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There is a cells v2 change up for review [1] which creates the flavor 
tables in the API DB.

I noted that those table definitions include the soft-delete columns 
(deleted and deleted_at), which at the YVR summit and in other threads 
[2] we've said we're not doing anymore for new tables.

The point raised to keep them soft-deletable is that the flavor API 
allows showing soft-deleted flavors if you know the id [3]. And you can 
get the flavor id for an instance (we always store the flavor info that 
was used to boot the instance).

The question is, can we break that wrinkle in the API by not allow 
soft-deleting the flavor in the API DB?

Note that in the normal nova DB, if the admin archives/purges the 
instance_types table, the wrinkle is already broken because the 
soft-deleted flavor is now hard-deleted, but that's maybe not a great 
justification for consciously removing this support in the API DB.

If we made the flavor soft-deletable in the API DB, one issue is we 
don't have an in-tree entrypoint for cleaning this up (there are no 
archive/purge CLIs for the API DB). We could always add that, but it's 
not there right now.

Another thing that came up in the cells meeting this week is that if we 
didn't make the flavor soft-deletable, we could still show the flavor 
information for a given instance via the server GET API. However, that 
would be a microversion change to show the full flavor information for 
the server rather than just the flavor id.

Thoughts? I'm cross-posting this to -dev and the -operators list to see 
what kind of user impact there would be if we didn't soft-delete flavors 
in the API DB (so you couldn't look up deleted flavors in the API).

[1] https://review.openstack.org/#/c/201606/
[2] 
http://lists.openstack.org/pipermail/openstack-dev/2015-November/080397.html
[3] 
https://github.com/openstack/nova/blob/347ebb20e3217c2f8abf261622ba420c9fd077bd/nova/api/openstack/compute/flavors.py#L54

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Thanks,

Matt Riedemann