Blueprints and Specs

Blueprints and Specs

The Neutron team uses the neutron-specs repository for its specification reviews. Detailed information can be found on the wiki. Please also find additional information in the reviews.rst file.

The Neutron team does not enforce deadlines for specs. These can be submitted throughout the release cycle. The drivers team will review this on a regular basis throughout the release, and based on the load for the milestones, will assign these into milestones or move them to the backlog for selection into a future release.

Please note that we use a template for spec submissions. It is not required to fill out all sections in the template. Review of the spec may require filling in information left out by the submitter.

Sub-Projects and Specs

The neutron-specs repository is only meant for specs from Neutron itself, and the advanced services repositories as well. This includes FWaaS, LBaaS, and VPNaaS. Other sub-projects are encouraged to fold their specs into their own devref code in their sub-project gerrit repositories. Please see additional comments in the Neutron teams section for reviewer requirements of the neutron-specs repository.

Neutron Request for Feature Enhancements

In Liberty the team introduced the concept of feature requests. Feature requests are tracked as Launchpad bugs, by tagging them with a set of tags starting with rfe, enabling the submission and review of feature requests before code is submitted. This allows the team to verify the validity of a feature request before the process of submitting a neutron-spec is undertaken, or code is written. It also allows the community to express interest in a feature by subscribing to the bug and posting a comment in Launchpad. The ‘rfe’ tag should not be used for work that is already well-defined and has an assignee. If you are intending to submit code immediately, a simple bug report will suffice. Note the temptation to game the system exists, but given the history in Neutron for this type of activity, it will not be tolerated and will be called out as such in public on the mailing list.

RFEs can be submitted by anyone and by having the community vote on them in Launchpad, we can gauge interest in features. The drivers team will evaluate these on a weekly basis along with the specs. RFEs will be evaluated in the current cycle against existing project priorities and available resources.

The workflow for the life an RFE in Launchpad is as follows:

  • The bug is submitted and will by default land in the “New” state. Anyone can make a bug an RFE by adding the rfe tag.

  • As soon as a member of the neutron-drivers team acknowledges the bug, the rfe tag will be replaced with the rfe-confirmed tag. No assignee, or milestone is set at this time. The importance will be set to ‘Wishlist’ to signal the fact that the report is indeed a feature or enhancement and there is no severity associated to it.

  • A member of the neutron-drivers team replaces the rfe-confirmed tag with the rfe-triaged tag when he/she thinks it’s ready to be discussed in the drivers meeting. The bug will be in this state while the discussion is ongoing.

  • The neutron-drivers team will evaluate the RFE and may advise the submitter to file a spec in neutron-specs to elaborate on the feature request, in case the RFE requires extra scrutiny, more design discussion, etc.

  • The PTL will work with the Lieutenant for the area being identified by the RFE to evaluate resources against the current workload.

  • A member of the Neutron release team (or the PTL) will register a matching Launchpad blueprint to be used for milestone tracking purposes, and for identifying the responsible assignee and approver. If the RFE has a spec the blueprint will have a pointer to the spec document, which will become available on specs.o.o. once it is approved and merged. The blueprint will then be linked to the original RFE bug report as a pointer to the discussion that led to the approval of the RFE. The blueprint submitter will also need to identify the following:

    • Priority: there will be only two priorities to choose from, High and Low. It is worth noting that priority is not to be confused with importance, which is a property of Launchpad Bugs. Priority gives an indication of how promptly a work item should be tackled to allow it to complete. High priority is to be chosen for work items that must make substantial progress in the span of the targeted release, and deal with the following aspects:

      • OpenStack cross-project interaction and interoperability issues;

      • Issues that affect the existing system’s usability;

      • Stability and testability of the platform;

      • Risky implementations that may require complex and/or pervasive changes to API and the logical model;

      Low priority is to be chosen for everything else. RFEs without an associated blueprint are effectively equivalent to low priority items. Bear in mind that, even though staffing should take priorities into account (i.e. by giving more resources to high priority items over low priority ones), the open source reality is that they can both proceed at their own pace and low priority items can indeed complete faster than high priority ones, even though they are given fewer resources.

