My first basic loadBalancer

files/README.md

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+### Documentatie Stack Node.js + Docker + Docker Compose + Nginx
+
+---
+
+# 1. Structura proiect
+
+```
+project/
+│
+├── Dockerfile             # imaginea Node.js
+├── docker-compose.yml     # orchestration containere + Nginx
+├── nginx.conf             # configuratie Nginx
+├── server.js              # cod Node.js
+├── package.json
+└── index.html             # pagina servita de Node
+```
+
+Stack-ul include:
+
+* Node.js – aplicatie stateless
+* 3 containere Node, fiecare cu INSTANCE_NAME
+* Nginx – reverse proxy si load balancer
+* Docker Compose – orchestrare containere + retea
+
+---
+
+# 2. Node.js
+
+## 2.1 server.js
+
+```js
+const express = require('express');
+const path = require('path');
+
+const instanceName = process.env.INSTANCE_NAME || 'unknown';
+
+const app = express();
+const port = 3000;
+
+app.get('/', (req, res) => {
+    console.log(`[${instanceName}] Request received`);
+    res.sendFile(path.join(__dirname, 'index.html'));
+});
+
+app.listen(port, () => {
+    console.log(`[${instanceName}] Node app listening on port ${port}`);
+});
+```
+
+Explicatii:
+
+* `process.env.INSTANCE_NAME` pentru identificarea containerului
+* Stateless design – aplicatia nu stie cate instante exista
+* Log-urile arata care container a servit request-ul
+* Servește `index.html`
+
+## 2.2 package.json
+
+```json
+{
+  "name": "node-app",
+  "version": "1.0.0",
+  "scripts": {
+    "start": "node server.js"
+  },
+  "dependencies": {
+    "express": "^4.17.1"
+  }
+}
+```
+
+---
+
+# 3. Dockerfile
+
+```dockerfile
+FROM node:18-alpine
+
+WORKDIR /app
+
+COPY package*.json .
+RUN npm install
+
+COPY index.html .
+COPY server.js .
+
+EXPOSE 3000
+
+CMD ["node", "server.js"]
+```
+
+Explicatii:
+
+* Imagine oficiala Node minimală
+* COPY package*.json pentru caching optim
+* EXPOSE 3000 – port intern container
+* CMD – comanda de start
+
+---
+
+# 4. Docker Compose
+
+```yaml
+version: "3.9"
+
+services:
+  app-1:
+    image: node-app:v1
+    ports:
+      - "3001:3000"
+    networks:
+      - app-network
+    environment:
+      - INSTANCE_NAME=app-1
+
+  app-2:
+    image: node-app:v1
+    ports:
+      - "3002:3000"
+    networks:
+      - app-network
+    environment:
+      - INSTANCE_NAME=app-2
+
+  app-3:
+    image: node-app:v1
+    ports:
+      - "3003:3000"
+    networks:
+      - app-network
+    environment:
+      - INSTANCE_NAME=app-3
+
+  nginx:
+    image: nginx:alpine
+    volumes:
+      - ./nginx.conf:/etc/nginx/nginx.conf:ro
+    depends_on:
+      - app-1
+      - app-2
+      - app-3
+    ports:
+      - "80:80"
+    networks:
+      - app-network
+
+networks:
+  app-network:
+```
+
+Explicatii:
+
+* 3 servicii Node identice, fiecare pe port intern 3000
+* Nginx ascultă pe port 80 și face proxy la Node
+* `depends_on` pentru startup order
+* retea comuna
+
+---
+
+# 5. Nginx Configuration (nginx.conf)
+
+```nginx
+events {}
+
+http {
+    upstream backend {
+        server app-1:3000;
+        server app-2:3000;
+        server app-3:3000;
+    }
+
+    server {
+        listen 80;
+
+        location / {
+            proxy_pass http://backend;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+        }
+    }
+}
+```
+
+Explicatii:
+
+* `upstream backend` = grup backend-uri Node pentru load balancing
+* `proxy_pass http://backend;` trimite request-ul la unul din backends
+* Header-ele ajuta Node sa stie IP-ul real
+* Nginx foloseste portul intern 3000
+
+---
+
+# 6. Workflow
+
+1. Build Node.js:
+
+```bash
+docker build -t node-app:v1 .
+```
+
+2. Pornire Compose:
+
+```bash
+docker-compose up -d
+```
+
+3. Verificare log-uri:
+
+```bash
+docker-compose logs -f
+```
+
+4. Test load balancing:
+
+* [http://localhost](http://localhost)
+* Refresh repetat → request-urile distribuite între app-1, app-2, app-3
+
+---

files/nginx.conf

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+events {
+    worker_connections 1024;
+}
+
+http {
+    upstream backend {
+        server app-1:3001;
+        server app-2:3002;
+        server app-3:3003;
+    }
+
+
+    server {
+        listen 80;
+
+        location / {
+            proxy_pass http://backend;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+        }
+    }
+}

files/package.json

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+{
+"name": "node-app",
+"version": "1.0.0",
+"scripts": {
+"start": "node server.js"
+},
+"dependencies": {
+"express": "^4.17.1"
+}
+}

files/server.js

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+const express = require('express');
+const path = require('path');
+
+
+const instanceName = process.env.INSTANCE_NAME || 'unknown';
+
+
+const app = express();
+const port = 3000;
+
+
+app.get('/', (req, res) => {
+console.log(`[${instanceName}] Request received`);
+res.sendFile(path.join(__dirname, 'index.html'));
+});
+
+
+app.listen(port, () => {
+console.log(`[${instanceName}] Node app listening on port ${port}`);
+});