@Override
    public void onBarrierCreated(String version) {
      // Start the timer for rebalancing
      startTime = System.nanoTime();

      metrics.barrierCreation.inc();
      if (leaderElector.amILeader()) {
        debounceTimer.scheduleAfterDebounceTime(barrierAction, (new ZkConfig(config)).getZkBarrierTimeoutMs(), () -> barrier.expire(version));
      }
    }
Builds the {@link GrouperMetadataImpl} based upon provided {@param jobModelVersion}
and {@param processorNodes}.
@param jobModelVersion the most recent jobModelVersion available in the zookeeper.
@param processorNodes the list of live processors in the zookeeper.
@return the built grouper metadata.
samza-core/src/main/java/org/apache/samza/zk/ZkJobCoordinator.java