Implement Detached Actor (#6036)

* Arg propagation works

* Implement persistent actor

* Add doc

* Initialize is_persistent_

* Rename persistent->detached

* Address comment

* Make test passes

* Address comment

* Python2 compatiblity

* Fix naming, py2

* Lint

python/ray/_raylet.pyx

@@ -948,7 +948,8 @@ cdef class CoreWorker:
                      uint64_t max_reconstructions,
                      resources,
                      placement_resources,
-                     c_bool is_direct_call):
+                     c_bool is_direct_call,
+                     c_bool is_detached):
         cdef:
             CRayFunction ray_function
             c_vector[CTaskArg] args_vector
@@ -969,7 +970,8 @@ cdef class CoreWorker:
                     ray_function, args_vector,
                     CActorCreationOptions(
                         max_reconstructions, is_direct_call, c_resources,
-                        c_placement_resources, dynamic_worker_options),
+                        c_placement_resources, dynamic_worker_options,
+                        is_detached),
                     &c_actor_id))
 
             return ActorID(c_actor_id.Binary())

python/ray/actor.py

@@ -307,7 +307,9 @@ class ActorClass(object):
                 memory=None,
                 object_store_memory=None,
                 resources=None,
-                is_direct_call=None):
+                is_direct_call=None,
+                name=None,
+                detached=False):
         """Create an actor.
 
         This method allows more flexibility than the remote method because
@@ -325,6 +327,9 @@ class ActorClass(object):
             resources: The custom resources required by the actor creation
                 task.
             is_direct_call: Use direct actor calls.
+            name: The globally unique name for the actor.
+            detached: Whether the actor should be kept alive after driver
+                exits.
 
         Returns:
             A handle to the newly created actor.
@@ -341,6 +346,23 @@ class ActorClass(object):
 
         meta = self.__ray_metadata__
 
+        if detached and name is None:
+            raise Exception("Detached actors must be named. "
+                            "Please use Actor._remote(name='some_name') "
+                            "to associate the name.")
+
+        # Check whether the name is already taken.
+        if name is not None:
+            try:
+                ray.experimental.get_actor(name)
+            except ValueError:  # name is not taken, expected.
+                pass
+            else:
+                raise ValueError(
+                    "The name {name} is already taken. Please use "
+                    "a different name or get existing actor using "
+                    "ray.experimental.get_actor('{name}')".format(name=name))
+
         # Set the actor's default resources if not already set. First three
         # conditions are to check that no resources were specified in the
         # decorator. Last three conditions are to check that no resources were
@@ -403,7 +425,7 @@ class ActorClass(object):
             actor_id = worker.core_worker.create_actor(
                 function_descriptor.get_function_descriptor_list(),
                 creation_args, meta.max_reconstructions, resources,
-                actor_placement_resources, is_direct_call)
+                actor_placement_resources, is_direct_call, detached)
 
         actor_handle = ActorHandle(
             actor_id,
@@ -417,6 +439,9 @@ class ActorClass(object):
             worker.current_session_and_job,
             original_handle=True)
 
+        if name is not None:
+            ray.experimental.register_actor(name, actor_handle)
+
         return actor_handle
 
 

python/ray/includes/common.pxd

@@ -207,7 +207,8 @@ cdef extern from "ray/core_worker/common.h" nogil:
             uint64_t max_reconstructions, c_bool is_direct_call,
             const unordered_map[c_string, double] &resources,
             const unordered_map[c_string, double] &placement_resources,
-            const c_vector[c_string] &dynamic_worker_options)
+            const c_vector[c_string] &dynamic_worker_options,
+            c_bool is_detached)
 
 cdef extern from "ray/gcs/gcs_client_interface.h" nogil:
     cdef cppclass CGcsClientOptions "ray::gcs::GcsClientOptions":

python/ray/tests/test_actor.py

@@ -21,12 +21,9 @@ import ray.ray_constants as ray_constants
 import ray.tests.utils
 import ray.tests.cluster_utils
 from ray.tests.conftest import generate_internal_config_map
-from ray.tests.utils import (
-    relevant_errors,
-    wait_for_condition,
-    wait_for_errors,
-    wait_for_pid_to_exit,
-)
+from ray.tests.utils import (relevant_errors, wait_for_condition,
+                             wait_for_errors, wait_for_pid_to_exit,
+                             run_string_as_driver)
 
 
 @pytest.fixture
@@ -2816,3 +2813,37 @@ def test_ray_wait_dead_actor(ray_start_cluster):
     failure_detected = False
     while not failure_detected:
         failure_detected = ray.get(parent_actor.wait.remote())
+
+
+def test_detached_actor(ray_start_regular):
+    @ray.remote
+    class DetachedActor(object):
+        def ping(self):
+            return "pong"
+
+    with pytest.raises(Exception, match="Detached actors must be named"):
+        DetachedActor._remote(detached=True)
+
+    with pytest.raises(ValueError, match="Please use a different name"):
+        _ = DetachedActor._remote(name="d_actor")
+        DetachedActor._remote(name="d_actor")
+
+    redis_address = ray_start_regular["redis_address"]
+
+    actor_name = "DetachedActor"
+    driver_script = """
+import ray
+ray.init(address="{}")
+
+@ray.remote
+class DetachedActor(object):
+    def ping(self):
+        return "pong"
+
+actor = DetachedActor._remote(name="{}", detached=True)
+ray.get(actor.ping.remote())
+""".format(redis_address, actor_name)
+
+    run_string_as_driver(driver_script)
+    detached_actor = ray.experimental.get_actor(actor_name)
+    assert ray.get(detached_actor.ping.remote()) == "pong"