code: static String getPrimaryRegistration(Configuration startupConf,
        Configuration conf, String fsname) throws IOException {
      AvatarZooKeeperClient zk = null;
      int maxTries = startupConf.getInt("dfs.avatarnode.zk.retries", 3);
      for (int i = 0; i < maxTries; i++) {
        try {
          zk = new AvatarZooKeeperClient(conf, null, false);
          String zkRegistry = zk.getPrimaryAvatarAddress(fsname, new Stat(),
              false);
          return zkRegistry;
        } catch (Exception e) {
          LOG.error(
              "Got Exception when reading primary registration. Will retry...", e);
        } finally {
          shutdownZkClient(zk);
        }
      }
      throw new IOException("Cannot connect to zk");
    }
docs: Obtain the registration of the primary from zk.