public boolean isExist(final String key) {
        try {
            return Objects.nonNull(client.checkExists().forPath(key));
        } catch (Exception e) {
            throw new ShenyuException(e);
        }
    }
check if key exist.

@param key zookeeper path
@return if exist.
shenyu-sync-data-center/shenyu-sync-data-zookeeper/src/main/java/org/apache/shenyu/sync/data/zookeeper/ZookeeperClient.java