Enable 'serve' tag-set in create_module_spec function call

[samsends]

It would be useful to export modules in a format that can be consumed by TensorFlow Serving. Servables would increase code reuse and further enable distributed workloads.

Example Usage (note passing "serve" instead of "train"):

hub.create_module_spec(
    module_fn,
    tags_and_args=[({"serve"}, {"is_training":False})],
    drop_collections=None)

[navneetrao]

+1
Making hub modules consumable by Tensorflow Serving would be very helpful.

[warynice]

Any workarounds for this currently? I want to serve a hub module using Tensorflow Serving.

[samsends]

I have not tested this, but I that suspect you could load the module into an empty graph and then export with savedmodelbuilder. We could build an automated tool.

[andresusanopinto]

For now one has to do it manually, 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}        
    )

Each modules differs slightly from others in input/output names, additionally each serving use case might have different requirements (e.g. raw features in vs serialized tf.Example protos). By having users creating the graph they want to serve (e.g. as done above) seems more flexible than require users to guess what Servo config to use and/or modify the client side each time they change the module being served.

[andresusanopinto]

Closing as this is now obsolete.

In TF-2 users should create reusable saved models with tf.saved_model.save().

[chenliu0831]

@andresusanopinto quick question, does it mean the pre-trained model on tensorflow hub won't have the serving_default signature by default and the user need to re-export it? Thanks

[arnoegw]

A TF2 SavedModel can both have signatures for deployment to TensorFlow Serving and tf.functions for reuse in a Python TensorFlow program.

See https://www.tensorflow.org/hub/tf2_saved_model#advanced_topic_what_to_expect_from_the_savedmodel_after_loading and https://www.tensorflow.org/guide/saved_model

[chenliu0831]

@arnoegw thanks for the pointer. I noticed some inconsistency of some TF2 models that some have serving_default signature while some does not. For example:

• Only default signature:
  • https://tfhub.dev/google/faster_rcnn/openimages_v4/inception_resnet_v2/1
  • https://tfhub.dev/google/openimages_v4/ssd/mobilenet_v2/1
• No signature: "https://tfhub.dev/google/imagenet/mobilenet_v2_100_224/feature_vector/4" (from the example notebook)
• Only serving_default https://tfhub.dev/tensorflow/resnet_50/classification/1

My understanding is if serving_default is not present, the model cannot be served as-is in TF serving. Should all TF2 models have this signature? Let me know if I should open a new issue to track this.

[arnoegw]

@chenliu0831, there's nothing wrong with those examples:

• The following are hub.Module assets for TF1 that use SavedModel's SignatureDef to define the signatures that hub.Module can invoke. They cannot be served as-is, because the hub.Module format and SavedModels for serving had some small but crucial differences (which were removed for TF2).
  https://tfhub.dev/google/faster_rcnn/openimages_v4/inception_resnet_v2/1
  https://tfhub.dev/google/openimages_v4/ssd/mobilenet_v2/1
• The following (and many more with similar names) is a TF2 SavedModel meant only for reuse in a Python TensorFlow program (put a to-be-learned layer on top of the features), so it has a @tf.function __call__ but not SignatureDefs:
  https://tfhub.dev/google/imagenet/mobilenet_v2_100_224/feature_vector/4
• The following is a TF2 SavedModel meant both for reuse and stand-alone serving, so it has both a @tf.function __call__ and a serving signature:
  https://tfhub.dev/tensorflow/resnet_50/classification/1

[chenliu0831]

@arnoegw Ah thanks for clarifying. I give a bad example for the second case since that's a feature vector.

I spot check another few on TF hub with the TF2 filter and with classification variants and looks like their signature map is empty as well:

• https://tfhub.dev/google/imagenet/mobilenet_v2_100_224/classification/4
• https://tfhub.dev/google/imagenet/nasnet_large/classification/4
• https://tfhub.dev/google/imagenet/mobilenet_v2_035_160/classification/4

In the detail page of above models I think they all show up as "TF2.0 Saved Model" format.