[Java] Enable direct call by default. (#7408)

* WIP

* Address comments.

* Linting

* Fix

* Fix

* Fix test

* Fix

* Fix single process ci

* Fix ut

* Update java/test/src/main/java/org/ray/api/test/PlasmaFreeTest.java

* Address comments

* Fix linting

* Minor update comments.

* Fix streaming CI

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

@@ -17,7 +17,6 @@ import org.ray.api.options.ActorCreationOptions;
 import org.ray.api.options.CallOptions;
 import org.ray.api.runtime.RayRuntime;
 import org.ray.api.runtimecontext.RuntimeContext;
-import org.ray.runtime.actor.NativeRayActor;
 import org.ray.runtime.config.RayConfig;
 import org.ray.runtime.context.RuntimeContextImpl;
 import org.ray.runtime.context.WorkerContext;
@@ -166,7 +165,7 @@ public abstract class AbstractRayRuntime implements RayRuntime {
   private RayObject callNormalFunction(FunctionDescriptor functionDescriptor,
       Object[] args, int numReturns, CallOptions options) {
     List<FunctionArg> functionArgs = ArgumentsBuilder
-        .wrap(args, functionDescriptor.getLanguage(), /*isDirectCall*/false);
+        .wrap(args, functionDescriptor.getLanguage());
     List<ObjectId> returnIds = taskSubmitter.submitTask(functionDescriptor,
         functionArgs, numReturns, options);
     Preconditions.checkState(returnIds.size() == numReturns && returnIds.size() <= 1);
@@ -180,7 +179,7 @@ public abstract class AbstractRayRuntime implements RayRuntime {
   private RayObject callActorFunction(RayActor rayActor,
       FunctionDescriptor functionDescriptor, Object[] args, int numReturns) {
     List<FunctionArg> functionArgs = ArgumentsBuilder
-        .wrap(args, functionDescriptor.getLanguage(), isDirectCall(rayActor));
+        .wrap(args, functionDescriptor.getLanguage());
     List<ObjectId> returnIds = taskSubmitter.submitActorTask(rayActor,
         functionDescriptor, functionArgs, numReturns, null);
     Preconditions.checkState(returnIds.size() == numReturns && returnIds.size() <= 1);
@@ -194,7 +193,7 @@ public abstract class AbstractRayRuntime implements RayRuntime {
   private RayActor createActorImpl(FunctionDescriptor functionDescriptor,
       Object[] args, ActorCreationOptions options) {
     List<FunctionArg> functionArgs = ArgumentsBuilder
-        .wrap(args, functionDescriptor.getLanguage(),  /*isDirectCall*/false);
+        .wrap(args, functionDescriptor.getLanguage());
     if (functionDescriptor.getLanguage() != Language.JAVA && options != null) {
       Preconditions.checkState(Strings.isNullOrEmpty(options.jvmOptions));
     }
@@ -202,13 +201,6 @@ public abstract class AbstractRayRuntime implements RayRuntime {
     return actor;
   }
 
-  private boolean isDirectCall(RayActor rayActor) {
-    if (rayActor instanceof NativeRayActor) {
-      return ((NativeRayActor) rayActor).isDirectCallActor();
-    }
-    return false;
-  }
-
   public WorkerContext getWorkerContext() {
     return workerContext;
   }

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

@@ -9,7 +9,6 @@ import org.apache.commons.io.FileUtils;
 import org.ray.api.RayActor;
 import org.ray.api.id.JobId;
 import org.ray.api.id.UniqueId;
-import org.ray.runtime.actor.NativeRayActor;
 import org.ray.runtime.config.RayConfig;
 import org.ray.runtime.context.NativeWorkerContext;
 import org.ray.runtime.functionmanager.FunctionManager;
@@ -137,9 +136,6 @@ public final class RayNativeRuntime extends AbstractRayRuntime {
 
   @Override
   public void killActor(RayActor<?> actor) {
-    if (!((NativeRayActor) actor).isDirectCallActor()) {
-      throw new UnsupportedOperationException("Only direct call actors can be killed.");
-    }
     nativeKillActor(nativeCoreWorkerPointer, actor.getId().getBytes());
   }
 

java/runtime/src/main/java/org/ray/runtime/actor/NativeRayActor.java

@@ -64,10 +64,6 @@ public abstract class NativeRayActor implements RayActor, Externalizable {
     return Language.forNumber(nativeGetLanguage(nativeCoreWorkerPointer, actorId));
   }
 
-  public boolean isDirectCallActor() {
-    return nativeIsDirectCallActor(nativeCoreWorkerPointer, actorId);
-  }
-
   @Override
   public void writeExternal(ObjectOutput out) throws IOException {
     out.writeObject(toBytes());
@@ -119,9 +115,6 @@ public abstract class NativeRayActor implements RayActor, Externalizable {
   private static native int nativeGetLanguage(
       long nativeCoreWorkerPointer, byte[] actorId);
 
-  private static native boolean nativeIsDirectCallActor(
-      long nativeCoreWorkerPointer, byte[] actorId);
-
   static native List<String> nativeGetActorCreationTaskFunctionDescriptor(
       long nativeCoreWorkerPointer, byte[] actorId);
 

java/runtime/src/main/java/org/ray/runtime/task/ArgumentsBuilder.java

@@ -2,12 +2,8 @@ package org.ray.runtime.task;
 
 import java.util.ArrayList;
 import java.util.List;
-import org.ray.api.Ray;
 import org.ray.api.RayObject;
 import org.ray.api.id.ObjectId;
-import org.ray.api.runtime.RayRuntime;
-import org.ray.runtime.AbstractRayRuntime;
-import org.ray.runtime.RayMultiWorkerNativeRuntime;
 import org.ray.runtime.generated.Common.Language;
 import org.ray.runtime.object.NativeRayObject;
 import org.ray.runtime.object.ObjectSerializer;
@@ -32,27 +28,17 @@ public class ArgumentsBuilder {
   /**
    * Convert real function arguments to task spec arguments.
    */
-  public static List<FunctionArg> wrap(Object[] args, Language language, boolean isDirectCall) {
+  public static List<FunctionArg> wrap(Object[] args, Language language) {
     List<FunctionArg> ret = new ArrayList<>();
     for (Object arg : args) {
       ObjectId id = null;
       NativeRayObject value = null;
       if (arg instanceof RayObject) {
-        if (isDirectCall) {
-          throw new IllegalArgumentException(
-              "Passing RayObject to a direct call actor is not supported.");
-        }
         id = ((RayObject) arg).getId();
       } else {
         value = ObjectSerializer.serialize(arg);
-        if (!isDirectCall && value.data.length > LARGEST_SIZE_PASS_BY_VALUE) {
-          RayRuntime runtime = Ray.internal();
-          if (runtime instanceof RayMultiWorkerNativeRuntime) {
-            runtime = ((RayMultiWorkerNativeRuntime) runtime).getCurrentRuntime();
-          }
-          id = ((AbstractRayRuntime) runtime).getObjectStore()
-              .putRaw(value);
-          value = null;
+        if (value.data.length > LARGEST_SIZE_PASS_BY_VALUE) {
+          // Do nothing since we are not support pass by reference in direct call.
         }
       }
       if (language == Language.PYTHON) {