Open Stack

On Wed, Jun 15, 2016 at 09:10:30AM -0400, Doug Hellmann wrote:
> Excerpts from Chris Hoge's message of 2016-06-14 16:37:06 -0700:
> > Top posting one note and direct comments inline, I’m proposing
> > this as a member of the DefCore working group, but this
> > proposal itself has not been accepted as the forward course of
> > action by the working group. These are my own views as the
> > administrator of the program and not that of the working group
> > itself, which may independently reject the idea outside of the
> > response from the upstream devs.
> > 
> > I posted a link to this thread to the DefCore mailing list to make
> > that working group aware of the outstanding issues.
> > 
> > > On Jun 14, 2016, at 3:50 PM, Matthew Treinish <mtreinish at kortar.org> wrote:
> > > 
> > > On Tue, Jun 14, 2016 at 05:42:16PM -0400, Doug Hellmann wrote:
> > >> Excerpts from Matthew Treinish's message of 2016-06-14 15:12:45 -0400:
> > >>> On Tue, Jun 14, 2016 at 02:41:10PM -0400, Doug Hellmann wrote:
> > >>>> Excerpts from Matthew Treinish's message of 2016-06-14 14:21:27 -0400:
> > >>>>> On Tue, Jun 14, 2016 at 10:57:05AM -0700, Chris Hoge wrote:
> > >>>>>> Last year, in response to Nova micro-versioning and extension updates[1],
> > >>>>>> the QA team added strict API schema checking to Tempest to ensure that
> > >>>>>> no additional properties were added to Nova API responses[2][3]. In the
> > >>>>>> last year, at least three vendors participating the the OpenStack Powered
> > >>>>>> Trademark program have been impacted by this change, two of which
> > >>>>>> reported this to the DefCore Working Group mailing list earlier this year[4].
> > >>>>>> 
> > >>>>>> The DefCore Working Group determines guidelines for the OpenStack Powered
> > >>>>>> program, which includes capabilities with associated functional tests
> > >>>>>> from Tempest that must be passed, and designated sections with associated
> > >>>>>> upstream code [5][6]. In determining these guidelines, the working group
> > >>>>>> attempts to balance the future direction of development with lagging
> > >>>>>> indicators of deployments and user adoption.
> > >>>>>> 
> > >>>>>> After a tremendous amount of consideration, I believe that the DefCore
> > >>>>>> Working Group needs to implement a temporary waiver for the strict API
> > >>>>>> checking requirements that were introduced last year, to give downstream
> > >>>>>> deployers more time to catch up with the strict micro-versioning
> > >>>>>> requirements determined by the Nova/Compute team and enforced by the
> > >>>>>> Tempest/QA team.
> > >>>>> 
> > >>>>> I'm very much opposed to this being done. If we're actually concerned with
> > >>>>> interoperability and verify that things behave in the same manner between multiple
> > >>>>> clouds then doing this would be a big step backwards. The fundamental disconnect
> > >>>>> here is that the vendors who have implemented out of band extensions or were
> > >>>>> taking advantage of previously available places to inject extra attributes
> > >>>>> believe that doing so means they're interoperable, which is quite far from
> > >>>>> reality. **The API is not a place for vendor differentiation.**
> > >>>> 
> > >>>> This is a temporary measure to address the fact that a large number
> > >>>> of existing tests changed their behavior, rather than having new
> > >>>> tests added to enforce this new requirement. The result is deployments
> > >>>> that previously passed these tests may no longer pass, and in fact
> > >>>> we have several cases where that's true with deployers who are
> > >>>> trying to maintain their own standard of backwards-compatibility
> > >>>> for their end users.
> > >>> 
> > >>> That's not what happened though. The API hasn't changed and the tests haven't
> > >>> really changed either. We made our enforcement on Nova's APIs a bit stricter to
> > >>> ensure nothing unexpected appeared. For the most these tests work on any version
> > >>> of OpenStack. (we only test it in the gate on supported stable releases, but I
> > >>> don't expect things to have drastically shifted on older releases) It also
> > >>> doesn't matter which version of the API you run, v2.0 or v2.1. Literally, the
> > >>> only case it ever fails is when you run something extra, not from the community,
> > >>> either as an extension (which themselves are going away [1]) or another service
> > >>> that wraps nova or imitates nova. I'm personally not comfortable saying those
> > >>> extras are ever part of the OpenStack APIs.
> > >>> 
> > >>>> We have basically three options.
> > >>>> 
> > >>>> 1. Tell deployers who are trying to do the right for their immediate
> > >>>>   users that they can't use the trademark.
