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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