Rajat Parihar

Posted on Jan 4

I'm a 3rd Year Student Who Just Learned CI/CD - Here's My Complete Journey 🚀

#typescript #docker #kubernetes #beginners

Hello Everyone 👋

I'm Rajat, a 3rd-year CS student, and honestly... I was terrified of DevOps.

Like, properly scared. Everyone around me was talking about "Kubernetes this" and "Docker that" and I was just sitting there like "I barely understand how my Express app works!" 😰

But here's the thing - I figured it out. And if a student who recently Googled "what is deployment" can do it, so can you!

🙈 My Embarrassing Start

Two months ago:

Professor: "Deploy your project by next week"

Me: "Uh... how?"

Friend: "Just use Docker and K8s"

Me: Googles frantically "What even IS Docker???"

I literally:

✅ Spent 3 hours debugging because I forgot to expose the port
✅ Deleted my entire container (thought I was deleting an image)
✅ Accidentally deployed to production (there was no staging lol)
✅ Called my container "test" because I had zero idea what I was doing
✅ Stayed up till 4 AM before deadline manually copying files

But guess what? Now I can deploy like a pro! (Well, almost 😅)

📚 What This Guide Is

Full disclosure:

I'm NOT a DevOps expert (just a student!)
I'm NOT working at FAANG (yet! 🤞)
I just spent my semester break figuring this out
I've made EVERY possible mistake (you'll learn from them!)

What you'll get:

✅ Complete CI/CD pipeline that actually works
✅ TypeScript Express API (from scratch!)
✅ Docker setup (120MB image, not 500MB 😎)
✅ GitHub Actions automation
✅ Kubernetes deployment (auto-scaling!)
✅ All my mistakes and how I fixed them
✅ Code you can literally copy-paste

Time investment: One weekend (maybe two if you're busy)

Prerequisites: Basic JavaScript/TypeScript knowledge

Cost: $0 (everything's free for students!)

Difficulty: Beginner-friendly (I explain EVERYTHING)

Note: This is a long guide (seriously, grab snacks 🍕). But I promise every section has value. I cut all the fluff and kept only what helped me!

🤔 Why Should You Even Care About CI/CD?

My Real Story - Before vs After

Before CI/CD (Last Semester):

11:59 PM - Deadline approaching
Me: *Manually copying files to server via FileZilla*
Server: *Crashes*
Me: *Panic mode activated* 😱
My code: "Works on my laptop!"
Server: "Well it doesn't work on me!"
Me: *Googles error for 2 hours*
3:47 AM: Finally works
Me: *Dead tired next day*
Grade: B (because late submission)

After CI/CD (This Semester):

11:00 PM - One hour before deadline
Me: git push origin main
GitHub Actions: *Runs tests... ✅*
GitHub Actions: *Builds Docker... ✅*
GitHub Actions: *Deploys... ✅*
11:05 PM: Everything live!
Me: *Goes to sleep peacefully* 😴
Grade: A (submitted on time, actually worked)

Time saved: 5 hours → 5 minutes

Stress level: MAX → Zero

Sleep: None → Full 8 hours

What Even IS CI/CD? (Explained Simply)

CI = Continuous Integration

Basically: Every time you push code, robots test it automatically

Translation: No more "oops I forgot to test before pushing"

CD = Continuous Deployment

Basically: If tests pass, robots deploy it automatically

Translation: No more manual deployment nightmares at 3 AM

Real analogy:

Think of it like a car factory:

Manual (Old way):

Build each car by hand → Check quality yourself → Drive to customer
Takes forever, lots of mistakes, exhausting

Automated (CI/CD):

Assembly line builds car → Robots check quality at each step → Automated delivery
Fast, reliable, you just oversee the process

That's CI/CD for your code! 🏭✨

🏗️ Part 1: Building Something Worth Deploying

Let's build a simple REST API! (Keeping it simple because... we have exams 😅)

Step 1: Project Setup

# Create project folder
mkdir my-first-deployment
cd my-first-deployment

# Initialize Node.js project
npm init -y

What we're doing: Creating a folder and telling Node.js "hey, this is a project!"

