b/examples/src/main/proto/helloworld.proto
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2018, OpenCensus 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.
+ */
+
+syntax = "proto3";
+
+option java_multiple_files = true;
+option java_package = "io.opencensus.examples.grpc.helloworld";
+option java_outer_classname = "HelloWorldProto";
+
+package helloworld;
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}