BentoML

This guide demonstrates how to serve a scikit-learn based iris classifier model with BentoML on a Kubernetes cluster. The same deployment steps are also applicable for models trained with other machine learning frameworks, see more BentoML examples here.

BentoML is an open-source platform for high-performance ML model serving. It makes building production API endpoint for your ML model easy and supports all major machine learning training frameworks, including Tensorflow, Keras, PyTorch, XGBoost, scikit-learn and etc.

BentoML comes with a high-performance API model server with adaptive micro-batching support, which achieves the advantage of batch processing in online serving. It also provides model management and model deployment functionality, giving ML teams an end-to-end model serving workflow, with DevOps best practices baked in.

Prerequisites

Before starting this tutorial, make sure you have the following:

• a Kubernetes cluster and kubectl installed on your local machine.
  • kubectl install instruction: https://kubernetes.io/docs/tasks/tools/install-kubectl/
• Docker and Docker Hub installed and configured in your local machine.
  • Docker install instruction: https://docs.docker.com/get-docker/
• Python 3.6 or above and required PyPi packages: bentoml, scikit-learn
  • pip install bentoml scikit-learn

Build an iris classifier model server with BentoML

The following code defines a BentoML prediction service that requires a scikit-learn model, and asks BentoML to figure out the required PyPI packages automatically. It also defines an API, which is the entry point for accessing this prediction service. And the API is expecting a pandas.DataFrame object as its input data.

# iris_classifier.py
from bentoml import env, artifacts, api, BentoService
from bentoml.handlers import DataframeHandler
from bentoml.artifact import SklearnModelArtifact

@env(auto_pip_dependencies=True)
@artifacts([SklearnModelArtifact('model')])
class IrisClassifier(BentoService):

    @api(DataframeHandler)
    def predict(self, df):
        return self.artifacts.model.predict(df)

The following code trains a classifier model and serves it with the IrisClassifier defined above:

# main.py
from sklearn import svm
from sklearn import datasets

from iris_classifier import IrisClassifier

if __name__ == "__main__":
    # Load training data
    iris = datasets.load_iris()
    X, y = iris.data, iris.target

    # Model Training
    clf = svm.SVC(gamma='scale')
    clf.fit(X, y)

    # Create a iris classifier service instance
    iris_classifier_service = IrisClassifier()

    # Pack the newly trained model artifact
    iris_classifier_service.pack('model', clf)

    # Save the prediction service to disk for model serving
    saved_path = iris_classifier_service.save()

The sample code above can be found in the BentoML repository, run them directly with the following command:

git clone git@github.com:bentoml/BentoML.git
python ./bentoml/guides/quick-start/main.py

After saving the BentoService instance, you can now start a REST API server with the model trained and test the API server locally:

# Start BentoML API server:
bentoml serve IrisClassifier:latest

# Send test request
curl -i \
  --header "Content-Type: application/json" \
  --request POST \
  --data '[[5.1, 3.5, 1.4, 0.2]]' \
  localhost:5000/predict

BentoML provides a convenient way of containerizing the model API server with Docker. To create a docker container image for the sample model above:

1. Find the file directory of the SavedBundle with bentoml get command, which is directory structured as a docker build context.
2. Running docker build with this directory produces a docker image containing the model API server

saved_path=$(bentoml get IrisClassifier:latest -q | jq -r ".uri.uri")

# Replace `{docker_username} with your Docker Hub username
docker build -t {docker_username}/iris-classifier $saved_path
docker push {docker_username}/iris-classifier

Deploy model server to Kubernetes

The following is an example YAML file for specifying the resources required to run and expose a BentoML model server in a Kubernetes cluster. Replace {docker_username} with your Docker Hub username and save it to iris-classifier.yaml:

apiVersion: v1
kind: Service
metadata:
  labels:
    app: iris-classifier
  name: iris-classifier
  namespace: kubeflow
spec:
  ports:
  - name: predict
    port: 5000
    targetPort: 5000
  selector:
    app: iris-classifier
  type: LoadBalancer
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: iris-classifier
  name: iris-classifier
  namespace: kubeflow
spec:
  selector:
    matchLabels:
      app: iris-classifier
  template:
    metadata:
      labels:
        app: iris-classifier
    spec:
      containers:
      - image: {docker_username}/iris-classifier
        imagePullPolicy: IfNotPresent
        name: iris-classifier
        ports:
        - containerPort: 5000

Use kubectl CLI to deploy the model API server to the Kubernetes cluster

kubectl apply -f iris-classifier.yaml

Send prediction request

Use kubectl describe command to get the NODE_PORT

kubectl describe svc iris-classifier --namespace kubeflow

And then send the request:

curl -i \
  --header "Content-Type: application/json" \
  --request POST \
  --data '[[5.1, 3.5, 1.4, 0.2]]' \
  http://EXTERNAL_IP:NODE_PORT/predict

Monitor metrics with Prometheus

Prerequisites

Before starting this section, make sure you have the following:

• Prometheus installed in the cluster
  • Prometheus documentation
  • Installation instruction with Helm chart

BentoML API server provides Prometheus support out of the box. It comes with a “/metrics” endpoint which includes the essential metrics for model serving and the ability to create and customize new metrics base on needs.

To enable Prometheus monitoring on the deployed model API server, update the YAML file with Prometheus related annotations. Change the deployment spec as the following, and replace {docker_username} with your Docker Hub username:

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: iris-classifier
  name: iris-classifier
  namespace: kubeflow
spec:
  selector:
    matchLabels:
      app: iris-classifier
  template:
    metadata:
      labels:
        app: iris-classifier
      annotations:
        prometheus.io/scrape: true
        prometheus.io/port: 5000
    spec:
      containers:
      - image: {docker_username}/iris-classifier
        imagePullPolicy: IfNotPresent
        name: iris-classifier
        ports:
        - containerPort: 5000

Apply the change with kubectl CLI.

kubectl apply -f iris-classifier.yaml

Remove deployment

kubectl delete -f iris-classifier.yaml

Additional resources

• GitHub repository
• BentoML documentation
• Quick start guide
• Community

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