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Dockerized NMT frameworks for nmt-wizard
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The aim of this project is to encapsulate training frameworks in Docker containers and expose a standardized interface for:

  • preprocessing
  • training
  • translating
  • serving

The training data are mounted at the container start and follow a specific directory structure (described later). Models and translation files can be fetched and pushed from various remote storage platform, including Amazon S3.


Each framework exposes the same command line interface for providing training, translation, and deployment services. See for example:

docker run nmtwizard/opennmt-tf -h


Environment variables

Some environment variables can be set (e.g. with the -e flags on docker run):

  • CORPUS_DIR (default: /root/corpus): Path to the training corpus.
  • MODELS_DIR (default: /root/models): Path to the models directory.
  • WORKSPACE_DIR (default: /root/workspace): Path to the framework workspace (generated and temporary files).
  • LOG_LEVEL (default: INFO): the Python log level.

Some frameworks may require additional environment variables, see their specific resources in frameworks/.

Run configuration

The JSON configuration file contains the parameters necessary to run the command. It has the following format:

    "source": "string",  // (mandatory) 2-letter iso code for source language
    "target": "string",  // (mandatory) 2-letter iso code for target language
    "model": "string",  // (mandatory for trans, serve) Full model name as uuid64
    "data": {
        //  (optional) Data distribution rules.
    "tokenization": {
        // Vocabularies and tokenization options (from OpenNMT/Tokenizer).
        "source": {
            "vocabulary": "string"
            // other source specific tokenization options
        "target": {
            "vocabulary": "string"
            // other target specific tokenization options
    "options": {
        // (optional) Run options specific to each framework.

Note: When loading an existing model and a configuration file is provided, it is merged with the saved model configuration file.

Storage configuration

Multiple storage destinations can be defined with the --storage_config option that references a JSON file:

    "storage_id_1": {
        "type": "s3",
        "bucket": "model-catalog",
        "aws_credentials": {
            "access_key_id": "...",
            "secret_access_key": "...",
            "region_name": "..."
    "storage_id_2": {
        "type": "ssh",
        "server": "",
        "basedir": "myrepo",
        "user": "root",
        "password": "root"

These storages can then be used to define model and file locations, e.g.:

docker run nmtwizard/opennmt-tf --storage_config storages.json \
    --model_storage storage_id_2: --model MODEL_ID \
    trans -i -o storage_id_2:test.en

If the configuration is not provided or a storage identifier is not set, the host filesystem is used.

Available storage types are:

  • local: local storage. Available options:
    • basedir (optional): defines base directory for relative paths
  • ssh: transfer files via SSH. Available options:
    • server: server hostname
    • port (default: 22): port to use for connecting
    • user: username for login
    • password or pkey: login credentials
    • basedir (optional): defines base directory for relative paths
  • s3: transfer files to and from Amazon S3. Available options:
    • bucket: name of the bucket
    • aws_credentials: Amazon credentials with,
      • access_key_id
      • secret_access_key
      • region_name
  • http: transfer files via GET and POST requests. Requires to configure patterns that are URLs containing the %s string placeholders that will be expanded with python % operator (e.g.
    • get_pattern
    • post_pattern
    • list_pattern

Training data sampling

The data section of the run configuration can be used to define advanced data selection based on file patterns. The distribution is a JSON list where each element is a dictionary with 2 elements:

  • path : Path to a directory on which theses rules apply
  • distribution: a dictionary of patterns/weights as defined here.

For example:

"data": {
    "sample": 10000,
    "sample_dist": [{
        "path": "${CORPUS_DIR}/en_nl/train",
        "distribution": [
            ["News", 0.7],
            ["IT", 0.3],
            ["Dialog", "*"]

will select 10,000 training examples from ${CORPUS_DIR}/en_nl/train and only from files containing News or IT in their name. The majority of the examples will come from News files (weight 0.7).

Note: If this section is not provided, all files from ${CORPUS_DIR}/train will be used for the training.


Data sampling and tokenization are preparing corpus for the training process. It is possible to get access sampled and tokenized corpus using preprocess command and by mounting /root/workspace volume.

The following command is sampling and tokenizing the corpus from ${PWD}/test/corpus into ${PWD}/workspace:

cat config.json | docker run -i --rm -v ${PWD}/test/corpus:/root/corpus -v ${PWD}/workspace:/root/workspace image -c - preprocess

Corpus structure

The corpus directory should contain:

  • train: Containing the training files, suffixed by the 2-letter iso language code.
  • vocab: Containing the vocabularies and BPE models.

When running the Docker container, the corpus directory should be mounted, e.g. with -v /home/corpus/en_fr:/root/corpus.

Note: ${CORPUS_DIR} can be used in the run configuration to locate data files in particular vocabulary files. ${TRAIN_DIR} can be used the same way - but the resources accessed through this variable will not be bundled in the translation model.


