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Excerpts from Eric Fried's message of 2018-08-22 09:13:25 -0500:
> For some time, nova has been using uuidsentinel [1] which conveniently
> allows you to get a random UUID in a single LOC with a readable name
> that's the same every time you reference it within that process (but not
> across processes). Example usage: [2].
> 
> We would like other projects (notably the soon-to-be-split-out placement
> project) to be able to use uuidsentinel without duplicating the code. So
> we would like to stuff it in an oslo lib.
> 
> The question is whether it should live in oslotest [3] or in
> oslo_utils.uuidutils [4]. The proposed patches are (almost) the same.
> The issues we've thought of so far:
> 
> - If this thing is used only for test, oslotest makes sense. We haven't
> thought of a non-test use, but somebody surely will.
> - Conversely, if we put it in oslo_utils, we're kinda saying we support
> it for non-test too. (This is why the oslo_utils version does some extra
> work for thread safety and collision avoidance.)
> - In oslotest, awkwardness is necessary to avoid circular importing:
> uuidsentinel uses oslo_utils.uuidutils, which requires oslotest. In
> oslo_utils.uuidutils, everything is right there.
> - It's a... UUID util. If I didn't know anything and I was looking for a
> UUID util like uuidsentinel, I would look in a module called uuidutils
> first.
> 
> We hereby solicit your opinions, either by further discussion here or as
> votes on the respective patches.
> 
> Thanks,
> efried
> 
> [1]
> https://github.com/openstack/nova/blob/17b69575bc240ca1dd8b7a681de846d90f3b642c/nova/tests/uuidsentinel.py
> [2]
> https://github.com/openstack/nova/blob/17b69575bc240ca1dd8b7a681de846d90f3b642c/nova/tests/functional/api/openstack/placement/db/test_resource_provider.py#L109-L115
> [3] https://review.openstack.org/594068
> [4] https://review.openstack.org/594179
> 

We discussed this during the Oslo team meeting today, and have settled
on the idea of placing Eric's version of the code (with the thread-safe
fix and the module-level global) in oslo_utils.fixture to allow it to
easily reuse the oslo_utils.uuidutils module and still be clearly marked
as test code.

Doug