Open Stack

At the summit session last week for group-based policy, there were many concerns voiced about the approach being undertaken.  I think those concerns deserve a wider audience, and I'm going to highlight some of them here.

The primary concern seemed to be related to the complexity of the approach implemented for the POC.  A number of session participants voiced concern that the simpler approach documented in the original proposal [1] (described in the section titled 'Policies applied between groups') had not been implemented in addition to or instead of what appeared in the POC (described in the section titled 'Policies applied as a group API').  The simpler approach was considered by those participants as having the advantage of clarity and immediate usefulness, whereas the complex approach was deemed hard to understand and without immediate utility.

A secondary but no less important concern is related to the impact on Neutron of the approach implemented in the POC.  The POC was developed monolithically, without oversight through gerrit, and the resulting patches were excessive in size (~4700 [2] and ~1500 [3] lines).  Such large patches are effectively impossible to review.  Even broken down into reviewable chunks, though, it does not seem realistic to target juno-1 for merging this kind of complexity.  The impact on stability could be considerable, and it is questionable whether the necessary review effort should be devoted to fast-tracking group-based policy at all, let alone an approach that is considered by many to be unnecessarily complicated.  

The blueprint for group policy [4] is currently listed as a 'High' priority.  With the above concerns in mind, does it make sense to continue prioritizing an effort that at present would seem to require considerably more resources than the benefit it appears to promise?


Maru

1: https://etherpad.openstack.org/p/group-based-policy
2: https://review.openstack.org/93853
3: https://review.openstack.org/93935
4: https://blueprints.launchpad.net/neutron/+spec/group-based-policy-abstraction