    • Drafter: who is going to submit and iterate on the spec proposal; he/she may be the RFE submitter.

    • Assignee: who is going to develop the bulk of the code, or the go-to contributor, if more people are involved. Typically this is the RFE submitter, but not necessarily.

    • Approver: a member of the Neutron team who can commit enough time during the ongoing release cycle to ensure that code posted for review does not languish, and that all aspects of the feature development are taken care of (client, server changes and/or support from other projects if needed - tempest, nova, openstack-infra, devstack, etc.), as well as comprehensive testing. This is typically a core member who has enough experience with what it takes to get code merged, but other resources amongst the wider team can also be identified. Approvers are volunteers who show a specific interest in the blueprint specification, and have enough insight in the area of work so that they can make effective code reviews and provide design feedback. An approver will not work in isolation, as he/she can and will reach out for help to get the job done; however he/she is the main point of contact with the following responsibilities:

      • Pair up with the drafter/assignee in order to help skip development blockers.

      • Review patches associated with the blueprint: approver and assignee should touch base regularly and ping each other when new code is available for review, or if review feedback goes unaddressed.

      • Reach out to other reviewers for feedback in areas that may step out of the zone of her/his confidence.

      • Escalate issues, and raise warnings to the release team/PTL if the effort shows slow progress. Approver and assignee are key parts to land a blueprint: should the approver and/or assignee be unable to continue the commitment during the release cycle, it is the Approver’s responsibility to reach out the release team/PTL so that replacements can be identified.

      • Provide a status update during the Neutron IRC meeting, if required.

      Approver assignments must be carefully identified to ensure that no-one overcommits. A Neutron contributor develops code himself/herself, and if he/she is an approver of more than a couple of blueprints in a single cycle/milestone (depending on the complexity of the spec), it may mean that he/she is clearly oversubscribed.

    The Neutron team will review the status of blueprints targeted for the milestone during their weekly meeting to ensure a smooth progression of the work planned. Blueprints for which resources cannot be identified will have to be deferred.

  • In either case (a spec being required or not), once the discussion has happened and there is positive consensus on the RFE, the report is ‘approved’, and its tag will move from rfe-triaged to rfe-approved.

  • An RFE can be occasionaly marked as ‘rfe-postponed’ if the team identifies a dependency between the proposed RFE and other pending tasks that prevent the RFE from being worked on immediately.

  • Once an RFE is approved, it needs volunteers. Approved RFEs that do not have an assignee but sound relatively simple or limited in scope (e.g. the addition of a new API with no ramification in the plugin backends), should be promoted during team meetings or the ML so that volunteers can pick them up and get started with neutron development. The team will regularly scan rfe-approved or rfe-postponed RFEs to see what their latest status is and mark them incomplete if no assignees can be found, or they are no longer relevant.

  • As for setting the milestone (both for RFE bugs or blueprints), the current milestone is always chosen, assuming that work will start as soon as the feature is approved. Work that fails to complete by the defined milestone will roll over automatically until it gets completed or abandoned.

  • If the code fails to merge, the bug report may be marked as incomplete, unassigned and untargeted, and it will be garbage collected by the Launchpad Janitor if no-one takes over in time. Renewed interest in the feature will have to go through RFE submission process once again.

In summary:




This is where all RFE’s start, as filed by the community.


Drivers/LTs - Move to this state to mean, “more needed before proceeding”


Drivers/LTs - Move to this state to mean, “yeah, I see that you filed it”


Drivers/LTs - Move to this state to mean, “discussion is ongoing”

Won’t Fix

Drivers/LTs - Move to this state to reject an RFE.

