title: How to handle backpressure in a Kafka Connect Sink?
body: <p>We build a custom Kafka Connect sink which in turn calls a remote REST API. How do I propagate backpressure to the Kafka Connect infrastructure, so put() is called less often in cases when the remote system is slower than the internal consumer delivers messages to put()?
  The Kafka connect documentation says that we should not block in put(), but block in flush(). But not blocking in put() means that we have to buffer data which surely leads to OOM exceptions at some point, if put() is called more often than flush().
  I've seen that a kafka consumer is allowed to call pause() or block in the loop(). Is it possible to leverage this in a kafka connect sink?</p>