Mazen's blog

Docker for Beginners: Containerizing Your First Web Application

mazen sayyed's photo
mazen sayyed
·

3 min read

Project Title: Containerizing a Simple "Hello World" Web App with Docker.

People new to Docker and containerization concepts.

Project Description:

This project will guide readers through creating a simple "Hello World" web application using Python and Flask, and then containerizing it using Docker. The blog post will break down each step, explaining the commands and concepts involved.

Project Steps (and blog post sections):

  1. Setting up the Web Application (Python & Flask):

    • Create a simple Python file (e.g., app.py) with a Flask web application that displays "Hello, World!"

    • Show the code:

Python

    from flask import Flask

    app = Flask(__name__)

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

    if __name__ == "__main__":
        app.run(debug=True, host='0.0.0.0', port=5000) # Host and port important for Docker
  • Explain the code briefly. Highlight the host='0.0.0.0' and port=5000 which are crucial for container networking.

  1. Creating a Dockerfile:

    • Explain what a Dockerfile is and its purpose.

    • Show the Dockerfile content:

Dockerfile

    FROM python:3.9-slim-buster  # Use a slim Python image
    WORKDIR /app
    COPY requirements.txt .  # We'll create this next
    RUN pip install -r requirements.txt
    COPY . .
    EXPOSE 5000
    CMD ["python", "app.py"]

  • Explain each line:

    • FROM: Base image.

    • WORKDIR: Sets the working directory inside the container.

    • COPY requirements.txt .: Copies the requirements file.

    • RUN pip install: Installs dependencies.

    • COPY . .: Copies the application code.

    • EXPOSE: Exposes the port.

    • CMD: Command to run when the container starts.

  1. Creating requirements.txt:

    • Explain why a requirements.txt file is used.

    • Create the file with the Flask dependency:

    Flask

  1. Building the Docker Image:

    • Explain the docker build command.

    • Show the command: docker build -t hello-world-app .

    • Explain the -t flag for tagging the image.

  2. Running the Docker Container:

    • Explain the docker run command.

    • Show the command: docker run -p 5000:5000 hello-world-app

    • Explain the -p flag for port mapping (host:container). This is how you access the application from your host machine.

  3. Testing the Application:

  4. Cleaning Up (Optional):

    • Show how to stop and remove the container and image.

    • docker stop <container_id>

    • docker rm <container_id>

    • docker rmi hello-world-app

Blog Post Structure:

  • Introduction: Briefly explain Docker and its benefits.

  • Project Overview: Describe the "Hello World" web app project.

  • Step-by-step guide: Follow the steps outlined above, providing clear explanations and code snippets.

  • Conclusion: Summarize the key takeaways and encourage further exploration of Docker.

Key Considerations for the Blog Post:

  • Keep it simple: Avoid jargon and complex explanations.

  • Use clear and concise language: Make it easy for beginners to understand.

  • Include screenshots: Visual aids can be very helpful.

  • Provide troubleshooting tips: Anticipate common errors and provide solutions.

  • Encourage interaction: Ask readers to share their experiences and ask questions.

Dockerdocker imagesAWSLinuxcicdAzureHashnodeBloggingprojectsnginxPython