gtid_current_pos on Galera Cluster is not updating

The gtid_current_pos variable on galera node does not get updated on other nodes.

I have 2 node galera cluster along with maxscale.

From maxscale :

[root@ip-172-31-12-219 centos]# maxctrl list servers
┌─────────┬──────────────┬──────┬─────────────┬─────────────────────────┬────────┐
│ Server │ Address │ Port │ Connections │ State │ GTID │
├─────────┼──────────────┼──────┼─────────────┼─────────────────────────┼────────┤
│ server1 │ 18.207.3.40 │ 3333 │ 0 │ Master, Synced, Running │ 1-1-15 │
├─────────┼──────────────┼──────┼─────────────┼─────────────────────────┼────────┤
│ server2 │ 54.237.3.158 │ 3333 │ 0 │ Slave, Synced, Running │ │
└─────────┴──────────────┴──────┴─────────────┴─────────────────────────┴────────┘

As per the maxscale, server1 is a master and it's showing gtid_current_pos "1-1-15".

Server 1:

MariaDB [(none)]> show global variables like '%gtid%';
-------------------------------+

-------------------------------+

-------------------------------+
11 rows in set (0.001 sec)

Server 2 :

MariaDB [(none)]> show global variables like 'gtid%';
-------------------------------+

-------------------------------+

-------------------------------+
9 rows in set (0.001 sec)

In server2 the gtid_current_pos is empty. Now I have stopped the mariadb service in server1.
Now server2 is my master.

[root@ip-172-31-12-219 centos]# maxctrl list servers
┌─────────┬──────────────┬──────┬─────────────┬─────────────────────────┬──────┐
│ Server │ Address │ Port │ Connections │ State │ GTID │
├─────────┼──────────────┼──────┼─────────────┼─────────────────────────┼──────┤
│ server1 │ 18.207.3.40 │ 3333 │ 0 │ Down │ │
├─────────┼──────────────┼──────┼─────────────┼─────────────────────────┼──────┤
│ server2 │ 54.237.3.158 │ 3333 │ 0 │ Master, Synced, Running │ │
└─────────┴──────────────┴──────┴─────────────┴─────────────────────────┴──────┘
Now I have inserted some data on server2 , and checked the gtid_current_pos still it's showing empty value.

MariaDB [test]> create table t1 (id int,name varchar(20));
Query OK, 0 rows affected (0.010 sec)

MariaDB [test]> insert into t1 values(1,'kjsdlad');
Query OK, 1 row affected (0.002 sec)

MariaDB [test]> insert into t1 values(2,'mmznb');
Query OK, 1 row affected (0.001 sec)

MariaDB [test]> insert into t1 values(3,'rock');
Query OK, 1 row affected (0.002 sec)

MariaDB [test]> insert into t1 values(4,'khlcsk');
Query OK, 1 row affected (0.002 sec)

MariaDB [test]> insert into t1 values(5,'lcsk');
Query OK, 1 row affected (0.004 sec)

MariaDB [test]> show global variables like 'gtid%';
-------------------------------+

-------------------------------+

-------------------------------+
9 rows in set (0.001 sec)

why we are not seeing gtid_current_pos for other slave servers ?

If I switch the master server still it's showing empty.