Multi-Container Docker Compose, nginx & postgres Project

This project demonstrates a multi-container application using Docker Compose, including a web application served by Nginx and a PostgreSQL database. The application, running in a Python Flask container, interacts with the PostgreSQL database. Nginx serves as a reverse proxy to the Flask application.

Prerequisites

• Docker
• Docker Compose

Setup

1. Clone the repository:

   git clone <repository_url>
   cd my_docker_compose_project

Build and run the containers:

docker-compose up --build

Access the web application at http://localhost.

Purpose and Actions of Each File

1. docker-compose.yml

Defines the multi-container setup:

• web:

  • Builds the application container from the app directory.
  • Sets the DATABASE_URL environment variable.
  • Maps port 5000 on the host to port 5000 in the container.

• nginx:

  • Builds the Nginx container from the nginx directory.
  • Maps port 80 on the host to port 80 in the container.
  • Forwards requests to the web service on port 5000.

• db:

  • Builds the PostgreSQL container from the postgres directory.
  • Sets environment variables for PostgreSQL (POSTGRES_USER, POSTGRES_PASSWORD, POSTGRES_DB).
  • Maps port 5432 on the host to port 5432 in the container.

2. nginx/Dockerfile

Builds the Nginx image:

• Uses the official Nginx image.
• Copies the Nginx configuration file and static HTML files into the container.

3. nginx/default.conf

Configures Nginx to proxy requests to the Flask application:

• Forwards requests from port 80 to the web service on port 5000.

4. nginx/html/index.html

A simple static HTML page served by Nginx:

• Displays a welcome message indicating that the application is connected to a PostgreSQL database.

5. app/Dockerfile

Builds the Flask application container:

• Uses the Python 3.9 slim image.
• Installs dependencies from requirements.txt.
• Runs the Flask application.

6. app/requirements.txt

Lists the Python packages needed for the application:

• flask for the web framework.
• psycopg2-binary for PostgreSQL database connectivity.

7. app/app.py

A simple Flask application:

• Connects to PostgreSQL using psycopg2.
• Exposes an endpoint that retrieves and returns data from the users table in PostgreSQL.

8. postgres/Dockerfile

Builds the PostgreSQL image:

• Uses the official PostgreSQL image.
• Copies the initialization SQL script into the container.

9. postgres/init.sql

Initial SQL script for PostgreSQL:

• Creates a users table.
• Inserts sample data into the table.

Conclusion

This project provides a practical example of using Docker Compose to set up a multi-container application with Nginx, a Flask application, and PostgreSQL. It demonstrates how to configure and connect these components in a development environment.

Summary

• Nginx: Serves as the reverse proxy for the Flask application.
• Flask App: Connects to the PostgreSQL database and provides an endpoint to retrieve data.
• PostgreSQL: Stores data and is initialized with a sample dataset.

License

This project is licensed under the MIT License.