Ref count objects created with ray.put (#5590)

* wip

* add weakref option

* tune util

* test ref

* doc

* fix tests

python/ray/tune/util.py

@@ -2,7 +2,6 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-import base64
 import copy
 import logging
 import threading
@@ -99,27 +98,17 @@ class UtilMonitor(Thread):
 
 
 def pin_in_object_store(obj):
-    """Pin an object in the object store.
+    """Deprecated, use ray.put(value, weakref=False) instead."""
 
-    It will be available as long as the pinning process is alive. The pinned
-    object can be retrieved by calling get_pinned_object on the identifier
-    returned by this call.
-    """
-
-    obj_id = ray.put(_to_pinnable(obj))
-    _pinned_objects.append(ray.get(obj_id))
-    return "{}{}".format(PINNED_OBJECT_PREFIX,
-                         base64.b64encode(obj_id.binary()).decode("utf-8"))
+    obj_id = ray.put(obj, weakref=False)
+    _pinned_objects.append(obj_id)
+    return obj_id
 
 
 def get_pinned_object(pinned_id):
-    """Retrieve a pinned object from the object store."""
+    """Deprecated."""
 
-    from ray import ObjectID
-
-    return _from_pinnable(
-        ray.get(
-            ObjectID(base64.b64decode(pinned_id[len(PINNED_OBJECT_PREFIX):]))))
+    return ray.get(pinned_id)
 
 
 class warn_if_slow(object):