public void closeConnection() throws IOException {
    if (hbaseAdmin != null) {
      Closeables.close(hbaseAdmin, true);
      hbaseAdmin = null;
    }
    AsyncClusterConnection asyncConnection = this.asyncConnection.getAndSet(null);
    if (asyncConnection != null) {
      Closeables.close(asyncConnection, true);
    }
  }
Get a assigned AsyncClusterConnection to the cluster. this method is thread safe.
@param user assigned user
@return An AsyncClusterConnection with assigned user.
hbase-server/src/test/java/org/apache/hadoop/hbase/HBaseTestingUtil.java