Open Stack

Excerpts from Alex Schultz's message of 2018-04-30 15:43:16 -0600:
> On Mon, Apr 30, 2018 at 3:16 PM, Ben Nemec <openstack at nemebean.com> wrote:
> > Resending from an address that is subscribed to the list.  Apologies to
> > those of you who get this twice.
> >
> > On 04/30/2018 10:06 AM, Doug Hellmann wrote:
> >>
> >> It would be useful to have more input from PTLs on this issue, so I'm
> >> CCing all of them to get their attention.
> >>
> >> Excerpts from Doug Hellmann's message of 2018-04-25 16:54:46 -0400:
> >>>
> >>> It's time to talk about the next steps in our migration from python
> >>> 2 to python 3.
> >>>
> >>> Up to this point we have mostly focused on reaching a state where
> >>> we support both versions of the language. We are not quite there
> >>> with all projects, as you can see by reviewing the test coverage
> >>> status information at
> >>>
> >>> https://wiki.openstack.org/wiki/Python3#Python_3_Status_of_OpenStack_projects
> >>>
> >>> Still, we need to press on to the next phase of the migration, which
> >>> I have been calling "Python 3 first". This is where we use python
> >>> 3 as the default, for everything, and set up the exceptions we need
> >>> for anything that still requires python 2.
> >>>
> >>> To reach that stage, we need to:
> >>>
> >>> 1. Change the documentation and release notes jobs to use python 3.
> >>>     (The Oslo team recently completed this, and found that we did
> >>>     need to make a few small code changes to get them to work.)
> >>> 2. Change (or duplicate) all functional test jobs to run under
> >>>     python 3.
> >>> 3. Change the packaging jobs to use python 3.
> >>> 4. Update devstack to use 3 by default and require setting a flag to
> >>>     use 2. (This may trigger other job changes.)
> >>>
> >>> At that point, all of our deliverables will be produced using python
> >>> 3, and we can be relatively confident that if we no longer had
> >>> access to python 2 we could still continue operating. We could also
> >>> start updating deployment tools to use either python 3 or 2, so
> >>> that users could actually deploy using the python 3 versions of
> >>> services.
> >>>
> >>> Somewhere in that time frame our third-party CI systems will need
> >>> to ensure they have python 3 support as well.
> >>>
> >>> After the "Python 3 first" phase is completed we should release
> >>> one series using the packages built with python 3. Perhaps Stein?
> >>> Or is that too ambitious?
> >>>
> >>> Next, we will be ready to address the prerequisites for "Python 3
> >>> only," which will allow us to drop Python 2 support.
> >>>
> >>> We need to wait to drop python 2 support as a community, rather
> >>> than going one project at a time, to avoid doubling the work of
> >>> downstream consumers such as distros and independent deployers. We
> >>> don't want them to have to package all (or even a large number) of
> >>> the dependencies of OpenStack twice because they have to install
> >>> some services running under python 2 and others under 3. Ideally
> >>> they would be able to upgrade all of the services on a node together
> >>> as part of their transition to the new version, without ending up
> >>> with a python 2 version of a dependency along side a python 3 version
> >>> of the same package.
> >>>
> >>> The remaining items could be fixed earlier, but this is the point
> >>> at which they would block us:
> >>>
> >>> 1. Fix oslo.service functional tests -- the Oslo team needs help
> >>>     maintaining this library. Alternatively, we could move all
> >>>     services to use cotyledon (https://pypi.org/project/cotyledon/).
> >
> >
> > For everyone's awareness, we discussed this in the Oslo meeting today and
> > our first step is to see how many, if any, services are actually relying on
> > the oslo.service functionality that doesn't work in Python 3 today.  From
> > there we will come up with a plan for how to move forward.
> >
> > https://bugs.launchpad.net/manila/+bug/1482633 is the original bug.
> >
> >>>
> >>> 2. Finish the unit test and functional test ports so that all of
> >>>     our tests can run under python 3 (this implies that the services
> >>>     all run under python 3, so there is no more porting to do).
> >
> >
> > And integration tests?  I know for the initial python 3 goal we said just
> > unit and functional, but it seems to me that we can't claim full python 3
> > compatibility until we can run our tempest jobs against python 3-based
> > OpenStack.
> >
> >>>
> >>> Finally, after we have *all* tests running on python 3, we can
> >>> safely drop python 2.
> >>>
> >>> We have previously discussed the end of the T cycle as the point
> >>> at which we would have all of those tests running, and if that holds
> >>> true we could reasonably drop python 2 during the beginning of the
> >>> U cycle, in late 2019 and before the 2020 cut-off point when upstream
> >>> python 2 support will be dropped.
> >>>
> >>> I need some info from the deployment tool teams to understand whether
> >>> they would be ready to take the plunge during T or U and start
> >>> deploying only the python 3 version. Are there other upgrade issues
> >>> that need to be addressed to support moving from 2 to 3? Something
> >>> that might be part of the platform(s), rather than OpenStack itself?
> >
> >
> > Alex can probably expand on this, but I know TripleO has some challenges in
> > this area.  Specifically the fact that CentOS 7 will only ever support
> > Python 2 and CentOS 8 is planned to only support Python 3. Since CentOS 8 is
> > not a thing yet and no release dates are announced they're having to use
> > Fedora for Python 3 testing, which isn't something that will be supported
> > long-term.  That makes things...complicated.
> >
> > Some more details are in the PTG discussion wrap-up thread:
> > http://lists.openstack.org/pipermail/openstack-dev/2018-March/128481.html
> >
> > That said, I believe the plan is to be testing on Python 3 by T, so I guess
> > that's ultimately the answer to your question.
> >
> 
> Yes from a TripleO perspective there are a few different ways to
> address this, but we will likely need to follow the availability of
> python3 on the current release of a given CentOS version.  With the
> switch to containers may allow us to decouple from the base OS python
> a bit, but that would mean that we'd need to be able to pull in a
> fedora images with python3 packages (via Kolla). The work on this
> front is very early on so I'm not sure we have a timeline to commit to
> T.
> 
> Thanks,
> -Alex

OK, so it sounds like no earlier than T for TripleO.

What about some of the other deployment tools? Can members of those
teams give us any sort of guidance about when python 3 support is
expected?

Doug