Treat actor creation like a regular task. (#1668)

* Treat actor creation like a regular task.

* Small cleanups.

* Change semantics of actor resource handling.

* Bug fix.

* Minor linting

* Bug fix

* Fix jenkins test.

* Fix actor tests

* Some cleanups

* Bug fix

* Fix bug.

* Remove cached actor tasks when a driver is removed.

* Add more info to taskspec in global state API.

* Fix cyclic import bug in tune.

* Fix

* Fix linting.

* Fix linting.

* Don't schedule any tasks (especially actor creaiton tasks) on local schedulers with 0 CPUs.

* Bug fix.

* Add test for 0 CPU case

* Fix linting

* Address comments.

* Fix typos and add comment.

* Add assertion and fix test.

python/ray/tune/registry.py

@@ -7,9 +7,7 @@ from types import FunctionType
 import numpy as np
 
 import ray
-from ray.tune import TuneError
 from ray.local_scheduler import ObjectID
-from ray.tune.trainable import Trainable, wrap_function
 
 TRAINABLE_CLASS = "trainable_class"
 ENV_CREATOR = "env_creator"
@@ -29,6 +27,8 @@ def register_trainable(name, trainable):
             automatically converted into a class during registration.
     """
 
+    from ray.tune.trainable import Trainable, wrap_function
+
     if isinstance(trainable, FunctionType):
         trainable = wrap_function(trainable)
     if not issubclass(trainable, Trainable):
@@ -83,6 +83,7 @@ class _Registry(object):
 
     def register(self, category, key, value):
         if category not in KNOWN_CATEGORIES:
+            from ray.tune import TuneError
             raise TuneError("Unknown category {} not among {}".format(
                 category, KNOWN_CATEGORIES))
         self._all_objects[(category, key)] = value

python/ray/tune/trial.py

@@ -12,7 +12,10 @@ import os
 
 from ray.tune import TuneError
 from ray.tune.logger import NoopLogger, UnifiedLogger, pretty_print
-from ray.tune.registry import _default_registry, get_registry, TRAINABLE_CLASS
+# NOTE(rkn): We import ray.tune.registry here instead of importing the names we
+# need because there are cyclic imports that may cause specific names to not
+# have been defined yet. See https://github.com/ray-project/ray/issues/1716.
+import ray.tune.registry
 from ray.tune.result import TrainingResult, DEFAULT_RESULTS_DIR
 from ray.utils import random_string, binary_to_hex
 
@@ -85,8 +88,8 @@ class Trial(object):
         in ray.tune.config_parser.
         """
 
-        if not _default_registry.contains(
-                TRAINABLE_CLASS, trainable_name):
+        if not ray.tune.registry._default_registry.contains(
+                ray.tune.registry.TRAINABLE_CLASS, trainable_name):
             raise TuneError("Unknown trainable: " + trainable_name)
 
         if stopping_criterion:
@@ -341,8 +344,8 @@ class Trial(object):
 
     def _setup_runner(self):
         self.status = Trial.RUNNING
-        trainable_cls = get_registry().get(
-            TRAINABLE_CLASS, self.trainable_name)
+        trainable_cls = ray.tune.registry.get_registry().get(
+            ray.tune.registry.TRAINABLE_CLASS, self.trainable_name)
         cls = ray.remote(
             num_cpus=self.resources.driver_cpu_limit,
             num_gpus=self.resources.driver_gpu_limit)(trainable_cls)
@@ -367,7 +370,7 @@ class Trial(object):
         # Logging for trials is handled centrally by TrialRunner, so
         # configure the remote runner to use a noop-logger.
         self.runner = cls.remote(
-            config=self.config, registry=get_registry(),
+            config=self.config, registry=ray.tune.registry.get_registry(),
             logger_creator=logger_creator)
 
     def set_verbose(self, verbose):