(easier to insert my questions at top of discussion as they are more general)

How would test deprecations work in a branchless Tempest?  Right now, there is 
the discussion on removing the XML tests from Tempest, yet they are still valid 
for Havana and Icehouse.  If they get "removed", will they still be accessible 
and runnable for Havana version tests?  I can see running from a tagged version 
for Havana, but if you are *not* running from the tag, then the files would be 
"gone".  So, I'm wondering how this would work for Refstack, testing backported 
bugfixes, etc.

Another related question arises from the discussion of Nova API versions.  
Tempest tests are being enhanced to do validation, and the newer API versions  
(2.1,  3.n, etc. when the approach is decided) will do validation, etc.  How 
will these "backward incompatible" tests be handled if the test that works for 
Havana gets modified to work for Juno and starts failing Havana code base?

With the discussion of project functional tests that could be maintained in one 
place, but run in two (maintenance location undecided, run locale local and 
Tempest/Integrated), how would this "cross project" effort be affected by a 
branchless Tempest?

Maybe we need some use cases to ferret out the corner cases of a branchless 
Tempest implementation?  I think we need to get more into some of the details 
to understand what would be needed to be added/modified/ removed to make this 
design proposal work.


From: David Kranz [mailto:dkr...@redhat.com]
Sent: Friday, April 04, 2014 6:10 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [RFC] Tempest without branches

On 04/04/2014 07:37 AM, Sean Dague wrote:

An interesting conversation has cropped up over the last few days in -qa

and -infra which I want to bring to the wider OpenStack community. When

discussing the use of Tempest as part of the Defcore validation we came

to an interesting question:

Why does Tempest have stable/* branches? Does it need them?

Historically the Tempest project has created a stable/foo tag the week

of release to lock the version of Tempest that will be tested against

stable branches. The reason we did that is until this cycle we had

really limited nobs in tempest to control which features were tested.

stable/havana means - test everything we know how to test in havana. So

when, for instance, a new API extension landed upstream in icehouse,

we'd just add the tests to Tempest. It wouldn't impact stable/havana,

because we wouldn't backport changes.

But is this really required?

For instance, we don't branch openstack clients. They are supposed to

work against multiple server versions. Tempest, at some level, is

another client. So there is some sense there.

Tempest now also have flags on features, and tests are skippable if

services, or even extensions aren't enabled (all explicitly setable in

the tempest.conf). This is a much better control mechanism than the

course grained selection of stable/foo.

If we decided not to set a stable/icehouse branch in 2 weeks, the gate

would change as follows:

Project masters: no change

Project stable/icehouse: would be gated against Tempest master

Tempest master: would double the gate jobs, gate on project master and

project stable/icehouse on every commit.

(That last one needs infra changes to work right, those are all in

flight right now to assess doability.)

Some interesting effects this would have:

 * Tempest test enhancements would immediately apply on stable/icehouse *

... giving us more confidence. A large amount of tests added to master

in every release are enhanced checking for existing function.

 * Tempest test changes would need server changes in master and

stable/icehouse *

In trying tempest master against stable/havana we found a number of

behavior changes in projects that there had been a 2 step change in the

Tempest tests to support. But this actually means that stable/havana and

stable/icehouse for the same API version are different. Going forward

this would require master + stable changes on the projects + Tempest

changes. Which would provide much more friction in changing these sorts

of things by accident.

 * Much more stable testing *

If every Tempest change is gating on stable/icehouse, the week long

stable/havana can't pass tests won't happen. There will be much more

urgency to keep stable branches functioning.

If we got rid of branches in Tempest the path would be:

 * infrastructure to support this in infra - in process, probably

landing today

 * don't set stable/icehouse - decision needed by Apr 17th

 * changes to d-g/devstack to be extra explicit about what features

stable/icehouse should support in tempest.conf

 * see if we can make master work with stable/havana to remove the

stable/havana Tempest branch (if this is doable in a month, great, if

not just wait for havana to age out).

I think we would still want to declare Tempest versions from time to

time. I'd honestly suggest a quarterly timebox. The events that are

actually important to Tempest are less the release itself, but the eol

of branches, as that would mean features which removed completely from

any supported tree could be removed.

My current leaning is that this approach would be a good thing, and

provide a better experience for both the community and the defcore

process. However it's a big enough change that we're still collecting

data, and it would be interesting to hear other thoughts from the

community at large on this approach.


With regard to havana, the problems with DefCore using stable/havana are the 
same as many of us have felt with testing real deployments of havana.
Master (now icehouse) has many more tests, is more robust to individual test 
failures, and is more configurable. But the work to backport improvements is 
difficult or impossible due to many refactorings on master, api changes, and 
the tempest backport policy that we don't want to spend our review time looking 
backwards. The reality is that almost nothing has been backported to 
stable/havana tempest, and we don't want to start doing that now. As 
defcore/refstack becomes a reality, more bugs and desired features in tempest 
will be found and it would be good if issues could be addressed on master.

The approach advocated here would prevent this from happening again with 
icehouse and going forward. That still leaves havana as an important case for 
many folks. I did an initial run of master tempest against havana using 
nova-network but no heat/ceilo/swift). 148 out of 2009 tests failed. The 
failures seemed to be in these categories:

1. An api change occurred such as change in response code, added fields in 
return dicts, and others I have not yet categorized.
2. A new feature was added in icehouse and the tempest test was not behind a 
config option to see if it was enabled.
3. A bug was fixed in icehouse which is still there in havana and the tempest 
test was changed or unskipped.
4. A new test was added that never ran against havana, but could have, and it 

Even if we adopt this approach going forward, case (3,4) will continue to exist 
in future iterations. That implies the need to have a config option and 
associated test tag to say which release is targeted so that the test will not 
run against an older release. This will create some ugliness around such cases 
but seems to me less ugly than what we have now, which is one giant switch (new 
branch) that controls everything.

The easiest way to get master running against havana would be to add such a 
config and then simply skip all of the failing tests when running against 
havana. There could also be conditionals in tempest saying what behaviour is 
expected but I'm not sure we want to go there.

This approach will add clarity to the notion that OpenStack releases are 
decoupled from API versions. As Sean said, doing a "tempest-two-step" to 
implement an api change would now need to also be done on a stable branch.



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