This section explains how to upgrade your cluster. Much of the process of upgrading an InnoDB cluster consists of upgrading the instances in the same way as documented at Section 18.7, “Upgrading Group Replication”. This section focuses on the additional considerations for upgrading InnoDB cluster. Before starting an upgrade, you can use the MySQL Shell Upgrade Checker Utility to verify instances are ready for the upgrade.
Although it is possible to have instances in a cluster which run
multiple MySQL versions, for example version 5.7 and 8.0, such a
mix is not recommended for prolonged use. For example, in a
cluster using a mix of versions, if an instance running version
5.7 leaves the cluster and then MySQL Clone is used for a recovery
operation, the instance running the lower version can no longer
join the cluster because the
BACKUP_ADMIN privilege becomes a
requirement. Running a cluster with multiple versions is intended
as a temporary situation to aid in migration from one version to
another, and should not be relied on for long term use.