Spring Boot与Spring Cloud Gateway的限流与熔断策略

Spring Boot和Spring Cloud Gateway都是基于Spring生态系统的流行框架，它们提供了丰富的功能来简化微服务架构的开发。在微服务架构中，限流和熔断是两种重要的保护机制，用于防止系统过载和故障扩散。下面分别介绍Spring Boot和Spring Cloud Gateway中的限流和熔断策略。

Spring Boot中的限流与熔断策略

限流

Spring Boot提供了多种限流策略，可以通过以下几种方式实现：

1. 基于Guava RateLimiter： Spring Boot可以集成Guava库中的RateLimiter来实现限流。首先，需要在pom.xml中添加Guava依赖：

   <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
       <version>30.1-jre</version>
   </dependency>
   

   然后，在配置类中配置RateLimiter：

   import com.google.common.util.concurrent.RateLimiter;
   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   
   @Configuration
   public class RateLimiterConfig {
   
       @Bean
       public RateLimiter rateLimiter() {
           return RateLimiter.create(1); // 每秒最多处理1个请求
       }
   }
   

   在需要限流的方法上使用@RateLimiter注解：

   import com.google.common.util.concurrent.RateLimiter;
   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   @RestController
   public class MyController {
   
       @Autowired
       private RateLimiter rateLimiter;
   
       @GetMapping("/limited")
       public String limited() {
           if (rateLimiter.tryAcquire()) {
               return "Request accepted";
           } else {
               return "Request rejected";
           }
       }
   }
   

2. 基于Redis的限流： 可以使用Spring Data Redis来实现基于Redis的限流。首先，需要在pom.xml中添加Redis依赖：

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-redis</artifactId>
   </dependency>
   

   然后，在配置类中配置Redis：

   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.data.redis.connection.RedisConnectionFactory;
   import org.springframework.data.redis.core.RedisTemplate;
   import org.springframework.data.redis.serializer.StringRedisSerializer;
   
   @Configuration
   public class RedisConfig {
   
       @Bean
       public RedisTemplate<String, String> redisTemplate(RedisConnectionFactory factory) {
           RedisTemplate<String, String> template = new RedisTemplate<>();
           template.setConnectionFactory(factory);
           template.setKeySerializer(new StringRedisSerializer());
           template.setValueSerializer(new StringRedisSerializer());
           return template;
       }
   }
   

   创建一个限流器：

   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.data.redis.core.RedisTemplate;
   import org.springframework.stereotype.Component;
   
   import java.util.concurrent.TimeUnit;
   
   @Component
   public class RedisRateLimiter {
   
       @Autowired
       private RedisTemplate<String, String> redisTemplate;
   
       public boolean tryAcquire(String key, int permits, long timeout, TimeUnit timeUnit) {
           String current = redisTemplate.opsForValue().get(key);
           if (current == null || Integer.parseInt(current) < permits) {
               redisTemplate.opsForValue().set(key, permits, timeout, timeUnit);
               return true;
           }
           return false;
       }
   }
   

   在需要限流的方法上使用@RedisRateLimiter注解：

   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RestController;
   
   @RestController
   public class MyController {
   
       @Autowired
       private RedisRateLimiter redisRateLimiter;
   
       @GetMapping("/redis-limited")
       public String redisLimited() {
           if (redisRateLimiter.tryAcquire("myKey", 1, 10, TimeUnit.SECONDS)) {
               return "Request accepted";
           } else {
               return "Request rejected";
           }
       }
   }
   

熔断

Spring Boot可以通过Hystrix来实现熔断功能。首先，需要在pom.xml中添加Hystrix依赖：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>

然后，在启动类上添加@EnableCircuitBreaker注解：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.hystrix.EnableCircuitBreaker;

@SpringBootApplication
@EnableCircuitBreaker
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

在需要熔断的方法上添加@HystrixCommand注解：

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.stereotype.Service;

@Service
public class MyService {

    @HystrixCommand(fallbackMethod = "fallbackMethod")
    public String myMethod() {
        // 实际的业务逻辑
        return "Success";
    }

    public String fallbackMethod() {
        return "Fallback response";
    }
}

Spring Cloud Gateway中的限流与熔断策略

限流

Spring Cloud Gateway提供了多种限流策略，可以通过以下几种方式实现：

1. 基于Guava RateLimiter： 可以使用Spring Cloud Gateway的RateLimiter GatewayFilter Factory来实现限流。首先，需要在pom.xml中添加Guava依赖：

