Data Migration on nova-cloud-controller

This document explains the details of the database migration for nova-cloud-controller.

nova-cloud-controller Database Migration Details

When users upgrade the Juju application nova-cloud-controller, the commands nova-manage db sync and nova-manage db online_data_migration will be executed.

  • nova-manage db sync - Upgrades the main database schema to the most recent version.

  • nova-manage db online_data_migration - Performs data migration to update all live data.

db sync

Before the Yoga version, nova-cloud-controller used SQLAlchemy to handle database migrations. Starting from Yoga, it switched to Alembic, a migrations tool for SQLAlchemy.

Below is a table showing the migration versions from Ussuri to Caracal.

Version

Migration Version

Ussuri

407

Victoria

412

Wallaby

417

Xena

422

Yoga

422 - (move to Alembic) - 8f2f1571d55b_initial_version - 16f1fbcab42b_resolve_shadow_table_diffs

Zed

ccb0fa1a2252_add_encryption_fields_to

2023.1 (Antelope)

960aac0e09ea_de_duplicate_indexes_in_instances

2023.2 (Bobcat)

1acf2c98e646_add_compute_id_to_instance - 1b91788ec3a6_drop_legacy_migrate_version_table

2024.1 (Caracal)

13863f4e1612_create_share_mapping_table

Details of each migration can be found at:

db online_data_migration

The list of online data migrations can be found at nova_online_migrations. There are only two online migration cases after Victoria:

  • pci_device_obj.PciDevice.populate_dev_uuids, added in Victoria

  • instance_obj.populate_instance_compute_id, added in 2023.2

On COU

Generally, the data migration operation load is not too high, as observed from previous information. COU provides two optional steps, purge and archive, to reduce the possible load during the upgrade. These two COU steps run the following commands on the nova-cloud-controller Juju unit:

  • db archive_deleted_rows - Run during the archive step; this command moves deleted rows from production tables to shadow tables.

  • db purge - Run during the purge step; this command deletes rows from shadow tables.

Make sure to check the details of database schema migrations and online data migrations before each upgrade.

More Information