序

feign默认集成了hystrix，那么问题来了，如何像hystrix command那样设置每个方法的hystrix属性呢。

实例

@FeignClient("product")
public interface RemoteProductService {

    @RequestMapping(method = RequestMethod.GET,value = "/product/{productId}")
    public Product getProduct(@PathVariable(value = "productId")  int productId);
}

FeignClientsConfiguration

spring-cloud-netflix-core-1.2.6.RELEASE-sources.jar!/org/springframework/cloud/netflix/feign/FeignClientsConfiguration.java

    @Configuration
    @ConditionalOnClass({ HystrixCommand.class, HystrixFeign.class })
    protected static class HystrixFeignConfiguration {
        @Bean
        @Scope("prototype")
        @ConditionalOnMissingBean
        @ConditionalOnProperty(name = "feign.hystrix.enabled", matchIfMissing = true)
        public Feign.Builder feignHystrixBuilder() {
            return HystrixFeign.builder();
        }
    }

HystrixFeign

feign-hystrix-9.3.1-sources.jar!/feign/hystrix/HystrixFeign.java

private SetterFactory setterFactory = new SetterFactory.Default();

SetterFactory

feign-hystrix-9.3.1-sources.jar!/feign/hystrix/SetterFactory.java

public interface SetterFactory {

  /**
   * Returns a hystrix setter appropriate for the given target and method
   */
  HystrixCommand.Setter create(Target<?> target, Method method);

  /**
   * Default behavior is to derive the group key from {@link Target#name()} and the command key from
   * {@link Feign#configKey(Class, Method)}.
   */
  final class Default implements SetterFactory {

    @Override
    public HystrixCommand.Setter create(Target<?> target, Method method) {
      String groupKey = target.name();
      String commandKey = Feign.configKey(target.type(), method);
      return HystrixCommand.Setter
          .withGroupKey(HystrixCommandGroupKey.Factory.asKey(groupKey))
          .andCommandKey(HystrixCommandKey.Factory.asKey(commandKey));
    }
  }
}

groupKey，这里为product，即@FeignClient("product")中的值。

Feign.configKey

feign-core-9.3.1-sources.jar!/feign/Feign.java

public static String configKey(Class targetType, Method method) {
    StringBuilder builder = new StringBuilder();
    builder.append(targetType.getSimpleName());
    builder.append('#').append(method.getName()).append('(');
    for (Type param : method.getGenericParameterTypes()) {
      param = Types.resolve(targetType, targetType, param);
      builder.append(Types.getRawType(param).getSimpleName()).append(',');
    }
    if (method.getParameterTypes().length > 0) {
      builder.deleteCharAt(builder.length() - 1);
    }
    return builder.append(')').toString();
  }

commandKey的构造，这里组装了类、方法名、参数，比如本文的实例，commandKey=RemoteProductService#getProduct(int)

配置文件指定

hystrix:
    command:
        "RemoteProductService#getProduct(int)":
            execution:
                isolation:
                    thread:
                        timeoutInMilliseconds: 500

Java中指定

    @Bean
    public Feign.Builder feignHystrixBuilder() {
        return HystrixFeign.builder().setterFactory(new SetterFactory() {
            @Override
            public HystrixCommand.Setter create(Target<?> target, Method method) {
                return HystrixCommand.Setter
                        .withGroupKey(HystrixCommandGroupKey.Factory.asKey(RemoteProductService.class.getSimpleName()))// 控制 RemoteProductService 下,所有方法的Hystrix Configuration
                        .andCommandPropertiesDefaults(
                                HystrixCommandProperties.Setter().withExecutionTimeoutInMilliseconds(10000) // 超时配置
                        );
            }
        });
    }

小结

论灵活程度，还是配置文件灵活一点，唯一的工作量就是根据规则构造commandKey，然后就可以进行相关配置了。

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