Open Stack

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

>>>
>>> What else have I missed in these phases? Other jobs? Other blocking
>>> conditions?
>>>
>>> Doug
>
>
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