The models are saved in a directory named by their ID. This package contains all the resources necessary for translation or deployment (BPE models, vocabularies, etc.). For instance, a typical OpenNMT-tf model will contain:

$ ls -1 952f4f9b-b446-4aa4-bfc0-28a510c6df73/

In the config.json file, the path to the model dependencies is prefixed by ${MODEL_DIR} which is automatically set when a model is loaded.

  • checksum.md5 file is generated from the content of the model and is used to check integrity of the model
  • optionally, a file can describe the model. It is generated from description field of the config file and is not taken into account for checksum.

Released version

Before serving a trained model, it is required to run a release step, for example:

docker run nmtwizard/opennmt-tf \
    --storage_config storages.json \
    --model_storage s3_model: \
    --model 952f4f9b-b446-4aa4-bfc0-28a510c6df73 \
    --gpuid 1 \
    release --destination s3_model:

will fetch the model 952f4f9b-b446-4aa4-bfc0-28a510c6df73 from the storage s3_model and push the released version 952f4f9b-b446-4aa4-bfc0-28a510c6df73_release to the same storage.

Released models are smaller and more efficient but can only be used for serving.


Compatible frameworks provide an uniform API for serving released model via the serve command, e.g.:

nvidia-docker run nmtwizard/opennmt-tf \
    --storage_config storages.json \
    --model_storage s3_model: \
    --model 952f4f9b-b446-4aa4-bfc0-28a510c6df73_release \
    --gpuid 1 \
    serve --host --port 5000

will fetch the released model 952f4f9b-b446-4aa4-bfc0-28a510c6df73_release from the storage s3_model (see the previous section), start a backend translation service on the first GPU, and serve translation on port 5000.

Serving accepts additional run configurations:

    "serving": {
        "timeout": 10.0,
        "max_batch_size": 64


  • timeout is the maximum duration in seconds to wait for the translation to complete
  • max_batch_size is the maximum batch size to execute at once

The timeout and max_batch_size values can be overriden for each request.


POST /translate

Input (minimum required):

    "src": [
        {"text": "Source sentence 1"},
        {"text": "Source sentence 2"}

Input (with optional fields):

    "options": {
        "timeout": 10.0,
        "max_batch_size": 32,
        "config": {}
    "src": [
        {"text": "Source sentence 1", "config": {}},
        {"text": "Source sentence 2", "config": {}}

The config fields define request-specific and sentence-specific overrides to the global configuration file.


    "tgt": [
            "text": "Phrase cible 1",
            "score": -2.16,
            "align": [
                {"tgt": [ {"range": [0, 5], "id": 0} ],
                 "src": [ {"range": [9, 14], "id": 1} ]},
                {"tgt": [ {"range": [7, 11], "id": 1} ],
                 "src": [ {"range": [0, 5], "id": 0} ]},
                {"tgt": [ {"range": [13, 13], "id": 2} ],
                 "src": [ {"range": [16, 16], "id": 2} ]}
            "text": "Phrase cible 2",
            "score": -2.17,
            "align": [
                {"tgt": [ {"range": [0, 5], "id": 0} ],
                 "src": [ {"range": [9, 14], "id": 1} ]},
                {"tgt": [ {"range": [7, 11], "id": 1} ],
                 "src": [ {"range": [0, 5], "id": 0} ]},
                {"tgt": [ {"range": [13, 13], "id": 2} ],
                 "src": [ {"range": [16, 16], "id": 2} ]}

The tgt field is a list the size of the batch where each entry is a list listing all hypotheses (the N best list) ordered from best to worst (higher score means better prediction).

Note that the score and align fields might not be set by all frameworks and model types.


  • HTTP 400
    • The input data is missing.
    • The input data is not a JSON object.
    • The input data does not contain the src field.
    • The src field is not a list.
  • HTTP 503
    • The backend service is unavailable.
  • HTTP 504
    • The translation request timed out.

POST /unload_model

Unload the model from the reserved resource. In its simplest form, this route will terminate the backend translation service.

POST /reload_model

Reload the model on the reserved resource. In its simplest form, this route will terminate the backend translation service if it is still running and start a new instance.



During development, can be invoked directly if the environment is properly set to run the required services (installed framework, set environment variables, etc.). See files of each framework in frameworks/ for specific instructions.

If you don't have the required environment, consider building the Docker image instead.


To be able to run the image on GPUs, you need nvidia-docker installed on the host machine.

Directory mounts

When running an image, the following mounting points can be used:

  • /root/corpus: Training corpus and resources.
  • /root/models (optional): Host repository of models.
  • /root/workspace (optional): internal workspace data used for corpus preparation. Has to be provided for sample.


Running the Docker image is equivalent to running You should pass the same command line options and mount required files or directories, e.g.:

cat config.json | nvidia-docker run -a STDIN -i --rm \
    -v /home/models:/root/models -v /home/corpus/en_fr:/root/corpus \
    my-image -c - -ms /root/models -g 2 train
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