No longer assume that the default job is "localhost" in graph mode

DistributionStrategy, since it depends on the session. Drop
"job:localhost" when canonicalizing in graph mode.

PiperOrigin-RevId: 199354215

tensorflow/python/training/device_util.py

@@ -27,13 +27,15 @@ def canonicalize(d, default=None):
   """Canonicalize device string.
 
   If d has missing components, the rest would be deduced from the `default`
-  argument or from '/job:localhost/replica:0/task:0/device:CPU:0'. For example:
+  argument or from '/replica:0/task:0/device:CPU:0'. For example:
     If d = '/cpu:0', default='/job:worker/task:1', it returns
       '/job:worker/replica:0/task:1/device:CPU:0'.
     If d = '/cpu:0', default='/job:worker', it returns
       '/job:worker/replica:0/task:0/device:CPU:0'.
     If d = '/gpu:0', default=None, it returns
-      '/job:localhost/replica:0/task:0/device:GPU:0'.
+      '/replica:0/task:0/device:GPU:0'.
+
+  Note: This uses "job:localhost" as the default if executing eagerly.
 
   Args:
     d: a device string.
@@ -47,7 +49,9 @@ def canonicalize(d, default=None):
       "Device type '%s' must be all-caps." % (d.device_type,))
   # Fill in missing device fields using defaults.
   result = tf_device.DeviceSpec(
-      job="localhost", replica=0, task=0, device_type="CPU", device_index=0)
+      replica=0, task=0, device_type="CPU", device_index=0)
+  if context.executing_eagerly():
+    result.job = "localhost"
   if default:
     result.merge_from(tf_device.DeviceSpec.from_string(default))
   result.merge_from(d)

tensorflow/python/training/device_util_test.py

@@ -52,7 +52,7 @@ def testCurrentDeviceWithEager(self):
   def testCanonicalizeWithoutDefaultDevice(self):
     self.assertEqual(
         device_util.canonicalize("/cpu:0"),
-        "/job:localhost/replica:0/task:0/device:CPU:0")
+        "/replica:0/task:0/device:CPU:0")
     self.assertEqual(
         device_util.canonicalize("/job:worker/cpu:0"),
         "/job:worker/replica:0/task:0/device:CPU:0")