如何允许在Hystrix中使用Feign时传播400个错误？

Question

我正在构建一个SpringBoot微服务，它调用另一个微服务，当然想使用Hystrix和Feign客户机，这两个客户机都包含在Spring Cloud中。我使用的是camden.sr5版本。

对于任何超时、连接失败和来自Feign的50倍响应代码，我希望Hystrix踢进并正常工作：跳闸断路器和调用回退（如果配置）等。它在默认情况下这样做，所以我很好。

使用以下代码开箱即用：

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.hateoas.Resource;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient(name = "dog-service", url = "http://...")
public interface DogsFeignClient {
  @RequestMapping(method = RequestMethod.POST, path = "/dogs")
  Resource<Dog> createDog(Dog dog);
}

生成这个异常，它不能很好地将40x响应传递回调用方：

com.netflix.hystrix.exception.HystrixRuntimeException: DogsFeignClient#createDog(Dog) failed and no fallback available.
    at com.netflix.hystrix.AbstractCommand$22.call(AbstractCommand.java:805) ~[hystrix-core-1.5.6.jar:1.5.6]
    ....lines ommited for brevity....
Caused by: feign.FeignException: status 400 reading DogsFeignClient#createDog(Dog); content:
{
  "errors" : [ {
    "entity" : "Dog",
    "property" : "numberOfLegs",
    "invalidValue" : "3",
    "message" : "All dogs must have 4 legs"
  } ]
}
    at feign.FeignException.errorStatus(FeignException.java:62) ~[feign-core-9.3.1.jar:na]
    at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:91) ~[feign-core-9.3.1.jar:na]
    at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:138) ~[feign-core-9.3.1.jar:na]
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) ~[feign-core-9.3.1.jar:na]
    at feign.hystrix.HystrixInvocationHandler$1.run(HystrixInvocationHandler.java:108) ~[feign-hystrix-9.3.1.jar:na]
    at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:301) ~[hystrix-core-1.5.6.jar:1.5.6]
    at com.netflix.hystrix.HystrixCommand$2.call(HystrixCommand.java:297) ~[hystrix-core-1.5.6.jar:1.5.6]
    at rx.internal.operators.OnSubscribeDefer.call(OnSubscribeDefer.java:46) ~[rxjava-1.1.10.jar:1.1.10]
    ... 26 common frames omitted

当然，我可以查看com.netflix.hystrix.exception.hystrixruntimeException、case字段，其中包含feign.feignException，并且隐藏在描述中的是JSON响应本身，包含换行符等。但是feign.FeignException的case字段是对其本身的引用。是否有一种方法可以传播更深层次的异常而不是HystrixRuntimeException？

还有一种方法可以让下游服务的响应包含原始主体，这样我就不必解构嵌套异常的消息字段了吗？

Answer 1

这可以使用单独的配置来实现，该配置将在HystrixBadRequestException的子类中包装400个，并将它们抛给客户端代码。这些例外不影响断路器的状态--如果电路关闭，它将保持关闭，如果它打开，它将保持开放。

@FeignClient(name = "dog-service", 
             url = "http://...", 
             configuration=FeignPropagateBadRequestsConfiguration.class)
public interface DogsFeignClient {
  @RequestMapping(method = RequestMethod.POST, path = "/dogs")
  Resource<Dog> createDog(Dog dog);
}

其中FeignPropagateBadRequestsConfiguration为

@Configuration
public class FeignSkipBadRequestsConfiguration {
    @Bean
    public ErrorDecoder errorDecoder() {
        return (methodKey, response) -> {
            int status = response.status();
            if (status == 400) {
                String body = "Bad request";
                try {
                    body = IOUtils.toString(response.body().asReader());
                } catch (Exception ignored) {}
                HttpHeaders httpHeaders = new HttpHeaders();
                response.headers().forEach((k, v) -> httpHeaders.add("feign-" + k, StringUtils.join(v,",")));
                return new FeignBadResponseWrapper(status, httpHeaders, body);
            }
            else {
                return new RuntimeException("Response Code " + status);
            }
        };
    }
}

FeignBadResponseWrapper是

@Getter
@Setter
public class FeignBadResponseWrapper extends HystrixBadRequestException {
    private final int status;
    private final HttpHeaders headers;
    private final String body;

    public FeignBadResponseWrapper(int status, HttpHeaders headers, String body) {
        super("Bad request");
        this.status = status;
        this.headers = headers;
        this.body = body;
    }
}

这有点麻烦，您只能在errordecoder中获得响应正文，因为在此之后流将被关闭。但是使用此方法，您可以将响应数据抛出给客户端代码，而不会影响电路：

    try {
        return dogsFeignClient.createDog(dog);
    } catch (HystrixBadRequestException he) {
        if (he instanceof FeignBadResponseWrapper) {
            // obtain data from wrapper and return it to client
        } else {
            // return basic error data for other exceptions
        }
    }