如果需要访问产生回退触发器的原因，可以使用@feignClient中的fallbackFactory属性：

pom：

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
    <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>

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

@FeignClient(value = "report-query",fallbackFactory =ReportQueryServiceHystrix.class )
public interface ReportQueryService {

    @RequestMapping(value = "/reportquery/index", method = RequestMethod.GET,produces = MediaType.APPLICATION_JSON_VALUE)
       String index();

}

@Component
public class ReportQueryServiceHystrix  implements FallbackFactory<ReportQueryService>{
private static final Logger log= LoggerFactory.getLogger(ReportQueryServiceHystrix.class);

    @Override
   public ReportQueryService create(Throwable arg0) {

               return  new ReportQueryService() {
                   @Override
                   public String index() {
                        ReportQueryServiceHystrix.log.info("fallback; reason was: {}", arg0.getMessage());
                       return arg0.getMessage();
                   }
               };
    }

}

yml： 开启熔断

feign:
   hystrix:
     enabled: true

启动类：

@SpringBootApplication
@EnableEurekaClient
@EnableDiscoveryClient
@EnableFeignClients
@EnableHystrix
public class WebserviceApplication {

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

}

访问结果:

com.netflix.client.ClientException: Load balancer does not have available server for client: report-query