> > >>>> 
> > >>>> 2. Flag the related tests or remove them from the DefCore enforcement
> > >>>>   suite entirely.
> > >>>> 
> > >>>> 3. Be flexible about giving consumers of Tempest time to meet the
> > >>>>   new requirement by providing a way to disable the checks.
> > >>>> 
> > >>>> Option 1 goes against our own backwards compatibility policies.
> > >>> 
> > >>> I don't think backwards compatibility policies really apply to what what define
> > >>> as the set of tests that as a community we are saying a vendor has to pass to
> > >>> say they're OpenStack. From my perspective as a community we either take a hard
> > >>> stance on this and say to be considered an interoperable cloud (and to get the
> > >>> trademark) you have to actually have an interoperable product. We slowly ratchet
> > >>> up the requirements every 6 months, there isn't any implied backwards
> > >>> compatibility in doing that. You passed in the past but not in the newer stricter
> > >>> guidelines.
> > >>> 
> > >>> Also, even if I did think it applied, we're not talking about a change which
> > >>> would fall into breaking that. The change was introduced a year and half ago
> > >>> during kilo and landed a year ago during liberty:
> > >>> 
> > >>> https://review.openstack.org/#/c/156130/
> > >>> 
> > >>> That's way longer than our normal deprecation period of 3 months and a release
> > >>> boundary.
> > >>> 
> > >>>> 
> > >>>> Option 2 gives us no winners and actually reduces the interoperability
> > >>>> guarantees we already have in place.
> > >>>> 
> > >>>> Option 3 applies our usual community standard of slowly rolling
> > >>>> forward while maintaining compatibility as broadly as possible.
> > >>> 
> > >>> Except in this case there isn't actually any compatibility being maintained.
> > >>> We're saying that we can't make the requirements for interoperability testing
> > >>> stricter until all the vendors who were passing in the past are able to pass
> > >>> the stricter version.
> > >>> 
> > >>>> 
> > >>>> No one is suggesting that a permanent, or even open-ended, exception
> > >>>> be granted.
> > >>> 
> > >>> Sure, I agree an permanent or open-ended exception would be even worse. But, I
> > >>> still think as a community we need to draw a hard line in the sand here. Just
> > >>> because this measure is temporary doesn't make it any more palatable.
> > >>> 
> > >>> By doing this, even as a temporary measure, we're saying it's ok to call things
> > >>> an OpenStack API when you add random gorp to the responses. Which is something we've
> > >>> very clearly said as a community is the exact opposite of the case, which the
> > >>> testing reflects. I still contend just because some vendors were running old
> > >>> versions of tempest and old versions of openstack where their incompatible API
> > >>> changes weren't caught doesn't mean they should be given pass now.
> > >> 
> > >> Nobody is saying random gorp is OK, and I'm not sure "line in the
> > >> sand" rhetoric is really constructive. The issue is not with the
> > >> nature of the API policies, it's with the implementation of those
> > >> policies and how they were rolled out.
> > >> 
> > >> DefCore defines its rules using named tests in Tempest.  If these
> > >> new enforcement policies had been applied by adding new tests to
> > >> Tempest, then DefCore could have added them using its processes
> > >> over a period of time and we wouldn't have had any issues. That's
> > >> not what happened. Instead, the behavior of a bunch of *existing*
> > >> tests changed. As a result, deployments that have not changed fail
> > >> tests that they used to pass, without any action being taken on the
> > >> deployer's part. We've moved the goal posts on our users in a way
> > >> that was not easily discoverable, because it couldn't be tracked
> > >> through the (admittedly limited) process we have in place for doing
> > >> that tracking.
> > >> 
> > >> So, we want a way to get the test results back to their existing
> > >> status, which will then let us roll adoption forward smoothly instead
> > >> of lurching from "pass" to "fail" to "pass".
> > > 
> > > It doesn't have to be a bright line pass or fail. My primary concern here is
> > > that making this change is basically saying we're going to let things "pass"
> > > when running out of tree stuff that's adding arbitrary fields to the response. This
> > > isn't really interoperable and isn't being honest with what the vendor clouds are
> > > actually doing. It would hide the truth from the people who rely on these results
> > > to determine interoperability. The proposal as I read it (and maybe it's my
> > > misconception) was to mask this and vendor clouds "pass" until they can fix it,
> > > which essentially hides the issue. Especially given there are a lot of clouds and
> > > products that don't have any issue here.
> > 
> > The opposite is the intention of this proposal. It’s a compromise that admits
> > that since the introduction of the OpenStack Powered program, and the release
> > of this strict checking on additional properties, vendors that once passed
> > now fail, and the incentives to force that change didn’t start being felt until
> > they hit their product renewal cycle.
