Hi Gurus, I'm building a new IO connector now, and I try to ack messages in the "UnboundedSource.CheckpointMark.finalizeCheckpoint()" method as MqttIO and JmsIO did, but I found in the javadoc it said
> It is NOT safe to assume the UnboundedSource.UnboundedReader from which this checkpoint was created still exists at the time this method is called. I do encounter this situation in my testing with the Direct Runner, the "msg.ack()" method failed when the finalizeCheckpoint() method is called since the related reader has already been closed! Is there any way to ask the runner to call finalizeCheckpoint() method before it closed the Reader?
