Flask + Redis Docker App

This is a simple multi-container application built with Flask and Redis, fully dockerized. Page visits are counted are stored using the Redis database connected with the Flask service.

• What it does:
  • / -> Displays a welcome message.
  • /count -> Displays the number of visits using Redis as a key-value store.

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Demo

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Features

• Simple visit counter using Redis
• Multi-container setup with Docker Compose
• Fully containerised, can run anywhere Docker is installed

Stack

• Python 3.8 + Flask
• Redis
• Docker / Docker Compose

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Project Structure

my-flask-redis-docker-app/
│
├── app.py           # Flask app, defines routes and Redis logic
├── requirements.txt # Python dependencies
├── Dockerfile       # Defines Flask container setup
├── docker-compose.yml # Defines multi-container setup with Flask + Redis
└── README.md 

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Setup Instructions

1. Clone the repo:

git clone <repo-url>
cd my-flask-redis-docker-app

2. Build and run the containers:

docker compose up --build

3. Access the app:

• Open your web browser:
  • Welcome page -> http://localhost:5000
  • Count page -> http://localhost:5000/count

4. Stop the app:

docker compose down

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Environment Variables

To make the app more production-ready in other environments without changing the code, we use environment variables.

In the docker-compose.yml file:

environment:
    - REDIS_HOST=redis
    - REDIS_PORT=6379

The Flask app reads these in app.py:

import os
from redis import Redis

redis_host = os.getenv('REDIS_HOST', 'redis')
redis_port = int(os.getenv('REDIS_PORT', 6379))
redis = Redis(host=redis_host, port=redis_port)

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Challenges faced:

• Issue: Initially tried using a multi-stage Dockerfile to keep images lean, but ran into COPY --from=build issues that caused Flask not to find the files.
• Solution: Fixed the copy order which fixed the problem, but reverted back to a single-stage Dockerfile since the project is small and the extra complexity was not needed.

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