On 5/23/18 6:49 PM, Sagi Shnaidman wrote:
Alex,
the problem is that you're working and focusing mostly on release
specific code like featuresets and some scripts. But
tripleo-quickstart(-extras) and tripleo-ci is much *much* more than set
of featuresets. Only 10% of the code may be related to releases and
branches, while other 90% is completely independent and not related to
releases.
So in 90% code we DO need to backport every change, take for example the
latest patch to extras: https://review.openstack.org/#/c/570167/, it's
fixing reproducer. If oooq-extra was branched, we would need to backport
this fix to every and every branch. And the same for all other 90% of
code, which is complete nonsense.
Just because not using "{% if release %}" construct - to block the whole
work of CI team and make the CI code is absolutely unmaintainable?
Some of release related templates we moved recently from tripleo-ci to
THT repo like scenarios, OC templates, etc. If we discover another
things in oooq that could be moved to branched THT I'd be only happy for
that.
Sometimes it could be hard to maintain one file in extras templates with
different logic for releases, like we have in tempest configuration for
example. The solution is to create a few release-related templates and
use one that match the current branch. It doesn't affect 90% of code and
still "branch-like" approach. But I didn't see other scripts that are so
release dependent. If we'll have ones, we could do the same. For now I
see "{% if release %}" construct working very well.
I didn't see still any advantage of branching CI code, except of a
little bit nicer jinja templates without "{% if release ", but amount of
disadvantages is so huge, that it'll literally block all current work in CI.
[tl;dr] branching allows to not run cloned branched jobs against master
patches. Or patches will wait longer in queues, and fail more often cuz
of intermittent infra issues. See explanation and some calculations below.
So my main concern against additional stable release cloned jobs
executed for master branches is that there is an "infra failure fee",
which is a failure unrelated to the patch under check or gate, like an
intermittent connectivity/timeout inducted failure. This normally is
followed by a 'recheck' comment posted by an engineer, and sometimes is
noticed by the elastic recheck bot as well. Say, that sort of a failure
has a probability of N. And the real "product failure", which is related
to the subject patch and not infra, takes P. So chances to fail for a job is
F = (1 - ((1 - N)*(1 - P)).
Now that we have added a two more "branched clones" for RDO CI OVB jobs
and a two more zuul jobs, we have this equation as
F = (1 - ((1 - N)^4*(1 - P)).
(I assumed the chances to face a product defect for the cloned branched
jobs remain unchanged).
This might bring significantly increased chances to fail (see some
examples [0] for the N/P distribution cases). So folks will start
posting 'recheck' comments now even more often, like x2 times more
often. Which would make zuul and RDO CI queues larger, and patches
sitting there longer - ending up with more time to wait for jobs to
start its check/gate pipelines. That's what I call 'recheck storms'. And
w/o branched quickstart/extras, we might have those storms amplified,
tho that fully depends on real N/P distributions.
[0] https://pastebin.com/ckG5G7NG
Thanks
On Wed, May 23, 2018 at 7:04 PM, Alex Schultz <aschu...@redhat.com
<mailto:aschu...@redhat.com>> wrote:
On Wed, May 23, 2018 at 8:30 AM, Sagi Shnaidman <sshna...@redhat.com
<mailto:sshna...@redhat.com>> wrote:
> Hi, Sergii
>
> thanks for the question. It's not first time that this topic is raised and
> from first view it could seem that branching would help to that sort of
> issues.
>
> Although it's not the case. Tripleo-quickstart(-extras) is part of CI
code,
> as well as tripleo-ci repo which have never been branched. The reason for
> that is relative small impact on CI code from product branching. Think
about
> backport almost *every* patch to oooq and extras to all supported
branches,
> down to newton at least. This will be a really *huge* price and non
> reasonable work. Just think about active maintenance of 3-4 versions of CI
> code in each of 3 repositories. It will take all time of CI team with
almost
> zero value of this work.
>
So I'm not sure I completely agree with this assessment as there is a
price paid for every {%if release in [...]%} that we have to carry in
oooq{,-extras}. These go away if we branch because we don't have to
worry about breaking previous releases or current release (which may
or may not actually have CI results).
> What regards patch you listed, we would have backport this change to
*every*
> branch, and it wouldn't really help to avoid the issue. The source of
> problem is not branchless repo here.
>
No we shouldn't be backporting every change. The logic in oooq-extras
should be version specific and if we're changing an interface in
tripleo in a breaking fashion we're doing it wrong in tripleo. If
we're backporting things to work around tripleo issues, we're doing it
wrong in quickstart.
> Regarding catching such issues and Bogdans point, that's right we added a
> few jobs to catch such issues in the future and prevent breakages, and a
few
> running jobs is reasonable price to keep configuration working in all
> branches. Comparing to maintenance nightmare with branches of CI code,
it's
> really a *zero* price.
>
Nothing is free. If there's a high maintenance cost, we haven't
properly identified the optimal way to separate functionality between
tripleo/quickstart. I have repeatedly said that the provisioning
parts of quickstart should be separate because those aren't tied to a
tripleo version and this along with the scenario configs should be the
only unbranched repo we have. Any roles related to how to
configure/work with tripleo should be branched and tied to a stable
branch of tripleo. This would actually be beneficial for tripleo as
well because then we can see when we are introducing backwards
incompatible changes.
Thanks,
-Alex
> Thanks
>
>
> On Wed, May 23, 2018 at 3:43 PM, Sergii Golovatiuk
<sgolo...@redhat.com <mailto:sgolo...@redhat.com>>
> wrote:
>>
>> Hi,
>>
>> Looking at [1], I am thinking about the price we paid for not
>> branching tripleo-quickstart. Can we discuss the options to prevent
>> the issues such as [1]? Thank you in advance.
>>
>> [1] https://review.openstack.org/#/c/569830/4
<https://review.openstack.org/#/c/569830/4>
>>
>> --
>> Best Regards,
>> Sergii Golovatiuk
>>
>>
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>
>
> --
> Best regards
> Sagi Shnaidman
>
>
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