Flask App with MySQL Docker Setup

A small two-tier app: a Flask web app that stores messages in MySQL. Submit a message in the form; it is saved in the database and listed on the page.

Stack: Python 3.13, Flask 3.1, gunicorn, PyMySQL, MySQL 8.4.

Route	What it does
GET /	Lists all messages and shows which server answered
POST /submit	Saves new_message (form field), returns it as JSON
GET /health	Returns {"status":"ok"} (no database call), used by health checks

Prerequisites

• Docker with the Compose plugin (docker compose)
• Git (optional, for cloning the repository)

Run with Docker Compose

1. Clone and enter the repo:

   git clone https://github.com/LondheShubham153/two-tier-flask-app.git
   cd two-tier-flask-app

2. (Optional) set your own database credentials. Without a .env file the defaults in docker-compose.yml are used.

   cp .env.example .env   # then edit the passwords

3. Start everything:

   docker compose up --build

4. Open http://localhost:5000, send a few messages. The messages table is created automatically.

   On macOS, port 5000 may already be used by AirPlay Receiver. Turn it off in System Settings, or change the left side of "5000:5000" in docker-compose.yml.

5. Stop and remove the containers (-v also deletes the database volume):

   docker compose down        # keep data
   docker compose down -v     # delete data too

make build, make run, make stop, make test and make clean are shortcuts for the common commands.

Run without Docker Compose

1. Build the image and create a network:

   docker build -t flaskapp .
   docker network create twotier

2. Start MySQL:

   docker run -d \
       --name mysql \
       -v mysql-data:/var/lib/mysql \
       --network=twotier \
       -e MYSQL_DATABASE=mydb \
       -e MYSQL_ROOT_PASSWORD=admin \
       -p 3306:3306 \
       mysql:8.4

3. Start the app (wait a few seconds for MySQL to be ready first):

   docker run -d \
       --name flaskapp \
       --network=twotier \
       -e MYSQL_HOST=mysql \
       -e MYSQL_USER=root \
       -e MYSQL_PASSWORD=admin \
       -e MYSQL_DB=mydb \
       -p 5000:5000 \
       flaskapp:latest

Configuration

The app reads its database settings from environment variables:

Variable	Default
MYSQL_HOST	localhost
MYSQL_PORT	3306
MYSQL_USER	default_user
MYSQL_PASSWORD	default_password
MYSQL_DB	default_db
FLASK_DEBUG	off (1 enables debug when running python app.py)

Tests

pip install -r requirements-dev.txt
pytest

What's in the repo

Path	Purpose
Dockerfile, Dockerfile-multistage	Container images (the second shows the multi-stage pattern)
docker-compose.yml, Makefile	Local run
Jenkinsfile	CI/CD pipeline
beanstalk/	Run the app on AWS Elastic Beanstalk (compose file for Standard Mode, Docker Hub image plus RDS for Cluster Mode)
k8s/, eks-manifests/	Kubernetes manifests (kubeadm cluster / Amazon EKS)
aws/	Step-by-step guide to run this app on AWS: VPC, EC2, RDS, ALB, Auto Scaling, CloudWatch

Notes

• This is a demo setup. For production use real secrets management, TLS and backups.
• If something fails, check docker compose logs.