Hystrix使用fallback完成消费降级

╰+哭是因爲堅強的太久メ 2023-01-01 03:47 138阅读 0赞

本篇调用接口基于[《Feign的基础应用(替代Eureka消费者)》][Feign_Eureka]

*  pom文件

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
    
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    
    	
        <dependency>
            <groupId>com.test</groupId>
            <artifactId>feign-client-intf</artifactId>
            <version>${project.version}</version>
        </dependency>
    
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
    </dependencies>

*  配置文件

eureka:
      client:
        serviceUrl:
          defaultZone: http://localhost:20000/eureka/
    # 开启Feign下面的Hystrix功能
    feign:
      hystrix:
        enabled: true
    # 是否开启服务降级
    hystrix:
      command:
        default:
          fallback:
            enabled: true
    server:
      port: 50000
    spring:
      application:
        name: hystrix-consumer
      main:
        allow-bean-definition-overriding: true

*  application

@EnableDiscoveryClient
    @SpringBootApplication
    @EnableFeignClients
    @EnableCircuitBreaker
    public class HystrixFallbackApplication { 
    
        public static void main(String[] args){ 
            new SpringApplicationBuilder(HystrixFallbackApplication.class)
                    .web(WebApplicationType.SERVLET)
                    .run(args);
        }
    
    }

*  MyService

继承于feign中的IService

@FeignClient(name = "feign-client", fallback = Fallback.class)
    public interface MyService extends IService { 
    
    }

这里我们对feign的service做一个小改造，新增一个抛出异常的方法

@FeignClient("feign-client")
    public interface IService { 
    
        @GetMapping("/error")
        public String error();
    
    }

以及它的实现

@Override
    publicString error() { 
        throw new RuntimeException("black sheep");
    }

*  Fallback

这里开始配置我们的降级策略

@Slf4j
    @Component
    public class Fallback implements MyService { 
    
        @Override
        public String error() { 
            log.info("Fallback: I'm not a black sheep any more");
            return "Fallback: I'm not a black sheep any more";
        }
    
    }

*  Controller  
    新建一个测试接口

@RestController
    public class Controller { 
    
        @Autowired
        private MyService myService;
    
        @GetMapping("/fallback")
        public String fallback() { 
            return myService.error();
        }
    
    }

依此启动Eureka -> Feign -> Hystrix  
我们尝试调用`localhost:50000/fallback`  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70]  
可以通过日志看到，请求进入了Feign，触发抛错，然后进入Hystrix的fallback，最后返回了fallback中定义的返回结果

[Feign_Eureka]: https://jiandansuifeng.blog.csdn.net/article/details/109687358
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2x0MzI2MDMwNDM0_size_16_color_FFFFFF_t_70]: /images/20221120/7cc2775a92874a62a44b2fca8229f41c.png