Introduction

If you've been trying to deploy a containerized application on AWS using Kubernetes, you've probably hit a wall somewhere — whether it's configuring the ALB Ingress Controller, setting up ECR, or getting GitHub Actions to push images automatically.

In this guide, I'll walk you through exactly how I built a production-style EKS setup with:

• A Flask application running in EKS

• Docker image stored in Amazon ECR

• GitHub Actions CI/CD pipeline for automated deployments

• ALB Ingress Controller via Helm

• Horizontal Pod Autoscaler (HPA)

This isn't theory. I built this on AWS (ap-south-1) and it works.

Architecture Overview

GitHub Push
    ↓
GitHub Actions
    ↓
Docker Build → Push to ECR
    ↓
kubectl apply → EKS Cluster
    ↓
ALB Ingress → Flask App (2 t3.medium nodes)

Prerequisites

• AWS CLI configured

• kubectl installed

• eksctl installed

• Helm installed

• Docker installed

• GitHub account

Step 1: Create the EKS Cluster

eksctl create cluster \
  --name flask-cluster \
  --region ap-south-1 \
  --nodegroup-name standard-workers \
  --node-type t3.medium \
  --nodes 2 \
  --nodes-min 1 \
  --nodes-max 3 \
  --managed

This takes about 15–20 minutes. Go grab a chai ☕

Verify:

kubectl get nodes

Step 2: Create ECR Repository

aws ecr create-repository \
  --repository-name flask-app \
  --region ap-south-1

Note down the repository URI — you'll need it in GitHub Actions.

Step 3: Dockerize Your Flask App

app.py

from flask import Flask
app = Flask(__name__)

@app.route('/')
def home():
    return "Hello from EKS! 🚀"

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

Dockerfile

FROM python:3.9-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
EXPOSE 5000
CMD ["python", "app.py"]

Step 4: Install ALB Ingress Controller via Helm

# Add EKS chart repo
helm repo add eks https://aws.github.io/eks-charts
helm repo update

# Install ALB controller
helm install aws-load-balancer-controller eks/aws-load-balancer-controller \
  -n kube-system \
  --set clusterName=flask-cluster \
  --set serviceAccount.create=false \
  --set serviceAccount.name=aws-load-balancer-controller

Step 5: GitHub Actions CI/CD Pipeline

Create .github/workflows/deploy.yml:

name: Deploy to EKS

on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3

      - name: Configure AWS credentials
        uses: aws-actions/configure-aws-credentials@v2
        with:
          aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
          aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
          aws-region: ap-south-1

      - name: Login to ECR
        run: |
          aws ecr get-login-password --region ap-south-1 | \
          docker login --username AWS --password-stdin ${{ secrets.ECR_REGISTRY }}

      - name: Build and push Docker image
        run: |
          docker build -t flask-app .
          docker tag flask-app:latest ${{ secrets.ECR_REGISTRY }}/flask-app:latest
          docker push ${{ secrets.ECR_REGISTRY }}/flask-app:latest

      - name: Deploy to EKS
        run: |
          aws eks update-kubeconfig --name flask-cluster --region ap-south-1
          kubectl apply -f k8s/
          kubectl rollout restart deployment/flask-deployment

Step 6: Set Up HPA (Horizontal Pod Autoscaler)

kubectl autoscale deployment flask-deployment \
  --cpu-percent=50 \
  --min=2 \
  --max=5

This automatically scales your pods when CPU goes above 50%.

Common Errors I Hit (and Fixed)

Error 1: exec format error when pod starts → You built the Docker image on ARM (M1 Mac). Fix:

docker buildx build --platform linux/amd64 -t flask-app .

Error 2: ALB not provisioning → Missing IAM permissions for the load balancer controller service account. Attach the correct policy from AWS docs.

Error 3: ImagePullBackOff → ECR login expired in the node. Re-attach the AmazonEC2ContainerRegistryReadOnly policy to the node IAM role.

Cost Breakdown (ap-south-1)

💡 Tip: Delete the cluster when not in use to save costs:

eksctl delete cluster --name flask-cluster --region ap-south-1

Conclusion

That's a complete EKS setup with CI/CD from scratch. Once this pipeline is running, every git push to main automatically builds, pushes, and deploys your app — zero manual steps.

If you found this helpful, follow my blog for more real-world AWS and DevOps guides.

Connect with me: GitHub: github.com/Ashishjo10 Blog: devopsbyashish.hashnode.dev