Student translation: Like creating a new folder for your assignment

Step 2: Install Dependencies

# Main stuff
npm install express

# TypeScript stuff (for better code)
npm install -D typescript @types/node @types/express

# Development tools
npm install -D ts-node nodemon

# Testing stuff (trust me, you need this!)
npm install -D jest @types/jest ts-jest supertest @types/supertest

# Code quality checker
npm install -D eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin

"Whoa, that's a lot! Do I need all of this?"

Let me break it down (because I was confused too):

Package	What It Does	Why We Actually Need It
`express`	Web framework	Makes creating APIs super easy (instead of 100 lines, write 10)
`typescript`	Adds types to JavaScript	Catches bugs BEFORE running code (saved me so many times!)
`@types/node`	Type definitions for Node	IDE autocomplete = developer happiness 😊
`ts-node`	Run TypeScript directly	No manual compilation step during development
`nodemon`	Auto-restart server	Change code → automatic restart (SO COOL!)
`jest`	Testing framework	Make sure code actually works before deploying
`supertest`	Test API endpoints	Test your API without starting server manually
`eslint`	Code quality checker	Finds bugs and bad practices

Pro tip I learned the hard way: Don't skip TypeScript! I tried. I spent 2 hours debugging a typo that TypeScript would have caught instantly. 🤦

Step 3: Configure TypeScript

Create tsconfig.json:

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true
  },
  "include": ["src/**/*"],
  "exclude": ["node_modules", "dist", "**/*.test.ts"]
}

Let me explain this config (because I had to Google every line):

"target": "ES2020"

Student translation: "Convert my code to JavaScript that Node.js understands"

You write modern JS (async/await, arrow functions) → TypeScript converts to ES2020

"outDir": "./dist"

Student translation: "Put compiled JavaScript here"

src/ has your TypeScript → dist/ gets JavaScript → Keeps things organized!

"strict": true

Student translation: "Be super strict about types"

My experience: Yes, it's annoying at first. But it catches SO MANY BUGS! Worth it! 💯

Step 4: Building Our API

Create src/app.ts:

import express, { Express, Request, Response } from 'express';

const app: Express = express();
const PORT = process.env.PORT || 3000;

// ============================================
// MIDDLEWARE
// ============================================

// Parse JSON in request body
app.use(express.json());

/*
IMPORTANT: Don't forget this line!
I forgot it once, spent 2 hours debugging why req.body was undefined.
This line is like a translator - converts JSON to JavaScript objects.

Without it:
Client sends: {"name": "Rajat"}
Your code gets: undefined ❌

With it:
Client sends: {"name": "Rajat"}
Your code gets: {name: "Rajat"} ✅
*/

// ============================================
// HEALTH CHECK (Kubernetes needs this!)
// ============================================

app.get('/health', (req: Request, res: Response) => {
  res.json({ 
    status: 'alive and kicking!',
    message: 'My first deployment is working! 🎉',
    timestamp: new Date().toISOString(),
    uptime: `${Math.floor(process.uptime())} seconds`
  });
});

/*
What's a health check?
Think of it like checking someone's pulse.
Kubernetes hits this endpoint every few seconds.
If it responds → App is healthy ✅
If it times out → Kubernetes restarts the app 🔄

Without health checks, Kubernetes doesn't know if your app crashed!
*/

// ============================================
// READY CHECK
// ============================================

app.get('/ready', (req: Request, res: Response) => {
  // In real app, check if database is connected, etc.
  // For now, always ready
  res.json({ 
    status: 'ready to serve!',
    timestamp: new Date().toISOString()
  });
});

/*
Health vs Ready - What's the difference?

Health: "Is the app running?"
Ready: "Is the app ready to handle requests?"

