Live, Ready, Deploy!

Implementing Liveness & Readiness Probes in Kubernetes with Docker & Helm

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📖 Story Time

A few months back, I deployed a Flask app to Kubernetes and assumed everything was perfect — until it wasn’t. The pod crashed silently, and my cluster kept thinking it was healthy. Why? I never added liveness and readiness probes.

Now, I never deploy anything without them.

In this blog, you’ll:

• Understand what probes actually do.

• Add them to a real Flask app.

• Package it with Docker.

• Deploy it using Helm.

Let’s make your apps live, ready, and unstoppable.

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🧪 What Are Liveness & Readiness Probes?

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The App – A Simple Flask Service

app.py:

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return "Welcome to the Live App"

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

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

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

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Dockerfile

FROM python:3.11-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
CMD ["python", "app.py"]

requirements.txt:

flask

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Helm Chart – With Probes Added

Helm chart folder: helm/flask-probe-app

values.yaml:

image:
  repository: your-dockerhub-username/flask-probe
  tag: latest
  pullPolicy: IfNotPresent

service:
  port: 80
  targetPort: 5000

livenessProbe:
  path: /healthz
  port: 5000
  initialDelaySeconds: 5
  periodSeconds: 10

readinessProbe:
  path: /readyz
  port: 5000
  initialDelaySeconds: 5
  periodSeconds: 10

templates/deployment.yaml (relevant part):

livenessProbe:
  httpGet:
    path: {{ .Values.livenessProbe.path }}
    port: {{ .Values.livenessProbe.port }}
  initialDelaySeconds: {{ .Values.livenessProbe.initialDelaySeconds }}
  periodSeconds: {{ .Values.livenessProbe.periodSeconds }}

readinessProbe:
  httpGet:
    path: {{ .Values.readinessProbe.path }}
    port: {{ .Values.readinessProbe.port }}
  initialDelaySeconds: {{ .Values.readinessProbe.initialDelaySeconds }}
  periodSeconds: {{ .Values.readinessProbe.periodSeconds }}

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Build & Deploy

1. Build & Push Docker Image

docker build -t your-dockerhub-username/flask-probe .
docker push your-dockerhub-username/flask-probe

2. Install with Helm

helm install flask-app helm/flask-probe-app

3. Verify Health Probes

kubectl describe pod [your-pod-name]
kubectl get endpoints
kubectl logs [your-pod-name]

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What You’ve Learned

• How to make your app production-ready with probes

• How to dockerize and Helm-deploy your app

• How Kubernetes treats probe failures (restart vs remove from service)

Final Thoughts

Adding health probes isn’t just a good practice — it’s a lifesaver for production workloads. Next time your pod misbehaves, K8s will know exactly what to do.