private void closeRocksDB() {
        if (this.db != null) {
            this.db.close();
            this.db = null;
        }
    }
Local KV store based on RocksDB

@author dennis
@author jiachun.fjc
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/storage/RocksRawKVStore.java