3. Docker and Docker Compose | Engineering Notes

🧠 Docker & Docker Compose

I use Docker to containerize applications and Docker Compose to manage multiple services together in a development or deployment environment.

🎯 Simple Idea

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Docker → package one application/service
Docker Compose → run multiple services together

Example:

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Laravel App
 ↓
Docker Container

Laravel + MySQL + Redis + Nginx
 ↓
Docker Compose

🧩 Docker

Docker helps package an application with its required environment.

Used for:

PHP / Node.js runtime

application dependencies

consistent local environment

easier deployment

Example:

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FROM php:8.3-fpm

WORKDIR /var/www

COPY . .

RUN composer install

👉 The app runs the same way across different machines.

🧩 Docker Compose

Docker Compose is used to run multiple containers together.

Example services:

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app
nginx
mysql
redis
queue

Example:

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services:
  app:
    build: .
    container_name: laravel_app

  mysql:
    image: mysql:8.0
    environment:
      MYSQL_DATABASE: app_db
      MYSQL_ROOT_PASSWORD: secret

  redis:
    image: redis:alpine

👉 Instead of starting containers one by one, I can run all services together.

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docker compose up-d

📌 Flow

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Dockerfile
 ↓
Build image
 ↓
Create container
 ↓
Run application

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docker-compose.yml
 ↓
Define multiple services
 ↓
Run app + database + cache together

🧠 Why I Use Docker

consistent environment across team members

avoids “works on my machine” issues

easier dependency management

faster onboarding for developers

useful for local development and deployment

⚖️ Trade-offs

requires Docker knowledge

configuration can be complex for large systems

volume, network, and permission issues can happen

containers need proper security and resource management

📌 Practical Rule

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Docker → containerize one service
Docker Compose → manage multiple services together

Example:

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Laravel only → Docker
Laravel + MySQL + Redis + Nginx → Docker Compose

💬 Summary

I use Docker and Docker Compose to create consistent, portable, and production-friendly application environments.

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Application
→ Docker Image
→ Container
→ Docker Compose Services

👉 This makes development, testing, and deployment more reliable and scalable.