The RequestRateLimiter GatewayFilter Factory is uses a RateLimiter implementation to determine if the current request is allowed to proceed. If it is not, a status of HTTP 429 - Too Many Requests (by default) is returned.

This filter takes an optional keyResolver parameter and parameters specific to the rate limiter (see below).

keyResolver is a bean that implements the KeyResolver interface. In configuration, reference the bean by name using SpEL. #{@myKeyResolver} is a SpEL expression referencing a bean with the name myKeyResolver.

KeyResolver.java. 

public interface KeyResolver {
	Mono<String> resolve(ServerWebExchange exchange);
}

The KeyResolver interface allows pluggable strategies to derive the key for limiting requests. In future milestones, there will be some KeyResolver implementations.

The default implementation of KeyResolver is the PrincipalNameKeyResolver which retrieves the Principal from the ServerWebExchange and calls Principal.getName().

	The RequestRateLimiter is not configurable via the "shortcut" notation. The example below is invalid

application.properties. 

# INVALID SHORTCUT CONFIGURATION
spring.cloud.gateway.routes[0].filters[0]=RequestRateLimiter=2, 2, #{@userkeyresolver}

spring:
  cloud:
    gateway:
      routes:
      - id: requestratelimiter_route
        uri: http://example.org
        filters:
        - name: RequestRateLimiter
          args:
            redis-rate-limiter.replenishRate: 10
            redis-rate-limiter.burstCapacity: 20

@Bean
KeyResolver userKeyResolver() {
    return exchange -> Mono.just(exchange.getRequest().getQueryParams().getFirst("user"));
}

spring:
  cloud:
    gateway:
      routes:
      - id: requestratelimiter_route
        uri: http://example.org
        filters:
        - name: RequestRateLimiter
          args:
            rate-limiter: "#{@myRateLimiter}"
            key-resolver: "#{@userKeyResolver}"

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

---
spring:
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true
      routes:
      - id: user-service
        uri: lb://user-service
        predicates:
        - Path=/user/**
        filters:
        - StripPrefix=1
        - name: RequestRateLimiter
          args:
            key-resolver: "#{@remoteAddrKeyResolver}"
            redis-rate-limiter.replenishRate: 1
            redis-rate-limiter.burstCapacity: 5

---
spring:
  redis:
    host: localhost
    port: 6379
    database: 0

import org.springframework.cloud.gateway.filter.ratelimit.KeyResolver;
import org.springframework.web.server.ServerWebExchange;

import reactor.core.publisher.Mono;

public class RemoteAddrKeyResolver implements KeyResolver {

    @Override
    public Mono<String> resolve(ServerWebExchange exchange) {
        // TODO Auto-generated method stub
        return Mono.just(exchange.getRequest().getRemoteAddress().getAddress().getHostAddress());
    }

}

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;

import com.example.demo.keyResolver.RemoteAddrKeyResolver;

@Component
public class RequestRateLimiterCustom {

    @Bean(name = "remoteAddrKeyResolver")
    public RemoteAddrKeyResolver remoteAddrKeyResolver() {
        return new RemoteAddrKeyResolver();
    }
}