Enable memstore by default (#6003)

python/ray/worker.py

@@ -11,7 +11,6 @@ import inspect
 import io
 import json
 import logging
-import numpy as np
 import os
 import redis
 import signal
@@ -1491,7 +1490,7 @@ def connect(node,
     # Put something in the plasma store so that subsequent plasma store
     # accesses will be faster. Currently the first access is always slow, and
     # we don't want the user to experience this.
-    temporary_object_id = ray.ObjectID(np.random.bytes(20))
+    temporary_object_id = ray.ObjectID.from_random()
     worker.put_object(1, object_id=temporary_object_id)
     ray.internal.free([temporary_object_id])