Implementação de um Gateway de API
Projete e configure um Gateway de API para atuar como ponto de entrada único das requisições dos clientes aos seus microsserviços.
Implementação de um Gateway de API é uma aula grátis de Node.js Backend Development Bootcamp no CoddyKit. Esta é a aula 3 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Node.js Backend Development Bootcamp, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Node.js Backend Development Bootcamp inclui 4 aulas no total.
Partes desta aula ainda não foram traduzidas e aparecem em inglês.
API Gateway: The Front Door
In a microservices architecture, clients often need to interact with many different services. An API Gateway acts as a single, unified entry point for all client requests.
Think of it as the front desk of a large hotel. Instead of guests having to find specific rooms (microservices) themselves, they go to the front desk which directs them to the right place and handles common requests.
Why Use an API Gateway?
API Gateways solve several challenges that arise when using microservices:
- Simplifies Clients: Clients only need to know one endpoint (the gateway) instead of many microservice URLs.
- Request Routing: Directs incoming requests to the correct backend service.
- Common Concerns: Handles cross-cutting concerns like authentication, rate limiting, and logging at a single point.
- Service Aggregation: Can combine responses from multiple services into a single client-friendly response.
Gateway vs. Load Balancer
It's easy to confuse an API Gateway with a Load Balancer, but they serve different purposes:
- Load Balancer: Operates at the network layer (Layer 4) or application layer (Layer 7) to distribute traffic across multiple instances of the same service for high availability and performance.
- API Gateway: Operates at the application layer (Layer 7) and focuses on API-specific concerns. It routes requests to different services and can perform transformations or security checks.
They often work together, with a load balancer sitting in front of the API Gateway.
Key Responsibilities of a Gateway
An API Gateway takes on several crucial roles:
- Request Routing: Mapping specific API paths (e.g.,
/users) to the appropriate microservice. - Authentication & Authorization: Verifying user identity and permissions before forwarding requests.
- Rate Limiting: Controlling the number of requests a client can make within a certain timeframe.
- Caching: Storing frequently accessed data to reduce load on backend services and improve response times.
- Logging & Monitoring: Centralizing logs for all incoming requests and outgoing responses.
Building a Simple Gateway
You can build a custom API Gateway using Node.js and frameworks like Express.js. A popular library for proxying HTTP requests in Express is http-proxy-middleware.
This library makes it easy to forward requests from your gateway to your backend microservices, acting as a reverse proxy.
Basic Proxy Setup
Let's set up a simple Express.js server that acts as a proxy. This gateway will listen on port 3000 and forward all requests starting with /api to a mock 'users' microservice on port 3001.
Remember, for full functionality, you'd need an actual microservice running at http://localhost:3001.
const express = require('express');
const { createProxyMiddleware } = require('http-proxy-middleware');
const app = express();
const GATEWAY_PORT = 3000;
// Proxy all requests starting with /api to the users microservice
app.use(
'/api',
createProxyMiddleware({
target: 'http://localhost:3001', // Target URL of your users microservice
changeOrigin: true, // Needed for virtual hosted sites
logLevel: 'debug' // Optional: for seeing proxy activity in console
})
);
// Simple root route for gateway status
app.get('/', (req, res) => {
res.send('API Gateway is running. Try /api/users (if microservice is active).');
});
app.listen(GATEWAY_PORT, () => {
console.log(`API Gateway listening on port ${GATEWAY_PORT}`);
console.log('Proxying /api to http://localhost:3001');
});Routing to Multiple Services
The power of an API Gateway comes from its ability to route requests to different microservices based on the request path, HTTP method, or other criteria.
You can define multiple proxy rules, each pointing to a different backend service. For example, /users goes to the user service, and /products goes to the product service.
Multi-Service Routing Example
Here, we extend our gateway to route requests for /users to a 'users-service' on port 3001 and requests for /products to a 'products-service' on port 3002.
The pathRewrite option is important: it removes the path prefix (e.g., /users) before forwarding the request to the target service.
const express = require('express');
const { createProxyMiddleware } = require('http-proxy-middleware');
const app = express();
const GATEWAY_PORT = 3000;
// Proxy for user-related requests
app.use(
'/users',
createProxyMiddleware({
target: 'http://localhost:3001', // Users Microservice URL
changeOrigin: true,
pathRewrite: { '^/users': '' }, // Remove /users prefix
logLevel: 'debug'
})
);
// Proxy for product-related requests
app.use(
'/products',
createProxyMiddleware({
target: 'http://localhost:3002', // Products Microservice URL
changeOrigin: true,
pathRewrite: { '^/products': '' }, // Remove /products prefix
logLevel: 'debug'
})
);
app.get('/', (req, res) => {
res.send('API Gateway is running. Try /users or /products (if microservices are active).');
});
app.listen(GATEWAY_PORT, () => {
console.log(`API Gateway listening on port ${GATEWAY_PORT}`);
console.log('Proxying /users to http://localhost:3001');
console.log('Proxying /products to http://localhost:3002');
});Centralized Middleware for Gateway
One of the biggest advantages of an API Gateway is applying middleware for common concerns before requests even reach your microservices.
You can implement Express middleware functions globally or for specific routes within your gateway to handle tasks like:
- Authentication: Verify JWTs or session tokens.
- Logging: Log every incoming request.
- Rate Limiting: Prevent abuse by limiting request frequency.
- Input Validation: Basic validation before forwarding.
Quick Check on Gateway
An API Gateway serves as a crucial component in a microservices setup. Let's test your understanding of its primary purpose.
Gateway Summary
You've learned about API Gateways, their importance in microservices, and how to implement a basic one using Express.js and http-proxy-middleware.
Key takeaways:
- API Gateways simplify client interactions by providing a single entry point.
- They handle routing, authentication, rate limiting, and other cross-cutting concerns.
- Express.js with
http-proxy-middlewareis a flexible way to build custom gateways.
Mastering API Gateways is essential for building robust and scalable microservices!
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Todas as aulas deste curso
- Introdução à Arquitetura de Microsserviços
- Desenvolvimento de Microsserviços com Node.js
- Implementação de um Gateway de API
- Comunicação entre serviços com filas de mensagens