MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

21.3.1 Rolling Upgrades

When upgrading the metadata schema of clusters deployed by MySQL Shell versions before 8.0.19, a rolling upgrade of existing MySQL Router instances is required. This process minimizes disruption to applications during the upgrade. The rolling upgrade process must be performed in the following order:

  1. Run the latest MySQL Shell version, connect the global session to the cluster and issue dba.upgradeMetadata(). This step ensures that any MySQL Router accounts configured for the cluster have their privileges modified to be compatible with the new version. The upgrade function stops if an outdated MySQL Router instance is detected, at which point you can stop the upgrade process in MySQL Shell to resume later.

  2. Upgrade any detected out of date MySQL Router instances to the latest version. It is recommended to use the same MySQL Router version as MySQL Shell version.

  3. Continue or restart the dba.upgradeMetadata() operation to complete the metadata upgrade.