Basic Async Actor Call (#6183)

* Start trying to figure out where to put fibers

* Pass is_async flag from python to context

* Just running things in fiber works

* Yield implemented, need some debugging to make it work

* It worked!

* Remove debug prints

* Lint

* Revert the clang-format

* Remove unnecessary log

* Remove unncessary import

* Add attribution

* Address comment

* Add test

* Missed a merge conflict

* Make test pass and compile

* Address comment

* Rename async -> asyncio

* Move async test to py3 only

* Fix ignore path

python/ray/actor.py

@@ -358,7 +358,8 @@ class ActorClass(object):
                 is_direct_call=None,
                 max_concurrency=None,
                 name=None,
-                detached=False):
+                detached=False,
+                is_asyncio=False):
         """Create an actor.
 
         This method allows more flexibility than the remote method because
@@ -381,6 +382,8 @@ class ActorClass(object):
             name: The globally unique name for the actor.
             detached: Whether the actor should be kept alive after driver
                 exits.
+            is_asyncio: Turn on async actor calls. This only works with direct
+                actor calls.
 
         Returns:
             A handle to the newly created actor.
@@ -400,6 +403,12 @@ class ActorClass(object):
         if max_concurrency < 1:
             raise ValueError("max_concurrency must be >= 1")
 
+        if is_asyncio and not is_direct_call:
+            raise ValueError(
+                "Setting is_asyncio requires is_direct_call=True.")
+        if is_asyncio and max_concurrency != 1:
+            raise ValueError("Setting is_asyncio requires max_concurrency=1.")
+
         worker = ray.worker.get_global_worker()
         if worker.mode is None:
             raise Exception("Actors cannot be created before ray.init() "
@@ -487,7 +496,7 @@ class ActorClass(object):
                 function_descriptor.get_function_descriptor_list(),
                 creation_args, meta.max_reconstructions, resources,
                 actor_placement_resources, is_direct_call, max_concurrency,
-                detached)
+                detached, is_asyncio)
 
         actor_handle = ActorHandle(
             actor_id,