docs: public List<Long> liveNodes() {
          String path = ArbitrateConstants.NODE_NID_ROOT;
          try {
              List<String> nids = zookeeper.getChildren(path);
              List<Long> result = new ArrayList<Long>();
              for (String nid : nids) {
                  result.add(Long.valueOf(nid));
              }
  
              return result;
          } catch (ZkException e) {
              throw new ArbitrateException("liveNodes", e);
          }
      }