[Java] add exitActor API for java (#10496)

java/runtime/src/main/java/io/ray/runtime/RayDevRuntime.java

@@ -84,6 +84,11 @@ public class RayDevRuntime extends AbstractRayRuntime {
     super.setAsyncContext(asyncContext);
   }
 
+  @Override
+  public void exitActor() {
+
+  }
+
   private JobId nextJobId() {
     return JobId.fromInt(jobCounter.getAndIncrement());
   }

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

@@ -9,6 +9,7 @@ import io.ray.api.runtimecontext.NodeInfo;
 import io.ray.runtime.config.RayConfig;
 import io.ray.runtime.context.NativeWorkerContext;
 import io.ray.runtime.exception.RayException;
+import io.ray.runtime.exception.RayIntentionalSystemExitException;
 import io.ray.runtime.gcs.GcsClient;
 import io.ray.runtime.gcs.GcsClientOptions;
 import io.ray.runtime.gcs.RedisClient;
@@ -245,6 +246,16 @@ public final class RayNativeRuntime extends AbstractRayRuntime {
     super.setAsyncContext(asyncContext);
   }
 
+  @Override
+  public void exitActor() {
+    if (rayConfig.workerMode != WorkerType.WORKER || runtimeContext.getCurrentActorId().isNil()) {
+      throw new RuntimeException("This shouldn't be called on a non-actor worker.");
+    }
+    LOGGER.info("Actor {} is exiting.", runtimeContext.getCurrentActorId());
+    throw new RayIntentionalSystemExitException(
+        String.format("Actor %s is exiting.", runtimeContext.getCurrentActorId()));
+  }
+
   @Override
   public void run() {
     Preconditions.checkState(rayConfig.workerMode == WorkerType.WORKER);

java/runtime/src/main/java/io/ray/runtime/exception/RayIntentionalSystemExitException.java

@@ -0,0 +1,15 @@
+package io.ray.runtime.exception;
+
+/**
+ * The exception represents that there is an intentional system exit.
+ */
+public class RayIntentionalSystemExitException extends RuntimeException {
+
+  public RayIntentionalSystemExitException(String message) {
+    super(message);
+  }
+
+  public RayIntentionalSystemExitException(String message, Throwable cause) {
+    super(message, cause);
+  }
+}

java/runtime/src/main/java/io/ray/runtime/task/TaskExecutor.java

@@ -6,6 +6,7 @@ import io.ray.api.id.JobId;
 import io.ray.api.id.TaskId;
 import io.ray.api.id.UniqueId;
 import io.ray.runtime.RayRuntimeInternal;
+import io.ray.runtime.exception.RayIntentionalSystemExitException;
 import io.ray.runtime.exception.RayTaskException;
 import io.ray.runtime.functionmanager.JavaFunctionDescriptor;
 import io.ray.runtime.functionmanager.RayFunction;
@@ -159,6 +160,12 @@ public abstract class TaskExecutor<T extends TaskExecutor.ActorContext> {
       }
       LOGGER.debug("Finished executing task {}", taskId);
     } catch (Throwable e) {
+      if (e instanceof RayIntentionalSystemExitException) {
+        // We don't need to fill the `returnObjects` with an exception metadata
+        // because the node manager or the direct actor task submitter will fill
+        // the return object with the ACTOR_DIED metadata.
+        throw (RayIntentionalSystemExitException) e;
+      }
       LOGGER.error("Error executing task " + taskId, e);
       if (taskType != TaskType.ACTOR_CREATION_TASK) {
         boolean hasReturn = rayFunction != null && rayFunction.hasReturn();

java/runtime/src/main/java/io/ray/runtime/util/SystemUtil.java

@@ -1,5 +1,6 @@
 package io.ray.runtime.util;
 
+import java.io.IOException;
 import java.lang.management.ManagementFactory;
 import java.lang.management.RuntimeMXBean;
 import java.util.concurrent.locks.ReentrantLock;
@@ -34,4 +35,15 @@ public class SystemUtil {
     return pid;
 
   }
+
+  public static boolean isProcessAlive(int pid) {
+    Process process;
+    try {
+      process = Runtime.getRuntime().exec(new String[]{"ps", "-p", String.valueOf(pid)});
+      process.waitFor();
+    } catch (InterruptedException | IOException e) {
+      throw new RuntimeException(e);
+    }
+    return process.exitValue() == 0;
+  }
 }