Open Stack

On Wed, Sep 12, 2018 at 2:28 PM, Doug Hellmann <doug at doughellmann.com>
wrote:

> Excerpts from Doug Hellmann's message of 2018-09-12 12:04:02 -0600:
> > Excerpts from Clark Boylan's message of 2018-09-12 10:44:55 -0700:
> > > On Wed, Sep 12, 2018, at 10:23 AM, Jim Rollenhagen wrote:
> > > > The process of operators upgrading Python versions across their
> fleet came
> > > > up this morning. It's fairly obvious that operators will want to do
> this in
> > > > a rolling fashion.
> > > >
> > > > Has anyone considered doing this in CI? For example, running
> multinode
> > > > grenade with python 2 on one node and python 3 on the other node.
> > > >
> > > > Should we (openstack) test this situation, or even care?
> > > >
> > >
> > > This came up in a Vancouver summit session (the python3 one I think).
> General consensus there seemed to be that we should have grenade jobs that
> run python2 on the old side and python3 on the new side and test the update
> from one to another through a release that way. Additionally there was
> thought that the nova partial job (and similar grenade jobs) could hold the
> non upgraded node on python2 and that would talk to a python3 control plane.
> > >
> > > I haven't seen or heard of anyone working on this yet though.
> > >
> > > Clark
> > >
> >
> > IIRC, we also talked about not supporting multiple versions of
> > python on a given node, so all of the services on a node would need
> > to be upgraded together.
> >
> > Doug
>
> I spent a little time talking with the QA team about setting up
> this job, and Attila pointed out that we should think about what
> exactly we think would break during a 2-to-3 in-place upgrade like
> this.
>
> Keeping in mind that we are still testing initial installation under
> both versions and upgrades under python 2, do we have any specific
> concerns about the python *version* causing upgrade issues?
>

A specific example brought up in the ironic room was the way we encode
exceptions in oslo.messaging for transmitting over RPC. I know that we've
found encoding bugs in that in the past, and one can imagine that RPC
between a service running on py2 and a service running on py3 could have
similar issues.

It's definitely edge cases that we'd be catching here (if any), so I'm
personally fine with assuming it will just work. But I wanted to pose the
question to the list, as we agreed this isn't only an ironic problem.

// jim
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