unfinalize the graph at exit of MonitoredSession if it wasn't finalized before MonitoredSession creation.

Change: 139481489

tensorflow/python/training/monitored_session.py

@@ -436,6 +436,7 @@ class MonitoredSession(object):
         `ChiefSessionCreator` which is the default one.
       hooks: An iterable of `SessionRunHook' objects.
     """
+    self._graph_was_finalized = ops.get_default_graph().finalized
     self._hooks = hooks or []
     for h in self._hooks:
       h.begin()
@@ -520,6 +521,8 @@ class MonitoredSession(object):
         self._sess = None
         self._coordinated_creator.tf_sess = None
         self._coordinated_creator.coord = None
+        if not self._graph_was_finalized:
+          ops.get_default_graph()._unsafe_unfinalize()  # pylint: disable=protected-access
 
   def _is_closed(self):
     """Return True if the supervised session is closed.  For tests only.

tensorflow/python/training/monitored_session_test.py

@@ -995,6 +995,23 @@ class MonitoredSessionTest(tf.test.TestCase):
       session = tf.train.MonitoredSession()
       self.assertEqual(g, session.graph)
 
+  def test_graph_finalized_during_run_unfinalized_after_exit(self):
+    with tf.Graph().as_default() as g:
+      a_var = tf.Variable(0)
+      with tf.train.MonitoredSession() as session:
+        self.assertEqual(0, session.run(a_var))
+        self.assertTrue(g.finalized)
+      self.assertFalse(g.finalized)
+
+  def test_keep_finalized_graph_as_finalized(self):
+    with tf.Graph().as_default() as g:
+      a_var = tf.Variable(0)
+      tf.train.Scaffold().finalize()
+      with tf.train.MonitoredSession() as session:
+        self.assertEqual(0, session.run(a_var))
+        self.assertTrue(g.finalized)
+      self.assertTrue(g.finalized)
+
   def test_merge_run_options_from_hooks(self):
     """Test for rewriting RunOptions and observing RunMetadata with hooks."""