   <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
       <version>30.1-jre</version>
   </dependency>
   

   然后，在配置类中配置RateLimiter：

   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;
   
   @Configuration
   public class RateLimiterConfig {
   
       @Bean
       public KeyResolver userKeyResolver() {
           return new KeyResolver() {
               @Override
               public Mono<String> resolve(ServerWebExchange exchange) {
                   return Mono.just(exchange.getRequest().getRemoteAddress().getAddress().getHostAddress());
               }
           };
       }
   }
   

   在路由配置中使用RateLimiter GatewayFilter Factory：

   spring:
     cloud:
       gateway:
         routes:
           - id: my_route
             uri: http://my-service-url
             filters:
               - name: RequestRateLimiter
                 args:
                   redis-rate-limiter.replenishRate: 10
                   redis-rate-limiter.burstCapacity: 20
                   key-resolver: "#{@userKeyResolver}"
   

2. 基于Redis的限流： 可以使用Spring Cloud Gateway的RedisRateLimiter GatewayFilter Factory来实现基于Redis的限流。首先，需要在pom.xml中添加Spring Data Redis依赖：

   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-data-redis</artifactId>
   </dependency>
   

   然后，在配置类中配置Redis：

   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.data.redis.connection.RedisConnectionFactory;
   import org.springframework.data.redis.core.RedisTemplate;
   import org.springframework.data.redis.serializer.StringRedisSerializer;
   
   @Configuration
   public class RedisConfig {
   
       @Bean
       public RedisTemplate<String, String> redisTemplate(RedisConnectionFactory factory) {
           RedisTemplate<String, String> template = new RedisTemplate<>();
           template.setConnectionFactory(factory);
           template.setKeySerializer(new StringRedisSerializer());
           template.setValueSerializer(new StringRedisSerializer());
           return template;
       }
   }
   

   在路由配置中使用RedisRateLimiter GatewayFilter Factory：

   spring:
     cloud:
       gateway:
         routes:
           - id: my_route
             uri: http://my-service-url
             filters:
               - name: RedisRateLimiter
                 args:
                   redis-rate-limiter.replenishRate: 10
                   redis-rate-limiter.burstCapacity: 20
   

熔断

Spring Cloud Gateway可以通过Resilience4j来实现熔断功能。首先，需要在pom.xml中添加Resilience4j依赖：

<dependency>
    <groupId>io.github.resilience4j</groupId>
    <artifactId>resilience4j-spring-boot2</artifactId>
</dependency>

然后，在配置类中配置Resilience4j：

import io.github.resilience4j.circuitbreaker.CircuitBreaker;
import io.github.resilience4j.circuitbreaker.CircuitBreakerConfig;
import io.github.resilience4j.circuitbreaker.CircuitBreakerRegistry;
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;

@Configuration
public class Resilience4jConfig {

    @Bean
    public KeyResolver userKeyResolver() {
        return new KeyResolver() {
            @Override
            public Mono<String> resolve(ServerWebExchange exchange) {
                return Mono.just(exchange.getRequest().getRemoteAddress().getAddress().getHostAddress());
            }
        };
    }

    @Bean
    public CircuitBreakerRegistry circuitBreakerRegistry() {
        CircuitBreakerConfig config = CircuitBreakerConfig.custom()
                .failureRateThreshold(50)
                .waitDurationInOpenState(Duration.ofMillis(1000))
                .permittedNumberOfCallsInHalfOpenState(10)
                .build();
        return CircuitBreakerRegistry.of(config);
    }

    @Bean
    public CircuitBreaker circuitBreaker(CircuitBreakerRegistry registry) {
        return registry.circuitBreaker("myCircuitBreaker");
    }
}

在路由配置中使用CircuitBreaker GatewayFilter Factory：

spring:
  cloud:
    gateway:
      routes:
        - id: my_route
          uri: http://my-service-url
          filters:
            - name: CircuitBreaker
              args:
                name: myCircuitBreaker
                fallbackUri: forward:/fallback

通过以上配置，可以实现Spring Boot和Spring Cloud Gateway中的限流和熔断策略。