In April 2021, I wrote an article about Online DDL and Group Replication. At that time we were dealing with MySQL 8.0.23 and also opened a bug report which did not have the right answer to the case presented.
Anyhow, in that article I have shown how an online DDL was de facto locking the whole cluster for a very long time even when using the consistency level set to EVENTUAL.
This article is to give justice to the work done by the MySQL/Oracle engineers to correct that annoying inconvenience.
Before going ahead, let us remember how an Online DDL was propagated in a group replication cluster, and identify the differences with what happens now, all with the consistency level set to EVENTUAL ( …[Read more]