docs: public static void createPersistentZKNodes(ZooKeeper zk) {
          LinkedList<ZKUtil.StringCallback> callbacks = new LinkedList<ZKUtil.StringCallback>();
          for (int i=0; i < VoltZK.ZK_HIERARCHY.length; i++) {
              ZKUtil.StringCallback cb = new ZKUtil.StringCallback();
              callbacks.add(cb);
              zk.create(VoltZK.ZK_HIERARCHY[i], null, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT, cb, null);
          }
          for (ZKUtil.StringCallback cb : callbacks) {
              try {
                  cb.get();
              } catch (org.apache.zookeeper_voltpatches.KeeperException.NodeExistsException e) {
                  // this is an expected race.
              } catch (Exception e) {
                  VoltDB.crashLocalVoltDB(e.getMessage(), true, e);
              }
          }
      }