Serving Keras Models With Tensorflow Serving

Question

Right now we are successfully able to serve models using Tensorflow Serving. We have used following method to export the model and host it with Tensorflow Serving.

     ------------
      For exporting 
     ------------------
     from tensorflow.contrib.session_bundle import exporter

     K.set_learning_phase(0)
     export_path = ... # where to save the exported graph
     export_version = ... # version number (integer)

     saver = tf.train.Saver(sharded=True)
     model_exporter = exporter.Exporter(saver)
     signature = exporter.classification_signature(input_tensor=model.input,
                                          scores_tensor=model.output)
     model_exporter.init(sess.graph.as_graph_def(),
                default_graph_signature=signature)
     model_exporter.export(export_path, tf.constant(export_version), sess)

      --------------------------------------

      For hosting
      -----------------------------------------------

      bazel-bin/tensorflow_serving/model_servers/tensorflow_model_server --port=9000 --model_name=default --model_base_path=/serving/models

However our issue is - we want keras to be integrated with Tensorflow serving. We would like to serve the model through Tensorflow serving using Keras. The reason we would like to have that is because - in our architecture we follow couple of different ways to train our model like deeplearning4j + Keras , Tensorflow + Keras, but for serving we would like to use only one servable engine that's Tensorflow Serving. We don't see any straight forward way to achieve that. Any comments ?

Thank you.

Answer 1

Very recently TensorFlow changed the way it exports the model, so the majority of the tutorials available on web are outdated. I honestly don't know how deeplearning4j works, but I use Keras quite often. I managed to create a simple example that I already posted on this issue in TensorFlow Serving Github.

I'm not sure whether this will help you, but I'd like to share how I did and maybe it will give you some insights. My first trial prior to creating my custom model was to use a trained model available on Keras such as VGG19. I did this as follows.

Model creation

import keras.backend as K
from keras.applications import VGG19
from keras.models import Model

# very important to do this as a first thing
K.set_learning_phase(0)

model = VGG19(include_top=True, weights='imagenet')

# The creation of a new model might be optional depending on the goal
config = model.get_config()
weights = model.get_weights()
new_model = Model.from_config(config)
new_model.set_weights(weights)

Exporting the model

from tensorflow.python.saved_model import builder as saved_model_builder
from tensorflow.python.saved_model import utils
from tensorflow.python.saved_model import tag_constants, signature_constants
from tensorflow.python.saved_model.signature_def_utils_impl import     build_signature_def, predict_signature_def
from tensorflow.contrib.session_bundle import exporter

export_path = 'folder_to_export'
builder = saved_model_builder.SavedModelBuilder(export_path)

signature = predict_signature_def(inputs={'images': new_model.input},
                                  outputs={'scores': new_model.output})

with K.get_session() as sess:
    builder.add_meta_graph_and_variables(sess=sess,
                                         tags=[tag_constants.SERVING],
                                         signature_def_map={'predict': signature})
    builder.save()

Some side notes

• It can vary depending on Keras, TensorFlow, and TensorFlow Serving version. I used the latest ones.
• Beware of the names of the signatures, since they should be used in the client as well.
• When creating the client, all preprocessing steps that are needed for the model (preprocess_input() for example) must be executed. I didn't try to add such step in the graph itself as Inception client example.

With respect to serving different models within the same server, I think that something similar to the creation of a model_config_file might help you. To do so, you can create a config file similar to this:

model_config_list: {
  config: {
    name: "my_model_1",
    base_path: "/tmp/model_1",
    model_platform: "tensorflow"
  },
  config: {
     name: "my_model_2",
     base_path: "/tmp/model_2",
     model_platform: "tensorflow"
  }
}

Finally, you can run the client like this:

bazel-bin/tensorflow_serving/model_servers/tensorflow_model_server --port=9000 --config_file=model_config.conf

Answer 2

try this script i wrote, you can convert keras models into tensorflow frozen graphs, ( i saw that some models give rise to strange behaviours when you export them without freezing the variables).

import sys
from keras.models import load_model
import tensorflow as tf
from keras import backend as K
from tensorflow.python.framework import graph_util
from tensorflow.python.framework import graph_io
from tensorflow.python.saved_model import signature_constants
from tensorflow.python.saved_model import tag_constants


