static HelixZkClient getHelixZkClient(String zkString) {
    HelixZkClient zkClient =
        DedicatedZkClientFactory.getInstance().buildZkClient(new HelixZkClient.ZkConnectionConfig(zkString));
    zkClient.setZkSerializer(ZN_RECORD_SERIALIZER);
    return zkClient;
  }
@return the {@link HelixZkClient} from the zookeeper connection string.
@param zkString the zookeeper connection string.
ambry-commons/src/main/java/com/github/ambry/clustermap/HelixVcrUtil.java