WebCal DevOps Project

A production-ready Java web calculator application demonstrating real-world DevOps practices, including CI/CD with Jenkins, Docker containerization, and Kubernetes orchestration.

Table of Contents

• WebCal DevOps Project
  • Table of Contents
  • Introduction
  • Features
  • Screenshot
  • Tech Stack
  • Architecture Overview
  • Project Structure
  • Prerequisites
  • Step 1: Build Maven Project
  • Step 2: Build Docker Image
  • Step 3: Apply Kubernetes Manifests
  • Step 4: Verify Deployments
  • Step 5: Configure Hosts File
    • Windows
    • Mac
    • Linux / Ubuntu
  • Step 6: Access the App (Ingress)
  • CI/CD (Jenkins)
    • Pipeline Flow
  • Step 7: Common Issues & Fixes
  • Project Notes
  • 👤 About the Architect

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Introduction

This project is a Java Servlet + JSP calculator application, containerized with Docker, deployed on Kubernetes with ClusterIP + Ingress, and automated via Jenkins CI/CD pipeline. It demonstrates full DevOps best practices including automated deployments, rollback on failures, and namespace isolation.

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Features

• Simple web-based calculator (addition, subtraction, multiplication, division)
• Dockerized Java application
• Kubernetes deployment with ClusterIP Service and Ingress
• CI/CD pipeline with Jenkins
• Fully namespaced Kubernetes resources
• Automatic image tagging using Git commit hash
• Rollback support on failed deployments

---

Screenshot

Tech Stack

• Backend: Java Servlets + JSP
• Build Tool: Maven
• Containerization: Docker
• Orchestration: Kubernetes (ClusterIP + Ingress)
• CI/CD: Jenkins
• Registry: Docker Hub (mayrhatte09)

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Architecture Overview

User → Browser
↓
Ingress (NGINX)
↓
┌─────────────┐
│ WebCal App  │
│ Java Servlet│
└───────┬─────┘
↓
Kubernetes Cluster
(Namespace: k8s)
↓
Docker Containers

CI/CD Flow:

GitHub → Jenkins → Docker → Docker Hub → Kubernetes (EKS/Minikube)

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Project Structure

webcal-project/
├── Jenkinsfile
├── dockerfile
├── pom.xml
└── kubernetes/
├── namespace.yaml
├── deployment.yaml
├── service.yaml
└── ingress.yaml
└── src/
└── main/
├── java/com/example/CalculatorServlet.java
└── webapp/
├── WEB-INF/web.xml
├── index.jsp
└── result.jsp

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Prerequisites

• Java 11+
• Maven
• Docker & Docker Hub account (mayrhatte09)
• Kubernetes cluster (Minikube, Kind, or AWS EKS)
• kubectl configured
• Jenkins server with Docker access
• NGINX Ingress Controller for routing

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Step 1: Build Maven Project

mvn clean package

Generates target/webcal.war file.

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Step 2: Build Docker Image

docker build -t mayrhatte09/webcal:latest .
docker tag mayrhatte09/webcal:latest mayrhatte09/webcal:<git-commit-hash>
docker push mayrhatte09/webcal:latest
docker push mayrhatte09/webcal:<git-commit-hash>

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Step 3: Apply Kubernetes Manifests

1. Apply namespace:

kubectl apply -f kubernetes/namespace.yaml

2. Apply deployment, service, and ingress:

kubectl apply -f kubernetes/deployment.yaml -n k8s
kubectl apply -f kubernetes/service.yaml -n k8s
kubectl apply -f kubernetes/ingress.yaml -n k8s

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Step 4: Verify Deployments

Check pods:

kubectl get pods -n k8s

Check services:

kubectl get svc -n k8s

Check ingress:

kubectl get ingress -n k8s

Example output:

NAME      CLASS    HOSTS           ADDRESS        PORTS   AGE
webcal    <none>   webcal.local    127.0.0.1     80      1m

Tip for Minikube users: If ADDRESS is <pending>, run:

minikube ip

Use the Minikube IP in the hosts file instead of 127.0.0.1.

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Step 5: Configure Hosts File

Map ingress host webcal.local to localhost.

Windows

• Open C:\Windows\System32\drivers\etc\hosts as Administrator
• Add line:

127.0.0.1 webcal.local

• Flush DNS:

ipconfig /flushdns

Mac

• Edit /etc/hosts:

sudo nano /etc/hosts

• Add line:

127.0.0.1 webcal.local

• Flush DNS:

sudo dscacheutil -flushcache

Linux / Ubuntu

• Edit hosts file:

sudo nano /etc/hosts

• Add line:

127.0.0.1 webcal.local

If using Minikube:

<minikube-ip> webcal.local

• Flush DNS if caching is enabled:

Systemd DNS (Ubuntu 18.04+):

sudo systemd-resolve --flush-caches

NSCD (if installed):

sudo service nscd restart

• Verify mapping:

ping webcal.local
# Should return 127.0.0.1 (or Minikube IP)

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Step 6: Access the App (Ingress)

• Open browser: http://webcal.local
• Use the calculator for basic operations.

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CI/CD (Jenkins)

Pipeline Flow

1. Git push triggers Jenkins pipeline
2. Jenkins builds Maven project & runs tests
3. Docker image is built & pushed to Docker Hub
4. Kubernetes namespace is created if not exists
5. Deployment, Service, and Ingress applied
6. Rollback occurs automatically if deployment fails

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Step 7: Common Issues & Fixes

Issue	Fix
Pod not running	Check kubectl get pods -n k8s and logs
Ingress not working	Ensure NGINX Ingress controller installed
ImagePullBackOff	Verify Docker image exists in Docker Hub
Wrong namespace	Use -n k8s in all kubectl commands
Port not accessible	Verify containerPort in deployment and service
Jenkins pipeline failed	Check Jenkins console logs
Hosts not resolving	Update /etc/hosts or flush DNS
Deployment not updating	Check image tag in deployment.yaml

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Project Notes

• All Kubernetes resources are namespaced under k8s
• Docker image tagging uses Git commit hash + latest
• Rollback enabled in Jenkins pipeline
• Fully modular for local (Minikube) or cloud (EKS) deployment

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👤 About the Architect

Mayur Hatte DevOps & Cloud Infrastructure Engineer Focused on building self-healing, automated infrastructure. Verified asset of MayurHatte09.

_{© 2026 | Mayur Hatte DevOps Projects}

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