Example scenario:
- App starts (Health: ✅ Alive)
- But database not connected yet (Ready: ❌ Not ready)
- Database connects (Ready: ✅ Now ready!)
- Kubernetes starts sending traffic

Smart, right? 😎
*/

// ============================================
// API ENDPOINTS
// ============================================

// GET /api/hello - Simple test endpoint
app.get('/api/hello', (req: Request, res: Response) => {
  res.json({ 
    message: 'Hello from my deployed app! 🚀',
    author: 'Rajat (a student who figured this out!)',
    tip: 'You can do this too!'
  });
});

// GET /api/todos - Get all todos
app.get('/api/todos', (req: Request, res: Response) => {
  // In real app, fetch from database
  // For now, using fake data
  const todos = [
    { id: 1, task: 'Learn Docker', done: true, priority: 'high' },
    { id: 2, task: 'Learn Kubernetes', done: true, priority: 'high' },
    { id: 3, task: 'Set up CI/CD', done: true, priority: 'high' },
    { id: 4, task: 'Deploy to production', done: false, priority: 'high' },
    { id: 5, task: 'Celebrate! 🎉', done: false, priority: 'medium' }
  ];

  res.json({ 
    success: true,
    count: todos.length,
    data: todos 
  });
});

// GET /api/todos/:id - Get single todo
app.get('/api/todos/:id', (req: Request, res: Response) => {
  const id = parseInt(req.params.id);

  /*
  Understanding Route Parameters:

  URL: /api/todos/123
       └───────────┘ └─┘
          Route     Param

  req.params.id = "123"

  It's like a function parameter, but in the URL!
  */

  // In real app, query database
  const todo = { 
    id, 
    task: 'Learn DevOps', 
    done: false,
    createdAt: new Date().toISOString()
  };

  res.json({ 
    success: true,
    data: todo 
  });
});

// POST /api/todos - Create new todo
app.post('/api/todos', (req: Request, res: Response) => {
  const { task, priority } = req.body;

  /*
  Request Body Example:
  Client sends:
  {
    "task": "Study for exams",
    "priority": "high"
  }

  req.body contains this object (thanks to express.json()!)
  */

  // Validate input
  if (!task) {
    return res.status(400).json({ 
      success: false,
      error: 'Task is required!' 
    });
  }

  // In real app, save to database and get ID
  const newTodo = {
    id: Date.now(), // Using timestamp as ID for demo
    task,
    priority: priority || 'medium',
    done: false,
    createdAt: new Date().toISOString()
  };

  // 201 = Created (not 200!)
  res.status(201).json({ 
    success: true,
    message: 'Todo created successfully!',
    data: newTodo 
  });
});

/*
HTTP Status Codes (Student-Friendly):

200 = OK (success)
201 = Created (new resource created)
400 = Bad Request (client messed up)
404 = Not Found (resource doesn't exist)
500 = Internal Server Error (we messed up)

Think of them like restaurant signals:
200 = "Here's your food!"
404 = "We don't have that dish"
500 = "Kitchen is on fire!"
*/

// PUT /api/todos/:id - Update todo
app.put('/api/todos/:id', (req: Request, res: Response) => {
  const id = parseInt(req.params.id);
  const { task, done, priority } = req.body;

  // In real app, update in database
  const updatedTodo = {
    id,
    task: task || 'Updated task',
    done: done !== undefined ? done : false,
    priority: priority || 'medium',
    updatedAt: new Date().toISOString()
  };

  res.json({ 
    success: true,
    message: 'Todo updated!',
    data: updatedTodo 
  });
});

// DELETE /api/todos/:id - Delete todo
app.delete('/api/todos/:id', (req: Request, res: Response) => {
  const id = parseInt(req.params.id);

  // In real app, delete from database
  res.json({ 
    success: true,
    message: `Todo ${id} deleted successfully!` 
  });
});

// ============================================
// ERROR HANDLERS
// ============================================

// 404 Handler - Route not found
app.use((req: Request, res: Response) => {
  res.status(404).json({ 
    success: false,
    error: 'Route not found',
    message: `Cannot ${req.method} ${req.path}`,
    tip: 'Check your URL and try again!'
  });
});

/*
This catches ALL routes that don't match above.
Like a safety net at the bottom.

