public static String getNamenodeNameServiceId(Configuration conf) {
    return getNameServiceId(conf, DFS_NAMENODE_RPC_ADDRESS_KEY);
  }
@Test
  public void getNameNodeNameServiceId() {
    Configuration conf = setupAddress(DFS_NAMENODE_RPC_ADDRESS_KEY);
    assertEquals("nn1", DFSUtil.getNamenodeNameServiceId(conf));
  }