code: public synchronized void store(long maxTxId) throws IOException {
      long currentMaxTxId = get();
      if (currentMaxTxId < maxTxId) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("Resetting maxTxId to " + maxTxId);
        }
        set(maxTxId);
      }
    }
docs: Store the specified transaction id in the maxTxId ZNode if the
  specified maxTxId is greater than the existing maxTxId.
  @param maxTxId Max transaction id to store
  @throws IOException If there is an unrecoverable error communicating with
  ZooKeeper