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Hi Armando:

Those are good points. I will let Bob Kukura chime in on the specifics of
how we intend to do that integration. But if what you see in the
prototype/PoC was our final design for integration with Neutron core, I
would be worried about that too. That specific part of the code
(events/notifications for DHCP) was done in that way just for the prototype
- to allow us to experiment with the part that was new and needed
experimentation, the APIs and the model.

That is the exact reason that we did not initially check the code to gerrit
- so that we do not confuse the review process with the prototype process.
But we were requested by other cores to check in even the prototype code as
WIP patches to allow for review of the API parts. That can unfortunately
create this very misunderstanding. For the review, I would recommend not
the WIP patches, as they contain the prototype parts as well, but just the
final patches that are not marked WIP. If you such issues in that part of
the code, please DO raise that as that would be code that we intend to
upstream.

I believe Bob did discuss the specifics of this integration issue with you
at the summit, but like I said it is best if he represents that side
himself.

Regards,
Mandeep



On Thu, May 22, 2014 at 8:19 PM, Armando M. <armamig at gmail.com> wrote:

> On 22 May 2014 13:59, Mandeep Dhami <dhami at noironetworks.com> wrote:
> >
> > Maru's concerns are that:
> > 1. It is large
> > 2. It is complex
> >
> > And Armando's related concerns are:
> > 3. Could dev/review cycles be better spent on refactoring
> > 4. If refactored neutron was available, would a simpler option become
> more
> > viable
>
> This is not what I meant to say, and if this was the message that came
> across I apologize for the confusion; let me rephrase:
>
> After looking (and relooking) at the initial patches proposed I
> started to question why the GP plugin functionality was so tightly
> integrated with the Neutron core functionality; even though I might
> guess the thinking process, I wonder if such tight coupling was the
> result of design decisions made without thoroughly considering
> alternative approaches. Without going too much into details during
> this email, I can see in the above mentioned patches that lots of
> plumbing code (like Nova and dhcp notifiers handling code) is put in
> place to make direct calls to core plugin methods: this spills
> implementation details across multiple parts of the project; it's
> fragile because it's prone to ripple effects due to lack of proper
> encapsulation: if a change is made in the plugin API or its
> implementation, the whole thing needs to be looked at, end-to-end:
> this does not scale from a human perspective (probably only a handful
> of people can really say that they know the Neutron codebase
> inside-out), it is difficult to maintain, it is difficult to test, it
> is difficult to extend. etc etc.
>
> Instead, I was advocating for an approach where GP and Neutron Core
> integrate via (a well defined and stable) REST API, or similar (more
> abstracted) mechanisms; this has obvious benefits because the two
> become suddenly loosely coupled: a change done in the way Neutron
> deals with DHCP messages is not going to have any effect to how the GP
> plugin create resources. Also, any potential refactoring of the
> Neutron Core will not cause the GP team to take the burden of bringing
> the current implementation forward.
>
> This is why I was proposing that we talk about the introduction of
> integration hooks, should they (or lack thereof) have been the culprit
> of such an initial design approach. Please, take my comments as
> initial reviews to the above patches, if you will :)
>
> To be constructive, as a core reviewer who should suggest
> alternatives, I would invite the people reading this thread to have a
> look at [1] and [2]: these were introduced by RAX to their cut of
> Neutron, having in mind exactly what I have been saying: adding
> functionality with zero impact to existing code. If something along
> those lines can be achieved, then this would be very beneficial for
> the progress of the GP effort as it transitions and evolves
> into/within Neutron, IMO.
>
> Having said that, I am making these points without particular
> reference to the complexity of the GP model being proposed, or the
> approach being taken to introduce it to the tree. Even though I share
> some of Maru's points, good architecture and design principles in
> software development should be followed wherever possible and
> irrespective of the domain where such development occur.
>
> Many thanks,
> Armando
>
>
> [1] - https://github.com/roaet/wafflehaus
> [2] - https://github.com/roaet/wafflehaus.neutron
>
> >
> > Let me address them in that order.
> >
> > 1. Re: It is large
> > Group policy has an ambitious goal  - provide devop teams with policy
> based
> > controls that are usable at scale and with automation (say a higher
> > governance layer like Congress). The fact that meeting a large challenge
> > requires more code is natural. We understand that challenge, and that is
> why
> > we did a prototype (as PoC that was demonstrated on the summit). And
> based
> > on that learning we are incrementally creating patches for building the
> > group based policy. Just because a task is large, we as neutron can not
> shy
> > away from building it. That will only drive people who need it out side
> > neutron (as we are seeing with the frustration that the LBaaS team had
> > because they have a requirement that is "large" as well).
> >
> > 2. Re: It is complex
> > Complexity depends on the context. Our goal was to make the end-user's
> life
> > simpler (and more automated). To achieve some of that simplicity, we
> > required a little more complexity in the implementation. We decide to
> make
