Notes App — Docker Assignment

What the application does

A simple Notes web application where users can create, view, and delete short text notes. Notes are stored persistently in a PostgreSQL database. The app is accessible via a web browser.

Services

Container	Image	Port	Description
app_frontend	custom (Nginx)	8080→80	Serves the static HTML/JS frontend and proxies /api/ requests to the backend
app_backend	custom (Flask/Python)	internal 5000	REST API for CRUD operations on notes
app_db	postgres:16-alpine	internal 5432	Relational database storing notes persistently
app_adminer	adminer:4	8081→8080	Web UI for browsing and managing the PostgreSQL database

Networks

Network	Purpose
frontend_net	Connects the Nginx frontend container (externally reachable)
backend_net	Internal network connecting frontend→backend→database and Adminer→database

The database is only on backend_net and is never directly exposed to the host.

Volumes

Volume	Used by	Purpose
postgres_data	app_db	Persists PostgreSQL data across container restarts and stops

Container configuration

• app_db: configured via environment variables (POSTGRES_DB, POSTGRES_USER, POSTGRES_PASSWORD). The db/init.sql file is mounted read-only into /docker-entrypoint-initdb.d/ and runs once on first startup to create the notes table and insert seed data.
• app_backend: receives DATABASE_URL as an environment variable pointing to the db service. Built from ./backend/Dockerfile using Python 3.12-slim with Flask and psycopg2.
• app_frontend: built from ./frontend/Dockerfile using Nginx 1.27-alpine. The custom nginx.conf proxies all /api/ requests to app_backend:5000 and serves index.html for all other paths.
• app_adminer: uses the official Adminer image with no extra configuration. Reachable on port 8081.
• All containers use restart: on-failure.

Requirements

• Linux OS
• Docker Engine ≥ 24 with the Compose plugin (docker compose)

Instructions

Prepare (build images)

./prepare-app.sh

Start

./start-app.sh

Stop (data is preserved)

./stop-app.sh

Remove everything

./remove-app.sh

Viewing the application

URL	Description
http://localhost:8080	Notes web application
http://localhost:8081	Adminer — log in with Server: db, User: appuser, Password: apppassword, Database: appdb

Example workflow

./prepare-app.sh
# Preparing app...

./start-app.sh
# Running app...
# The app is available at http://localhost:8080
# Adminer (DB UI) is available at http://localhost:8081

# Open browser, add/delete notes

./stop-app.sh
# Stopping app...
# App stopped. Data in volumes is preserved.

./start-app.sh
# Notes are still there — volume was preserved

./remove-app.sh
# Removing app.

Resources used

• Docker documentation
• Flask documentation
• Nginx documentation
• PostgreSQL Docker image
• Adminer Docker image

Use of artificial intelligence

This project was created with the assistance of Kiro AI (kiro-cli chat agent). The AI generated the initial structure of all files including the Docker Compose configuration, Flask application, Nginx configuration, frontend HTML/JS, and shell scripts. All generated code was reviewed and understood by the author. The AI was used as a coding assistant, not as a replacement for understanding the solution.