private State state; /* FLUID, FREEZING, FROZEN */

public void freeze() throws Exception {
  this.state = FREEZING;
}

  public ScenarioManagerEx getScenarioManager() throws Exception {
    if (isStale()) {
      buildScenarioManager();
    } else {
      logger.info("ScenarioManager is not stale ... Returning the current instance");
    }
    if (FREEZING == state) {
      state = FROZEN;
      logger.info("ScenarioManager frozen");
    }
    return scenarioManager;
  }

  private boolean isStale() {
    return scenarioManager == null ||
            ((FROZEN != state) && confDao.get().getScenarioLastUpdated().after(scenarioLastUpdated));

  }