K.set_learning_phase(0)
K.set_image_data_format('channels_last')

INPUT_MODEL = sys.argv[1]
NUMBER_OF_OUTPUTS = 1
OUTPUT_NODE_PREFIX = 'output_node'
OUTPUT_FOLDER= 'frozen'
OUTPUT_GRAPH = 'frozen_model.pb'
OUTPUT_SERVABLE_FOLDER = sys.argv[2]
INPUT_TENSOR = sys.argv[3]


try:
    model = load_model(INPUT_MODEL)
except ValueError as err:
    print('Please check the input saved model file')
    raise err

output = [None]*NUMBER_OF_OUTPUTS
output_node_names = [None]*NUMBER_OF_OUTPUTS
for i in range(NUMBER_OF_OUTPUTS):
    output_node_names[i] = OUTPUT_NODE_PREFIX+str(i)
    output[i] = tf.identity(model.outputs[i], name=output_node_names[i])
print('Output Tensor names: ', output_node_names)


sess = K.get_session()
try:
    frozen_graph = graph_util.convert_variables_to_constants(sess, sess.graph.as_graph_def(), output_node_names)    
    graph_io.write_graph(frozen_graph, OUTPUT_FOLDER, OUTPUT_GRAPH, as_text=False)
    print(f'Frozen graph ready for inference/serving at {OUTPUT_FOLDER}/{OUTPUT_GRAPH}')
except:
    print('Error Occured')



builder = tf.saved_model.builder.SavedModelBuilder(OUTPUT_SERVABLE_FOLDER)

with tf.gfile.GFile(f'{OUTPUT_FOLDER}/{OUTPUT_GRAPH}', "rb") as f:
    graph_def = tf.GraphDef()
    graph_def.ParseFromString(f.read())

sigs = {}
OUTPUT_TENSOR = output_node_names
with tf.Session(graph=tf.Graph()) as sess:
    tf.import_graph_def(graph_def, name="")
    g = tf.get_default_graph()
    inp = g.get_tensor_by_name(INPUT_TENSOR)
    out = g.get_tensor_by_name(OUTPUT_TENSOR[0] + ':0')

    sigs[signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY] = \
        tf.saved_model.signature_def_utils.predict_signature_def(
            {"input": inp}, {"outout": out})

    builder.add_meta_graph_and_variables(sess,
                                         [tag_constants.SERVING],
                                         signature_def_map=sigs)
    try:
        builder.save()
        print(f'Model ready for deployment at {OUTPUT_SERVABLE_FOLDER}/saved_model.pb')
        print('Prediction signature : ')
        print(sigs['serving_default'])
    except:
        print('Error Occured, please checked frozen graph')

Answer 3

I have recently added this blogpost that explain how to save a Keras model and serve it with Tensorflow Serving.

TL;DR: Saving an Inception3 pretrained model:

### Load a pretrained inception_v3
inception_model = keras.applications.inception_v3.InceptionV3(weights='imagenet')

# Define a destination path for the model
MODEL_EXPORT_DIR = '/tmp/inception_v3'
MODEL_VERSION = 1
MODEL_EXPORT_PATH = os.path.join(MODEL_EXPORT_DIR, str(MODEL_VERSION))

# We'll need to create an input mapping, and name each of the input tensors.
# In the inception_v3 Keras model, there is only a single input and we'll name it 'image'
input_names = ['image']
name_to_input = {name: t_input for name, t_input in zip(input_names, inception_model.inputs)}

# Save the model to the MODEL_EXPORT_PATH
# Note using 'name_to_input' mapping, the names defined here will also be used for querying the service later
tf.saved_model.simple_save(
    keras.backend.get_session(),
    MODEL_EXPORT_PATH,
    inputs=name_to_input,
    outputs={t.name: t for t in inception_model.outputs})

And then starting a TF serving Docker:

1. Copy the saved model to the hosts' specified directory. (source=/tmp/inception_v3 in this example)

2. Run the docker:

docker run -d -p 8501:8501 --name keras_inception_v3 --mount type=bind,source=/tmp/inception_v3,target=/models/inception_v3 -e MODEL_NAME=inception_v3 -t tensorflow/serving

3. Verify that there's network access to the Tensorflow service. In order to get the local docker ip (172.*.*.*) for testing run:

docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' keras_inception_v3