🐳 Dockerized Node.js Backend

A containerized Node.js + Express backend service — built, tagged, and published to Docker Hub. Demonstrates the full Docker workflow from writing a Dockerfile to running a portable container from a public registry.

Docker Hub: kuhata/testrepo:latest  ·  Image size: 55.9 MB  ·  Port: 3000

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🚀 Run It Instantly (No Clone Needed)

Pull and run the image directly from Docker Hub:

docker pull kuhata/testrepo:latest
docker run -p 3000:3000 kuhata/testrepo:latest

Then visit: http://localhost:3000

You'll get a JSON response confirming the service is running.

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🏗️ How It Works

Dockerfile
    │
    ▼
docker build → Local Image
    │
    ▼
docker push → Docker Hub (kuhata/testrepo:latest)
    │
    ▼
docker pull + run → Container running on port 3000

The app is a lightweight Node.js + Express server. Docker packages it with all its dependencies into a portable image that runs identically on any machine — no "works on my machine" issues.

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🛠️ Tech Stack

Layer	Tool
Runtime	Node.js + Express
Containerization	Docker
Image Registry	Docker Hub
Port	3000
Image Size	55.9 MB

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📁 Project Structure

dockerized-backend/
├── index.js          # Express server — main app entry point
├── dockerfile        # Docker build instructions
├── .dockerignore     # Excludes node_modules and other files from image
├── package.json      # Node.js dependencies
└── package-lock.json

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🔍 Dockerfile Explained

# Use official Node.js base image
FROM node:18-alpine

# Set working directory inside container
WORKDIR /app

# Copy dependency files first (layer caching optimization)
COPY package*.json ./

# Install dependencies
RUN npm install

# Copy rest of the source code
COPY . .

# Expose the port the app runs on
EXPOSE 3000

# Start the app
CMD ["node", "index.js"]

Why alpine? The Alpine-based Node image is significantly smaller than the default, keeping the final image lean.

Why copy package.json before source code? Docker caches each layer — by copying dependencies first, npm install only re-runs when dependencies actually change, not on every code change. This speeds up builds.

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🔑 Key Docker Concepts Demonstrated

.dockerignore — Prevents node_modules/ from being copied into the image. The image installs its own clean dependencies via npm install, keeping the build reproducible and avoiding OS-incompatible binaries from the host machine.

Port mapping (-p 3000:3000) — Maps port 3000 on your local machine to port 3000 inside the container. Format is host:container.

Image tagging — The image is tagged as kuhata/testrepo:latest, following the Docker Hub naming convention of username/repository:tag.

Public registry — Published to Docker Hub so the image can be pulled and run by anyone on any machine without needing the source code.

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📋 Full Command Reference

# Build the image locally
docker build -t kuhata/testrepo:latest .

# Run the container
docker run -p 3000:3000 kuhata/testrepo:latest

# Run in detached (background) mode
docker run -d -p 3000:3000 kuhata/testrepo:latest

# List running containers
docker ps

# Stop a running container
docker stop <container-id>

# Push to Docker Hub (requires docker login)
docker login
docker push kuhata/testrepo:latest

# Pull from Docker Hub
docker pull kuhata/testrepo:latest

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🔜 What's Next

• Add a docker-compose.yml to orchestrate the app with a MongoDB container
• Set up GitHub Actions to auto-build and push the image on every commit (CI/CD)
• Deploy the container on AWS EC2 instead of a raw Node.js process
• Add multi-stage builds to further reduce image size

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🔗 Related Projects

• Node.js AWS EC2 Deployment — Deployed Node.js on EC2 with Nginx + PM2
• Weather App — Live frontend on Vercel

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👤 Author

Harsh Thakur LinkedIn · GitHub · Docker Hub