@Transition(to = "ONLINE", from = "OFFLINE")
  public void onTransitionToOnlineFromOffline(Message message, NotificationContext context) {
    logger.info("{} Transitioning to ONLINE from OFFLINE for Partition {}",
        helixVcrClusterParticipant.getCurrentDataNodeId(), message.getPartitionName());
    helixVcrClusterParticipant.addPartition(message.getPartitionName());
  }
{@link StateModel} to use when the VCR participants register to Helix. The methods are callbacks
that get called within a participant whenever its state changes in Helix.
ambry-cloud/src/main/java/com/github/ambry/cloud/OnlineOfflineHelixVcrStateModel.java