kubernetes-hello-world-on-minikube

A Kubernetes Hello World Project for Python Flask. This project uses a simple Flask app that returns correct change as the base project and converts it to Kubernetes.

This recipe is in the book Practical MLOps.

Assets in Repo

• Makefile: Builds project
• Dockerfile: Container configuration
• app.py: Flask app
• kube-hello-change.yaml: Kubernetes YAML Config

Get Started

• Create Python virtual environment python3 -m venv ~/.kube-hello && source ~/.kube-hello/bin/activate
• Run make all to install python libraries, lint project, including Dockerfile and run tests

Build and Run Docker Container

• Install Docker Desktop

• To build the image locally do the following.

docker build -t flask-change:latest . or run make build which has the same command.

• To verify container run docker image ls

• To run do the following: docker run -p 8080:8080 flask-change or run make run which has the same command

• In a separate terminal invoke the web service via curl, or run make invoke which has the same command

curl http://127.0.0.1:8080/change/1/34

[
  {
    "5": "quarters"
  }, 
  {
    "1": "nickels"
  }, 
  {
    "4": "pennies"
  }
]

• Stop the running docker container by using control-c command

Running Kubernetes On MiniKube

• Verify Kubernetes is working via minicube context

$ kubectl get nodes
NAME       STATUS   ROLES                  AGE     VERSION
minikube   Ready    control-plane,master   7h44m   v1.23.1

• First save your docker image and load it on minikube:

make image-export # saves the image
make copy-image # copies it to minikube, in case this didn't work run the code on terminal
minikube ssh # ssh to minikube
docker load -i flask-change.bz2 # load the docker image

• then apply the deployment on minikube:

kubectl apply -f kube-hello-change.yaml or run make run-kube which has the same command

You can see from the config file that a load-balancer along with three nodes is the configured application.

apiVersion: v1
kind: Service
metadata:
  name: hello-flask-change-service
spec:
  selector:
    app: hello-python
  ports:
  - protocol: "TCP"
    port: 8080
    targetPort: 8080
    nodePort: 32000 # output port
  type: LoadBalancer

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-python
spec:
  selector:
    matchLabels:
      app: hello-python
  replicas: 3
  template:
    metadata:
      labels:
        app: hello-python
    spec:
      containers:
      - name: flask-change
        image: flask-change:latest
        imagePullPolicy: Never
        ports:
        - containerPort: 8080

• Verify the container is running

kubectl get pods

Here is the output:

NAME                            READY   STATUS    RESTARTS   AGE
flask-change-7b7d7f467b-26htf   1/1     Running   0          8s
flask-change-7b7d7f467b-fh6df   1/1     Running   0          7s
flask-change-7b7d7f467b-fpsxr   1/1     Running   0          6s

• Describe the load balanced service:

kubectl describe services hello-flask-change-service

You should see output similar to this:

Name:                     hello-flask-change-service
Namespace:                default
Labels:                   <none>
Annotations:              <none>
Selector:                 app=hello-python
Type:                     LoadBalancer
IP Family Policy:         SingleStack
IP Families:              IPv4
IP:                       10.99.135.200
IPs:                      10.99.135.200
Port:                     <unset>  8080/TCP
TargetPort:               8080/TCP
NodePort:                 <unset>  32000/TCP
Endpoints:                172.17.0.6:8080,172.17.0.7:8080,172.17.0.8:8080
Session Affinity:         None
External Traffic Policy:  Cluster
Events:                   <none>

To create a visible ip on minikube run the following:

minikube service hello-flask-change-service

Invoke the endpoint to curl it:

make minikube-invoke

curl http://192.168.59.102:32000//change/1/34
[
  {
    "5": "quarters"
  }, 
  {
    "1": "nickels"
  }, 
  {
    "4": "pennies"
  }
]

To cleanup the deployment do the following:

kubectl delete deployment hello-python
minikube stop # to stop the minicube

References

• All credits go to https://github.com/noahgift/kubernetes-hello-world-python-flask
• Azure Kubernetes deployment strategy
• Service Cluster Config YAML file
• Kubernetes.io Hello World