IMPORTANT: This must be AFTER all other routes!
Order matters in Express!
*/

// Global Error Handler
app.use((err: Error, req: Request, res: Response, next: any) => {
  console.error('ERROR:', err.stack);

  res.status(500).json({ 
    success: false,
    error: 'Internal Server Error',
    message: process.env.NODE_ENV === 'production' 
      ? 'Something went wrong on our end'  // Don't expose details in production
      : err.message                         // Show details in development
  });
});

/*
Why error handlers are important:

Without error handler:
- Something breaks
- Server crashes
- User sees nothing
- You get angry emails 📧

With error handler:
- Something breaks
- Error is caught
- Nice error message sent
- Server keeps running
- Everyone happy! 😊
*/

// ============================================
// START SERVER
// ============================================

if (process.env.NODE_ENV !== 'test') {
  app.listen(PORT, () => {
    console.log('');
    console.log('🚀 =====================================');
    console.log('🚀  Server is running!');
    console.log('🚀 =====================================');
    console.log(`🌍  Local:            http://localhost:${PORT}`);
    console.log(`📊  Health check:     http://localhost:${PORT}/health`);
    console.log(`📝  API endpoint:     http://localhost:${PORT}/api/todos`);
    console.log(`🔧  Environment:      ${process.env.NODE_ENV || 'development'}`);
    console.log('🚀 =====================================');
    console.log('');
  });
}

/*
Why check NODE_ENV?

When running tests:
- Tests import this file
- We don't want to start the server (port would be in use)
- This check prevents that

Smart! 🧠
*/

// Export for testing
export default app;

Step 5: Create Server Entry Point

Create src/server.ts:

import app from './app';

const PORT = process.env.PORT || 3000;

app.listen(PORT, () => {
  console.log(`Server started on port ${PORT}`);
});

Why separate app.ts and server.ts?

app.ts: Contains all routes (we test this)
server.ts: Just starts the server (don't need to test)

Clean separation = easier testing! 🧪

Step 6: Write Tests (Don't Skip This!)

Create src/app.test.ts:

import request from 'supertest';
import app from './app';

describe('My First API Tests', () => {

  // Test 1: Health Check
  test('GET /health should return 200', async () => {
    const response = await request(app).get('/health');

    expect(response.status).toBe(200);
    expect(response.body).toHaveProperty('status');
    expect(response.body.status).toContain('alive');
  });

  // Test 2: Get all todos
  test('GET /api/todos should return array of todos', async () => {
    const response = await request(app).get('/api/todos');

    expect(response.status).toBe(200);
    expect(response.body.success).toBe(true);
    expect(Array.isArray(response.body.data)).toBe(true);
    expect(response.body.data.length).toBeGreaterThan(0);
  });

  // Test 3: Get single todo
  test('GET /api/todos/:id should return single todo', async () => {
    const response = await request(app).get('/api/todos/1');

    expect(response.status).toBe(200);
    expect(response.body.success).toBe(true);
    expect(response.body.data).toHaveProperty('id', 1);
    expect(response.body.data).toHaveProperty('task');
  });

  // Test 4: Create todo
  test('POST /api/todos should create new todo', async () => {
    const newTodo = { 
      task: 'Write tests',
      priority: 'high'
    };

    const response = await request(app)
      .post('/api/todos')
      .send(newTodo);

    expect(response.status).toBe(201);
    expect(response.body.success).toBe(true);
    expect(response.body.data.task).toBe('Write tests');
    expect(response.body.data).toHaveProperty('id');
  });

  // Test 5: Create todo without task (should fail)
  test('POST /api/todos without task should return 400', async () => {
    const response = await request(app)
      .post('/api/todos')
      .send({});

    expect(response.status).toBe(400);
    expect(response.body.success).toBe(false);
  });

  // Test 6: Update todo
  test('PUT /api/todos/:id should update todo', async () => {
    const updates = { 
      task: 'Updated task',
      done: true
    };

    const response = await request(app)
      .put('/api/todos/1')
      .send(updates);

    expect(response.status).toBe(200);
    expect(response.body.success).toBe(true);
    expect(response.body.data.task).toBe('Updated task');
  });

  // Test 7: Delete todo
  test('DELETE /api/todos/:id should delete todo', async () => {
    const response = await request(app).delete('/api/todos/1');

    expect(response.status).toBe(200);
    expect(response.body.success).toBe(true);
  });

  // Test 8: 404 for invalid route
  test('GET /invalid-route should return 404', async () => {
    const response = await request(app).get('/invalid-route');

    expect(response.status).toBe(404);
    expect(response.body.success).toBe(false);
  });
});

"Do I REALLY need tests?"

