[xlang] Cross language serialization for ActorHandle (#10335)

python/ray/_raylet.pyx

@@ -297,7 +297,8 @@ cdef prepare_args(
             if language != Language.PYTHON:
                 if metadata not in [
                         ray_constants.OBJECT_METADATA_TYPE_CROSS_LANGUAGE,
-                        ray_constants.OBJECT_METADATA_TYPE_RAW]:
+                        ray_constants.OBJECT_METADATA_TYPE_RAW,
+                        ray_constants.OBJECT_METADATA_TYPE_ACTOR_HANDLE]:
                     raise Exception("Can't transfer {} data to {}".format(
                         metadata, language))
             size = serialized_arg.total_bytes

python/ray/includes/serialization.pxi

@@ -436,15 +436,14 @@ cdef class MessagePackSerializedObject(SerializedObject):
         const uint8_t *msgpack_header_ptr
         const uint8_t *msgpack_data_ptr
 
-    def __init__(self, metadata, msgpack_data,
+    def __init__(self, metadata, msgpack_data, contained_object_refs,
                  SerializedObject nest_serialized_object=None):
         if nest_serialized_object:
-            contained_object_refs = (
+            contained_object_refs.extend(
                 nest_serialized_object.contained_object_refs
             )
             total_bytes = nest_serialized_object.total_bytes
         else:
-            contained_object_refs = []
             total_bytes = 0
         super(MessagePackSerializedObject, self).__init__(
             metadata,

python/ray/ray_constants.py

@@ -193,6 +193,13 @@ OBJECT_METADATA_TYPE_PYTHON = b"PYTHON"
 # A constant used as object metadata to indicate the object is raw bytes.
 OBJECT_METADATA_TYPE_RAW = b"RAW"
 
+# A constant used as object metadata to indicate the object is an actor handle.
+# This value should be synchronized with the Java definition in
+# ObjectSerializer.java
+# TODO(fyrestone): Serialize the ActorHandle via the custom type feature
+# of XLANG.
+OBJECT_METADATA_TYPE_ACTOR_HANDLE = b"ACTOR_HANDLE"
+
 AUTOSCALER_RESOURCE_REQUEST_CHANNEL = b"autoscaler_resource_request"
 
 # The default password to prevent redis port scanning attack.

python/ray/serialization.py

@@ -250,6 +250,9 @@ class SerializationContext:
                 if data is None:
                     return b""
                 return data.to_pybytes()
+            elif metadata == ray_constants.OBJECT_METADATA_TYPE_ACTOR_HANDLE:
+                obj = self._deserialize_msgpack_data(data, metadata)
+                return actor_handle_deserializer(obj)
             # Otherwise, return an exception object based on
             # the error type.
             try:
@@ -349,10 +352,20 @@ class SerializationContext:
     def _serialize_to_msgpack(self, value):
         # Only RayTaskError is possible to be serialized here. We don't
         # need to deal with other exception types here.
+        contained_object_refs = []
+
         if isinstance(value, RayTaskError):
             metadata = str(
                 ErrorType.Value("TASK_EXECUTION_EXCEPTION")).encode("ascii")
             value = value.to_bytes()
+        elif isinstance(value, ray.actor.ActorHandle):
+            # TODO(fyresone): ActorHandle should be serialized via the
+            # custom type feature of cross-language.
+            serialized, actor_handle_id = value._serialization_helper()
+            contained_object_refs.append(actor_handle_id)
+            # Update ref counting for the actor handle
+            metadata = ray_constants.OBJECT_METADATA_TYPE_ACTOR_HANDLE
+            value = serialized
         else:
             metadata = ray_constants.OBJECT_METADATA_TYPE_CROSS_LANGUAGE
 
@@ -373,6 +386,7 @@ class SerializationContext:
             pickle5_serialized_object = None
 
         return MessagePackSerializedObject(metadata, msgpack_data,
+                                           contained_object_refs,
                                            pickle5_serialized_object)
 
     def serialize(self, value):