Implement retries on "unknown errors"

[miparnisari]

See

aws-dax-go/dax/internal/client/dax_retryer.go

Lines 64 to 68 in 9976852

	func (r DaxRetryer) ShouldRetry(req *request.Request) bool {
	daxErr := req.Error.(daxError)
	codes := daxErr.CodeSequence()
	return len(codes) > 0 && (codes[0] == 1 || codes[0] == 2) || req.IsErrorThrottle() || isAuthCRequiredException(codes)
	}

It is not clear to me what code this error has:

aws-dax-go/dax/internal/client/error.go

Line 339 in 07563aa

return awserr.NewRequestFailure(awserr.New(ErrCodeUnknown, e.Message(), nil), e.StatusCode(), e.RequestID())

But from what i'm seeing in my application, which is calling TransactWriteItemsWithContext, DAX is not retrying on this specific error. I think it should.

Or do you recommend us implementing a retrier?

[sumitsa-amazon]

We recommend application level retry in such cases. The rational is that in case of UnknownErrors, DAX client isn't really aware if the changes made it to DDB and can't determine if it is safe to perform retries. The application is expected to perform sanity validations (if required), and attempt a retry.

This behavior is similar to AmbiguousWriteFailureException in DAX Java SDK ref.