[openstack-dev] [Neutron] Group Based Policy and the way forward

Mark McClain mmcclain at yahoo-inc.com
Mon Aug 4 20:27:32 UTC 2014



* Group Based Policy API is the kind of experimentation we be should attempting.
* Experiments should be able to fail fast.
* The master branch does not fail fast.
* StackForge is the proper home to conduct this experiment.

Why this email?
Our community has been discussing and working on Group Based Policy (GBP) for many months.  I think the discussion has reached a point where we need to openly discuss a few issues before moving forward.  I recognize that this discussion could create frustration for those who have invested significant time and energy, but the reality is we need ensure we are making decisions that benefit all members of our community (users, operators, developers and vendors).

I like that as a community we are exploring alternate APIs.  The process of exploring via real user experimentation can produce valuable results.  A good experiment should be designed to fail fast to enable further trials via rapid iteration.

Merging large changes into the master branch is the exact opposite of failing fast.

The master branch deliberately favors small iterative changes over time.  Releasing a new version of the proposed API every six months limits our ability to learn and make adjustments.

In the past, we’ve released LBaaS, FWaaS, and VPNaaS as experimental APIs.  The results have been very mixed as operators either shy away from testing/offering the API or embrace the API with the expectation that the community will provide full API support and migration.  In both cases, the experiment fails because we either could not get the data we need or are unable to make significant changes without accepting a non-trivial amount of technical debt via migrations or draft API support.

Next Steps
Previously, the GPB subteam used a Github account to host the development, but the workflows and tooling do not align with OpenStack's development model. I’d like to see us create a group based policy project in StackForge.  StackForge will host the code and enable us to follow the same open review and QA processes we use in the main project while we are developing and testing the API. The infrastructure there will benefit us as we will have a separate review velocity and can frequently publish libraries to PyPI.  From a technical perspective, the 13 new entities in GPB [1] do not require any changes to internal Neutron data structures.  The docs[2] also suggest that an external plugin or service would work to make it easier to speed development.

End State
APIs require time to fully bake and right now it is too early to know the final outcome.  Using StackForge will allow the team to retain all of its options including: merging the code into Neutron, adopting the repository as sub-project of the Network Program, leaving the project in StackForge project or learning that users want something completely different.  I would expect that we'll revisit the status of the repo during the L or M cycles since the Kilo development cycle does not leave enough time to experiment and iterate.


[1] http://git.openstack.org/cgit/openstack/neutron-specs/tree/specs/juno/group-based-policy-abstraction.rst#n370
[2] https://docs.google.com/presentation/d/1Nn1HjghAvk2RTPwvltSrnCUJkidWKWY2ckU7OYAVNpo/edit#slide=id.g12c5a79d7_4078
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