Netflix Feign - Propagate Status and Exception through Microservices

Question

I'm using Netflix Feign to call to one operation of a Microservice A to other other operation of a Microservice B which validates a code using Spring Boot.

The operation of Microservice B throws an exception in case of the validation has been bad. Then I handled in the Microservices and return a HttpStatus.UNPROCESSABLE_ENTITY (422) like next:

@ExceptionHandler({
       ValidateException.class
    })
    @ResponseStatus(HttpStatus.UNPROCESSABLE_ENTITY)
    @ResponseBody
    public Object validationException(final HttpServletRequest request, final validateException exception) {
        log.error(exception.getMessage(), exception);
        error.setErrorMessage(exception.getMessage());
        error.setErrorCode(exception.getCode().toString());
        return error;
    }

So, when Microservice A calls to B in a interface as next:

@Headers("Content-Type: " + MediaType.APPLICATION_JSON_UTF8_VALUE)
@RequestLine("GET /other")
void otherOperation(@Param("other")  String other );

@Headers("Content-Type: " + MediaType.APPLICATION_JSON_UTF8_VALUE)
@RequestLine("GET /code/validate")
Boolean validate(@Param("prefix") String prefix);

static PromotionClient connect() {

    return Feign.builder()
        .encoder(new GsonEncoder())
        .decoder(new GsonDecoder())
        .target(PromotionClient.class, Urls.SERVICE_URL.toString());
}

and the validations fails it returns a internal error 500 with next message:

{
  "timestamp": "2016-08-05T09:17:49.939+0000",
  "status": 500,
  "error": "Internal Server Error",
  "exception": "feign.FeignException",
  "message": "status 422 reading Client#validate(String); content:\n{\r\n  \"errorCode\" : \"VALIDATION_EXISTS\",\r\n  \"errorMessage\" : \"Code already exists.\"\r\n}",
  "path": "/code/validate"
}

But I need to return the same as the Microservice operation B.

Which would be the best ways or techniques to propagate Status and Exceptions through microservices using Netflix Feign?

Answer 1

You could use a feign ErrorDecoder

https://github.com/OpenFeign/feign/wiki/Custom-error-handling

Here is an example

public class MyErrorDecoder implements ErrorDecoder {

    private final ErrorDecoder defaultErrorDecoder = new Default();

    @Override
    public Exception decode(String methodKey, Response response) {
        if (response.status() >= 400 && response.status() <= 499) {
            return new MyBadRequestException();
        }
        return defaultErrorDecoder.decode(methodKey, response);
    }

}

For spring to pick up the ErrorDecoder you have to put it on the ApplicationContext:

@Bean
public MyErrorDecoder myErrorDecoder() {
  return new MyErrorDecoder();
}