Consodiate CI Python tests and fix bug about multiple ray.init (#4195)

python/ray/remote_function.py

@@ -57,9 +57,11 @@ class RemoteFunction(object):
         self._function_signature = ray.signature.extract_signature(
             self._function)
 
-        # # Export the function.
+        # Export the function.
         worker = ray.worker.get_global_worker()
         worker.function_actor_manager.export(self)
+        # In which session this function was exported last time.
+        self._last_export_session = worker._session_index
 
     def __call__(self, *args, **kwargs):
         raise Exception("Remote functions cannot be called directly. Instead "
@@ -97,6 +99,13 @@ class RemoteFunction(object):
         """An experimental alternate way to submit remote functions."""
         worker = ray.worker.get_global_worker()
         worker.check_connected()
+
+        if self._last_export_session < worker._session_index:
+            # If this function was exported in a previous session, we need to
+            # export this function again, because current GCS doesn't have it.
+            self._last_export_session = worker._session_index
+            worker.function_actor_manager.export(self)
+
         kwargs = {} if kwargs is None else kwargs
         args = ray.signature.extend_args(self._function_signature, args,
                                          kwargs)