[direct call] Retry failed tasks with delay (#6453)

* retry failed tasks with delay

* set to 0 for direct tests

python/ray/remote_function.py

@@ -2,11 +2,11 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-import os
 import logging
 from functools import wraps
 
 from ray import cloudpickle as pickle
+from ray import ray_constants
 from ray.function_manager import FunctionDescriptor
 import ray.signature
 
@@ -95,7 +95,7 @@ class RemoteFunction(object):
             return self._remote(args=args, kwargs=kwargs)
 
         self.remote = _remote_proxy
-        self.direct_call_enabled = bool(os.environ.get("RAY_FORCE_DIRECT"))
+        self.direct_call_enabled = ray_constants.direct_call_enabled()
 
     def __call__(self, *args, **kwargs):
         raise Exception("Remote functions cannot be called directly. Instead "