title: Kafka ConsumerGroupState explaination
body: <p>I saw the following constants in <code>ConsumerGroupState</code>. What situation would cause a consumer group hold DEAD or UNKNOWN state? </p>
  
  <pre class="lang-java prettyprint-override"><code>UNKNOWN("Unknown"),
  PREPARING_REBALANCE("PreparingRebalance"),
  COMPLETING_REBALANCE("CompletingRebalance"),
  STABLE("Stable"),
  DEAD("Dead"),
  EMPTY("Empty");
  </code></pre>
  
  <p>I think EMPTY means members are empty. PREPARING_REBALANCE means new consumer joins / old consumer left and COMPLETING_REBALANCE is similar to it.</p>
  
  <p>My goal is to find a state which indicates the consumer group is inactive , and as I understand, I can simply take EMPTY state.</p>