<div dir="ltr">Hi,<div><br></div><div>Robert Kukura's proposal does address the following:</div><div><br></div><div>1. Make it explicit to the user that an API is in "preview" until it's moved out of the preview directories</div>
<div>2. One of the criteria to accept a BP for preview is for the functionality to be optional via configuration. This will not impact the stability of neutron in the general case</div><div>3. Allows for new API/functionality to be built leveraging all the neutron infrastructure available</div>
<div>4. Allows for users to adopt new API, increasing the footprint of neutron users</div><div><br></div><div>+1 on this proposal from my side.</div><div><br></div><div>Regards,</div><div>-hemanth</div></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Fri, Aug 8, 2014 at 3:28 PM, Salvatore Orlando <span dir="ltr"><<a href="mailto:sorlando@nicira.com" target="_blank">sorlando@nicira.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div class="gmail_extra"><div>"If we want to keep everything the way it is, we have to change everything" [1]<br></div><div><br></div><div>This is pretty much how I felt after reading this proposal, and I felt that this quote, which Ivar will probably appreciate, was apt to the situation.</div>
<div>Recent events have spurred a discussion about the need for a change in process. It is not uncommon indeed to believe that by fixing the process, things will inevitably change for better. While no-one argues that flaws in processes need to be fixed, no process change will ever change anything, in my opinion, unless it is aimed at spurring change in people as well. </div>
<div><br></div><div>From what I understand, this proposal starts with the assumption that any new feature which is committed to Neutron (ie: has a blueprint approved), and is not a required neutron component should be considered as a preview. This is not different from the process, which, albeit more informally, has been adopted so far. Load Balancing, Firewall, VPN, have all been explicitly documented as experimental in their first release; I would argue that even if not experimental anymore, they may not be considered stable until their stability was proven by upstream QA with API and scenario tests - but this is not sanctioned anywhere currently, I think.</div>
<div><br></div><div>According to this proposal, for preview features:</div><div>- all the code would be moved to a "preview" package</div><div>- Options will be marked as "preview"</div><div>- URIs should be prefixed with "preview"</div>
<div>- CLIs will note the features are "preview" in their help strings</div><div>- Documentation will explicitly state this feature is "preview" (I think we already mark them as experimental, frankly I don't think there are a lot of differences in terminology here)</div>
<div>- Database migrations will be in the main alembic path as usual</div><div>- CLI, Devstack and Heat support will be available</div><div>- Can be used by non-preview neutron code</div><div>- Will undergo the usual review process</div>
<div>- QA will be desirable, but will done either with "WIP" tempest patches or merging the relevant scenario tests in the preview feature iself</div><div>- The feature might be promoted or removed, but the process for this is not yet defined.</div>
<div><br></div><div>I don't think this change in process will actually encourage better behaviour both by contributors and core reviewers.</div><div>I reckon that better behaviour might be encouraged by forcing developer and reviewers to merge in the neutron source code tree only code which meets the highest quality standards. A change in process should enforce this - and when I think about the criteria, I think at the same kind of criteria we're being imposed to declare parity with nova. Proven reliability, and scalability should be a must. Proven usability should be a requirement for all new APIs.</div>
<div>On the other hand we also need to avoid to over bureaucratise Neutron - nobody loves that - and therefore ensure this process is enforced only when really needed.</div><div><br></div><div>Looking at this proposal I see a few thing I'm not comfortable with:</div>
<div>- having no clear criterion for exclusion a feature might imply that will be silently bit-rotting code in the preview package. Which what would happen for instance if we end up with a badly maintained feature , but since one or two core devs care about it, they'll keep vetoing the removal</div>
<div>- using the normal review process will still not solve the problem of slow review cycles, pointless downvotes for reviewers which actually just do not understand the subject matter, and other pains associated with lack of interest from small or large parts of the core team. For instance, I think there is a line of pretty annoyed contributors as we did not even bother reviewing their specs.</div>
<div>- The current provision about QA seems to state that it's ok to keep code in the main repo that does not adhere to appropriate quality standards. Which is the mistake we did with lbaas and other features, and I would like to avoid. And to me it is not sufficient that the code is buried in the 'preview' package.</div>
<div>- Mostly important, this process provides a justification for contributors to push features which do not meet the same standards as other neutron parts and expect them to be merged and eventually promoted, and on the other hand provides the core team with the entitlement for merging them - therefore my main concern that it does not encourages better behaviour in people, which should be the ultimate aim of a process change.</div>
<div><br></div><div>If you managed to read through all of this, and tolerated my dorky literature references, I really appreciate your patience, and would like to conclude that here we're discussing proposals for a process change, whereas I expect to discuss in the next neutron meeting the following:</div>
<div>- whether is acceptable to change the process now</div><div>- what did go wrong in our spec review process, as we ended up with at least an approved spec which is actually fiercely opposed by other core team members.</div>
<div><br></div><div>Have a good weekend,<br></div><div>Salvatore</div><div><br></div><div>[1] Quote from "Il Gattopardo" by Giuseppe Tomasi di Lampedusa (english name: The Leopard)</div><div><div class="h5"><div>
<br></div><br><div class="gmail_quote">
On 8 August 2014 22:21, Robert Kukura <span dir="ltr"><<a href="mailto:kukura@noironetworks.com" target="_blank">kukura@noironetworks.com</a>></span> wrote:</div><div class="gmail_quote"><br></div><div class="gmail_quote">
<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">[Note - I understand there are ongoing discussion that may lead to a proposal for an out-of-tree incubation process for new Neutron features. This is a complementary proposal that describes how our existing development process can be used to stabilize new features in-tree over the time frame of a release cycle or two. We should fully consider both proposals, and where each might apply. I hope something like the approach I propose here will allow the implementations of Neutron BPs with non-trivial APIs that have been targeted for the Juno release to be included in that release, used by early adopters, and stabilized as quickly as possible for general consumption.]<br>
