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RabbitMQ RFC process

Summary

One paragraph explanation of the feature.

Motivation

Why are we doing this? What use cases does it support? What is the expected outcome?

Guide-level explanation

Explain the proposal as if it was already included in the RabbitMQ Project and you were teaching it to another RabbitMQ developer or end-user. That generally means:

  • Introducing new named concepts.
  • Explaining the feature largely in terms of examples.
  • Explaining how RabbitMQ developers or end-users should think about the feature, and how it should impact the way they use the impacted RabbitMQ Project components. It should explain the impact as concretely as possible.
  • If applicable, provide sample error messages, deprecation warnings, or migration guidance.
  • If applicable, describe the differences between teaching this to both existing and new RabbitMQ developers and end-users.

For implementation-oriented RFCs, this section should focus on how contributors should think about the change, and give examples of its concrete impact. For policy RFCs, this section should provide an example-driven introduction to the policy, and explain its impact in concrete terms.

Reference-level explanation

This is the technical portion of the RFC. Explain the design in sufficient detail that:

  • Its interaction with other features is clear.
  • It is reasonably clear how the feature would be implemented.
  • Corner cases are dissected by example.

The section should return to the examples given in the previous section, and explain more fully how the detailed proposal makes those examples work.

Drawbacks

Why should we not do this?

Rationale and alternatives

  • Why is this design the best in the space of possible designs?
  • What other designs have been considered and what is the rationale for not choosing them?
  • What is the impact of not doing this?

Prior art

Discuss prior art, both the good and the bad, in relation to this proposal. A few examples of what this can include are:

  • For broker, plugins, client libraries and tools proposals: Does this feature exist in other projects and what experience have their community had?
  • For community proposals: Is this done by some other community and what were their experiences with it?
  • Papers: Are there any published papers or great posts that discuss this? If you have some relevant papers to refer to, this can serve as a more detailed theoretical background.

This section is intended to encourage you as an author to think about the lessons from other projects, provide readers of your RFC with a fuller picture. If there is no prior art, that is fine - your ideas are interesting to us whether they are brand new or if it is an adaptation from other projects.

Note that while precedent set by other projects is some motivation, it does not on its own motivate an RFC. Please also take into consideration that the RabbitMQ Project sometimes intentionally diverges from common features.

Unresolved questions

  • What parts of the design do you expect to resolve through the RFC process before this gets merged?
  • What parts of the design do you expect to resolve through the implementation of this feature before stabilization?
  • What related issues do you consider out of scope for this RFC that could be addressed in the future independently of the solution that comes out of this RFC?

Future possibilities

Think about what the natural extension and evolution of your proposal would be and how it would affect the project as a whole in a holistic way. Try to use this section as a tool to more fully consider all possible interactions with the project in your proposal. Also consider how this all fits into the roadmap for the project and of the Core team.

This is also a good place to "dump ideas", if they are out of scope for the RFC you are writing but otherwise related.

If you have tried and cannot think of any future possibilities, you may simply state that you cannot think of anything.

Note that having something written down in the future-possibilities section is not a reason to accept the current or a future RFC; such notes should be in the section on motivation or rationale in this or subsequent RFCs. The section merely provides additional information.

RabbitMQ RFCs

Many changes, including bug fixes and documentation improvements can be implemented and reviewed via the normal GitHub pull request workflow in the appropriate repository under the RabbitMQ Organization.

Some changes though are "substantial", and we ask that these be put through a bit of a design process and produce a consensus among the RabbitMQ community and the Core team.

The "RFC" (request for comments) process is intended to provide a consistent and controlled path for new features so that all stakeholders can be confident about the direction the project is evolving in.

The RFC process is to be followed by both the RabbitMQ Core team and external contributors. The goal is to include end-users into the design of new features.

Table of Contents

When you need to follow this process

You need to follow this process if you intend to make "substantial" changes to the RabbitMQ broker, the plugins, the client libraries, tools, workflows or the RFC process itself. What constitutes a "substantial" change is evolving based on community norms and varies depending on what part of the ecosystem you are proposing to change, but may include the following.

