🛒 E-Commerce Microservices Application

Linux → Docker → Docker Compose (Production & Interview Ready)

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📌 Project Objective

This project is built to learn and demonstrate real DevOps practices starting from:

• Linux basics
• Docker fundamentals
• Docker multi-stage builds
• Docker Compose orchestration
• Persistent volumes
• Environment variables
• Microservices architecture
• API Gateway pattern

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🧠 Architecture Overview (3-Tier)

User Browser ↓ Frontend (React served by Nginx) ↓ API Gateway (Nginx) ↓ Backend Microservices (Auth - Node.js | Product - Python | Order - Node.js) ↓ PostgreSQL Database (Persistent Volume)

📁 Project Directory Structure

ecommerce-devops-project/ │ ├── docker-compose.yml ├── .env ├── .gitignore ├── README.md │ ├── frontend/ │ ├── Dockerfile │ ├── package.json │ └── src/App.js │ ├── gateway/ │ ├── Dockerfile │ └── nginx.conf │ ├── services/ │ ├── auth-service/ │ │ ├── Dockerfile │ │ └── index.js │ │ │ ├── product-service/ │ │ ├── Dockerfile │ │ └── app.py │ │ │ └── order-service/ │ ├── Dockerfile │ └── index.js │ └── database/ └── init.sql

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🐧 PART 1 — LINUX BASICS (FOUNDATION)

Essential Linux Commands (Interview Must)

Command	Purpose
ls	List files
pwd	Current directory
cd	Change directory
mkdir	Create directory
touch	Create file
rm -rf	Delete file/folder
cat	View file
nano / vim	Edit file
chmod	Change permissions
chown	Change ownership
ps -ef	Running processes
top / htop	Resource usage
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA	df -h
�OA�OA�OA�OA�OA	free -m
�OA�OA�OA�OA�OA
�OA�OA�OA�OA�OA�OA---

�OA�OA�OA�OA�OA�OA# 🐳 PART 2 — DOCKER INSTALLATION (LINUX) �OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OB�OB�OB�OB�OB

sudo apt update && sudo apt upgrade -y
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OAsudo apt install docker.io -y
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OAsudo systemctl start docker
sudo systemctl enable docker
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OAdocker --version

�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OARun Docker without sudo

sudo usermod -aG docker $USER
newgrp docker

�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA
�OA�OA�OA�OA�OA⸻

�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA🐳 PART 3 — DOCKER CORE COMMANDS (INTERVIEW GOLD)
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA
Images
�OA�OA�OA�OA�OA
docker images
docker build -t image-name .
docker rmi image-id
�OA�OA�OA�OA�OA�OA
Containers
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA
docker ps
�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OA�OAdocker ps -a
�OAdocker run -d -p 8080:80 image
docker stop container
�OA�OA�OA�OA�OA�OA�OAdocker rm container

�OADebugging

�OAdocker logs container
�OAdocker exec -it container sh


⸻

🐳 PART 4 — DOCKERFILE (MULTI-STAGE BUILD)


	•	Smaller image size
	•	Faster deployment
	•	No dev dependencies in production
	•	Best practice in real projects

Example (Frontend)

FROM node:18-alpine AS build
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=build /app/build /usr/share/nginx/html

Explanation

Line	Meaning
FROM	Base image
AS build	Build stage
WORKDIR	Container directory
COPY	Copy files
RUN	Execute commands
--from=build	Copy from build stage


⸻

🐳 PART 5 — DOCKER COMPOSE (ORCHESTRATION)


	•	Run multiple containers together
	•	Single command startup
	•	Automatic networking
	•	Service-name based communication

⸻

docker-compose.yml (Core Concepts)

version: "3.9"

services:

  frontend:
    build: ./frontend
    ports:
      - "3000:80"
    depends_on:
      - gateway

Explanation
	•	services → All containers
	•	build → Dockerfile location
	•	ports → Host:Container mapping
	•	depends_on → Startup order

⸻


  product-service:
    build: ./services/product-service
    depends_on:
      - db

👉 Product service waits for database.

⸻


  db:
    image: postgres:15
    env_file:
      - .env
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./database/init.sql:/docker-entrypoint-initdb.d/init.sql

 Volumes
	•	Data persistence
	•	Containers can be deleted safely
	•	Mandatory in production

⸻


volumes:
  postgres_data:


⸻

Docker Compose Commands

docker-compose up
docker-compose up --build
docker-compose down
docker-compose down -v
docker-compose ps
docker-compose logs


⸻

🔐 PART 6 — ENVIRONMENT VARIABLES

.env file

POSTGRES_USER=admin
POSTGRES_PASSWORD=admin123
POSTGRES_DB=ecommerce

Why .env?
	•	No secrets in code
	•	Easy configuration
	•	Industry best practice

⸻

🗃️ PART 7 — DATABASE INITIALIZATION

init.sql

CREATE TABLE products (
  id SERIAL PRIMARY KEY,
  name TEXT
);

INSERT INTO products (name)
VALUES ('Laptop'), ('Mobile'), ('Headphones');


⸻

🧪 PART 8 — TESTING

Check	URL
Frontend	http://localhost:3000
Products API	http://localhost/products
Docker Volume	docker volume ls


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🧠 HOW TO EXPLAIN IN INTERVIEW

“I built a 3-tier microservices e-commerce application using Docker and Docker Compose.
I used multi-stage Dockerfiles for optimization, Docker Compose for orchestration, persistent volumes for database data, environment variables for secrets, and an API Gateway for routing.”