Spring Cloud Feign 熔断配置的一些小坑

最近在做微服务的学习，发现在使用feign做服务调用时，使用继承的方式调用服务，加入Hystrix的熔断处理fallback配置时，会报错，代码如下：

@RequestMapping("/demo/api")
public interface HelloApi {

    @GetMapping("user/{id}")
    User getUserById(@PathVariable("id") long id);

    @GetMapping("hello")
    String echo(@RequestParam("name") String name);
}

@FeignClient(value = "ms-server", fallback = ConsumerFeignServiceFallBack.class)
public interface ConsumerFeignService extends HelloApi {

}

@Component
public class ConsumerFeignServiceFallBack implements ConsumerFeignService {
    @Override
    public User getUserById(long id) {
        return new User();
    }

    @Override
    public String echo(String name) {
        return "echo error: " + name;
    }
}

报错如下：

Caused by: java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'com.thoughtworks.demo.consumer.service.ConsumerFeignService' method 
public abstract java.lang.String com.thoughtworks.demo.api.HelloApi.echo(java.lang.String)
to {[/demo/api/hello],methods=[GET]}: There is already 'consumerFeignServiceFallBack' bean method
public java.lang.String com.thoughtworks.demo.consumer.service.ConsumerFeignServiceFallBack.echo(java.lang.String) mapped.
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.assertUniqueMethodMapping(AbstractHandlerMethodMapping.java:576) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:540) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.registerHandlerMethod(AbstractHandlerMethodMapping.java:264) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.detectHandlerMethods(AbstractHandlerMethodMapping.java:250) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initHandlerMethods(AbstractHandlerMethodMapping.java:214) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.afterPropertiesSet(AbstractHandlerMethodMapping.java:184) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.afterPropertiesSet(RequestMappingHandlerMapping.java:127) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.14.RELEASE.jar:4.3.14.RELEASE]
	... 21 common frames omitted

错误原因是这里继承的接口类是一个controller接口，继承时会继承到父类的

@RequestMapping("/demo/api")

SpringMvc在做mapping映射的时候发现ConsumerFeignService和ConsumerFeignServiceFallBack的mapping重复了，所以抛出异常，如何解决呢？

解决的方法有2个：

一是更改ConsumerFeignServiceFallBack的mapping配置，代码如下：

@Component
@RequestMapping("fallback/demo/api")
public class ConsumerFeignServiceFallBack implements ConsumerFeignService {
    @Override
    public User getUserById(long id) {
        return new User();
    }

    @Override
    public String echo(String name) {
        return "echo error: " + name;
    }
}

二是使用fallbackFactory，代码如下：

@Component
public class ConsumerFeignServiceFallBack implements FallbackFactory<ConsumerFeignService> {

    @Override
    public ConsumerFeignService create(Throwable cause) {
        return new ConsumerFeignService() {
            @Override
            public User getUserById(long id) {
                return new User();
            }

            @Override
            public String echo(String name) {
                return "echo error: " + name;
            }
        };
    }
}

运行后，关闭服务提供者，发现熔断并没有生效，没有像单独使用@HystrixCommand时进入fallback方法，查了很多方式，发现原来是feign的hystix的配置开关没有打开

解决方法，在application.yml中增加配置如下：

feign:
  hystrix:
    enabled: true

在IntelliJ IDEA里也没有这个配置的提示，还报告警告，不知道算不算是个BUG，这里我使用的版本是

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springBootVersion = '1.5.10.RELEASE'
springCloudVersion = 'Edgware.SR3'

以上就是我在使用feign时发现的一些小坑，如有问题，欢迎随时拍砖~