[Bug 2024258] [NEW] Performance degradation archiving DB with large numbers of FK related records

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[Impact]
Originally, Nova archives deleted rows in batches consisting of a maximum number of parent rows (max_rows) plus their child rows, all within a single database transaction.
This approach limits the maximum value of max_rows that can be specified by the caller due to the potential size of the database transaction it could generate.
Additionally, this behavior can cause the cleanup process to frequently encounter the following error:
oslo_db.exception.DBError: (pymysql.err.InternalError) (3100, "Error on observer while running replication hook 'before_commit'.")

The error arises when the transaction exceeds the group replication transaction size limit, a safeguard implemented to prevent potential MySQL crashes [1].
The default value for this limit is approximately 143MB.

[Fix]
An upstream commit has changed the logic to archive one parent row and its related child rows in a single database transaction.
This change allows operators to choose more predictable values for max_rows and achieve more progress with each invocation of archive_deleted_rows.
Additionally, this commit reduces the chances of encountering the issue where the transaction size exceeds the group replication transaction size limit.

commit 697fa3c000696da559e52b664c04cbd8d261c037
Author:     melanie witt <melwittt at gmail.com>
CommitDate: Tue Jun 20 20:04:46 2023 +0000

    database: Archive parent and child rows "trees" one at a time

[Test Plan]
1. Create an instance and delete it in OpenStack.
2. Log in to the Nova database and confirm that there is an entry with a deleted_at value that is not NULL.
select display_name, deleted_at from instances where deleted_at <> 0;
3. Execute the following command, ensuring that the timestamp specified in --before is later than the deleted_at value:
nova-manage db archive_deleted_rows --before "XXX-XX-XX XX:XX:XX" --verbose --until-complete
4. Log in to the Nova database again and confirm that the entry has been archived and removed.
select display_name, deleted_at from instances where deleted_at <> 0;

[Where problems could occur]
The commit changes the logic for archiving deleted entries to reduce the size of transactions generated during the operation.
If the patch contains errors, it will only impact the archiving of deleted entries and will not affect other functionalities.

[1] https://bugs.mysql.com/bug.php?id=84785

** Affects: nova
     Importance: Undecided
     Assignee: melanie witt (melwitt)
         Status: Fix Released

** Affects: nova/antelope
     Importance: Undecided
         Status: In Progress

** Affects: nova/wallaby
     Importance: Undecided
         Status: In Progress

** Affects: nova/xena
     Importance: Undecided
         Status: In Progress

** Affects: nova/yoga
     Importance: Undecided
         Status: In Progress

** Affects: nova/zed
     Importance: Undecided
         Status: In Progress

** Affects: nova (Ubuntu)
     Importance: Undecided
         Status: New

** Affects: nova (Ubuntu Focal)
     Importance: Undecided
     Assignee: Chengen Du (chengendu)
         Status: In Progress

** Affects: nova (Ubuntu Jammy)
     Importance: Undecided
     Assignee: Chengen Du (chengendu)
         Status: In Progress


** Tags: db patch performance
-- 
Performance degradation archiving DB with large numbers of FK related records 
https://bugs.launchpad.net/bugs/2024258
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