Train scikit-learn models at scale with Azure Machine Learning

In this article, learn how to run your scikit-learn training scripts with Azure Machine Learning.

The example scripts in this article are used to classify iris flower images to build a machine learning model based on scikit-learn's iris dataset.

Whether you're training a machine learning scikit-learn model from the ground-up or you're bringing an existing model into the cloud, you can use Azure Machine Learning to scale out open-source training jobs using elastic cloud compute resources. You can build, deploy, version, and monitor production-grade models with Azure Machine Learning.

Prerequisites

Run this code on either of these environments:

  • Azure Machine Learning compute instance - no downloads or installation necessary

    • Complete the Tutorial: Setup environment and workspace to create a dedicated notebook server pre-loaded with the SDK and the sample repository.
    • In the samples training folder on the notebook server, find a completed and expanded notebook by navigating to this directory: how-to-use-azureml > ml-frameworks > scikit-learn > train-hyperparameter-tune-deploy-with-sklearn folder.
  • Your own Jupyter Notebook server

Set up the experiment

This section sets up the training experiment by loading the required Python packages, initializing a workspace, defining the training environment, and preparing the training script.

Initialize a workspace

The Azure Machine Learning workspace is the top-level resource for the service. It provides you with a centralized place to work with all the artifacts you create. In the Python SDK, you can access the workspace artifacts by creating a workspace object.

Create a workspace object from the config.json file created in the prerequisites section.

from azureml.core import Workspace

ws = Workspace.from_config()

Prepare scripts

In this tutorial, the training script train_iris.py is already provided for you here. In practice, you should be able to take any custom training script as is and run it with Azure ML without having to modify your code.

Notes:

  • The provided training script shows how to log some metrics to your Azure ML run using the Run object within the script.
  • The provided training script uses example data from the iris = datasets.load_iris() function. To use and access your own data, see how to train with datasets to make data available during training.

Define your environment

To define the Azure ML Environment that encapsulates your training script's dependencies, you can either define a custom environment or use and Azure ML curated environment.

Use a curated environment

Optionally, Azure ML provides prebuilt, curated environments if you don't want to define your own environment. For more info, see here. If you want to use a curated environment, you can run the following command instead:

from azureml.core import Environment

sklearn_env = Environment.get(workspace=ws, name='AzureML-Tutorial')

Create a custom environment

You can also create your own your own custom environment. Define your conda dependencies in a YAML file; in this example the file is named conda_dependencies.yml.

dependencies:
  - python=3.6.2
  - scikit-learn
  - numpy
  - pip:
    - azureml-defaults

Create an Azure ML environment from this Conda environment specification. The environment will be packaged into a Docker container at runtime.

from azureml.core import Environment

sklearn_env = Environment.from_conda_specification(name='sklearn-env', file_path='conda_dependencies.yml')

For more information on creating and using environments, see Create and use software environments in Azure Machine Learning.

Configure and submit your training run

Create a ScriptRunConfig

Create a ScriptRunConfig object to specify the configuration details of your training job, including your training script, environment to use, and the compute target to run on. Any arguments to your training script will be passed via command line if specified in the arguments parameter.

The following code will configure a ScriptRunConfig object for submitting your job for execution on your local machine.

from azureml.core import ScriptRunConfig

src = ScriptRunConfig(source_directory='.',
                      script='train_iris.py',
                      arguments=['--kernel', 'linear', '--penalty', 1.0],
                      environment=sklearn_env)

If you want to instead run your job on a remote cluster, you can specify the desired compute target to the compute_target parameter of ScriptRunConfig.

from azureml.core import ScriptRunConfig

compute_target = ws.compute_targets['<my-cluster-name>']
src = ScriptRunConfig(source_directory='.',
                      script='train_iris.py',
                      arguments=['--kernel', 'linear', '--penalty', 1.0],
                      compute_target=compute_target,
                      environment=sklearn_env)

Submit your run

from azureml.core import Experiment

run = Experiment(ws,'train-iris').submit(src)
run.wait_for_completion(show_output=True)

Warning

Azure Machine Learning runs training scripts by copying the entire source directory. If you have sensitive data that you don't want to upload, use a .ignore file or don't include it in the source directory . Instead, access your data using an Azure ML dataset.

What happens during run execution

As the run is executed, it goes through the following stages:

  • Preparing: A docker image is created according to the environment defined. The image is uploaded to the workspace's container registry and cached for later runs. Logs are also streamed to the run history and can be viewed to monitor progress. If a curated environment is specified instead, the cached image backing that curated environment will be used.

  • Scaling: The cluster attempts to scale up if the Batch AI cluster requires more nodes to execute the run than are currently available.

  • Running: All scripts in the script folder are uploaded to the compute target, data stores are mounted or copied, and the script is executed. Outputs from stdout and the ./logs folder are streamed to the run history and can be used to monitor the run.

  • Post-Processing: The ./outputs folder of the run is copied over to the run history.

Save and register the model

Once you've trained the model, you can save and register it to your workspace. Model registration lets you store and version your models in your workspace to simplify model management and deployment.

Add the following code to your training script, train_iris.py, to save the model.

import joblib

joblib.dump(svm_model_linear, 'model.joblib')

Register the model to your workspace with the following code. By specifying the parameters model_framework, model_framework_version, and resource_configuration, no-code model deployment becomes available. No-code model deployment allows you to directly deploy your model as a web service from the registered model, and the ResourceConfiguration object defines the compute resource for the web service.

from azureml.core import Model
from azureml.core.resource_configuration import ResourceConfiguration

model = run.register_model(model_name='sklearn-iris', 
                           model_path='outputs/model.joblib',
                           model_framework=Model.Framework.SCIKITLEARN,
                           model_framework_version='0.19.1',
                           resource_configuration=ResourceConfiguration(cpu=1, memory_in_gb=0.5))

Deployment

The model you just registered can be deployed the exact same way as any other registered model in Azure ML. The deployment how-to contains a section on registering models, but you can skip directly to creating a compute target for deployment, since you already have a registered model.

(Preview) No-code model deployment

Instead of the traditional deployment route, you can also use the no-code deployment feature (preview) for scikit-learn. No-code model deployment is supported for all built-in scikit-learn model types. By registering your model as shown above with the model_framework, model_framework_version, and resource_configuration parameters, you can simply use the deploy() static function to deploy your model.

web_service = Model.deploy(ws, "scikit-learn-service", [model])

NOTE: These dependencies are included in the pre-built scikit-learn inference container.

    - azureml-defaults
    - inference-schema[numpy-support]
    - scikit-learn
    - numpy

The full how-to covers deployment in Azure Machine Learning in greater depth.

Next steps

In this article, you trained and registered a scikit-learn model, and learned about deployment options. See these other articles to learn more about Azure Machine Learning.