> > 
> > It’s not trying to mask anything, to the contrary by bringing it up here and
> > stating their public test results would indicate which APIs send additional
> > properties back, it’s shining a light on the issue and publicly stating that it’s
> > not an acceptable long-term solution.
> > 
> > > But, if we add another possible state on the defcore side like conditional pass,
> > > warning, yellow, etc. (the name doesn't matter) which is used to indicate that
> > > things on product X could only pass when strict validation was disabled (and
> > > be clear about where and why) then my concerns would be alleviated. I just do
> > > not want this to end up not being visible to end users trying to evaluate
> > > interoperability of different clouds using the test results.
> > 
> > The OpenStack Marketplace is where these comparisons would happen,
> > and the APIs with additional response data would be stated.
> > 
> > >> 
> > >> We should, separately, address the process issues and the limitations
> > >> this situation has exposed.  That may mean changing the way DefCore
> > >> defines its policies, or tracks things, or uses Tempest.  For
> > >> example, in the future, we may want tie versions of Tempest to
> > >> versions of the trademark more closely, so that it's possible for
> > >> someone running the Mitaka version of OpenStack to continue to use
> > >> the Mitaka version of Tempest and not have to upgrade Tempest in
> > >> order to retain their trademark (maybe that's how it already works?).
> > > 
> > > Tempest master supports all currently supported stable branches. So right now
> > > any commit to master is tested against a master cloud, a mitaka cloud, and a
> > > liberty cloud in the gate. We tag/push a release whenever we add or drop support
> > > for a release, the most recent being dropping kilo. [1][2] That being said the
> > > openstack apis **should** be backwards compatible so ideally master tempest would
> > > work fine on older clouds. (although this might not be reality) The primary
> > > wrinkle here are the tests which would depend on feature flags to indicate it's
> > > availability on newer versions. We eventually remove flags after all supported
> > > releases have a given feature. But, this can be worked around with test
> > > selection. (ie don't even try to run tests that require a feature juno didn’t
> > > have)
> > 
> > The current active guidelines cover icehouse through mitaka. The release
> > of 2016.08 will change that to cover juno through mitaka (with newton
> > as an add-on to 2016.08 when it’s released). There’s overlap between
> > the guidelines, so 2016.01 covers juno through mitaka while 2016.08
> > will cover kilo through newton. Essentially two years of releases.
> > 
> > >> We may also need to consider that test implementation details may
> > >> change, and have a review process within DefCore to help expose
> > >> those changes to make them clearer to deployers.
> > >> 
> > >> Fixing the process issue may also mean changing the way we implement
> > >> things in Tempest. In this case, adding a flag helps move ahead
> > >> more smoothly. Perhaps we adopt that as a general policy in the
> > >> future when we make underlying behavioral changes like this to
> > >> existing tests.  Perhaps instead we have a policy that we do not
> > >> change the behavior of existing tests in such significant ways, at
> > >> least if they're tagged as being used by DefCore. I don't know --
> > >> those are things we need to discuss.
> > > 
> > > Sure I agree, this thread raises larger issues which need to be figured out.
> > > But, that is probably an independent discussion.
> > 
> > I’m beginning to wonder if we need to make DefCore use release
> > branches then back-port bug-fixes and relevant features additions
> > as necessary.
> 
> We should definitely have that conversation, to understand what
> effect it would have both on Tempest and on DefCore.
> 

While from a quick glance this would seem like it would solve some of the
problems when you start to dig into it you'll see that it actually wouldn't,
and would just end up causing more issues in the long run. Branchless tempest
was originally started back at the icehouse release and was implemented to
actually enforce the API is the same across release boundaries. We had hit many
issues where incompatibilities inadvertently were introduced into projects' APIs
which weren't caught because of divergence between tempest master and tempest
stable/*. If you decide to branch you'll end up having to do the same thing or
you'll risk the same types of regressions. Testing stable branches against
master puts you in a weird place where upstream changes could break things for
your branch and you'd never know until you tried to land something. From a
tempest dev standpoint branching quite frankly doesn't make any sense.

Also, the other thing to consider is that there wouldn't actually be anything to
branch on. Tempest always supports whatever releases the community is
supporting. Every commit is tested against all the branches of OpenStack that
still exist. When we EOL a stable branch there is no longer anything to run
tests against. Assuming you're primarily motivated by the fact defcore attempts
to support branches that no longer have upstream support you wouldn't actually
be able to do this by branching. When a branch is removed there isn't anything
for you to test tempest changes against, and merging code without testing it
first is a terrible idea and the opposite of how we do things in the openstack
community.


-Matt Treinish
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