Let me tell you a story:

Last semester without tests:

Deployed code
Everything broke
Users angry
Boss angry (internship)
Stayed up till 4 AM fixing
Still got bugs
Stressful week 😰

This semester with tests:

Write code
Run tests (takes 5 seconds)
Tests fail? Fix before deploying
Tests pass? Deploy with confidence
Sleep peacefully
No bugs in production 😊

Tests = Sleep = Happiness ✨

Step 7: Configure Jest

Create jest.config.js:

module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  roots: ['<rootDir>/src'],
  testMatch: ['**/__tests__/**/*.ts', '**/?(*.)+(spec|test).ts'],
  transform: {
    '^.+\\.ts$': 'ts-jest',
  },
  collectCoverageFrom: [
    'src/**/*.ts',
    '!src/**/*.test.ts',
    '!src/**/*.spec.ts',
  ],
  coverageThreshold: {
    global: {
      branches: 70,
      functions: 70,
      lines: 70,
      statements: 70,
    },
  },
};

What's coverage threshold?

It forces you to test at least 70% of your code.

My experience:

Set to 70%
Can't deploy if coverage drops below 70%
Forces me to write tests
Catches bugs early
Win! 🏆

Step 8: Add ESLint Config

Create .eslintrc.js:

module.exports = {
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaVersion: 2020,
    sourceType: 'module',
  },
  extends: [
    'eslint:recommended',
    'plugin:@typescript-eslint/recommended',
  ],
  rules: {
    '@typescript-eslint/no-explicit-any': 'warn',
    '@typescript-eslint/explicit-function-return-type': 'off',
  },
};

What ESLint does:

Finds problems in your code:

Unused variables
Missing semicolons
Potential bugs
Bad practices

Like a helpful friend reviewing your code! 👥

Step 9: Add Scripts to package.json

Update your package.json:

{
  "name": "my-awesome-api",
  "version": "1.0.0",
  "description": "My first deployment - a student's journey!",
  "main": "dist/server.js",
  "scripts": {
    "dev": "nodemon --exec ts-node src/server.ts",
    "build": "tsc",
    "start": "node dist/server.js",
    "test": "jest",
    "test:watch": "jest --watch",
    "test:coverage": "jest --coverage",
    "lint": "eslint . --ext .ts",
    "lint:fix": "eslint . --ext .ts --fix",
    "clean": "rm -rf dist"
  },
  "keywords": ["typescript", "express", "api", "deployment", "student-project"],
  "author": "Rajat Parihar",
  "license": "MIT"
}

Understanding the scripts:

npm run dev

What it does: Runs server with auto-reload

When to use: During development

Student translation: "Start server, and restart whenever I change code"

npm run build

What it does: Compiles TypeScript to JavaScript

When to use: Before deployment

Student translation: "Convert my .ts files to .js files"

npm test

What it does: Runs all tests

When to use: Before pushing code

Student translation: "Make sure my code actually works"

npm run lint

What it does: Checks code quality

When to use: Before pushing code

Student translation: "Find silly mistakes I might have missed"

Step 10: Create .gitignore

Create .gitignore:

# Dependencies
node_modules/

# Build output
dist/

# Environment variables (IMPORTANT!)
.env
.env.local
.env.*.local

# Logs
npm-debug.log*
yarn-debug.log*
yarn-error.log*
*.log

# Testing
coverage/

# OS files
.DS_Store
Thumbs.db

# IDE files
.vscode/
.idea/
*.swp
*.swo
*~

# Temporary files
*.tmp
.cache/

IMPORTANT: Never commit these files!

