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Using OpenVINO™ Model Server in a Docker Container

Building the Image

OpenVINO™ model server Docker image can be built from DLDT sources with ubuntu base image Dockerfile, intelpython base image Dockerfile_intelpython or with Intel Distribution of OpenVINO™ toolkit package via Dockerfile_binary_openvino.

The latter option requires downloaded OpenVINO™ toolkit and placed in the repository root folder along the Dockerfile. A registration process is required to download the toolkit. It is recommended to use online installation package because this way the resultant image will be smaller. An example file looks like: l_openvino_toolkit_p_2019.1.094_online.tgz.

From the root of the git repository, execute the command:

cp (download path)/l_openvino_toolkit_p_2019.1.094_online.tgz . 
make docker_build_bin http_proxy=$http_proxy https_proxy=$https_proxy


make docker_build_src_ubuntu http_proxy=$http_proxy https_proxy=$https_proxy


make docker_build_src_intelpython http_proxy=$http_proxy https_proxy=$https_proxy

Note: You can use also publicly available docker image from dockerhub

docker pull intelaipg/openvino-model-server

Preparing the Models

After the Docker image is built, you can use it to start the model server container, but you should start from preparing the models to be served.

AI models should be created in Intermediate Representation (IR) format (a pair of files with .bin and .xml extensions). OpenVINO™ toolkit includes a model_optimizer tool for converting TensorFlow, Caffe and MXNet trained models into IR format.
Refer to the model optimizer documentation for more details.

Predefined IR models should be placed and mounted in a folder structure as depicted below:

tree models/
├── model1
│   ├── 1
│   │   ├── ir_model.bin
│   │   └── ir_model.xml
│   └── 2
│       ├── ir_model.bin
│       └── ir_model.xml
└── model2
    └── 1
        ├── ir_model.bin
        ├── ir_model.xml
        └── mapping_config.json

Each model should be stored in a dedicated folder (model1 and model2 in the examples above) and should include subfolders representing its versions. The versions and the subfolder names should be positive integer values.

Every version folder must include a pair of model files with .bin and .xml extensions; however, the file name can be arbitrary.

Each model in IR format defines input and output tensors in the AI graph. By default OpenVINO™ model server is using tensors names as the input and output dictionary keys. The client is passing the input values to the gRPC request and reads the results by referring to the correspondent tensor names.

Below is the snippet of the example client code:

input_tensorname = 'input'
request.inputs[input_tensorname].CopyFrom(make_tensor_proto(img, shape=(1, 3, 224, 224)))


output_tensorname = 'resnet_v1_50/predictions/Reshape_1'
predictions = make_ndarray(result.outputs[output_tensorname])

It is possible to adjust this behavior by adding an optional json file with name mapping_config.json which can map the input and output keys to the appropriate tensors.

           { "tensor_name":"grpc_custom_input_name"},

This extra mapping can be handy to enable model user friendly names on the client when the model has cryptic tensor names.

OpenVINO™ model server is enabling all the versions present in the configured model folder. To limit the versions exposed, for example to reduce the mount of RAM, you need to delete the subfolders representing unnecessary model versions.

While the client is not defining the model version in the request specification, OpenVINO™ model server will use the latest one stored in the subfolder of the highest number.

Starting Docker Container with a Single Model

When the models are ready and stored in correct folders structure, you are ready to start the Docker container with the OpenVINO™ model server. To enable just a single model, you do not need any extra configuration file, so this process can be completed with just one command like below:

docker run --rm -d  -v /models/:/opt/ml:ro -p 9001:9001 ie-serving-py:latest \
/ie-serving-py/ ie_serving model --model_path /opt/ml/model1 --model_name my_model --port 9001
  • option -v defines how the models folder should be mounted inside the docker container.

  • option -p exposes the model serving port outside the docker container.

  • ie-serving-py:latest represent the image name which can be different depending the tagging and building process.

  • script activates the python virtual environment inside the docker container.

  • ie_serving command starts the model server which has the following parameters:

usage: ie_serving model [-h] --model_name MODEL_NAME --model_path MODEL_PATH
                        [--batch_size BATCH_SIZE] [--model_version_policy MODEL_VERSION_POLICY] [--port PORT] 

optional arguments:
  -h, --help            show this help message and exit
  --model_name MODEL_NAME
                        name of the model
  --model_path MODEL_PATH
                        absolute path to model,as in tf serving
  --batch_size BATCH_SIZE
                        sets models batchsize, int value or auto
  --model_version_policy MODEL_VERSION_POLICY 
                        sets model version policy for model
  --port PORT           server port

The model path could be local on docker container like mounted during startup or it could be Google Cloud Storage path in a format gs://<bucket>/<model_path>. In this case it will be required to pass GCS credentials to the docker container, unless GKE kubernetes cluster, which handled the authorization automatically, is used.

Below is an example presenting how to start docker container with a support for GCS paths to the models. The variable GOOGLE_APPLICATION_CREDENTIALS contain a path to GCP authentication key.

docker run --rm -d  -p 9001:9001 ie-serving-py:latest \
/ie-serving-py/ ie_serving model --model_path gs://bucket/model_path --model_name my_model --port 9001

Learn more about GCP authentication.

