code: public ZookeeperTxId getPrimaryLastTxId(String address, boolean sync)
        throws IOException,
        KeeperException, InterruptedException, ClassNotFoundException {
      Stat stat = new Stat();
      String node = getLastTxIdNode(address);
      byte[] data = getNodeData(node, stat, false, sync);
      if (data == null) {
        return null;
      }
      return ZookeeperTxId.getFromBytes(data);
    }
docs: Retrieves the last transaction id of the primary from zookeeper.
  
  @param address
  the address of the cluster
  @param sync
  whether or not to perform a sync before read
  @throws IOException
  @throws KeeperException
  @throws InterruptedException