Continuing this short series of writing a simple echo service web API along with the docker and k8s requirements, we’re now going to turn our attention to a Python implementation.

Implementation

I’m using JetBrains PyCharm for this project, so I created a project named echo_service.

Next, add the file app.py with the following code

from flask import Flask, request

app = Flask(__name__)

@app.route('/echo')
def echo():
    text = request.args.get('text', '')
    return f"Python Echo: {text}", 200

@app.route('/livez')
def livez():
    return "OK", 200

@app.route('/readyz')
def readyz():
    return "Ready", 200

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080)

Add a requirements.txt file with the following

flask
gunicorn

Don’t forget to install the packages via the IDE.

Dockerfile

Next up we need to create our Dockerfile

# Use a lightweight Python base
FROM python:3.11-slim

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY app.py .

CMD ["gunicorn", "-w", "2", "-b", "0.0.0.0:8080", "app:app"]

Note: we’ll be using gunicorn instead of the development server.

Note: In Linux port 80 might be locked down, hence we use port 8080 by default.

To build this, run

docker build -t putridparrot.echo_service:v1 .

Don’t forget to change the name to your preferred name.

and to test this, run

docker run -p 8080:8080 putridparrot.echo_service:v1

Kubernetes

If all wen well we’ve not tested our application and see it working from a docker image, so now we need to create the deployment etc. for Kubernete’s. Let’s assume you’ve pushed you image to Docker or another container registry such as Azure – I’m call my container registry putridparrotreg.

I’m also not going to use helm at this point as I just want a (relatively) simple yaml file to run from kubectl, so create a deployment.yaml file, we’ll store all the configurations, deployment, service and ingress in this one file jus for simplicity.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: echo
  namespace: dev
  labels:
    app: echo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo
  template:
    metadata:
      labels:
        app: echo
    spec:
      containers:
      - name: echo
        image: putridparrotreg/putridparrot.echo_service:v1
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "100Mi"
            cpu: "100m"
          limits:
            memory: "200Mi"
            cpu: "200m"
        livenessProbe:
          httpGet:
            path: /livez
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /readyz
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5

---
apiVersion: v1
kind: Service
metadata:
  name: echo_service
  namespace: dev
  labels:
    app: echo
spec:
  type: ClusterIP
  selector:
    app: echo 
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: echo-ingress
  namespace: dev
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - host: mydomain.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: echo_service
            port:
              number: 80

Don’t forget to change the “host” and image to suit, also this assume you created a namespace “dev” for your app. See Creating a local container registry for information on setting up your own container registry.