Once the triaging (discussion is complete) and the RFE is approved, the tag goes from ‘rfe’ to ‘rfe-approved’, and at this point the bug report goes through the usual state transition. Note, that the importance will be set to ‘wishlist’, to reflect the fact that the bug report is indeed not a bug, but a new feature or enhancement. This will also help have RFEs that are not followed up by a blueprint standout in the Launchpad milestone dashboards.

The drivers team will be discussing the following bug reports during their IRC meeting:

RFE Submission Guidelines

Before we dive into the guidelines for writing a good RFE, it is worth mentioning that depending on your level of engagement with the Neutron project and your role (user, developer, deployer, operator, etc.), you are more than welcome to have a preliminary discussion of a potential RFE by reaching out to other people involved in the project. This usually happens by posting mails on the relevant mailing lists (e.g. openstack-discuss - include [neutron] in the subject) or on #openstack-neutron IRC channel on Freenode. If current ongoing code reviews are related to your feature, posting comments/questions on gerrit may also be a way to engage. Some amount of interaction with Neutron developers will give you an idea of the plausibility and form of your RFE before you submit it. That said, this is not mandatory.

When you submit a bug report on, there are two fields that must be filled: ‘summary’ and ‘further information’. The ‘summary’ must be brief enough to fit in one line: if you can’t describe it in a few words it may mean that you are either trying to capture more than one RFE at once, or that you are having a hard time defining what you are trying to solve at all.

The ‘further information’ section must be a description of what you would like to see implemented in Neutron. The description should provide enough details for a knowledgeable developer to understand what is the existing problem in the current platform that needs to be addressed, or what is the enhancement that would make the platform more capable, both for a functional and a non-functional standpoint. To this aim it is important to describe ‘why’ you believe the RFE should be accepted, and motivate the reason why without it Neutron is a poorer platform. The description should be self contained, and no external references should be necessary to further explain the RFE.

In other words, when you write an RFE you should ask yourself the following questions:

  • What is that I (specify what user - a user can be a human or another system) cannot do today when interacting with Neutron? On the other hand, is there a Neutron component X that is unable to accomplish something?

  • Is there something that you would like Neutron handle better, ie. in a more scalable, or in a more reliable way?

  • What is that I would like to see happen after the RFE is accepted and implemented?

  • Why do you think it is important?

Once you are happy with what you wrote, add ‘rfe’ as tag, and submit. Do not worry, we are here to help you get it right! Happy hacking.

Missing your target

There are occasions when a spec will be approved and the code will not land in the cycle it was targeted at. For these cases, the work flow to get the spec into the next release is as follows:

  • During the RC window, the PTL will create a directory named ‘<release>’ under the ‘backlog’ directory in the neutron specs repo, and he/she will move all specs that did not make the release to this directory.

  • Anyone can propose a patch to neutron-specs which moves a spec from the previous release into the new release directory.

The specs which are moved in this way can be fast-tracked into the next release. Please note that it is required to re-propose the spec for the new release.


The above process involves two places where any given feature can start to be documented - namely in the RFE bug, and in the spec - and in addition to those Neutron has a substantial developer reference guide (aka ‘devref’), and user-facing docs such as the networking guide. So it might be asked:

  • What is the relationship between all of those?

  • What is the point of devref documentation, if everything has already been described in the spec?

The answers have been beautifully expressed in an openstack-dev post:

  1. RFE: “I want X”

  2. Spec: “I plan to implement X like this”

  3. devref: “How X is implemented and how to extend it”

  4. OS docs: “API and guide for using X”

Once a feature X has been implemented, we shouldn’t have to go to back to its RFE bug or spec to find information on it. The devref may reuse a lot of content from the spec, but the spec is not maintained and the implementation may differ in some ways from what was intended when the spec was agreed. The devref should be kept current with refactorings, etc., of the implementation.

Devref content should be added as part of the implementation of a new feature. Since the spec is not maintained after the feature is implemented, the devref should include a maintained version of the information from the spec.

If a feature requires OS docs (4), the feature patch shall include the new, or updated, documentation changes. If the feature is purely a developer facing thing, (4) is not needed.

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