@Override
    public void scan() {
        if (null != connections && !connections.isEmpty()) {
            for (Connection conn : connections) {
                if (!conn.isFine()) {
                    logger.warn(
                        "Remove bad connection when scanning conns of ConnectionPool - {}:{}",
                        conn.getRemoteIP(), conn.getRemotePort());
                    conn.close();
                    removeAndTryClose(conn);
                }
            }
        }
    }
do mark async create connection start
src/main/java/com/alipay/remoting/ConnectionPool.java