Servicestack Exception Handling: Passing a Status That Came From Web - servicestack

Question

Let's say I have multiple services. One service is calling another service to get something. That service also gets some information from a third party vendor. Let's say the third party vendor returned a Too Many Requests message with 429 status code. The method that calls the third party vendor is used by lots of other methods and can be called directly via GET Request or within another Http Request.
When I detect the 429 status code, I was throwing a custom exception (let's say TooManyRequestsException) and using the Mapper to send the code to the requester.
Config.MapExceptionToStatusCode.Add(typeof(TooManyRequestsException),429);
It works if the method is called directly. But obviously I forgot the fact that this method was called by many other methods inside the service and all other methods are wrapping this exception with generic System.Exception objects with custom messages inside their catch blocks.
What other options do I have other than changing all the methods that wrap the exception with System.Exception? I tried to go over http://docs.servicestack.net/error-handling but couldn't really find a way that would help me, or couldn't make sense of it.

Answer 1

I recommend looking at Overriding OnExceptionTypeFilter in your AppHost which will let you apply custom logic to inspect the Exception and customize the ResponseStatus returned:
public override void OnExceptionTypeFilter(
Exception ex, ResponseStatus responseStatus)
{
var argEx = ex as ArgumentException;
var isValidationSummaryEx = argEx is ValidationException;
if (argEx != null && !isValidationSummaryEx && argEx.ParamName != null)
{
var paramMsgIndex = argEx.Message.LastIndexOf("Parameter name:");
var errorMsg = paramMsgIndex > 0
? argEx.Message.Substring(0, paramMsgIndex)
: argEx.Message;
responseStatus.Errors.Add(new ResponseError
{
ErrorCode = ex.GetType().Name,
FieldName = argEx.ParamName,
Message = errorMsg,
});
}
}