Course 31 - Dive Into Docker | Episode 6: A Hands-On Guide to Dockerizing Web Applications

In this lesson, you’ll learn about: dockerizing a web app, writing Dockerfiles, and optimizing builds1. The Application Architecture (Real-World Example)

This lab uses a simple microservices setup:
- Flask web application (frontend/API)
- Redis (backend datastore)
Key idea:
- Each service runs in its own container
- They communicate over a Docker network

👉 This mirrors real production systems (microservices architecture)2. Writing a Dockerfile from ScratchA Dockerfile is the blueprint for building an image in Docker.🧱 FROM — Base ImageFROM python:2.7-alpine

Uses an official image
Alpine = very small size → faster builds & less storage

⚙️ RUN — Execute CommandsRUN mkdir /app

Runs shell commands inside the image
Typically used for:
- Installing dependencies
- Preparing the environment

📁 WORKDIR — Set Working DirectoryWORKDIR /app

Defines where commands will run
Avoids hardcoding full paths everywhere

📦 COPY — Add Files to ImageCOPY . .

Copies your application code into the container
Includes:
- Source code
- Requirements file

3. Build Optimization (Layer Caching)

Docker builds images in layers
Order of instructions matters a lot

✅ Optimized Approach:COPY requirements.txt . RUN pip install -r requirements.txt COPY . .

Why?
- Dependencies don’t change often
- Docker caches this layer
- Rebuilds become much faster

4. Metadata with LABELLABEL maintainer="[email protected]"

Adds useful metadata:
- Author
- Version
- Description

👉 Helpful for team environments and production tracking5. Running the Application with CMDCMD ["python", "app.py"]

Defines the default command when the container starts
In this case:
- Launches the Flask app on port 5000

6. How Everything Works Together

Build the image:docker build -t myapp .
Run the container:docker run -p 5000:5000 myapp
Access app:
- Open browser → localhost:5000

7. Key Concepts You Just Learned

How to dockerize a real application
Core Dockerfile instructions:
- FROM, RUN, WORKDIR, COPY, LABEL, CMD
How layer caching speeds up builds
How services like Flask + Redis work together in containers

Key Takeaways

Dockerfile = reproducible build recipe
Instruction order = performance optimization
Containers isolate services cleanly
This workflow is used in:
- DevOps
- CI/CD
- Cloud deployments

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Course 31 - Dive Into Docker | Episode 6: A Hands-On Guide to Dockerizing Web Applications

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