@Override
  public TezSessionState reopen(TezSessionState sessionState) throws Exception {
    HiveConf sessionConf = sessionState.getConf();
    if (sessionState.getQueueName() != null
        && sessionConf.get(TezConfiguration.TEZ_QUEUE_NAME) == null) {
      sessionConf.set(TezConfiguration.TEZ_QUEUE_NAME, sessionState.getQueueName());
    }
    reopenInternal(sessionState);
    return sessionState;
  }
Reopens the session that was found to not be running.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/TezSessionPoolManager.java