title: Error UNKNOWN_MEMBER_ID occurred while committing offsets for group xxx
body: <p>With Kafka client Java library, consuming logs has worked for some time but with the following errors it doesn't work any more:</p>
  
  <pre><code>2016-07-15 19:37:54.609  INFO 4342 --- [main] o.a.k.c.c.internals.AbstractCoordinator  : Marking the coordinator 2147483647 dead.
  2016-07-15 19:37:54.933 ERROR 4342 --- [main] o.a.k.c.c.internals.ConsumerCoordinator  : Error UNKNOWN_MEMBER_ID occurred while committing offsets for group logstash
  2016-07-15 19:37:54.933  WARN 4342 --- [main] o.a.k.c.c.internals.ConsumerCoordinator  : Auto offset commit failed: Commit cannot be completed due to group rebalance
  2016-07-15 19:37:54.941 ERROR 4342 --- [main] o.a.k.c.c.internals.ConsumerCoordinator  : Error UNKNOWN_MEMBER_ID occurred while committing offsets for group logstash
  2016-07-15 19:37:54.941  WARN 4342 --- [main] o.a.k.c.c.internals.ConsumerCoordinator  : Auto offset commit failed:
  2016-07-15 19:37:54.948  INFO 4342 --- [main] o.a.k.c.c.internals.AbstractCoordinator  : Attempt to join group logstash failed due to unknown member id, resetting and retrying.
  </code></pre>
  
  <p>It keeps resetting.</p>
  
  <p>Running another instance of the same application gets errors immediately.</p>
  
  <p>I suspect Kafka or its ZooKeeper has a problem but there's no error log.</p>
  
  <p>Any one who has idea on what's going on here?</p>
  
  <p>This is the application I'm using: <a href="https://github.com/izeye/log-redirector" rel="noreferrer">https://github.com/izeye/log-redirector</a></p>