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. -Sean
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 fails.
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.
-David
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