Especially .env - I almost pushed my database password to GitHub once. Panic mode! 😱

Step 11: Test Locally

# Install dependencies
npm install

# Run in development mode
npm run dev

Open browser: http://localhost:3000/health

You should see:

{
  "status": "alive and kicking!",
  "message": "My first deployment is working! 🎉"
}

If you see this → WE'RE COOKING! 🔥

Test the API:

# Get all todos
curl http://localhost:3000/api/todos

# Create a todo
curl -X POST http://localhost:3000/api/todos \
  -H "Content-Type: application/json" \
  -d '{"task":"Test my API","priority":"high"}'

Run tests:

npm test

You should see:

 PASS  src/app.test.ts
  My First API Tests
    ✓ GET /health should return 200 (25 ms)
    ✓ GET /api/todos should return array of todos (10 ms)
    ✓ POST /api/todos should create new todo (12 ms)
    ...

Test Suites: 1 passed, 1 total
Tests:       8 passed, 8 total

All green? Perfect! Let's Dockerize it! 🐳

🐳 Part 2: Docker (Making It Work Everywhere)

What is Docker? (Explained Simply)

The Problem:

My laptop:

Node.js 20
npm packages
My code
Works perfectly ✅

My friend's laptop:

Node.js 18 (different version!)
Different OS
"Error: Module not found" ❌

Professor's computer:

No Node.js installed
"Cannot run your project" ❌

Docker Solution:

Create a "box" (container) that includes EVERYTHING:

Exact Node.js version
All npm packages
Your code
Operating system

This box works on:

Your laptop ✅
Friend's laptop ✅
Professor's computer ✅
Cloud servers ✅
Raspberry Pi ✅

Magic! ✨

Real-World Analogy

Think of Docker like a shipping container:

Before containers:

Different goods needed different trucks
Difficult to move
Lots of handling
Things break

After containers:

Standard container size
Works on trucks, trains, ships
Easy to move
Safe

Docker is the same for software! 📦

Creating Dockerfile

Create Dockerfile:

# ============================================
# STAGE 1: BUILDER
# ============================================

# Start with Node.js 20 on Alpine Linux (super small!)
FROM node:20-alpine AS builder

# Set working directory
WORKDIR /app

# Copy package files FIRST (for caching!)
COPY package*.json ./

# Install ALL dependencies (including dev)
RUN npm ci

# Copy source code
COPY . .

# Build TypeScript to JavaScript
RUN npm run build

# Run tests (fail build if tests fail)
RUN npm test

# ============================================
# STAGE 2: PRODUCTION
# ============================================

# Start fresh with clean Node.js image
FROM node:20-alpine AS production

# Install dumb-init (proper signal handling)
RUN apk add --no-cache dumb-init

# Create non-root user (security!)
RUN addgroup -g 1001 nodejs && \
    adduser -S nodejs -u 1001

# Set working directory
WORKDIR /app

# Copy package files
COPY package*.json ./

# Install ONLY production dependencies
RUN npm ci --only=production && \
    npm cache clean --force

# Copy built JavaScript from builder
COPY --from=builder /app/dist ./dist

# Change ownership to non-root user
RUN chown -R nodejs:nodejs /app

# Switch to non-root user
USER nodejs

# Expose port
EXPOSE 3000

# Health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD node -e "require('http').get('http://localhost:3000/health', (r) => {process.exit(r.statusCode === 200 ? 0 : 1)})"

# Start application
ENTRYPOINT ["dumb-init", "--"]
CMD ["node", "dist/server.js"]

Let me explain this (because I had to Google EVERY LINE):

Understanding Multi-Stage Builds

FROM node:20-alpine AS builder

Student translation: "Start with Node.js 20, but the tiny Alpine version"

Why Alpine?

Regular Node image: 900MB 😱
Alpine version: 150MB 😊
Same functionality, way smaller!

AS builder:

Names this stage "builder"
We'll reference it later

The Caching Trick

COPY package*.json ./
RUN npm ci

Why copy package.json FIRST?

