如果Hystrix在类路径上并且feign.hystrix.enabled = true，Feign将用断路器包装所有方法。还可以返回com.netflix.hystrix.HystrixCommand。这可让您使用响应模式（调用.toObservable（）或.observe（）或异步使用（调用.queue（））。
要以每个客户端为基础禁用Hystrix支持，请创建一个具有“prototype”范围。
在Spring Cloud Dalston发布之前，如果Hystrix在类路径上，Feign默认情况下会将所有方法封装在断路器中。 Spring Cloud Dalston改变了这种默认行为，以支持选择加入方式。
@Configuration public class FooConfiguration { @Bean @Scope("prototype") public Feign.Builder feignBuilder() { return Feign.builder(); } }
Hystrix支持回退的概念：当电路断开或出现错误时执行的默认代码路径。要为给定的@FeignClient启用回退，请将fallback属性设置为实现回退的类名称。您还需要将您的实现声明为Spring bean。
@FeignClient(name = "hello", fallback = HystrixClientFallback.class) protected interface HystrixClient { @RequestMapping(method = RequestMethod.GET, value = "/hello") Hello iFailSometimes(); } static class HystrixClientFallback implements HystrixClient { @Override public Hello iFailSometimes() { return new Hello("fallback"); } }
如果需要访问作为回退触发器的原因，则可以使用@FeignClient中的fallbackFactory属性。
为指定的客户端接口定义一个回退工厂。回退工厂必须产生回退类的实例，这些实例实现由FeignClient注释的接口。
如果同时设置fallback和fallbackfactory不可以有冲突，fallback生效，fallbackfactory不能使用，fallbackFactory 是fallback的一个升级版，注释fallback设置即可
@FeignClient(name = "hello", fallbackFactory = HystrixClientFallbackFactory.class) protected interface HystrixClient { @RequestMapping(method = RequestMethod.GET, value = "/hello") Hello iFailSometimes(); } @Component static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> { @Override public HystrixClient create(Throwable cause) { return new HystrixClient() { @Override public Hello iFailSometimes() { return new Hello("fallback; reason was: " + cause.getMessage()); } }; } }
查看FallbackFactory
public interface FallbackFactory<T> { /** * Returns an instance of the fallback appropriate for the given cause * * @param cause corresponds to {@link com.netflix.hystrix.AbstractCommand#getExecutionException()} * often, but not always an instance of {@link FeignException}. */ T create(Throwable cause); /** Returns a constant fallback after logging the cause to FINE level. */ final class Default<T> implements FallbackFactory<T> { // jul to not add a dependency final Logger logger; final T constant; public Default(T constant) { this(constant, Logger.getLogger(Default.class.getName())); } Default(T constant, Logger logger) { this.constant = checkNotNull(constant, "fallback"); this.logger = checkNotNull(logger, "logger"); } @Override public T create(Throwable cause) { if (logger.isLoggable(Level.FINE)) { logger.log(Level.FINE, "fallback due to: " + cause.getMessage(), cause); } return constant; } @Override public String toString() { return constant.toString(); } } }
注意事项：在Feign中实施回退以及Hystrix回退的工作方式存在限制。目前，com.netflix.hystrix.HystrixCommand和rx.Observable的方法不支持回退。
示例参看：https://github.com/bjlhx15/spring-cloud/tree/master/microservice-comsumer-movie-feign-with-hystrix
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
feign.hystrix.enabled=true
@EnableCircuitBreaker
@FeignClient(name = "microservice-provider-user", fallback = HystrixClientFallback.class) public interface UserFeignClient { // @GetMapping("/sample/{id}") @RequestMapping(method = RequestMethod.GET, value = "/sample/{id}") public User findById(@PathVariable("id") Long id); }
@Component public class HystrixClientFallback implements UserFeignClient { @Override public User findById(Long id) { User user = new User(); user.setId(0L); return user; } }
@FeignClient(name = "xxxx", url = "http://localhost:8761/", configuration = Configuration2.class,fallback = FeignClient2Fallback.class) public interface FeignClient2 { @RequestMapping(value = "/eureka/apps/{serviceName}") public String findServiceInfoFromEurekaByServiceName(@PathVariable("serviceName") String serviceName); }
@Component public class FeignClient2Fallback implements FeignClient2 { @Override public String findServiceInfoFromEurekaByServiceName(String serviceName) { return "haha"; } }
@Configuration public class Configuration2 { @Bean public BasicAuthRequestInterceptor basicAuthRequestInterceptor() { return new BasicAuthRequestInterceptor("user", "a123"); } @Bean @Scope("prototype") public Feign.Builder feignBuilder() { return Feign.builder(); } }
可以看到这里主要增加了feignBuilder创建
参考代码：
@FeignClient(name = "microservice-provider-user", fallbackFactory = HystrixClientFallbackFactory.class) public interface UserFeignClient { // @GetMapping("/sample/{id}") @RequestMapping(method = RequestMethod.GET, value = "/sample/{id}") public User findById(@PathVariable("id") Long id); }
注意：配置了fallbackFactory ，如果同时设置fallback和fallbackfactory不可以有冲突，只能设置一个，fallbackFactory 是fallback的一个升级版
@Component public class HystrixClientFallbackFactory implements FallbackFactory<UserFeignClient> { private static final Logger logger = LoggerFactory.getLogger(HystrixClientFallbackFactory.class); @Override public UserFeignClient create(Throwable arg0) { HystrixClientFallbackFactory.logger.info("fallback reason was:{}", arg0.getMessage()); return new UserFeignClientWithFactory() { @Override public User findById(Long id) { User user = new User(); user.setId(-1L); return user; } }; } }
public interface UserFeignClientWithFactory extends UserFeignClient { }
0503-Hystrix保护应用-feign的hystrix支持
原文：https://www.cnblogs.com/bjlhx/p/8909577.html