在 HystrixFeign 客户端回退中获取原因的问题

Question

我有 HystrixFeign 客户端，我正试图在我的回退实现中获得 cause/exception，因为我真的很想知道回退的原因，这样我就可以解决服务调用失败的问题. 但是下面的实现并没有让我明白原因。这工作得很好，回退一直被调用。但我不知道为什么。我是 Feign 和 Hystrix 的新手。我的应用程序是在 java 1.6 年前编写的，这是一种增强调用。所以我不能使用任何 lambda 表达式。

我的客户端界面定义如下

public interface MyServiceFeignClient {
      @RequestLine("POST /myService/order")
      @Headers("Content-Type:application/vnd.org.company.domain.order+json;version=1.0")
      ServiceResponse sendOrder(String content);
}

我的 FeignClientFacory 如下所示

public class FeignClientFactory {

    private static final Logger LOG = LoggerFactory.getLogger(FeignClientFactory.class);

    private String serviceUrl;

    public FeignClientFactory(final String serviceUrl) {
        this.serviceUrl = serviceUrl;
    }

    public MyServiceFeignClient newInstance() {
        return HystrixFeign.builder()
            .decoder(new GsonDecoder())
            .target(MyServiceFeignClient.class, serviceUrl);

    }

    class ClientFallbackFactory implements MyServiceFeignClient, FallbackFactory<ClientFallbackFactory> {

        final Throwable cause;

        public ClientFallbackFactory() {
            this(null);
        }

        ClientFallbackFactory(Throwable cause) {
            this.cause = cause;
        }
        // note that this method is not getting called at all
        @Override
        public ClientFallbackFactory create(Throwable cause) {
            if (cause != null) {
                String errMessage = StringUtils.isNotBlank(cause.getMessage()) ? cause.getMessage() : "unknown error occured";
                LOG.debug("Client fallback called for the cause : {}", errMessage);
            }
            return new ClientFallbackFactory(cause);

        }
        // everytime this method is called as fallback and the cause is just null
        @Override
        public ServiceResponse sendOrder(String content) {
            LOG.debug("service client api fallback called");
            ServiceResponse response = new ServiceResponse();
            String errMessage = (cause == null ? "service client api fallback called" : cause.getMessage());
            response.setErrorMessage(errMessage);
            response.setResultStatus("WARN");
            return response;
        }

    }

}

Answer 1

从 open feign git hub 获取 retroApi 示例测试用例代码并开始一个一个地修改帮助我解决了这个问题。下面是工作代码。

public static class ClientFallbackFactory implements MyServiceFeignClient, FallbackFactory<ClientFallbackFactory> {

    @Override
    public ClientFallbackFactory create(Throwable cause) {
        return new PRSClientFallback(cause);
    }

    final Throwable cause; // nullable

    public ClientFallbackFactory() {
        this(null);
    }

    ClientFallbackFactory(Throwable cause) {
        this.cause = cause;
    }

    @Override
    public PaymentRiskServiceResponse sendOrder(String content) {
        String errorMessage = (cause == null) ? "No cause returned" : cause.getMessage();
        LOG.debug("Client fallback called : {} ", errorMessage);
        MyServiceResponse response = new MyServiceResponse();
        response.setResultStatus("WARN");
        response.setErrorMessage("Client fallback called");
        return response;
    }
}

确保在调用 HystrixFeign 目标方法时对 Fallback 工厂进行类型转换，因为 Fallback class 正在实现您的客户端界面和 FallbackFactory。

return HystrixFeign.builder()
        .encoder(new JacksonEncoder(mapper))
        .decoder(new GsonDecoder())
        .target(MyServiceFeignClient.class, prsUrl, (FallbackFactory<ClientFallbackFactory>) new ClientFallbackFactory());

你可以追踪这个问题的对话[https://github.com/OpenFeign/feign/issues/458]

在 HystrixFeign 客户端回退中获取原因的问题

Issue in getting cause in HystrixFeign client fallback

java

fallback

hystrix

spring-cloud-feign

feign