@Override
  public void cancelDelegationToken(SessionHandle sessionHandle, HiveAuthFactory authFactory,
      String tokenStr) throws HiveSQLException {
    sessionManager.getSession(sessionHandle).
    cancelDelegationToken(authFactory, tokenStr);
    LOG.info(sessionHandle  + ": cancelDelegationToken()");
  }
If this is a background operation run asynchronously,
we block for a duration determined by a step function, before we return
However, if the background operation is complete, we return immediately.
service/src/java/org/apache/hive/service/cli/CLIService.java