Setting up slave_parallel_type = LOGICAL_CLOCK dynamically not working in pxc

Hi,

Here, not able to set the slave_parallel_type='LOGICAL_CLOCK' dynamically but able to change with cnf and restart:
node1 [localhost:26530] {msandbox} ((none)) > set global slave_parallel_type='LOGICAL_CLOCK';
ERROR 1105 (HY000): Percona-XtraDB-Cluster prohibits enabling slave_preserve_commit_order as it conflicts with galera multi-master commit order semantics
mysql [localhost:6739] {msandbox} ((none)) > show global variables like 'slave_%';
----------------------------------------------------------------------------------+

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

----------------------------------------------------------------------------------+
17 rows in set (0.00 sec)
 

But when we edit the cnf like below and restarting makes the changes: (changed node2's cnf for testing)
relay_log_info_repository = TABLE
slave_parallel_type = LOGICAL_CLOCK
slave_parallel_workers = 4
relay_log_recovery = ON
 

after restart:
node2 [localhost:26531] {msandbox} ((none)) > show global variables like 'slave_paral%';
---------------------------------------+

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

---------------------------------------+
2 rows in set (0.01 sec)node2 [localhost:26531] {msandbox} ((none)) > show global variables like 'slave_p%';
--------------------------------------------+

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

--------------------------------------------+
4 rows in set (0.01 sec)
 
node2 [localhost:26531] {msandbox} ((none)) > status
--------------
/home/vinodh.krishnaswamy/opt/mysql/pxc5.7.28/bin/mysql Ver 14.14 Distrib 5.7.28-31, for Linux (x86_64) using 6.2Connection id: 5
Current database:
Current user: msandbox@localhost
SSL: Not in use
Current pager: stdout
Using outfile: ''
Using delimiter: ;
Server version: 5.7.28-31-31.41-log Percona XtraDB Cluster binary (GPL) 5.7.28-31.41, Revision ef2fa88, wsrep_31.41
Protocol version: 10
Connection: Localhost via UNIX socket
Server characterset: latin1
Db characterset: latin1
Client characterset: utf8
Conn. characterset: utf8
UNIX socket: /tmp/mysql_sandbox26531.sock
Uptime: 13 min 26 secThreads: 4 Questions: 9 Slow queries: 0 Opens: 112 Flush tables: 1 Open tables: 27 Queries per second avg: 0.011
--------------
 

Please check why it is behaving like it.

Apart from this, noted from the doc, from 5.7.12rc, setting up slave_preserve_commit_order is not supported. But this is not related with slave_parallel_type's value setting issue above.

https://www.percona.com/doc/percona-xtradb-cluster/5.7/release-notes/Percona-XtraDB-Cluster-5.7.12-5rc1-26.16.html

• Disabled switching of slave_preserve_commit_order to ON when running PXC in cluster mode, as it conflicts with existing multi-master commit ordering resolution algorithm in Galera.