code: public void suspendZooKeeper() {
          val zk = this.zkServer.get();
          Preconditions.checkState(zk != null, "ZooKeeper not started.");
  
          // Stop, but do not close, the ZK runner.
          zk.stop();
          log.info("ZooKeeper suspended.");
      }
docs: Suspends (stops) ZooKeeper, without destroying its underlying data (so a subsequent resume can pick up from the
  state where it left off).