Implement Python global state API for xray. (#2125)

* Implement global state API for xray.

* Fix object table.

* Fixes for log structure.

* Implement cluster_resources.

* Add driver task to task table.

* Remove python flatbuffers code

* Get some global state API tests running.

* Python linting.

* Fix linting.

* Fix mock modules for doc

* Copy over flatbuffer bindings.

* Fix for tests.

* Linting

* Fix monitor crash.

python/ray/services.py

@@ -400,6 +400,7 @@ def start_redis(node_ip_address,
                 redis_shard_ports=None,
                 num_redis_shards=1,
                 redis_max_clients=None,
+                use_raylet=False,
                 redirect_output=False,
                 redirect_worker_output=False,
                 cleanup=True,
@@ -418,6 +419,8 @@ def start_redis(node_ip_address,
             shard.
         redis_max_clients: If this is provided, Ray will attempt to configure
             Redis with this maxclients number.
+        use_raylet: True if the new raylet code path should be used. This is
+            not supported yet.
         redirect_output (bool): True if output should be redirected to a file
             and false otherwise.
         redirect_worker_output (bool): True if worker output should be
@@ -472,6 +475,11 @@ def start_redis(node_ip_address,
     port = assigned_port
     redis_address = address(node_ip_address, port)
 
+    redis_client = redis.StrictRedis(host=node_ip_address, port=port)
+
+    # Store whether we're using the raylet code path or not.
+    redis_client.set("UseRaylet", 1 if use_raylet else 0)
+
     # Register the number of Redis shards in the primary shard, so that clients
     # know how many redis shards to expect under RedisShards.
     primary_redis_client = redis.StrictRedis(host=node_ip_address, port=port)
@@ -1314,6 +1322,7 @@ def start_ray_processes(address_info=None,
             redis_shard_ports=redis_shard_ports,
             num_redis_shards=num_redis_shards,
             redis_max_clients=redis_max_clients,
+            use_raylet=use_raylet,
             redirect_output=True,
             redirect_worker_output=redirect_worker_output,
             cleanup=cleanup)