Project 01: Flask + PostgreSQL + Nginx

A 3-tier containerized web application demonstrating core DevOps practices.

Architecture

Browser → Nginx (80) → Flask (5000) → PostgreSQL (5432)
  Proxy      Web App        Database

Quick Start

# Clone the repo
git clone https://github.com/zeroxin2003/project-01-flask-docker.git
cd project-01-flask-docker

# Start all services
docker compose up -d --build

# Visit http://localhost

What's Included

Component	Tech	Purpose
Reverse Proxy	Nginx Alpine	SSL termination, load balancing ready
Web App	Flask 3.1 + Python 3.12	Application logic
Database	PostgreSQL 16 Alpine	Persistent data storage
Orchestration	Docker Compose	Multi-container management

Key Features

• Health checks on all 3 services with proper startup ordering
• Persistent data via named Docker volume (db_data)
• Nginx reverse proxy hides internal Flask port from external access
• Environment variables for database configuration (no hardcoded secrets)
• Layer-optimized Dockerfile (requirements.txt copied before code for cache efficiency)

Useful Commands

# Start services
docker compose up -d --build

# Check service status and health
docker compose ps

# View logs
docker compose logs -f

# Stop and remove containers (data preserved)
docker compose down

# Stop and remove containers + data
docker compose down -v

# Restart a single service
docker compose restart web

DevOps Concepts Demonstrated

1. Containerization — Each service runs in its own isolated container
2. Docker Compose networking — Services communicate by service name
3. Volume persistence — Database survives container restarts
4. Reverse proxy pattern — Nginx as single entry point
5. Health checks — depends_on with condition: service_healthy ensures correct startup order
6. Layer caching — Dockerfile copies requirements.txt before source code
7. Environment-based config — Database credentials via environment variables

Project Structure

├── app.py                  # Flask application
├── requirements.txt        # Python dependencies
├── Dockerfile              # Flask container build
├── docker-compose.yml      # Multi-service orchestration
├── nginx/
│   └── default.conf        # Nginx reverse proxy config
├── .dockerignore
└── .gitignore