[Streaming] operator chain (#8910)

streaming/python/runtime/graph.py

@@ -1,4 +1,5 @@
 import enum
+import logging
 
 import ray
 import ray.streaming.generated.remote_call_pb2 as remote_call_pb
@@ -6,6 +7,8 @@ import ray.streaming.operator as operator
 import ray.streaming.partition as partition
 from ray.streaming.generated.streaming_pb2 import Language
 
+logger = logging.getLogger(__name__)
+
 
 class NodeType(enum.Enum):
     """
@@ -43,7 +46,13 @@ class ExecutionVertex:
         self.parallelism = vertex_pb.parallelism
         if vertex_pb.language == Language.PYTHON:
             operator_bytes = vertex_pb.operator  # python operator descriptor
-            self.stream_operator = operator.load_operator(operator_bytes)
+            if vertex_pb.chained:
+                logger.info("Load chained operator")
+                self.stream_operator = operator.load_chained_operator(
+                    operator_bytes)
+            else:
+                logger.info("Load operator")
+                self.stream_operator = operator.load_operator(operator_bytes)
         self.worker_actor = ray.actor.ActorHandle. \
             _deserialization_helper(vertex_pb.worker_actor)
         self.container_id = vertex_pb.container_id