How to make the tensorflow hub embeddings servable

Question

I am trying use an embeddings module from tensorflow hub as servable. I am new to tensorflow. Currently, I am using Universal Sentence Encoder embeddings as a lookup to convert sentences to embeddings and then using those embeddings to find a similarity to another sentence.

My current code to convert sentences into embeddings is:

with tf.Session() as session:
  session.run([tf.global_variables_initializer(), tf.tables_initializer()])
  sen_embeddings = session.run(self.embed(prepared_text))

Prepared_text is a list of sentences. How do I take this model and make it a servable?

Answer 1

Currently, the hub modules cannot be consumed by Tensorflow Serving directly. You will have to load the module into an empty graph and then export it using the SavedModelBuilder. For example:

import tensorflow as tf
import tensorflow_hub as hub

with tf.Graph().as_default():
  module = hub.Module("http://tfhub.dev/google/universal-sentence-encoder/2")
  text = tf.placeholder(tf.string, [None])
  embedding = module(text)

  init_op = tf.group([tf.global_variables_initializer(), tf.tables_initializer()])
  with tf.Session() as session:
    session.run(init_op)
    tf.saved_model.simple_save(
        session,
        "/tmp/serving_saved_model",
        inputs = {"text": text},
        outputs = {"embedding": embedding},
        legacy_init_op = tf.tables_initializer()        
    )

This will export your model (to the folder /tmp/serving_saved_model) in the desired format for serving. After this, you can follow the instructions given in the documentation here: https://www.tensorflow.org/serving/serving_basic

Answer 2

Right now you probably need to do this by hand. Here is my solution, similar to previous answer but more general - show how to use any other module without guessing input parameters, as well as extended with verification and usage:

import tensorflow as tf
import tensorflow_hub as hub
from tensorflow.saved_model import simple_save

export_dir = "/tmp/tfserving/universal_encoder/00000001"
with tf.Session(graph=tf.Graph()) as sess:
    module = hub.Module("https://tfhub.dev/google/universal-sentence-encoder/2") 
    input_params = module.get_input_info_dict()
    # take a look at what tensor does the model accepts - 'text' is input tensor name

    text_input = tf.placeholder(name='text', dtype=input_params['text'].dtype, 
        shape=input_params['text'].get_shape())
    sess.run([tf.global_variables_initializer(), tf.tables_initializer()])

    embeddings = module(text_input)

    simple_save(sess,
        export_dir,
        inputs={'text': text_input},
        outputs={'embeddings': embeddings},
        legacy_init_op=tf.tables_initializer())

Thanks to module.get_input_info_dict() you know what tensor names you need to pass to the model - you use this name as a key for inputs={} in simple_save method.

Remember that to serve the model it needs to be in directory path ending with version, that's why '00000001' is the last path in which saved_model.pb resides.

After exporting your module, quickest way to see if your model is exported properly for serving is to use saved_model_cli API:

saved_model_cli run --dir /tmp/tfserving/universal_encoder/00000001 --tag_set serve --signature_def serving_default --input_exprs 'text=["what this is"]'

To serve the model from docker:

docker pull tensorflow/serving  
docker run -p 8501:8501 -v /tmp/tfserving/universal_encoder:/models/universal_encoder -e MODEL_NAME=universal_encoder -t tensorflow/serving