Move default protocol parameter to a platforms library.

PiperOrigin-RevId: 260998356

tensorflow/python/eager/remote.py

@@ -24,6 +24,7 @@ from tensorflow.core.protobuf.tensorflow_server_pb2 import ServerDef
 from tensorflow.python import pywrap_tensorflow
 from tensorflow.python.distribute.cluster_resolver import cluster_resolver
 from tensorflow.python.eager import context
+from tensorflow.python.platform import remote_utils
 from tensorflow.python.training import server_lib
 from tensorflow.python.util import nest
 from tensorflow.python.util.tf_export import tf_export
@@ -73,11 +74,10 @@ def connect_to_remote_host(remote_host=None, job_name="worker"):
 
 
 @tf_export("config.experimental_connect_to_cluster")
-def connect_to_cluster(
-    cluster_spec_or_resolver,
-    job_name="localhost",
-    task_index=0,
-    protocol="grpc"):
+def connect_to_cluster(cluster_spec_or_resolver,
+                       job_name="localhost",
+                       task_index=0,
+                       protocol=None):
   """Connects to the given cluster.
 
   Will make devices on the cluster available to use. Note that calling this more
@@ -92,8 +92,10 @@ def connect_to_cluster(
       the cluster.
     job_name: The name of the local job.
     task_index: The local task index.
-    protocol: The communication protocol.
+    protocol: The communication protocol, such as `"grpc"`. If unspecified, will
+      use the default from `python/platform/remote_utils.py`.
   """
+  protocol = protocol or remote_utils.get_default_communication_protocol()
   if isinstance(cluster_spec_or_resolver, server_lib.ClusterSpec):
     cluster_spec = cluster_spec_or_resolver
   elif isinstance(cluster_spec_or_resolver, cluster_resolver.ClusterResolver):

tensorflow/python/platform/remote_utils.py

@@ -0,0 +1,22 @@
+# Copyright 2019 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Platform-specific helpers for connecting to remote servers."""
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+
+def get_default_communication_protocol():
+  return 'grpc'

tensorflow/tools/api/golden/v1/tensorflow.config.pbtxt

@@ -14,7 +14,7 @@ tf_module {
   }
   member_method {
     name: "experimental_connect_to_cluster"
-    argspec: "args=[\'cluster_spec_or_resolver\', \'job_name\', \'task_index\', \'protocol\'], varargs=None, keywords=None, defaults=[\'localhost\', \'0\', \'grpc\'], "
+    argspec: "args=[\'cluster_spec_or_resolver\', \'job_name\', \'task_index\', \'protocol\'], varargs=None, keywords=None, defaults=[\'localhost\', \'0\', \'None\'], "
   }
   member_method {
     name: "experimental_connect_to_host"

tensorflow/tools/api/golden/v2/tensorflow.config.pbtxt

@@ -14,7 +14,7 @@ tf_module {
   }
   member_method {
     name: "experimental_connect_to_cluster"
-    argspec: "args=[\'cluster_spec_or_resolver\', \'job_name\', \'task_index\', \'protocol\'], varargs=None, keywords=None, defaults=[\'localhost\', \'0\', \'grpc\'], "
+    argspec: "args=[\'cluster_spec_or_resolver\', \'job_name\', \'task_index\', \'protocol\'], varargs=None, keywords=None, defaults=[\'localhost\', \'0\', \'None\'], "
   }
   member_method {
     name: "experimental_connect_to_host"