Enable including Java worker for ray start command (#3838)

java/runtime/pom.xml

@@ -77,4 +77,38 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-dependency-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>copy-dependencies-to-build</id>
+            <phase>package</phase>
+            <goals>
+              <goal>copy-dependencies</goal>
+            </goals>
+            <configuration>
+              <outputDirectory>${basedir}/../../build/java</outputDirectory>
+              <overWriteReleases>false</overWriteReleases>
+              <overWriteSnapshots>false</overWriteSnapshots>
+              <overWriteIfNewer>true</overWriteIfNewer>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-jar-plugin</artifactId>
+        <version>2.3.1</version>
+        <configuration>
+          <outputDirectory>${basedir}/../../build/java</outputDirectory>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+
 </project>

java/runtime/src/main/java/org/ray/runtime/RayNativeRuntime.java

@@ -71,6 +71,7 @@ public final class RayNativeRuntime extends AbstractRayRuntime {
     }
     redisClient = new RedisClient(rayConfig.getRedisAddress());
 
+    // TODO(qwang): Get object_store_socket_name and raylet_socket_name from Redis.
     objectStoreProxy = new ObjectStoreProxy(this, rayConfig.objectStoreSocketName);
 
     rayletClient = new RayletClientImpl(

java/test/src/main/java/org/ray/api/test/ActorTest.java

@@ -4,7 +4,6 @@ import org.ray.api.Ray;
 import org.ray.api.RayActor;
 import org.ray.api.RayObject;
 import org.ray.api.annotation.RayRemote;
-import org.ray.api.function.RayFunc2;
 import org.ray.api.id.UniqueId;
 import org.ray.runtime.RayActorImpl;
 import org.testng.Assert;

java/test/src/main/java/org/ray/api/test/MultiLanguageClusterTest.java

@@ -0,0 +1,115 @@
+package org.ray.api.test;
+
+import com.google.common.collect.ImmutableList;
+import java.io.File;
+import java.io.IOException;
+import java.lang.ProcessBuilder.Redirect;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import org.ray.api.Ray;
+import org.ray.api.RayObject;
+import org.ray.api.annotation.RayRemote;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.testng.Assert;
+import org.testng.SkipException;
+import org.testng.annotations.AfterMethod;
+import org.testng.annotations.BeforeMethod;
+import org.testng.annotations.Test;
+
+/**
+ * Test starting a ray cluster with multi-language support.
+ */
+public class MultiLanguageClusterTest {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(MultiLanguageClusterTest.class);
+
+  private static final String PLASMA_STORE_SOCKET_NAME = "/tmp/ray/test/plasma_store_socket";
+  private static final String RAYLET_SOCKET_NAME = "/tmp/ray/test/raylet_socket";
+
+  @RayRemote
+  public static String echo(String word) {
+    return word;
+  }
+
+  /**
+   * Execute an external command.
+   * @return Whether the command succeeded.
+   */
+  private boolean executeCommand(List<String> command, int waitTimeoutSeconds) {
+    try {
+      LOGGER.info("Executing command: {}", String.join(" ", command));
+      Process process = new ProcessBuilder(command).redirectOutput(Redirect.INHERIT)
+          .redirectError(Redirect.INHERIT).start();
+      process.waitFor(waitTimeoutSeconds, TimeUnit.SECONDS);
+      return process.exitValue() == 0;
+    } catch (Exception e) {
+      throw new RuntimeException("Error executing command " + String.join(" ", command), e);
+    }
+  }
+
+  @BeforeMethod
+  public void setUp() {
+    // Check whether 'ray' command is installed.
+    boolean rayCommandExists = executeCommand(ImmutableList.of("which", "ray"), 5);
+    if (!rayCommandExists) {
+      throw new SkipException("Skipping test, because ray command doesn't exist.");
+    }
+
+    // Delete existing socket files.
+    for (String socket : ImmutableList.of(RAYLET_SOCKET_NAME, PLASMA_STORE_SOCKET_NAME)) {
+      File file = new File(socket);
+      if (file.exists()) {
+        file.delete();
+      }
+    }
+
+    // Start ray cluster.
+    final List<String> startCommand = ImmutableList.of(
+        "ray",
+        "start",
+        "--head",
+        "--redis-port=6379",
+        "--include-java",
+        String.format("--plasma-store-socket-name=%s", PLASMA_STORE_SOCKET_NAME),
+        String.format("--raylet-socket-name=%s", RAYLET_SOCKET_NAME),
+        "--java-worker-options=-classpath ../../build/java/*:../../java/test/target/*"
+    );
+    if (!executeCommand(startCommand, 10)) {
+      throw new RuntimeException("Couldn't start ray cluster.");
+    }
+
+    // Connect to the cluster.
+    System.setProperty("ray.home", "../..");
+    System.setProperty("ray.redis.address", "127.0.0.1:6379");
+    System.setProperty("ray.object-store.socket-name", PLASMA_STORE_SOCKET_NAME);
+    System.setProperty("ray.raylet.socket-name", RAYLET_SOCKET_NAME);
+    Ray.init();
+  }
+
+  @AfterMethod
+  public void tearDown() {
+    // Disconnect to the cluster.
+    Ray.shutdown();
+    System.clearProperty("ray.home");
+    System.clearProperty("ray.redis.address");
+    System.clearProperty("ray.object-store.socket-name");
+    System.clearProperty("ray.raylet.socket-name");
+
+    // Stop ray cluster.
+    final List<String> stopCommand = ImmutableList.of(
+        "ray",
+        "stop"
+    );
+    if (!executeCommand(stopCommand, 10)) {
+      throw new RuntimeException("Couldn't stop ray cluster");
+    }
+  }
+
+  @Test
+  public void testMultiLanguageCluster() {
+    RayObject<String> obj = Ray.call(MultiLanguageClusterTest::echo, "hello");
+    Assert.assertEquals("hello", obj.get());
+  }
+
+}