Keras SavedModel: Ignore custom metrics failure when compile=False

tensorflow/python/keras/saving/saved_model/load.py

@@ -135,7 +135,7 @@ def load(path, compile=True, options=None):  # pylint: disable=redefined-builtin
 
   # Recreate layers and metrics using the info stored in the metadata.
   keras_loader = KerasObjectLoader(metadata, object_graph_def)
-  keras_loader.load_layers()
+  keras_loader.load_layers(compile=compile)
 
   # Generate a dictionary of all loaded nodes.
   nodes_to_load = {'root': None}
@@ -360,7 +360,7 @@ class KerasObjectLoader(object):
           obj_child, child_proto, child_id)
       self.loaded_nodes[child_id] = obj_child, setter
 
-  def load_layers(self):
+  def load_layers(self, compile=True):  # pylint: disable=redefined-builtin
     """Load all layer nodes from the metadata."""
     # Load metrics after models and layers, since it's likely that models
     # and layers will create the metric when initialized (this avoids wasting
@@ -376,9 +376,21 @@ class KerasObjectLoader(object):
           node_metadata.metadata)
 
     for node_metadata in metric_list:
-      self.loaded_nodes[node_metadata.node_id] = self._load_layer(
-          node_metadata.node_id, node_metadata.identifier,
-          node_metadata.metadata)
+      try:
+        self.loaded_nodes[node_metadata.node_id] = self._load_layer(
+            node_metadata.node_id, node_metadata.identifier,
+            node_metadata.metadata)
+      except ValueError:
+        # Metrics are only needed when the model is compiled later. We ignore
+        # errors when trying to load custom metrics when `compile=False` until
+        # custom metrics are serialized properly (b/135550038).
+        if compile:
+          raise
+        logging.warning('Unable to restore custom metric. Please ensure that '
+                        'the layer implements `get_config` and `from_config` '
+                        'when saving. In addition, please use the '
+                        '`custom_objects` arg when calling `load_model()`.')
+
 
   def _load_layer(self, node_id, identifier, metadata):
     """Load a single layer from a SavedUserObject proto."""

tensorflow/python/keras/saving/saved_model/saved_model_test.py

@@ -1147,6 +1147,26 @@ class MetricTest(test.TestCase, parameterized.TestCase):
       self._test_metric_save_and_load(
           metric, self._save_model_dir(), 1, test_sample_weight=False)
 
+  @keras_parameterized.run_with_all_model_types
+  def test_custom_metric_model(self):
+
+    class CustomMetric(keras.metrics.MeanSquaredError):
+      pass
+
+    model = testing_utils.get_small_mlp(1, 4, input_dim=3)
+    model.compile(
+        loss='mse',
+        optimizer='rmsprop',
+        metrics=[CustomMetric()])
+
+    saved_model_dir = self._save_model_dir()
+    tf_save.save(model, saved_model_dir)
+    with self.assertRaisesRegex(ValueError, 'custom_objects'):
+      keras_load.load(saved_model_dir)
+
+    keras_load.load(saved_model_dir, compile=False)
+
+
 
 if __name__ == '__main__':
   test.main()