  • New features in the broker, plugins, client libraries, tools or workflows which affect end-users.
  • Any change to existing behaviors of the broker, plugins, client libraries or tools which affect end-users.
  • Removing features.

Some changes do not require an RFC:

  • Rephrasing, reorganizing, refactoring, or otherwise "changing shape does not change meaning".
  • Additions that strictly improve objective, numerical quality criteria (warning removal, speedup, better platform coverage, more parallelism, trap more errors, etc.)
  • Additions only likely to be noticed by other developers-of-rabbitmq, invisible to users-of-rabbitmq.

If you submit a pull request to implement a new feature without going through the RFC process, it may be closed with a polite request to submit an RFC first.

Before creating an RFC

A hastily-proposed RFC can hurt its chances of acceptance. Low quality proposals, proposals for previously-rejected features, or those that don't fit into the near-term roadmap, may be quickly rejected, which can be demotivating for the unprepared contributor. Laying some groundwork ahead of the RFC can make the process smoother.

Although there is no single way to prepare for submitting an RFC, it is generally a good idea to pursue feedback from other project developers beforehand, to ascertain that the RFC may be desirable; having a consistent impact on the project requires concerted effort toward consensus-building.

The most common preparation for writing and submitting an RFC s to discuss the topic using one of our official contact channels, and occasionally posting "pre-RFCs".

As a rule of thumb, receiving encouraging feedback from long-standing project developers is a good indication that the RFC is worth pursuing.

What the process is

In short, to get a major feature added to the RabbitMQ Project (in any of the area mentioned above), one must first get the RFC merged into the RFC repository as a markdown file. At that point the RFC is "active" and may be implemented with the goal of eventual inclusion into the RabbitMQ Project.

  • Fork the RFC repo RFC repository
  • Copy 0000-template.md to text/0000-my-feature.md (where "my-feature" is descriptive. don't assign an RFC number yet).
  • Fill in the RFC. Put care into the details: RFCs that do not present convincing motivation, demonstrate lack of understanding of the design's impact, or are disingenuous about the drawbacks or alternatives tend to be poorly-received.
  • Submit a pull request. As a pull request the RFC will receive design feedback from the larger community, and the author should be prepared to revise it in response.
  • Build consensus and integrate feedback. RFCs that have broad support are much more likely to make progress than those that don't receive any comments. Feel free to reach out to the RFC assignee in particular to get help identifying stakeholders and obstacles.
  • The Core team will discuss the RFC pull request, as much as possible in the comment thread of the pull request itself. Offline discussion will be summarized on the pull request comment thread.
  • RFCs rarely go through this process unchanged, especially as alternatives and drawbacks are shown. You can make edits, big and small, to the RFC to clarify or change the design, but make changes as new commits to the pull request, and leave a comment on the pull request explaining your changes. Specifically, do not squash or rebase commits after they are visible on the pull request.
  • At some point, a member of the Core team will propose a "motion for final comment period" (FCP), along with a disposition for the RFC (merge, close, or postpone).
    • This step is taken when enough of the tradeoffs have been discussed that the Core team is in a position to make a decision. That does not require consensus amongst all participants in the RFC thread (which is usually impossible). However, the argument supporting the disposition on the RFC needs to have already been clearly articulated, and there should not be a strong consensus against that position outside of the Core team. The Core team members use their best judgment in taking this step, and the FCP itself ensures there is ample time and notification for stakeholders to push back if it is made prematurely.
    • For RFCs with lengthy discussion, the motion to FCP is usually preceded by a summary comment trying to lay out the current state of the discussion and major tradeoffs/points of disagreement.
    • Before actually entering FCP, all members of the Core team must sign off; this is often the point at which many Core team members first review the RFC in full depth.
  • The FCP lasts ten calendar days, so that it is open for at least 5 business days. It is also advertised widely, e.g. in our official channels use to announce new releases and This Month in RabbitMQ. This way all stakeholders have a chance to lodge any final objections before a decision is reached.
  • In most cases, the FCP period is quiet, and the RFC is either merged or closed. However, sometimes substantial new arguments or ideas are raised, the FCP is canceled, and the RFC goes back into development mode.