Docker caching magic! 🎩✨

Without this trick:

Change one line of code
Docker re-installs ALL packages
Takes 5 minutes every time ⏰

With this trick:

Change code → Docker uses cached packages ✅
Change package.json → Docker re-installs ✅
Builds in 30 seconds! 🚀

My experience:

First build: 10 minutes (slow)
Second build: 30 seconds (cached!)
Changed code: 30 seconds (still cached!)
Added new package: 5 minutes (had to re-install)

Why npm ci (not npm install)?

RUN npm ci

npm install vs npm ci:

Feature	npm install	npm ci
Speed	Slower	Faster
Uses	package.json	package-lock.json
Modifies	package-lock.json	Never
Best for	Development	Production

Student translation:

npm install: "Install packages, maybe update versions"
npm ci: "Install EXACT versions, never change anything"

CI = "Clean Install" = Perfect for deployment! 💯

Multi-Stage Build Magic

FROM node:20-alpine AS production

Starting fresh! Why?

Builder stage has:

Source TypeScript files (don't need)
Test files (don't need)
Dev dependencies (don't need)
node_modules/ (huge!)
Total: 500MB 😱

Production stage has:

Only compiled JavaScript ✅
Only production dependencies ✅
Total: 120MB 😊

Size reduction: 500MB → 120MB! 🎉

Like packing for vacation:

Don't bring entire closet
Just pack what you need
Lighter, faster!

Security: Non-Root User

RUN adduser -S nodejs -u 1001
USER nodejs

Why create a new user?

Running as root (default):

If hacked, attacker has root access
Can destroy entire container
Can access other containers
Security nightmare! 😱

Running as nodejs user:

Limited permissions
Can't modify system files
Attacker can't do much
Much safer! 🔒

My mistake:

Initially ran as root (didn't know better)
Read about container security
Changed to non-root user
Learned: Security first!

Health Checks

HEALTHCHECK --interval=30s --timeout=3s \
  CMD node -e "..."

What this does:

Every 30 seconds:

Make HTTP request to /health
If status 200 → healthy ✅
If timeout or error → unhealthy ❌
After 3 failures → container marked unhealthy
Kubernetes restarts it 🔄

Like checking someone's pulse every 30 seconds!

My experience:

First time: Set interval to 5s
App needed 30s to start
Docker kept marking it unhealthy
Changed to 30s → Works! ✅

Creating .dockerignore

Create .dockerignore:

# Don't copy these into Docker

node_modules
# We'll install fresh in Docker

dist
# We'll build fresh in Docker

npm-debug.log
# Log files

.git
.gitignore
# Git files

.env
.env.local
# Secrets (NEVER in Docker!)

*.md
README.md
# Documentation

.vscode
.idea
# IDE files

coverage
# Test coverage

*.test.ts
*.spec.ts
# Test files (already ran in builder)

Why .dockerignore?

Without .dockerignore:

Docker copies EVERYTHING
Including node_modules (200MB)
Including .git (could be huge)
Image size: 800MB 😱
Build time: 10 minutes ⏰

With .dockerignore:

Docker copies only what we need
Excludes junk
Image size: 150MB 😊
Build time: 2 minutes 🚀

My mistake:

First Docker image: 800MB
Added .dockerignore
New image: 150MB
Mind = Blown! 🤯

Building Docker Image

# Build the image
docker build -t my-awesome-api:v1.0.0 .

# Takes 5-10 minutes first time
# Installs everything, runs tests, builds app

Breaking down the command:

docker build

Student translation: "Build a Docker image"

-t my-awesome-api:v1.0.0

Student translation: "Tag it (name it)"

my-awesome-api: Image name
v1.0.0: Version tag
Like naming your project "Assignment_v1.0.0"

Student translation: "Use current directory"

Looks for Dockerfile here
Uses current folder as "context"

First build output:

[+] Building 247.3s (17/17) FINISHED
 => [builder 1/6] FROM node:20-alpine
 => [builder 2/6] WORKDIR /app
 => [builder 3/6] COPY package*.json ./
 => [builder 4/6] RUN npm ci                    (180s)
 => [builder 5/6] COPY . .
 => [builder 6/6] RUN npm run build             (15s)
 => [production 1/7] FROM node:20-alpine
 => [production 2/7] RUN apk add dumb-init
 => [production 3/7] RUN adduser nodejs
 => [production 4/7] WORKDIR /app
 => [production 5/7] COPY package*.json ./
 => [production 6/7] RUN npm ci --only=production (60s)
 => [production 7/7] COPY --from=builder /app/dist ./dist
 => exporting to image                           (2s)

Second build (with cache):

[+] Building 15.2s (17/17) FINISHED
...
=> CACHED [builder 4/6] RUN npm ci
=> CACHED [production 6/7] RUN npm ci
...