> > that arbitrage - a little higher complexity in implementation to allow
> for
> > simpler usage. But we were careful and did not want to impose that
> > complexity on every use case - hence a lot of that is optional (and
> > exercised only if the use case needs it). Unfortunately the model, has to
> > model all of it so as it not add complexity later in upgrade and backward
> > compatibility issues. We choose to do architecture upfront, and then
> > implement it incrementally.
> >
> > The team came up with the model currently in model based on that review
> and
> > evaluation all the proposals in the document that you refer. It is easy
> to
> > make general comments, but unless you participate in the process and
> sign up
> > to writing the code, those comments are not going to help with solving
> the
> > original problem. And this _is_ open-source. If you disagree, please
> write
> > code and the community can decide for itself as to what model is actually
> > simple to use for them. Curtailing efforts from other developers just
> > because their engineering trade-offs are different from what you believe
> > your use-case needs is not why we like open source. We enjoy the mode
> where
> > different developers try different things, we experiment, and the
> software
> > evolves to what the user demands. Or maybe, multiple models live in
> harmony.
> > Let the users decide that.
> >
> > 3. Re: Could dev/review cycles be better spent on refactoring
> > I think that most people agree that policy control is an important
> feature
> > that fundamentally improves neutron (by solving the automation and scale
> > issues). In a large project, multiple sub-projects can, and for a healthy
> > project should, work in parallel. I understand that the neutron core
> team is
> > stretched. But we still need to be able to balance the needs of today
> > (paying off the technical debt/existing-issues by doing refactoring) with
> > needs of tomorrow (new features like GP and LBaaS). GP effort was
> started in
> > Havana, and now we are trying to get this in Juno. I think that is
> > reasonable and a long enough cycle for a "high priority" project to be
> able
> > to get some core attention. Again I refer to LBaaS experience, as they
> > struggled with very similar issues.
> >
> > 4. Re: If refactored neutron was available, would a simpler option become
> > more viable
> > We would love to be able to answer that question. We have been trying to
> > understand the refactoring work to understand this (see another ML
> thread)
> > and we are open to understanding your position on that. We will call the
> > ad-hoc meeting that you suggested and we would like to understand the
> > refactoring work that might be reused for simpler policy implementation.
> At
> > the same time, we would like to build on what is available today, and
> when
> > the required refactored neutron becomes available (say Juno or
> K-release),
> > we are more than happy to adapt to it at that time. Serializing all
> > development around an effort that is still in inception phase is not a
> good
> > solution. We are looking forward to participating in the core refactoring
> > work, and based on the final spec that come up with, we would love to be
> > able to eventually make the policy implementation simpler.
> >
> > Regards,
> > Mandeep
> >
> >
> >
> >
> > On Thu, May 22, 2014 at 11:44 AM, Armando M. <armamig at gmail.com> wrote:
> >>
> >> I would second Maru's concerns, and I would also like to add the
> >> following:
> >>
> >> We need to acknowledge the fact that there are certain architectural
> >> aspects of Neutron as a project that need to be addressed; at the
> >> summit we talked about the core refactoring, a task oriented API, etc.
> >> To me these items have been neglected far too much over the past and
> >> would need a higher priority and a lot more attention during the Juno
> >> cycle. Being stretched as we are I wonder if dev/review cycles
> >> wouldn't be better spent devoting more time to these efforts rather
> >> than GP.
> >>
> >> That said, I appreciate that GP is important and needs to move
> >> forward, but at the same time I am thinking that there must be a
> >> better way for addressing it and yet relieve some of the pressure that
> >> GP complexity imposes to the Neutron team. One aspect it was discussed
> >> at the summit was that the type of approach shown in [2] and [3]
> >> below, was chosen because of lack of proper integration hooks...so I
> >> am advocating: let's talk about those first before ruling them out in
> >> favor of a monolithic approach that seems to violate some engineering
> >> principles, like modularity and loose decoupling of system components.
> >>
> >> I think we didn't have enough time during the summit to iron out some
> >> of the concerns voiced here, and it seems like the IRC meeting for
> >> Group Policy would not be the right venue to try and establish a
> >> common ground among the people driving this effort and the rest of the
> >> core team.
> >>
> >> Shall we try and have an ad-hoc meeting and an ad-hoc agenda to find a
> >> consensus?
> >>
> >> Many thanks,
> >> Armando
> >>
> >> On 22 May 2014 11:38, Maru Newby <marun at redhat.com> wrote:
> >> >
> >> > On May 22, 2014, at 11:03 AM, Maru Newby <marun at redhat.com> wrote:
> >> >
> >> >> 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
> >> >
> >> > Apologies, this link is to the summit session etherpad.  The link to
> the
> >> > original proposal is:
> >> >
> >> >
> >> >
> https://docs.google.com/document/d/1ZbOFxAoibZbJmDWx1oOrOsDcov6Cuom5aaBIrupCD9E/edit
> >> >
> >> >> 2: https://review.openstack.org/93853
> >> >> 3: https://review.openstack.org/93935
> >> >> 4:
> >> >>
> https://blueprints.launchpad.net/neutron/+spec/group-based-policy-abstraction
> >> >>
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> >> >
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