Backup stacks should be hard-deleted

[Zane Bitter]

During a stack update, we create a "backup" stack in which we temporarily store resources we are expecting to delete later while their replacements are created. Due to the fact that stacks are only soft-deleted, the backup stack, its template, and any associated resources are not removed from the DB when the update completes successfully. (They will be removed when the operator does a periodic clean-out of deleted stacks.)

This is both a waste of DB space and could cause potentially cause problems (in _theory_ it's OK...) on a future update due to the out-of-date template & resources. We should probably do a hard delete of the backup stack on conclusion of a successful stack update.

[Anant Patil (ananta)]

Is there a particular test case which failed for you? I did a simple test where I had only VMs as resources and when I update the stack, the old resources (VMs) are deleted.

[Pavlo Shchelokovskyy (pshchelo)]

IMO this is not about actual resources, but about a stack object and it's representation in the Heat database. The change should be somewhere around this

https://github.com/openstack/heat/blob/master/heat/engine/parser.py#L672

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/111986
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=7cf6e52cacd2382b44b9255e9a5ed13271841261
Submitter: Jenkins
Branch: master

commit 7cf6e52cacd2382b44b9255e9a5ed13271841261
Author: ananta <email address hidden>
Date: Tue Aug 5 17:07:25 2014 +0530

    Hard delete backup stack after successful update.

    After successful update of a stack, the backup stack and it's associated
    template, resources and events should be permanently deleted.

    Closes-Bug: #1332300

    Change-Id: I3a462690b5f6bfadfbcf16eeb6bdec7c5ece2e83

[Zane Bitter (zaneb)]

Reopening since we had to revert the fix: https://review.openstack.org/#/c/126084/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/128918

[OpenStack Infra (hudson-openstack)]

Change abandoned by Anant Patil (<email address hidden>) on branch: master
Review: https://review.openstack.org/128918