can not login to server after PM failover

env desc:
install mcs with mode multi+separate+external,
with 1 UM and 2 PMs,
using glusterfs as external storage,
/etc/fstab is modified properly,
originally, PM1 is the OAM

related shell script
a.sh:
while true
do
date > /tmp/b
mysql -uroot -h127.0.0.1 -P3306 -e "set names utf8; select * from test.t2 limit 100" >> /tmp/b
done

reproduce steps:
1. create a table
CREATE TABLE `t2` (
`c0` varchar(30) DEFAULT NULL,
`c1` varchar(30) DEFAULT NULL,
`c2` varchar(30) DEFAULT NULL,
`c3` varchar(30) DEFAULT NULL,
`c4` varchar(30) DEFAULT NULL,
`c5` varchar(30) DEFAULT NULL,
`c6` varchar(30) DEFAULT NULL,
`c7` varchar(30) DEFAULT NULL,
`c8` varchar(30) DEFAULT NULL,
`c9` varchar(30) DEFAULT NULL,
`c10` varchar(30) DEFAULT NULL,
`c11` varchar(30) DEFAULT NULL,
`c12` varchar(30) DEFAULT NULL,
`c13` varchar(30) DEFAULT NULL,
`c14` varchar(30) DEFAULT NULL,
`c15` varchar(30) DEFAULT NULL,
`c16` varchar(30) DEFAULT NULL,
`c17` varchar(30) DEFAULT NULL,
`c18` varchar(30) DEFAULT NULL,
`c19` varchar(30) DEFAULT NULL,
`c20` varchar(30) DEFAULT NULL,
`c21` varchar(30) DEFAULT NULL,
`c22` varchar(30) DEFAULT NULL,
`c23` varchar(30) DEFAULT NULL,
`c24` varchar(30) DEFAULT NULL,
`c25` varchar(30) DEFAULT NULL,
`c26` varchar(30) DEFAULT NULL,
`c27` varchar(30) DEFAULT NULL,
`c28` varchar(30) DEFAULT NULL,
`c29` varchar(30) DEFAULT NULL
) ENGINE=Columnstore DEFAULT CHARSET=utf8;

2. load 25000000 lines of data into t2.
3. run a.sh, the script should always be running during the failover.
4. use command "shutdown -h now" to shut down the machine of PM1.
5. after mcs handle the failover, it report everything is ok. but you can not login from mysql client (mysql -uroot -P3306 -h127.0.0.1) to the UM's mysqld instance. in fact the failover was failed.

comment:
1. after some checks, I found /usr/local/mariadb/columnstore/mysql/lib/mysql/mysql.sock is not exist, but no error logged in the mysql instance's start up log.
2. stopped a.sh and startup the machine of PM1, after mcs finished the failover again, the system worked again.

columnstoreSupport related file is attached.