🏗️ Microservices Architecture

// user-service/server.js const express = require('express'); const app = express(); app.use(express.json()); // In-memory database (use real DB in production) let users = []; // Health check endpoint app.get('/health', (req, res) => { res.json({ status: 'healthy', service: 'user-service' }); }); // Register user app.post('/api/users/register', (req, res) => { const { name, email, password } = req.body; // Check if user exists if (users.find(u => u.email === email)) { return res.status(400).json({ error: 'User already exists' }); } const newUser = { id: users.length + 1, name, email, password, // Hash in production! createdAt: new Date() }; users.push(newUser); res.status(201).json({ id: newUser.id, name, email }); }); // Get user by ID app.get('/api/users/:id', (req, res) => { const user = users.find(u => u.id === parseInt(req.params.id)); if (!user) { return res.status(404).json({ error: 'User not found' }); } // Don't send password const { password, ...userWithoutPassword } = user; res.json(userWithoutPassword); }); // Login app.post('/api/users/login', (req, res) => { const { email, password } = req.body; const user = users.find(u => u.email === email && u.password === password); if (!user) { return res.status(401).json({ error: 'Invalid credentials' }); } res.json({ message: 'Login successful', userId: user.id }); }); const PORT = process.env.PORT || 3001; app.listen(PORT, () => { console.log(`User Service running on port ${PORT}`); });

// product-service/server.js const express = require('express'); const app = express(); app.use(express.json()); let products = [ { id: 1, name: 'Laptop', price: 999, stock: 10 }, { id: 2, name: 'Phone', price: 699, stock: 25 } ]; // Health check app.get('/health', (req, res) => { res.json({ status: 'healthy', service: 'product-service' }); }); // Get all products app.get('/api/products', (req, res) => { res.json(products); }); // Get product by ID app.get('/api/products/:id', (req, res) => { const product = products.find(p => p.id === parseInt(req.params.id)); if (!product) { return res.status(404).json({ error: 'Product not found' }); } res.json(product); }); // Create product app.post('/api/products', (req, res) => { const { name, price, stock } = req.body; const newProduct = { id: products.length + 1, name, price, stock }; products.push(newProduct); res.status(201).json(newProduct); }); // Update stock (called by order service) app.patch('/api/products/:id/stock', (req, res) => { const product = products.find(p => p.id === parseInt(req.params.id)); if (!product) { return res.status(404).json({ error: 'Product not found' }); } const { quantity } = req.body; if (product.stock < quantity) { return res.status(400).json({ error: 'Insufficient stock' }); } product.stock -= quantity; res.json(product); }); const PORT = process.env.PORT || 3002; app.listen(PORT, () => { console.log(`Product Service running on port ${PORT}`); });

// order-service/server.js const express = require('express'); const axios = require('axios'); const app = express(); app.use(express.json()); let orders = []; const USER_SERVICE = 'http://localhost:3001'; const PRODUCT_SERVICE = 'http://localhost:3002'; // Health check app.get('/health', (req, res) => { res.json({ status: 'healthy', service: 'order-service' }); }); // Create order app.post('/api/orders', async (req, res) => { try { const { userId, productId, quantity } = req.body; // 1. Verify user exists const userResponse = await axios.get(`${USER_SERVICE}/api/users/${userId}`); const user = userResponse.data; // 2. Get product details const productResponse = await axios.get(`${PRODUCT_SERVICE}/api/products/${productId}`); const product = productResponse.data; // 3. Check stock and update await axios.patch(`${PRODUCT_SERVICE}/api/products/${productId}/stock`, { quantity }); // 4. Create order const newOrder = { id: orders.length + 1, userId, productId, quantity, totalPrice: product.price * quantity, status: 'pending', createdAt: new Date() }; orders.push(newOrder); res.status(201).json(newOrder); } catch (error) { console.error('Order creation failed:', error.message); res.status(500).json({ error: 'Failed to create order', details: error.response?.data || error.message }); } }); // Get user orders app.get('/api/orders/user/:userId', (req, res) => { const userOrders = orders.filter(o => o.userId === parseInt(req.params.userId)); res.json(userOrders); }); // Get order by ID app.get('/api/orders/:id', (req, res) => { const order = orders.find(o => o.id === parseInt(req.params.id)); if (!order) { return res.status(404).json({ error: 'Order not found' }); } res.json(order); }); const PORT = process.env.PORT || 3003; app.listen(PORT, () => { console.log(`Order Service running on port ${PORT}`); });

