[Java] Release actor instance reference when Ray.exitActor() is invoked (#11324)

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

@@ -282,6 +282,11 @@ public abstract class AbstractRayRuntime implements RayRuntimeInternal {
     return objectStore;
   }
 
+  @Override
+  public TaskExecutor getTaskExecutor() {
+    return taskExecutor;
+  }
+
   @Override
   public FunctionManager getFunctionManager() {
     return functionManager;

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

@@ -6,6 +6,7 @@ import io.ray.runtime.context.WorkerContext;
 import io.ray.runtime.functionmanager.FunctionManager;
 import io.ray.runtime.gcs.GcsClient;
 import io.ray.runtime.object.ObjectStore;
+import io.ray.runtime.task.TaskExecutor;
 
 /**
  * This interface is required to make {@link RayRuntimeProxy} work.
@@ -21,6 +22,8 @@ public interface RayRuntimeInternal extends RayRuntime {
 
   ObjectStore getObjectStore();
 
+  TaskExecutor getTaskExecutor();
+
   FunctionManager getFunctionManager();
 
   RayConfig getRayConfig();

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

@@ -45,6 +45,11 @@ public class NativeTaskExecutor extends TaskExecutor<NativeTaskExecutor.NativeAc
     return new NativeActorContext();
   }
 
+  public void onWorkerShutdown(byte[] workerIdBytes) {
+    // This is to make sure no memory leak when `Ray.exitActor()` is called.
+    removeActorContext(new UniqueId(workerIdBytes));
+  }
+
   @Override
   protected void maybeSaveCheckpoint(Object actor, ActorId actorId) {
     if (!(actor instanceof Checkpointable)) {

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

@@ -65,6 +65,10 @@ public abstract class TaskExecutor<T extends TaskExecutor.ActorContext> {
     this.actorContextMap.put(runtime.getWorkerContext().getCurrentWorkerId(), actorContext);
   }
 
+  protected void removeActorContext(UniqueId workerId) {
+    this.actorContextMap.remove(workerId);
+  }
+
   private RayFunction getRayFunction(List<String> rayFunctionInfo) {
     JobId jobId = runtime.getWorkerContext().getCurrentJobId();
     JavaFunctionDescriptor functionDescriptor = parseFunctionDescriptor(rayFunctionInfo);

java/test/src/main/java/io/ray/test/ExitActorTest.java

@@ -9,9 +9,12 @@ import io.ray.api.Ray;
 import io.ray.api.id.ActorId;
 import io.ray.api.id.UniqueId;
 import io.ray.runtime.exception.RayActorException;
+import io.ray.runtime.task.TaskExecutor;
 import io.ray.runtime.util.SystemUtil;
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import org.testng.Assert;
 import org.testng.annotations.Test;
@@ -31,6 +34,17 @@ public class ExitActorTest extends BaseTest {
       return pid();
     }
 
+    public int getSizeOfActorContextMap() {
+      TaskExecutor taskExecutor = TestUtils.getRuntime().getTaskExecutor();
+      try {
+        Field field = TaskExecutor.class.getDeclaredField("actorContextMap");
+        field.setAccessible(true);
+        return ((Map<?, ?>)field.get(taskExecutor)).size();
+      } catch (Exception e) {
+        throw new RuntimeException(e);
+      }
+    }
+
     @Override
     public boolean shouldCheckpoint(CheckpointContext checkpointContext) {
       return true;
@@ -77,6 +91,8 @@ public class ExitActorTest extends BaseTest {
     ActorHandle<ExitingActor> actor1 = Ray.actor(ExitingActor::new)
         .setMaxRestarts(10000).remote();
     int pid = actor1.task(ExitingActor::getPid).remote().get();
+    Assert.assertEquals(
+        1, (int) actor1.task(ExitingActor::getSizeOfActorContextMap).remote().get());
     ActorHandle<ExitingActor> actor2;
     while (true) {
       // Create another actor which share the same process of actor 1.
@@ -86,11 +102,17 @@ public class ExitActorTest extends BaseTest {
         break;
       }
     }
+    Assert.assertEquals(
+        2, (int) actor1.task(ExitingActor::getSizeOfActorContextMap).remote().get());
+    Assert.assertEquals(
+        2, (int) actor2.task(ExitingActor::getSizeOfActorContextMap).remote().get());
     ObjectRef<Boolean> obj1 = actor1.task(ExitingActor::exit).remote();
     Assert.assertThrows(RayActorException.class, obj1::get);
     Assert.assertTrue(SystemUtil.isProcessAlive(pid));
     // Actor 2 shouldn't exit or be reconstructed.
     Assert.assertEquals(1, (int) actor2.task(ExitingActor::incr).remote().get());
+    Assert.assertEquals(
+        1, (int) actor2.task(ExitingActor::getSizeOfActorContextMap).remote().get());
     Assert.assertEquals(pid, (int) actor2.task(ExitingActor::getPid).remote().get());
     Assert.assertTrue(SystemUtil.isProcessAlive(pid));
   }