Three-Tier Application on Kubernetes

This project is a three-tier web application consisting of a React frontend, a Node.js backend, and a MySQL database, deployed on a Kubernetes cluster using Terraform for infrastructure as code, Ansible for automation, and GitLab CI/CD for continuous integration and deployment. The application is designed to run in environments like Killercoda or Play with Kubernetes (PWK).

Project Structure

• frontend/: React application serving the user interface.
• backend/: Node.js API handling CRUD operations with MySQL.
• database/: MySQL database configuration.
• kubernetes/: Kubernetes YAML manifests for manual deployment.
• terraform/: Terraform configurations for infrastructure provisioning.
• .gitlab-ci.yml: GitLab CI/CD pipeline for building and pushing Docker images.
• deploy.yml: Ansible playbook for automating setup in Killercoda.

Prerequisites

• GitLab Account: For repository and CI/CD pipeline.
• Docker Hub Account: For storing Docker images.
• Killercoda or Play with Kubernetes: For Kubernetes cluster.
• Tools:
  • Git
  • Docker
  • kubectl
  • Terraform (v1.5.7 or later)
  • Ansible (v2.9 or later)

Setup Instructions

1. Clone the Repository

git clone https://gitlab.com/amin4m/three-tier-app.git
cd three-tier-app

2. Configure CI/CD

In GitLab, set up CI/CD Variables: DOCKER_USERNAME: Your Docker Hub username (e.g., amin4m).

DOCKER_PASSWORD: Docker Hub access token.

BACKEND_IMAGE: amin4m/three-tier-backend.

FRONTEND_IMAGE: amin4m/three-tier-frontend.

DATABASE_IMAGE: amin4m/three-tier-database.

Push changes to the main branch to trigger the pipeline:

git add .
git commit -m "Initial commit"
git push origin main

Verify that Docker images (amin4m/three-tier-:v1) are pushed to Docker Hub.

3. Deploy in Killercoda

Option 1: Using Ansible Install Ansible:

apt update
apt install -y ansible

Create a GitLab Personal Access Token with api and read_repository scopes.

Export the token:

export GITLAB_TOKEN=<your-gitlab-token>

Run the Ansible playbook:

ansible-playbook deploy.yml

This automates: Installing Terraform.

Cloning the repository.

Running terraform init and terraform apply.

Setting the default namespace to three-tier-app.

Waiting for pods to be Running.

Displaying the frontend URL.

Option 2: Manual Deployment with Terraform Install Terraform:

wget https://releases.hashicorp.com/terraform/1.5.7/terraform_1.5.7_linux_amd64.zip
unzip terraform_1.5.7_linux_amd64.zip
mv terraform /usr/local/bin/

Navigate to the Terraform directory:

cd terraform
terraform init
terraform apply -auto-approve

Option 3: Manual Deployment with YAMLs

kubectl apply -f kubernetes/

4. Access the Application

Get the frontend NodePort:

kubectl get svc frontend-service

In Killercoda, enter the NodePort (e.g., 30611) in the "Add New Port" field.

Open the URL (e.g., https://-30611.killercoda.com) in a browser.

Test the app by adding and viewing items

Troubleshooting Backend CrashLoopBackOff: Check logs: kubectl logs .

Ensure backend/index.js uses host: (not host =) in the MySQL connection.

Verify the backend image (amin4m/three-tier-backend:v1) is updated in Docker Hub.

ENOTFOUND mysql_service: Ensure mysql-service exists: kubectl get svc.

Test connectivity: kubectl exec -it -- ping mysql-service.

Pipeline Failure: Check GitLab CI/CD logs for Docker login or build errors.

Verify DOCKER_USERNAME and DOCKER_PASSWORD in GitLab CI/CD Variables.

Pods Pending: Check for taints: kubectl describe node | grep -i taint.

Remove taints if needed: kubectl taint nodes node-role.kubernetes.io/control-plane:NoSchedule-.

Known Issues Killercoda’s temporary environment may cache old images. Use imagePullPolicy: Always in deployments.

Play with Kubernetes requires kubeadm init and a CNI plugin (e.g., Weave Net)

kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml

Future Improvements Add monitoring with Prometheus and Grafana.

Implement auto-scaling for backend replicas.

Optimize CI/CD to build only changed components.

Use Helm charts for easier Kubernetes management.

Contact For issues or contributions, contact [amin4m] via GitLab.

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