Some time ago I wrote this article explaining how to find which node was the Primary Master in a MySQL Group Replication cluster running in Single-Primary Mode.
In the latest release of Group Replication, MySQL 8.0.2 dmr, Jaideep improved the visibility of Group Replication extending the performance_schema tables (see his article).
Thanks to these improvements, it’s now very easy to find which host is acting a Primary-Master. This is the query you can use:
mysql-sql> SELECT MEMBER_HOST as `PRIMARY`
FROM performance_schema.replication_group_members
WHERE MEMBER_ROLE='PRIMARY';
+---------+
| PRIMARY |
+---------+
| mysql3 |
+---------+
1 row in set (0.00 sec)
Much easier isn’t it ?
I let you discover the other improvements and features in MySQL 8.0.2 and don’t forget that your feedback is very important !
[…] MySQL Group Replication: who is the primary master – updated! […]
this is a good improvement. but i want to know two questions：
1、is it will support rejoin when one member is offline after a network issue？
2、at present，mysql shell can not start the cluster stabilize，now have a bug can not fetch the mgr group_name, is it will have feature after cluster restart with all members，mgr will auto recover cluster like galera cluster？
the same question.
Hi,
There is a rejoinInstance() adminAPI command to rejoin a node after it was offline. There is also another command when the full cluster was down: rebootClusterFromCompleteOutage()
Check: https://dev.mysql.com/doc/dev/mysqlsh-api-javascript/1.0/classmysqlsh_1_1dba_1_1_cluster.html#af56d9116e7d6d0cd111aed0971163248 and https://dev.mysql.com/doc/dev/mysqlsh-api-javascript/1.0/classmysqlsh_1_1dba_1_1_dba.html#a64e1c660242082f000a6e0eb60140769
Cheers,