[rllib] Reserve CPUs for replay actors in apex (#4217)

python/ray/rllib/agents/dqn/dqn.py

@@ -12,6 +12,7 @@
 from ray.rllib.evaluation.metrics import collect_metrics
 from ray.rllib.utils.annotations import override
 from ray.rllib.utils.schedules import ConstantSchedule, LinearSchedule
+from ray.tune.trial import Resources
 
 logger = logging.getLogger(__name__)
 
@@ -141,6 +142,21 @@ class DQNAgent(Agent):
     _policy_graph = DQNPolicyGraph
     _optimizer_shared_configs = OPTIMIZER_SHARED_CONFIGS
 
+    @classmethod
+    @override(Agent)
+    def default_resource_request(cls, config):
+        cf = dict(cls._default_config, **config)
+        Agent._validate_config(cf)
+        if cf["optimizer_class"] == "AsyncReplayOptimizer":
+            extra = cf["optimizer"]["num_replay_buffer_shards"]
+        else:
+            extra = 0
+        return Resources(
+            cpu=cf["num_cpus_for_driver"],
+            gpu=cf["num_gpus"],
+            extra_cpu=cf["num_cpus_per_worker"] * cf["num_workers"] + extra,
+            extra_gpu=cf["num_gpus_per_worker"] * cf["num_workers"])
+
     @override(Agent)
     def _init(self):
         self._validate_config()

python/ray/rllib/optimizers/async_replay_optimizer.py

@@ -225,7 +225,8 @@ def _step(self):
         return sample_timesteps, train_timesteps
 
 
-@ray.remote(num_cpus=0)
+# reserve 1 CPU so that our method calls don't get stalled
+@ray.remote(num_cpus=1)
 class ReplayActor(object):
     """A replay buffer shard.
 

python/ray/rllib/tests/test_supported_spaces.py

@@ -105,7 +105,7 @@ def check_support_multiagent(alg, config):
 
 class ModelSupportedSpaces(unittest.TestCase):
     def setUp(self):
-        ray.init(num_cpus=4)
+        ray.init(num_cpus=10)
 
     def tearDown(self):
         ray.shutdown()