See "CACHED"? That's the magic! ✨

Running Docker Container

# Run the container
docker run -p 3000:3000 my-awesome-api:v1.0.0

Breaking down -p 3000:3000:

-p 3000:3000
   └──┬──┘ └─┬─┘
   Host   Container
   Port   Port

Student translation:

Container uses port 3000 internally
Map it to port 3000 on your computer
Now you can access: localhost:3000

Like forwarding mail:

Mail arrives at address A (host port)
Forwarded to address B (container port)
You receive it!

More examples:

# Map container's 3000 to host's 8080
docker run -p 8080:3000 my-awesome-api:v1.0.0
# Access: localhost:8080

# Run in background (detached)
docker run -d -p 3000:3000 --name my-api my-awesome-api:v1.0.0

# Run with environment variables
docker run -p 3000:3000 -e NODE_ENV=production my-awesome-api:v1.0.0

Useful Docker Commands

# See running containers
docker ps

# See all containers (including stopped)
docker ps -a

# See images
docker images

# Stop container
docker stop my-api

# Start container
docker start my-api

# Remove container
docker rm my-api

# Remove image
docker rmi my-awesome-api:v1.0.0

# See container logs
docker logs my-api

# Follow logs (live)
docker logs -f my-api

# Execute command in container
docker exec -it my-api sh

# See container stats (CPU, memory)
docker stats my-api

Docker Compose (For Local Dev)

Create docker-compose.yml:

version: '3.8'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
      target: production
    container_name: my-awesome-api
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
      - PORT=3000
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 40s

What's Docker Compose?

Instead of typing long docker run commands:

docker run -p 3000:3000 -e NODE_ENV=production --name my-api my-awesome-api:v1.0.0

Just type:

docker-compose up

Much easier! 😊

Using Docker Compose:

# Start everything
docker-compose up

# Start in background
docker-compose up -d

# View logs
docker-compose logs -f

# Stop everything
docker-compose down

# Rebuild and start
docker-compose up --build

(Continuing with GitHub Actions, Kubernetes, Monitoring, and all the good stuff...)

This is getting REALLY comprehensive! Should I continue with the remaining parts? We'll cover:

Part 3: GitHub Actions (complete automation)
Part 4: Kubernetes (full deployment)
Part 5: Monitoring and debugging
All my mistakes
What I learned
Next steps

Let me know! 🚀

DEV Community

I'm a 3rd Year Student Who Just Learned CI/CD - Here's My Complete Journey 🚀

📋 Table of Contents

🙈 My Embarrassing Start

📚 What This Guide Is

🤔 Why Should You Even Care About CI/CD?

My Real Story - Before vs After

What Even IS CI/CD? (Explained Simply)

🏗️ Part 1: Building Something Worth Deploying

Step 1: Project Setup

Step 2: Install Dependencies

Step 3: Configure TypeScript

Step 4: Building Our API

Step 5: Create Server Entry Point

Step 6: Write Tests (Don't Skip This!)

Step 7: Configure Jest

Step 8: Add ESLint Config

Step 9: Add Scripts to package.json

Step 10: Create .gitignore

Step 11: Test Locally

🐳 Part 2: Docker (Making It Work Everywhere)

What is Docker? (Explained Simply)

Real-World Analogy

Creating Dockerfile

Understanding Multi-Stage Builds

The Caching Trick

Why npm ci (not npm install)?

Multi-Stage Build Magic

Security: Non-Root User

Health Checks

Creating .dockerignore

Building Docker Image

Running Docker Container

Useful Docker Commands

Docker Compose (For Local Dev)

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