Building a Flask Application with Docker Compose

Table of Contents

  1. Introduction
  2. Prerequisites
  3. Overview
  4. Step 1: Setting Up Flask
  5. Step 2: Creating a Dockerfile
  6. Step 3: Creating a Docker Compose File
  7. Step 4: Building and Running the Flask Application
  8. Conclusion

Introduction

In this tutorial, we will learn how to build a Flask application using Docker Compose. Flask is a popular web framework for Python, and Docker Compose is a tool for defining and running multi-container Docker applications. By the end of this tutorial, you will have a basic understanding of how to use Docker Compose to set up a Flask application.

Prerequisites

Before starting this tutorial, you should have the following:

  1. Basic knowledge of Python programming.
  2. Docker installed on your machine.
  3. Familiarity with command-line tools.

Overview

Here are the main steps we will follow in this tutorial:

  1. Set up a Flask application.
  2. Create a Dockerfile to define the Docker image for our Flask application.
  3. Create a Docker Compose file to define and configure our application’s services.
  4. Build and run the Flask application with Docker Compose.

Now, let’s dive into the details of each step.

Step 1: Setting Up Flask

To begin, we need to set up a basic Flask application. Follow the steps below:

  1. Create a new directory for your project: 
    $ mkdir flask-docker
$ cd flask-docker
  2. Initialize a new virtual environment and activate it: 
    $ python3 -m venv venv
$ source venv/bin/activate
  3. Install Flask: 
    (venv) $ pip install Flask
  4. Create a new file called app.py and add the following code: 
    from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return "Hello, Flask!"

if __name__ == '__main__':
    app.run(debug=True, host='0.0.0.0')
  5. Save the file and exit the text editor.

Congratulations! You have set up a basic Flask application.

Step 2: Creating a Dockerfile

Now, we will create a Dockerfile to define the Docker image for our Flask application. Follow the steps below:

  1. Create a new file called Dockerfile in the project directory.

  2. Open the Dockerfile in a text editor and add the following lines: 
    # Use the official Python base image
FROM python:3.9-slim-buster
   
# Set the working directory in the container
WORKDIR /app
   
# Copy the dependencies file to the working directory
COPY requirements.txt .
   
# Install the dependencies
RUN pip install --no-cache-dir -r requirements.txt
   
# Copy the content of the current directory to the working directory
COPY . .
   
# Specify the command to run the flask application
CMD [ "python", "app.py" ]
  3. Save the file and exit the text editor.

We have now created a Dockerfile that will be used to build the Docker image for our Flask application.

Step 3: Creating a Docker Compose File

Next, we will create a Docker Compose file to define and configure our application’s services. Follow the steps below:

  1. Create a new file called docker-compose.yml in the project directory.

  2. Open the docker-compose.yml file in a text editor and add the following lines: 
    version: '3'
services:
  web:
    build: .
    ports:
      - 5000:5000
  3. Save the file and exit the text editor.

We have now created a Docker Compose file that will define and configure our application’s services.

Step 4: Building and Running the Flask Application

In this final step, we will build and run the Flask application using Docker Compose. Follow the steps below:

  1. Open a command-line interface and navigate to the project directory.

  2. Run the following command to build the Docker image: 
    $ docker-compose build
  3. Once the build process is complete, run the following command to start the Flask application: 
    $ docker-compose up
  4. You should see output indicating that the Flask application is running. Open a web browser and navigate to http://localhost:5000 to access the application.

Congratulations! You have successfully built and run the Flask application using Docker Compose.

Conclusion

In this tutorial, we learned how to build a Flask application using Docker Compose. We started by setting up a basic Flask application, then created a Dockerfile to define the Docker image for our application. We then created a Docker Compose file to define and configure our application’s services. Finally, we built and ran the Flask application using Docker Compose.

Using Docker Compose allows us to easily containerize and manage our application’s services, making it convenient for development and deployment. Flask and Docker Compose are powerful tools that can help simplify the process of building and deploying web applications.

Feel free to explore more advanced features of Flask and Docker Compose to further enhance your application or customize your development environment.

Published:

Related Articles