Layer caching and ordering in Docker - Mini Project: Build & Apply

Layer caching and ordering

📖 Scenario: You are building a Docker image for a simple web application. Efficient layer caching can speed up your build times when you make changes.

🎯 Goal: Learn how to order Dockerfile instructions to maximize layer caching and reduce build time.

📋 What You'll Learn

Create a Dockerfile with a base image

Add a working directory

Copy application files

Install dependencies

Run the application

💡 Why This Matters

🌍 Real World

Efficient Docker builds save time and resources during development and deployment.

💼 Career

Understanding layer caching is essential for DevOps roles to optimize CI/CD pipelines and container builds.

1

Create the base image and working directory

Write a Dockerfile that starts with the base image python:3.12-slim and sets the working directory to /app using WORKDIR.

Docker

# Your code here

Need a hint?

Use FROM to specify the base image and WORKDIR to set the working directory.

2

Add a requirements file and copy it

Add a line to copy the file requirements.txt from your local directory to the image's /app directory using COPY.

Docker

FROM python:3.12-slim
WORKDIR /app
# Your code here

Need a hint?

Use COPY requirements.txt /app/ to copy the requirements file.

3

Install dependencies before copying app files

Add a line to install dependencies by running pip install -r requirements.txt using RUN. Then copy the rest of the application files from the local directory to /app using COPY . /app/. This order helps caching.

Docker

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt /app/
# Your code here

Need a hint?

Install dependencies before copying app files to use Docker cache efficiently.

4

Set the command to run the app

Add a CMD instruction to run the application with python app.py.

Docker

FROM python:3.12-slim
WORKDIR /app
COPY requirements.txt /app/
RUN pip install -r requirements.txt
COPY . /app/
# Your code here

Need a hint?

Use CMD ["python", "app.py"] to run the app when the container starts.