title: What ways can a Consumer consume message in Kafka?
body: <p>If there is a Kafka server "over there" somewhere across the network I would assume that there might be two ways that a Consumer could consume the messages:</p>
  
  <ol>
  <li><p>By first of all 'subscribing' to the Topic and in effect telling the Kafka server where it is listening so that when a new message is Produced, Kafka proactively sends the message to the Consumer, across the network.</p></li>
  <li><p>The Consumer has to poll the Kafka server asking for any new messages, using the offset of the messages it has currently taken.</p></li>
  </ol>
  
  <p>Is this how Kafka works, and is the option configurable for which one to use?</p>