跟我學Spring Cloud（Finchley版）-14-Feign使用Hystrix

Feign默認已經整合了Hystrix，本節詳細探討Feign使用Hystrix的具體細節。

服務降級

• 加配置，默認Feign是不啓用Hystrix的，需要添加如下配置啓用Hystrix，這樣所有的Feign Client都會受到Hystrix保護！

  feign:
  hystrix:
    enabled: true

• 提供Fallback：

  @FeignClient(name = "microservice-provider-user", fallback = UserFeignClientFallback.class)
  public interface UserFeignClient {
  @GetMapping("/users/{id}")
  User findById(@PathVariable("id") Long id);
  }
  
  @Component
  class UserFeignClientFallback implements UserFeignClient {
  @Override
  public User findById(Long id) {
    return new User(id, "默認用戶", "默認用戶", 0, new BigDecimal(1));
  }
  }

獲得造成fallback的原因

@FeignClient(name = "microservice-provider-user", fallbackFactory = UserFeignClientFallbackFactory.class)
public interface UserFeignClient {
  @GetMapping("/users/{id}")
  User findById(@PathVariable("id") Long id);
}

@Component
@Slf4j
class UserFeignClientFallbackFactory implements FallbackFactory<UserFeignClient> {
  @Override
  public UserFeignClient create(Throwable throwable) {
    return new UserFeignClient() {
      @Override
      public User findById(Long id) {
        log.error("進入回退邏輯", throwable);
        return new User(id, "默認用戶", "默認用戶", 0, new BigDecimal(1));
      }
    };
  }
}

Feign啓用/禁用Hystrix

全局啓用

feign.hystrix.enabled: true

全局禁用

feign.hystrix.enabled: false

或直接省略不寫。

局部啓用

利用Feign配置的自定義，爲指定Feign Client指定如下配置類即可，Feign配置自定義詳見：跟我學Spring Cloud（Finchley版）-10-Feign深入

public class FeignDisableHystrixConfiguration {
    @Bean
    @Scope("prototype")
    public HystrixFeign.Builder feignBuilder() {
        return HystrixFeign.builder();
    }
}

局部禁用

public class FeignDisableHystrixConfiguration {
    @Bean
    @Scope("prototype")
    public Feign.Builder feignBuilder() {
        return Feign.builder();
    }
}

配套代碼

服務降級：

• GitHub：<https://github.com/eacdy/spring-cloud-study/tree/master/2018-Finchley/microservice-consumer-movie-feign-hystrix&gt;
• Gitee：<https://gitee.com/itmuch/spring-cloud-study/tree/master/2018-Finchley/microservice-consumer-movie-feign-hystrix&gt;

獲得造成fallback的原因：

• GitHub：<https://github.com/eacdy/spring-cloud-study/tree/master/2018-Finchley/microservice-consumer-movie-feign-hystrix-fallback-factory&gt;
• Gitee：<https://gitee.com/itmuch/spring-cloud-study/tree/master/2018-Finchley/microservice-consumer-movie-feign-hystrix-fallback-factory&gt;

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<http://www.itmuch.com/spring-cloud/finchley-14/&gt;

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