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LiteCDN – Quick-Start Guide

📁 Project Structure

LiteCDN/
├── backend/
│   ├── config.js              # Shared port/URL configuration
│   ├── origin/
│   │   ├── origin.js          # Origin Server (port 4000)
│   │   └── static/            # Static files served by Origin
│   │       ├── hello.txt
│   │       ├── data.json
│   │       └── sample.txt
│   ├── edge/
│   │   └── edge.js            # Edge Server (ports 3001-3003)
│   └── cdn/
│       ├── cdn.js             # CDN Gateway / Router (port 3000)
│       └── routing.js         # Round-Robin RoutingService
├── frontend/
│   └── index.html             # Browser-based test dashboard
├── scripts/
│   └── startAll.js            # One-command launcher for all servers
├── package.json
├── GUIDE.md                   # ← You are here
└── README.md

⚙️ Prerequisites

  • Node.js ≥ 16
  • npm (comes with Node.js)

🚀 Installation

cd LiteCDN
npm install

▶️ Starting the Servers

Option A – Start everything at once

npm run start:all

This launches the Origin Server, three Edge Servers, and the CDN Gateway in one terminal.

Option B – Start each server individually (separate terminals)

Open 5 terminals, all in the LiteCDN folder:

# Terminal 1 – Origin Server (port 4000)
npm run start:origin

# Terminal 2 – Edge Server 1 (port 3001)
npm run start:edge1

# Terminal 3 – Edge Server 2 (port 3002)
npm run start:edge2

# Terminal 4 – Edge Server 3 (port 3003)
npm run start:edge3

# Terminal 5 – CDN Gateway (port 3000)
npm run start:cdn

🧪 Testing the Flow

Using curl

# First request → CACHE MISS (fetches from Origin, caches at Edge)
curl -i http://localhost:3000/cdn/content/hello.txt

# Second request → may be CACHE HIT (if routed to the same edge)
curl -i http://localhost:3000/cdn/content/hello.txt

# Third request → will go to the next edge (round-robin)
curl -i http://localhost:3000/cdn/content/hello.txt

# Fetch JSON data
curl -i http://localhost:3000/cdn/content/data.json

# Fetch dynamic mock API data
curl -i http://localhost:3000/cdn/mock/api

Using PowerShell (Invoke-RestMethod)

Invoke-RestMethod http://localhost:3000/cdn/content/hello.txt
Invoke-RestMethod http://localhost:3000/cdn/content/data.json

Using the Browser Dashboard

Open frontend/index.html in a browser, select a resource, and click "Fetch via CDN". The dashboard shows the cache status (HIT/MISS), the Edge Server that handled the request, and the response time.

🔍 Useful Debug Endpoints

Endpoint Description
http://localhost:3000/health CDN Gateway health
http://localhost:3000/status Routing info & edge list
http://localhost:3001/health Edge-1 health + cache size
http://localhost:3001/cache Edge-1 cached keys
http://localhost:4000/health Origin Server health

📊 Expected Console Output

When you run curl http://localhost:3000/cdn/content/hello.txt, the terminal logs will show:

[CDNSystem]  📥  Request received: GET /cdn/content/hello.txt
[RoutingService] 🔀 Round-Robin → selected Edge-1 (http://localhost:3001)
[CDNSystem]  🔀 Routed to Edge-1 (http://localhost:3001)
[CDNSystem]  ➡️  Forwarding to: http://localhost:3001/fetch/content/hello.txt

[Edge-1] 📥  GET /fetch/content/hello.txt
[Edge-1] ❌ CACHE MISS → "/content/hello.txt"
[Edge-1] 🔄 Fetching from Origin: http://localhost:4000/content/hello.txt

[OriginServer] 📥  GET /content/hello.txt

[Edge-1] 💾 Stored in cache: "/content/hello.txt"
[CDNSystem] ✅  Response from Edge-1 | Cache: MISS

A second request to the same edge will show:

[Edge-1] ⚡ CACHE HIT → "/content/hello.txt"

📝 Scope

Requirement Status
CDNSystem accepts HTTP requests ✅
Round-Robin routing to Edge Servers ✅
Request forwarding to selected Edge ✅
Basic in-memory cache (Map) ✅
Cache hit → serve from cache ✅
Cache miss → fetch from Origin ✅
Return origin content to client ✅
Store fetched content in cache ✅
Console logging at each step ✅