It is also possible to provide paths to models located in S3 compatible storage in a format s3://<bucket>/<model_path>. In this case it is necessary to provide credentials to bucket by setting environmental variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. You can also set AWS_REGION variable, although it's not always required. If you are using custom storage server compatible with S3, you must set S3_ENDPOINT environmental variable in a HOST:PORT format. In an example below you can see how to start docker container serving single model located in S3.

docker run --rm -d  -p 9001:9001 ie-serving-py:latest \
/ie-serving-py/ ie_serving model --model_path 
s3://bucket/model_path --model_name my_model --port 9001 --batch_size auto --model_version_policy '{"all": {}}'

If you need to expose multiple models, you need to create a model server configuration file, which is explained in the following section.

Starting docker container with a configuration file

Model server configuration file defines multiple models, which can be exposed for clients requests. It uses json format as shown in the example below:

            "batch_size": "16"
            "batch_size": "auto",
            "model_version_policy": {"all": {}}
            "model_version_policy": {"specific": { "versions":[1, 3] }}

It has a mandatory array model_config_list, which includes a collection of config objects for each served model. Each config object includes values for the model name and the base_path attributes.

When the config file is present, the docker container can be started in a similar manner as a single model. Keep in mind that models with cloud storage path require specific environmental variables set. Configuration file above contains both GCS and S3 paths so starting docker container supporting all those models can be done with:

docker run --rm -d  -v /models/:/opt/ml:ro -p 9001:9001 ie-serving-py:latest \
/ie-serving-py/ ie_serving config --config_path /opt/ml/config.json --port 9001

Below is the explanation of the ie_serving config parameters

usage: ie_serving config [-h] --config_path CONFIG_PATH [--port PORT]

optional arguments:
  -h, --help            show this help message and exit
  --config_path CONFIG_PATH
                        absolute path to json configuration file
  --port PORT           server port

Starting docker container with NCS

Plugin for Intel® Movidius™ Neural Compute Stick is distributed only in a binary form, so loading models on NCS is possible only with binary built docker image.

Neural Compute Stick must be visible and accessible on host machine. You may need to update udev rules:

Updating udev rules
  1. Create file 97-usbboot.rules and fill it with:
   SUBSYSTEM=="usb", ATTRS{idProduct}=="2150", ATTRS{idVendor}=="03e7", GROUP="users", MODE="0666", ENV{ID_MM_DEVICE_IGNORE}="1" 
   SUBSYSTEM=="usb", ATTRS{idProduct}=="2485", ATTRS{idVendor}=="03e7", GROUP="users", MODE="0666", ENV{ID_MM_DEVICE_IGNORE}="1"
   SUBSYSTEM=="usb", ATTRS{idProduct}=="f63b", ATTRS{idVendor}=="03e7", GROUP="users", MODE="0666", ENV{ID_MM_DEVICE_IGNORE}="1"
  1. In the same directory execute following:
  sudo cp 97-usbboot.rules /etc/udev/rules.d/
  sudo udevadm control --reload-rules
  sudo udevadm trigger
  sudo ldconfig
  rm 97-usbboot.rules

To start server with NCS you can use command similar to:

docker run --rm -it --net=host --privileged -v /opt/model:/opt/model -v /dev:/dev -e DEVICE=MYRIAD -p 9001:9001 ie-serving-py:latest /ie-serving-py/ ie_serving model --model_path /opt/model --model_name my_model --port 9001

--net=host and --privileged parameters are required for USB connection to work properly.

-v /dev:/dev mounts USB drives.

DEVICE environment variable indicates that model will be loaded on Neural Compute Stick.

A single stick can handle one model at a time. If there are multiple sticks plugged in, OpenVINO Toolkit chooses to which one the model is loaded.

Batch Processing

batch_size parameter is optional. By default is accepted the batch size derived from the model. It is set by the model optimizer. When that parameter is set to numerical value, it is changing the model batch size at service start up. It accepts also a value auto - this special phrase make the served model to set the batch size automatically based on the incoming data at run time. Each time the input data change the batch size, the model is reloaded. It might have extra response delay for the first request. This feature is useful for sequential inference requests of the same batch size.

OpenVINO™ Model Server determines the batch size based on the size of the first dimension in the first input. For example with the input shape (1, 3, 225, 225), the batch size is set to 1. With input shape (8, 3, 225, 225) the batch size is set to 8.

Note: Dynamic batch size is not supported.

Processing bigger batches of requests increases the throughput but the side effect is higher latency.

Model Version Policy

Model version policy makes it possible to decide which versions of model will be served by OVMS. This parameter allows you to control the memory consumption of the server and decide which versions will be used regardless of what is located under the path given when the server is started. model_version_policy parameter is optional. By default server serves only latest version for model. Accepted format for parameter in CLI and in config is json. Accepted values:

{"all": {}}
{"latest": { "num_versions": Integer}
{"specific": { "versions": List }}


{"latest": { "num_versions":2 } # server will serve only 2 latest versions of model
{"specific": { "versions":[1, 3] }} # server will serve only 1 and 3 versions of given model
{"all": {}} # server will serve all available versions of given model

Updating model versions

Served versions are updated online by monitoring file system changes in the model storage. OpenVINO Model Server will add new version to the serving list when new numerical subfolder with the model files is added. The default served version will be switched to the one with the highest number. When the model version is deleted from the file system, it will become unavailable on the server and it will release RAM allocation. Updates in the model version files will not be detected and they will not trigger changes in serving.

By default model server is detecting new and deleted versions in 1 second intervals. The frequency can be changed by setting environment variable FILE_SYSTEM_POLL_WAIT_SECONDS.

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