// api-gateway/server.js const express = require('express'); const { createProxyMiddleware } = require('http-proxy-middleware'); const app = express(); // Route requests to appropriate services app.use('/api/users', createProxyMiddleware({ target: 'http://localhost:3001', changeOrigin: true })); app.use('/api/products', createProxyMiddleware({ target: 'http://localhost:3002', changeOrigin: true })); app.use('/api/orders', createProxyMiddleware({ target: 'http://localhost:3003', changeOrigin: true })); // Health check for all services app.get('/health', async (req, res) => { const services = [ { name: 'user-service', url: 'http://localhost:3001/health' }, { name: 'product-service', url: 'http://localhost:3002/health' }, { name: 'order-service', url: 'http://localhost:3003/health' } ]; const healthChecks = await Promise.all( services.map(async (service) => { try { const response = await axios.get(service.url); return { ...service, status: 'healthy' }; } catch (error) { return { ...service, status: 'unhealthy' }; } }) ); res.json({ gateway: 'healthy', services: healthChecks }); }); const PORT = 3000; app.listen(PORT, () => { console.log(`API Gateway running on port ${PORT}`); });

// Install: npm install amqplib // Publisher (Order Service) const amqp = require('amqplib'); async function publishOrderCreated(orderData) { const connection = await amqp.connect('amqp://localhost'); const channel = await connection.createChannel(); const exchange = 'orders'; await channel.assertExchange(exchange, 'fanout', { durable: false }); const message = JSON.stringify(orderData); channel.publish(exchange, '', Buffer.from(message)); console.log('Order created event published:', orderData); setTimeout(() => { connection.close(); }, 500); } // Subscriber (Notification Service) async function subscribeToOrders() { const connection = await amqp.connect('amqp://localhost'); const channel = await connection.createChannel(); const exchange = 'orders'; await channel.assertExchange(exchange, 'fanout', { durable: false }); const q = await channel.assertQueue('', { exclusive: true }); channel.bindQueue(q.queue, exchange, ''); console.log('Waiting for order events...'); channel.consume(q.queue, (msg) => { const order = JSON.parse(msg.content.toString()); console.log('Received order:', order); // Send notification sendEmailNotification(order); }, { noAck: true }); }

# user-service/Dockerfile FROM node:18-alpine WORKDIR /app COPY package*.json ./ RUN npm install COPY . . EXPOSE 3001 CMD ["node", "server.js"]

# docker-compose.yml version: '3.8' services: user-service: build: ./user-service ports: - "3001:3001" environment: - PORT=3001 - DB_HOST=user-db depends_on: - user-db product-service: build: ./product-service ports: - "3002:3002" environment: - PORT=3002 - DB_HOST=product-db depends_on: - product-db order-service: build: ./order-service ports: - "3003:3003" environment: - PORT=3003 - USER_SERVICE_URL=http://user-service:3001 - PRODUCT_SERVICE_URL=http://product-service:3002 api-gateway: build: ./api-gateway ports: - "3000:3000" depends_on: - user-service - product-service - order-service user-db: image: postgres:15 environment: POSTGRES_DB: users POSTGRES_PASSWORD: password product-db: image: postgres:15 environment: POSTGRES_DB: products POSTGRES_PASSWORD: password # Run all services: docker-compose up