Error response returned by the server is ignored by resilience4j

Hi

I am using the resilience4j with Feign client for communication with another server (lets say it is running on localhost:8090 with 1 exposed endpoint i.e. /sample). I am testing a case when I want to record only specific exceptions from the underlying http client library. So following is my config:

resilience4j.circuitbreaker:
  configs:
    default:
      registerHealthIndicator: true
      ringBufferSizeInClosedState: 4
      ringBufferSizeInHalfOpenState: 2
      automaticTransitionFromOpenToHalfOpenEnabled: true
      waitDurationInOpenState: 20s
      failureRateThreshold: 50
      eventConsumerBufferSize: 10
      ignoreExceptions:
        - com.resilience4j.exception.BusinessException
      recordExceptions:
        - java.net.SocketTimeoutException
        - feign.RetryableException

Now when the /sample endpoint returns a response with http status 400, which is a valid case and due to incorrect data passed. The /sample endpoint returns the following response if called separately

{
    "message": "this is a bad request"
}

But the resilience4j library ignores this response and returns the following response:

{
    "timestamp": "2019-08-14T09:40:00.568+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "status 400 reading MyFeignClient#feignMessage()",
    "path": "/resilience4j/feignClient"
}

How can I preserve the original response returned by the other server?

[RobWin]

recordExceptions: Configures a list of classes that are recorded as a failure and thus increase the failure rate. Any exception matching or inheriting from one of the list should count as a failure, unless ignored via ignoreExceptions. All other exceptions are not recorded, which means that they are ignored and thus do not count as success nor failure. If you add an exception to recordExceptions it’s like: ignore all exceptions except this one. If you add an exception to ignoreExceptions it’s like: record all exceptions except this one.

The combination of ignoreExceptions and recordExceptions is helpful when you want to handle inheritance. For example: ignoreExceptions(Exception.class) and recordExceptions(Throwable.class) would record java.lang.Error as a failure.

[RobWin]

Closed in favor of #568