Group Replication SYSTEM messages in the error log

Group Replication enables you to create fault-tolerant systems with redundancy by replicating the system state to a set of servers. Even if some of the servers subsequently fail, as long it is not all or a majority, the system is still available.

In order to allow DBAs to do post observation of the main events on a group lifetime, it is essential that those events are always logged. Users could already instruct the server to do that by increasing verbosity of the error log before 8.0.21. There is an easier way now.

On MySQL 8.0.21 we did a facelift on Group Replication log messages with one goal in mind:

A MySQL DBA must be capable of observing the main events of the group through the server’s error log, regardless of the error log verbosity.

To allow that we did reclassify many log messages as system messages. System messages are always logged, independently of the server log level.
Example of a primary failover:

The best thing of this improvement, the DBA/operator does not need to do any configuration change.


Following our tradition of steady improvements, we are once again making Group Replication simpler to use by using the same server default values.

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About Nuno Carvalho

Nuno Carvalho is a Principal Software Engineer and MySQL Replication Service Team lead at Oracle, the team in charge of MySQL Group Replication plugin. His research interests include replication technologies, dependable systems and high availability. Before joining the MySQL team, he was a post-graduate student and a researcher at the University of Minho, Portugal, where he designed and implemented techniques to improve distributed systems scalability.

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