private void closeSession(ISession session) {
    if (session != null) {
      try {
        session.close();
      } catch (Exception e2) {
        // do nothing. We just want to guarantee the session is closed.
        LOGGER.warn(CLOSE_THE_SESSION_FAILED, e2);
      }
    }
  }
close all connections in the pool
iotdb-client/session/src/main/java/org/apache/iotdb/session/pool/SessionPool.java