code: public synchronized void forceTxRollover() {
          if (async) {
              try {
                  forceTxRolloverFlag = false;
                  indexCommandQueue.put(FORCE_TX_ROLLOVER);
                  while (!forceTxRolloverFlag) {
                      Thread.sleep(5);
                  }
              } catch (InterruptedException e) {
                  throw new RuntimeException(e);
              }
          }
  
      }
docs: to be used from unit tests to ensure a tx rollover has happenend