🚀 Load Balancer Project – NGINX + Docker + Round Robin + Canary + Weighted Rollout

This project demonstrates real-world load balancing behavior using NGINX, Docker, and multiple backend microservices.
You will learn how modern systems gradually roll out features, balance traffic efficiently, and prevent outages using traffic weights, canary releases, sticky routing, and circuit-breaker principles.

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🔥 Features Implemented

Functionality	Status
Round Robin Load Balancing	✔
Weighted Load Balancing (90/10 Canary)	✔
Sticky Session Routing	✔
Canary Release Simulation	✔
Circuit Breaker Failure Handling	✔
Auto Canary Monitoring Script	✔

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📂 Project Structure

LoadBalancer-Project/ │ ├── backend1/ # Stable Version (Blue) │ ├── server.js │ └── Dockerfile │ ├── backend2/ # Canary Version (Green) │ ├── server.js │ └── Dockerfile │ ├── nginx.conf # NGINX Load Balancer Configuration ├── docker-compose.yaml # Runs all services ├── canary-monitor.js # Health Test Script └── README.md # Documentation

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🖥 Backend Services

backend1/server.js

const express = require("express"); const app = express(); app.get("/", (req, res) => res.send("⚡ Backend 1 - Stable OK")); app.listen(3001, () => console.log("Backend1 running on port 3001"));

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backend2/server.js

const express = require("express"); const app = express(); app.get("/", (req, res) => res.send("🌱 Backend 2 - Canary OK")); app.listen(3002, () => console.log("Backend2 running on port 3002"));

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🐳 Docker Configuration

Shared Dockerfile (inside each backend folder)

FROM node:18 WORKDIR /app COPY server.js . RUN npm install express EXPOSE 3001 # backend2 uses 3002 CMD ["node","server.js"]

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⚙ docker-compose.yaml

services: backend1: build: ./backend1 ports: ["3001:3001"]

backend2: build: ./backend2 ports: ["3002:3002"]

nginx: image: nginx ports: ["8080:8080"] depends_on: [backend1, backend2] volumes: - ./nginx.conf:/etc/nginx/nginx.conf:ro

Run project:

docker-compose up --build

Visit:

http://localhost:8080

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🌐 NGINX Load Balancer (90% Blue / 10% Green)

http { upstream backend_servers { server backend1:3001 weight=9; # 90% server backend2:3002 weight=1; # 10% Canary }

server {
    listen 8080;
    location / {
        proxy_pass http://backend_servers;
    }
}

}

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🔁 Testing Load Balancer

for i in {1..20}; do curl -s localhost:8080; echo ""; done

Expected Output:

⚡ Backend1 ⚡ Backend1 🌱 Backend2 ← Canary Hit ⚡ Backend1 🌱 Backend2

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📌 Sticky Sessions (IP Hash)

upstream backend_servers { ip_hash; server backend1:3001; server backend2:3002; }

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🛑 Circuit Breaker Behavior Test

docker stop System self-heals using only backend1.

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📊 Canary Monitoring Script

const { execSync } = require("child_process"); let success=0, fail=0;

for(let i=0;i<200;i++){ try{ execSync("curl -s localhost:8080"); success++; } catch{ fail++; } }

console.log(Total: ${success+fail} Success: ${success} Failures: ${fail});

Run:

node canary-monitor.js

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🎯 Summary

Concept	Status
Round Robin LB	✔
Weighted Canary	✔
Sticky Sessions	✔
Circuit Breaker	✔
Real Deployment Simulation	✔

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