spring cloud 断路器 Hystrix

一、微服务架构中使用断路器的原因

二、代码实现

1、在Ribbon中使用短路器

1.1、引入依赖

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

1.2、在Springboot类中增加@EnableHystrix来开启Hystrix

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableHystrix
public class ServiceRibbonApplication {

    public static void main(String[] args) {
        SpringApplication.run( ServiceRibbonApplication.class, args );
    }

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

1.3、在服务方法上增加@HystrixCommand(fallbackMethod = "backError")，该注解对该方法创建了熔断器的功能，并指定了fallbackMethod熔断方法，熔断方法直接返回了一个字符串，字符串为"hi,"+name+",sorry,error!"

@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "backError")
    public String hiService(String name) {
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }
    public String hiError(String name) {
        return "hi,"+name+",sorry,error!";
    }
}

1.4、启动：service-ribbon 工程，当我们访问http://localhost:8764/hi?name=henry,浏览器显示：

hi ,henry,sorry,error!

2、Feign中使用断路器

2.1、配置文件中开启断路器

feign.hystrix.enabled=true

2.2、在FeignClient的SchedualServiceHi接口的注解中加上fallback的指定类就行了

@FeignClient(value = "service-hi",fallback = SchedualServiceHiHystric.class)
public interface SchedualServiceHi {
    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

2.3、SchedualServiceHiHystric需要实现SchedualServiceHi 接口，并注入容器

@Component
public class SchedualServiceHiHystric implements SchedualServiceHi {
    @Override
    public String sayHiFromClientOne(String name) {
        return "sorry "+name;
    }
}

2.4、比较开启服务和关闭服务返回的结果