DevOps Mini Project: CI/CD Pipeline for a Node.js App Using Jenkins and Docker

In this blog, we’ll walk through setting up a CI/CD pipeline for a simple Node.js application using Jenkins, Docker, and GitHub.

🛠️ Prerequisites:

• Jenkins installed (locally or on an EC2 instance)

• Docker installed and running

• DockerHub account

• GitHub account

📁 1. Create a Simple Node.js App

Folder Structure:

nodejs-app/
├── Dockerfile
├── Jenkinsfile
├── package.json
└── index.js

📄 index.js

const express = require('express');
const app = express();
const PORT = process.env.PORT || 3000;

app.get('/', (req, res) => {
  res.send('Hello from DevOps CI/CD Pipeline!');
});

app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`);
});

📄 package.json

{
  "name": "nodejs-app",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "start": "node index.js"
  },
  "dependencies": {
    "express": "^4.17.1"
  }
}

🐳 2. Create Dockerfile

📄 Dockerfile

FROM node:14

WORKDIR /app

COPY package*.json ./
RUN npm install

COPY . .

EXPOSE 3000
CMD ["npm", "start"]

🤖 3. Add Jenkinsfile for Pipeline

📄 Jenkinsfile

pipeline {
    agent any

    environment {
        DOCKER_IMAGE = 'yourdockerhubusername/nodejs-app'
    }

    stages {
        stage('Clone Repo') {
            steps {
                git 'https://github.com/yourusername/nodejs-app.git'
            }
        }

        stage('Build Docker Image') {
            steps {
                script {
                    sh 'docker build -t $DOCKER_IMAGE .'
                }
            }
        }

        stage('Push to DockerHub') {
            steps {
                withCredentials([usernamePassword(credentialsId: 'dockerhub-creds', usernameVariable: 'USERNAME', passwordVariable: 'PASSWORD')]) {
                    sh """
                        echo "$PASSWORD" | docker login -u "$USERNAME" --password-stdin
                        docker push $DOCKER_IMAGE
                    """
                }
            }
        }

        stage('Deploy Container') {
            steps {
                sh "docker run -d -p 3000:3000 $DOCKER_IMAGE"
            }
        }
    }
}

📝 Note: In Jenkins > Credentials, add your DockerHub credentials with ID dockerhub-creds.

☁️ 4. Push Code to GitHub
Create a GitHub repo and push all your code:

git init
git remote add origin https://github.com/yourusername/nodejs-app.git
git add .
git commit -m "Initial commit"
git push -u origin main

⚙️ 5. Set Up Jenkins Pipeline Job

1. Open Jenkins dashboard.

2. Click New Item → Pipeline → Give a name.

3. In the pipeline configuration:

   • Choose Pipeline script from SCM

   • SCM: Git

   • Repository URL: https://github.com/yourusername/nodejs-app.git

   • Branch: main

   • Script Path: Jenkinsfile

4. Click Save and then Build Now.

🔄 6. Setup Webhook (Optional)

To trigger builds automatically:

1. Go to your GitHub repo → Settings → Webhooks → Add webhook.

2. Payload URL: http://<jenkins-server>:8080/github-webhook/

3. Content type: application/json

4. Events: Just the push event

✅ 7. Final Output

After successful build:

• Jenkins pulls code → builds Docker image → pushes to DockerHub → runs container.

• Access your app at http://<server-ip>:3000.