[rllib] Disable explicit free, which is no longer needed and causes memory leaks

rllib/utils/memory.py

@@ -1,5 +1,6 @@
 import numpy as np
 import time
+import os
 
 import ray
 
@@ -8,6 +9,10 @@ MAX_FREE_QUEUE_SIZE = 100
 _last_free_time = 0.0
 _to_free = []
 
+# TODO(ekl) remove this feature entirely. It's here for now just in case we
+# need to turn it on for debugging.
+RLLIB_DEBUG_EXPLICIT_FREE = bool(os.environ.get("RLLIB_DEBUG_EXPLICIT_FREE"))
+
 
 def ray_get_and_free(object_ids):
     """Call ray.get and then queue the object ids for deletion.
@@ -23,6 +28,9 @@ def ray_get_and_free(object_ids):
         The result of ray.get(object_ids).
     """
 
+    if not RLLIB_DEBUG_EXPLICIT_FREE:
+        return ray.get(object_ids)
+
     global _last_free_time
     global _to_free