Suppress warning for serializing different unique ID types in Python. (#3872)

* Suppress warning for serializing different unique ID types in Python.

* Add _ID_TYPES variable.

python/ray/__init__.py

@@ -51,7 +51,7 @@ sys.path.append(modin_path)
 
 from ray._raylet import (UniqueID, ObjectID, DriverID, ClientID, ActorID,
                          ActorHandleID, FunctionID, ActorClassID, TaskID,
-                         Config as _Config)  # noqa: E402
+                         _ID_TYPES, Config as _Config)  # noqa: E402
 
 _config = _Config()
 
@@ -77,7 +77,8 @@ __all__ = [
     "remote", "profile", "actor", "method", "get_gpu_ids", "get_resource_ids",
     "get_webui_url", "register_custom_serializer", "shutdown",
     "is_initialized", "SCRIPT_MODE", "WORKER_MODE", "LOCAL_MODE",
-    "PYTHON_MODE", "global_state", "_config", "__version__", "internal"
+    "PYTHON_MODE", "global_state", "_config", "__version__", "internal",
+    "_ID_TYPES"
 ]
 
 __all__ += [

python/ray/includes/unique_ids.pxi

@@ -4,6 +4,8 @@ We define different types for different IDs for type safety.
 See https://github.com/ray-project/ray/issues/3721.
 """
 
+# WARNING: Any additional ID types defined in this file must be added to the
+# _ID_TYPES list at the bottom of this file.
 from ray.includes.common cimport (
     CUniqueID, CTaskID, CObjectID, CFunctionID, CActorClassID, CActorID,
     CActorHandleID, CWorkerID, CDriverID, CConfigID, CClientID,
@@ -278,3 +280,7 @@ cdef class ActorClassID(UniqueID):
 
     def __repr__(self):
         return "ActorClassID(" + self.hex() + ")"
+
+
+_ID_TYPES = [UniqueID, ObjectID, TaskID, ClientID, DriverID, ActorID,
+             ActorHandleID, FunctionID, ActorClassID]

python/ray/worker.py

@@ -1099,22 +1099,11 @@ def _initialize_serialization(driver_id, worker=global_worker):
     serialization_context.set_pickle(pickle.dumps, pickle.loads)
     pyarrow.register_torch_serialization_handlers(serialization_context)
 
-    # Define a custom serializer and deserializer for handling Object IDs.
-    def object_id_custom_serializer(obj):
-        return obj.binary()
-
-    def object_id_custom_deserializer(serialized_obj):
-        return ObjectID(serialized_obj)
-
-    # We register this serializer on each worker instead of calling
-    # register_custom_serializer from the driver so that isinstance still
-    # works.
-    serialization_context.register_type(
-        ObjectID,
-        "ray.ObjectID",
-        pickle=False,
-        custom_serializer=object_id_custom_serializer,
-        custom_deserializer=object_id_custom_deserializer)
+    for id_type in ray._ID_TYPES:
+        serialization_context.register_type(
+            id_type,
+            "{}.{}".format(id_type.__module__, id_type.__name__),
+            pickle=True)
 
     def actor_handle_serializer(obj):
         return obj._serialization_helper(True)