<br>
According to our existing development process, once a blueprint and associated specification for a new Neutron feature have been reviewed, approved, and targeted to a release, development proceeds, resulting in a series of patches to be reviewed and merged to the Neutron source tree. This source tree is then the basis for milestone releases and the final release for the cycle.<br>
<br>
Ideally, this development process would conclude successfully, well in advance of the cycle's final release, and the resulting feature and its API would be considered fully "stable" in that release. Stable features are ready for widespread general deployment. Going forward, any further modifications to a stable API must be backwards-compatible with previously released versions. Upgrades must not lose any persistent state associated with stable features. Upgrade processes and their impact on a deployments (downtime, etc.) should be consistent for all stable features.<br>
<br>
In reality, we developers are not perfect, and minor (or more significant) changes may be identified as necessary or highly desirable once early adopters of the new feature have had a chance to use it. These changes may be difficult or impossible to do in a way that honors the guarantees associated with stable features.<br>
<br>
For new features that effect the "core" Neutron API and therefore impact all Neutron deployments, the stability requirement is strict. But for features that do not effect the core API, such as services whose deployment is optional, the stability requirement can be relaxed initially, allowing time for feedback from early adopters to be incorporated before declaring these APIs stable. The key in doing this is to manage the expectations of developers, packagers, operators, and end users regarding these new optional features while they stabilize.<br>
<br>
I therefore propose that we manage these expectations, while new optional features in the source tree stabilize, by clearly labeling these features with the term "preview" until they are declared stable, and sufficiently isolating them so that they are not confused with stable features. The proposed guidelines would apply during development as the patches implementing the feature are first merged, in the initial release containing the feature, and in any subsequent releases that are necessary to fully stabilize the feature.<br>
<br>
Here are my initial not-fully-baked ideas for how our current process can be adapted with a "preview feature" concept supporting in-tree stabilization of optional features:<br>
<br>
* Preview features are implementations of blueprints that have been reviewed, approved, and targeted for a Neutron release. The process is intended for features for which there is a commitment to add the feature to Neutron, not for experimentation where "failing fast" is an acceptable outcome.<br>
<br>
* Preview features must be optional to deploy, such as by configuring a service plugin or some set of drivers. Blueprint implementations whose deployment is not optional are not eligible to be treated as preview features.<br>
<br>
* Patches implementing a preview feature are merged to the the master branch of the Neutron source tree. This makes them immediately available to all direct consumers of the source tree, such as developers, trunk-chasing operators, packagers, and evaluators or end-users that use DevStack, maximizing the opportunity to get the feedback that is essential to quickly stabilize the feature.<br>
<br>
* The process for reviewing, approving and merging patches implementing preview features is exactly the same as for all other Neutron patches. The patches must meet HACKING standards, be production-quality code, have adequate test coverage, have DB migration scripts, etc., and require two +2s and a +A from Neutron core developers to merge.<br>
<br>
* DB migrations for preview features are treated similarly to other DB migrations, forming a single ordered list that results in the current overall DB schema, including the schema for the preview feature. But DB migrations for a preview feature are not yet required to preserve existing persistent state in a deployment, as would be required for a stable feature.<br>
<br>
* All code that is part of a preview feature is located under neutron/preview/<feature>/. Associated unit tests are located under neutron/tests/unit/preview/<<u></u>feature>/, and similarly for other test categories. This makes the feature's status clear to developers and other direct consumers of the source tree, and also allows packagers to easily partition all preview features or individual preview features into separate optionally installable packages.<br>
<br>
* The tree structures underneath these locations should make it straightforward to move the preview feature code to its proper tree location once it is considered stable.<br>
<br>
* Tempest API and scenario tests for preview features are highly desirable. We need to agree on how to accomplish this without preventing necessary API changes. Posting WIP patches to the Tempest project may be sufficient initially. Putting Tempest-like tests in the Neutron tree until preview features stabilize, then moving them to Tempest when stabilization is complete, might be a better long term solution.<br>
<br>
* No non-preview Neutron code should import code from anywhere under the neutron.preview module, unless necessary for special cases like DB migrations.<br>
<br>
* URIs for the resources provided by preview features should contain the string "preview".<br>
<br>
* Configuration file content related to preview features should be clearly labeled as "preview".<br>
<br>
* Preview features should be documented similarly to any stable Neutron feature, but documents or sections of documents related to preview features should have an easily recognizable label that clearly identifies the feature as a "preview".<br>
<br>
* Support for preview features in client libraries, and in other projects such as Horizon, Heat, and DevStack, are essential to get the feedback needed from early adopters during feature stabilization. They are implemented normally, but should be labeled "preview" appropriately, such as in GUIs, in CLI help strings and in documentation so that end user expectations regarding stability are managed.<br>
<br>
* A process is needed to prevent long-term stagnation of features in the preview sub-tree. It is reasonable to expect a new feature to remain for one or two cycles, possibly with little change (other than bug fixes), before stabilizing. A suggested rule is that a new approved BP is required after two cycles, or the feature gets removed from the Neutron source tree (maybe moved (back) to an incubation repository).<br>
<br>
<br>
I would appreciate feedback via this email thread on whether this "preview feature" concept is worth further consideration, refinement and potential usage for approved feature blueprints, especially during the Juno cycle. I've also posted the proposal text at <a href="https://etherpad.openstack.org/p/neutron-preview-features" target="_blank">https://etherpad.openstack.<u></u>org/p/neutron-preview-features</a> for those interested in helping refine the proposal.<br>
<br>
Thanks,<br>
<br>
-Bob<br>
<br>
<br>
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