title: what happens to the messages in producer 'buffer.memory' if the producer app is crashed before they were sent to the broker?
body: <p>I am using spring-kafka 2.2.8 and writing a simple producer with the below settings:
  linger.ms : 5
  max.block.ms: 60000</p>
  <p>Now my question is, what happens to the messages in producer 'buffer.memory' if the producer app is crashed before they were sent to the broker (especially in a asynchronous producer call mode)?</p>
  <p>Is there any option to capture the status of these messages?</p>