API Gateways & Service Discovery

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spring:
  cloud:
    gateway:
      routes:
        - id: order-service-route
          uri: lb://order-service
          predicates:
            - Path=/api/orders/**
          filters:
            - StripPrefix=1
            - AddRequestHeader=X-Gateway-Forwarded, true

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package com.example.gateway;

import org.springframework.cloud.gateway.filter.ratelimit.KeyResolver;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import reactor.core.publisher.Mono;

import java.security.Principal;

@Configuration(proxyBeanMethods = false)
public class RateLimiterConfig {

    @Bean
    public KeyResolver userKeyResolver() {
        // Resolve rate limit key by authenticated user ID or client IP
        return exchange -> exchange.getPrincipal()
            .map(Principal::getName)
            .defaultIfEmpty(exchange.getRequest().getRemoteAddress().getAddress().getHostAddress());
    }
}

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# 1. Send request through Gateway to routed service
curl -i http://localhost:8080/api/orders/ORD-42
# HTTP/1.1 200 OK -> Gateway routes to lb://order-service and strips /api prefix

# 2. Exceed token bucket rate limit
for i in {1..20}; do curl -s -o /dev/null -w "%{http_code}\n" http://localhost:8080/api/orders/ORD-42; done
# Output: 200 ... 200 ... 429 (Too Many Requests returned by Gateway)