public static String readMyEphemeralNodeOnDisk() throws IOException {
    String fileName = getMyEphemeralNodeFileName();
    if (fileName == null) {
      throw new FileNotFoundException("No filename; set environment variable HBASE_ZNODE_FILE");
    }
    FileReader znodeFile = new FileReader(fileName);
    BufferedReader br = null;
    try {
      br = new BufferedReader(znodeFile);
      String file_content = br.readLine();
      return file_content;
    } finally {
      if (br != null) br.close();
    }
  }
read the content of znode file, expects a single line.
hbase-server/src/main/java/org/apache/hadoop/hbase/ZNodeClearer.java