@Override
    public void update(ClickHouseNode node, Status status) {
        lock.writeLock().lock();
        try {
            if (node.config.getNodeCheckInterval() > 0) {
                node.lastUpdateTime.set(System.currentTimeMillis());
            }
            policy.update(this, node, status);
        } finally {
            lock.writeLock().unlock();
        }
    }
Checks whether it's single node or not.

@return true if it's single node; false otherwise
clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseNodes.java