[rllib] support local mode (#2795)

python/ray/experimental/internal_kv.py

@@ -4,6 +4,8 @@ from __future__ import print_function
 
 import ray
 
+_local = {}  # dict for local mode
+
 
 def _internal_kv_initialized():
     worker = ray.worker.get_global_worker()
@@ -14,6 +16,9 @@ def _internal_kv_get(key):
     """Fetch the value of a binary key."""
 
     worker = ray.worker.get_global_worker()
+    if worker.mode == ray.worker.LOCAL_MODE:
+        return _local.get(key)
+
     return worker.redis_client.hget(key, "value")
 
 
@@ -27,6 +32,12 @@ def _internal_kv_put(key, value, overwrite=False):
     """
 
     worker = ray.worker.get_global_worker()
+    if worker.mode == ray.worker.LOCAL_MODE:
+        exists = key in _local
+        if not exists or overwrite:
+            _local[key] = value
+        return exists
+
     if overwrite:
         updated = worker.redis_client.hset(key, "value", value)
     else: