public void subscribeToJobModelVersionChange(GenerationAwareZkDataListener dataListener) {
    LOG.info(" subscribing for jm version change at:" + keyBuilder.getJobModelVersionPath());
    zkClient.subscribeDataChanges(keyBuilder.getJobModelVersionPath(), dataListener);
    metrics.subscriptions.inc();
  }
subscribe for changes of JobModel version
@param dataListener describe this
samza-core/src/main/java/org/apache/samza/zk/ZkUtils.java