The RFC life-cycle

Once an RFC becomes "active" then authors may implement it and submit the feature as a pull request to the appropriate RabbitMQ Organization repository. Being "active" is not a rubber stamp, and in particular still does not mean the feature will ultimately be merged; it does mean that in principle all the major stakeholders have agreed to the feature and are amenable to merging it.

Furthermore, the fact that a given RFC has been accepted and is "active" implies nothing about what priority is assigned to its implementation, nor does it imply anything about whether a Core team developer has been assigned the task of implementing the feature. While it is not necessary that the author of the RFC also write the implementation, it is by far the most effective way to see an RFC through to completion: authors should not expect that other project developers will take on responsibility for implementing their accepted feature.

Modifications to "active" RFCs can be done in follow-up pull requests. We strive to write each RFC in a manner that it will reflect the final design of the feature; but the nature of the process means that we cannot expect every merged RFC to actually reflect what the end result will be at the time of the next major release.

In general, once accepted, RFCs should not be substantially changed. Only very minor changes should be submitted as amendments. More substantial changes should be new RFCs, with a note added to the original RFC. Exactly what counts as a "very minor change" is up to the Core team to decide.

Reviewing RFCs

While the RFC pull request is up, the Core team may schedule meetings with the author and/or relevant stakeholders to discuss the issues in greater detail, and in some cases the topic may be discussed at a Core team meeting. In either case a summary from the meeting will be posted back to the RFC pull request.

The Core team makes final decisions about RFCs after the benefits and drawbacks are well understood. These decisions can be made at any time, but the Core team will regularly issue decisions. When a decision is made, the RFC pull request will either be merged or closed. In either case, if the reasoning is not clear from the discussion in thread, the Core team will add a comment describing the rationale for the decision.

Implementing an RFC

Some accepted RFCs represent vital features that need to be implemented right away. Other accepted RFCs can represent features that can wait until some arbitrary developer feels like doing the work. Every accepted RFC has an associated issue tracking its implementation in the appropriate repository.

The author of an RFC is not obligated to implement it. Of course, the RFC author (like any other developer) is welcome to post an implementation for review after the RFC has been accepted.

If you are interested in working on the implementation for an "active" RFC, but cannot determine if someone else is already working on it, feel free to ask (e.g. by leaving a comment on the associated issue).

RFC Postponement

Some RFC pull requests are tagged with the "postponed" label when they are closed (as part of the rejection process). An RFC closed with "postponed" is marked as such because we want neither to think about evaluating the proposal nor about implementing the described feature until some time in the future, and we believe that we can afford to wait until then to do so. Postponed pull requests may be re-opened when the time is right. We don't have any formal process for that, you should ask members of the Core team.

Usually an RFC pull request marked as "postponed" has already passed an informal first round of evaluation, namely the round of "do we think we would ever possibly consider making this change, as outlined in the RFC pull request, or some semi-obvious variation of it." (When the answer to the latter question is "no", then the appropriate response is to close the RFC, not postpone it.)

Closed-source changes and Enterprise components

Sometimes, an RFC is about a change targetting the Enterprise components of the RabbitMQ Project. If the RFC is accepted and implemented, the result will be closed-source and included in the Enterprise components only.

If an RFC is about such a change, the RFC must mention it clearly. Anyone can participate to the design but they should be well aware that only customers of the Enterprise components will benefit from the result. In other words, the FOSS versions of those components, if any, will not have the change described by the RFC.

From an intellectual property point of view, it means that all contributors agree with this section and accept they will benefit from the change only if they are customers of the Enterprise components.

License

This repository is licensed under either of:

at your option.

Contributions

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

@acogoluegnes
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"submit the feature as a pull request to the appropriate RabbitMQ Organization. reposotiry." => "submit the feature as a pull request to the appropriate RabbitMQ Organization repository."

@dumbbell
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"submit the feature as a pull request to the appropriate RabbitMQ Organization. reposotiry." => "submit the feature as a pull request to the appropriate RabbitMQ Organization repository."

Fixed, thank you!

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