Simple Docker Project - Containerized Web App

Overview

This project demonstrates how to containerize a simple web application using Docker. We’ll create a basic Python Flask app and package it with Docker, including a Dockerfile and docker-compose configuration for easy deployment.

Project Structure

docker-project/
├── app/
│   ├── app.py
│   └── requirements.txt
├── Dockerfile
├── docker-compose.yml
└── README.md

Application Code

app/app.py

A simple Flask web application:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return '<h1>Hello from Docker!</h1><p>This app is running inside a container.</p>'

@app.route('/health')
def health():
    return {'status': 'healthy'}, 200

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

app/requirements.txt

Flask==3.0.0

Dockerfile

Create a Dockerfile in the project root:

# Use Python 3.11 slim image as base
FROM python:3.11-slim

# Set working directory
WORKDIR /app

# Copy requirements first for better caching
COPY app/requirements.txt .

# Install dependencies
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY app/ .

# Expose port 5000
EXPOSE 5000

# Run the application
CMD ["python", "app.py"]

Docker Compose

Create docker-compose.yml for easier management:

version: '3.8'

services:
  web:
    build: .
    ports:
      - "5000:5000"
    volumes:
      - ./app:/app
    environment:
      - FLASK_ENV=development
    restart: unless-stopped

Usage

Build and Run with Docker

# Build the image
docker build -t docker-web-app .

# Run the container
docker run -d -p 5000:5000 --name web-app docker-web-app

# Check if it's running
docker ps

# View logs
docker logs web-app

# Stop and remove
docker stop web-app
docker rm web-app

Using Docker Compose

# Build and start services
docker-compose up -d

# View logs
docker-compose logs -f

# Stop services
docker-compose down

# Rebuild after changes
docker-compose up -d --build

Testing

Once the container is running, test the application:

# Test main endpoint
curl http://localhost:5000

# Test health endpoint
curl http://localhost:5000/health

Or open http://localhost:5000 in your browser.

Key Docker Concepts Demonstrated

• Base Images: Using official Python image
• Layer Caching: Copying requirements.txt before app code for better build caching
• Port Mapping: Exposing container port 5000 to host
• Volume Mounting: Using volumes for development (hot reload)
• Multi-stage Builds: Can be extended for production optimization

Next Steps

• Add a database service (PostgreSQL/MySQL) to docker-compose.yml
• Implement multi-stage builds for smaller production images
• Add health checks and resource limits
• Set up CI/CD pipeline for automated builds
• Use Docker networks for service communication

Resources

• Docker Documentation
• Docker Compose Documentation
• Flask Documentation