Comments on: Upgrading to MySQL 8: Embrace the Challenge https://www.percona.com/blog/upgrading-to-mysql-8/ Fri, 02 Jun 2023 11:06:30 +0000 hourly 1 https://wordpress.org/?v=6.5.2 By: Mike Benshoof https://www.percona.com/blog/upgrading-to-mysql-8/#comment-10973119 Fri, 02 Apr 2021 19:00:42 +0000 https://www.percona.com/blog/?p=75138#comment-10973119 In reply to john.

Thanks for your feedback John! While upgrading the cluster from 5.7 to 8.0 in place is technically supported, it comes with some caveats and definitely IS NOT recommended. If the cluster is in read-only or all writes go to a single node, you could go through a rolling upgrade of each node until there is only one remaining 5.7 node. At this point, you would need to drop that node out of the cluster to ensure no writes are sent from 8.0 to 5.7.

The recommended approach would be to build a single node cluster, keep it in sync via standard asynchronous replication, build out the new cluster from there, and then cutover.

Likewise, with 8.x minor upgrades, they follow the same paradigm and it is strongly recommended to follow the same new cluster/replication approach.

]]> By: john https://www.percona.com/blog/upgrading-to-mysql-8/#comment-10973117 Fri, 02 Apr 2021 13:22:02 +0000 https://www.percona.com/blog/?p=75138#comment-10973117 Your post is very informative and useful. We do have a few remaining primary/replica mysql instances, but most of our environment is now converted to use PXC clusters. So exactly how can we upgrade a PXC node to 8.x while the remainder of the cluster is 5.x. It seems impossible.

So at least for the initial jump to 8.x it would appear we are faced with creating three new 5T nodes and making that a replica and then cutting over to the new cluster. What a pain.

At least once we make the initial jump to 8.x we should be able to take out one 5T node, upgrade that to 8.x.y and see if it breaks anything before we upgrade the entire cluster. But of course there is always that chance we are wrong. What then?

]]>