[openstack-dev] [swift] Plan to add Python 3 support to Swift

Victor Stinner vstinner at redhat.com
Mon Feb 8 13:42:05 UTC 2016


Hi,

The Swift port was blocked during 6 months by a complex issue related to 
PyEClib. Good news: this issue was fixed 2 months ago. After the Liberty 
Summit, a plan was defined to port Swift to Python 3 (end of october), 
and I understood that the whole Swift team agreed on it.

Some Python 3 changes were merged, but less than I expected. My 3 latest 
patches are waiting for reviews since october 19, 2015:

https://review.openstack.org/#/c/237027/
https://review.openstack.org/#/c/236998/
https://review.openstack.org/#/c/237019/

I can write patches, but it takes time to rebase them and to regularly 
try various ways to try to get a review (like ping on IRC).

Because of the general lack of interest of Swift developers for Python 
3, I think that I will simply abandon my patches and let others port Swift.

Victor


Le 30/10/2015 06:54, John Dickinson a écrit :
> Thanks for the update. This seems like a reasonable way forward, but also one that will take a long time. Thank you for your work.
>
> I think this will result in larger and larger chunks of work, and so it will eventually result in large patches to move different components to py3. So you'll be able to start small, but the work will get larger as you go.
>
> You're right about needing the voting gate job. That should be the first priority for py3 work.
>
> --John
>
>
>
>
> On 30 Oct 2015, at 12:47, Victor Stinner wrote:
>
>> Hi,
>>
>> We talked about Python 3 with Christian Schwede, Alistair Coles, Samuel Meritt, Jaivish Kothari and others (sorry, I don't recall all names :-/) during Swift contributor meetup. It looks like we had an agreement on how to add Python 3 support to Swift. The plan is:
>>
>> 1) Fix the gate-swift-python34 check job
>>
>> 2) Make the gate-swift-python34 check job voting
>>
>> 3) Port remaining code step by step (incremental development)
>>
>> Python 3 issues had been fixed in the past in Swift, but came back. So it's important to not reintroduce such regressions by making the gate voting.
>>
>> Christian said that he will explain the plan at the next Swift meeting (Wednesday). I don't think that I will be able to attend this meeting, I have another one at the same time with my team :-/
>>
>> I can put this plan in a blueprint if you want. So we can refer to the blueprint in Python 3 changes. It's up to you.
>>
>>
>> Plan in detail.
>>
>> (1) To fix the Python 3 job, the idea is to only run a subset of tests on Python 3. For example, if we fix Python 3 issues with dnspython (dnspython3) and PyEClib dependencies, we can run
>> "nosetests test/unit/common/test_exceptions.py" on Python 3 (the test pass on Python 3).
>>
>> We need these two changes:
>>
>> * "py3: Update pbr and dnspython requirements"
>> https://review.openstack.org/#/c/217423/
>>
>> * "py3: Add py34 test environment to tox"
>> https://review.openstack.org/#/c/199034/
>>
>>
>> (2) When the gate-swift-python34 check job will pass and we waited long enough to consider that it's stable, we can make it voting. At this point, we cannot introduced Python 3 regressions on the code tested on Python 3. Then the idea is to run more and more tests on Python 3.
>>
>>
>> (3) Ok, now the interesting part. To port remaining code, following changes will enlarge the code coverage of Python 3 tests by adding new tests to tox.ini. For example, port utils.py to Python 3 and add test_utils.py to tox.ini.
>>
>>
>> Misc questions.
>>
>> Q: "Is it possible to port Swift to Python 3 in a single patch?"
>>
>> A: Yes, it is technically possible. But it would be one unique giant patch simply impossible to review and that will conflict at each merged change. Some changes required by Python 3 need discussions and to make technical choices.  It's more convenient to work on smaller patches.
>>
>> Q: "How much changes do we need to port Swift to Python ?"
>>
>> A: Sorry, I don't know. Since we cannot run all tests on Python 3 right now, we cannot see all issues. It's really hard to estimate the number of required changes. Anyway, the plan is to port the code step by step.
>>
>> Victor
>>
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