public long getFencingToken() {
        return this.acquirer.getFencingToken();
    }
Making the lock safe with fencing token.

Is simply a number that increases (e.g. incremented by the lock
service) every time a client acquires the lock.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/util/concurrent/DistributedLock.java