If you would like to contribute to the development of OpenStack, you must follow the steps in this page:

If you already have a good understanding of how the system works and your OpenStack accounts are set up, you can skip to the development workflow section of this documentation to learn how changes to OpenStack should be submitted for review via the Gerrit tool:

Pull requests submitted through GitHub will be ignored.

Bugs should be filed on Launchpad in the neutron project using the lib tag, not GitHub:

As your code is subject to the review guidelines, please take the time to familiarize yourself with those guidelines.

Rehoming Existing Code

The checklist below aims to provide guidance for developers rehoming (moving) code into neutron-lib. Rehoming approaches that fall outside the scope herein will need to be considered on a case by case basis.

Please note that the effort to rehome existing code from neutron to neutron-lib so that no stadium projects would import directly from neutron has been suspended.

The rehoming workflow procedure has four main phases:

  1. Phase 1: Rehome the code from neutron into neutron-lib.

  2. Phase 2: Enhance the code in neutron-lib if necessary.

  3. Phase 3: Release neutron-lib with the code so consumers can use it.

  4. Phase 4: Consume by removing the rehomed code from its source and changing references to use neutron-lib.

Phase 1: Rehome

  1. Identify the chunk of code for rehoming. Applicable code includes common classes/functions/modules/etc. that are consumed by networking project(s) outside of neutron. Optimal consumption patterns of the code at hand must also be considered to ensure the rehomed code addresses any technical debt. Finally, leave low-hanging fruit for last and tackle the most commonly used code first. If you have any doubt about the applicability of code for rehoming, reach out to one of the neutron core developers before digging in.

  2. Find and identify any unit tests for the code being rehomed. These unit tests can often be moved into neutron-lib with minimal effort. After inspecting the applicable unit tests, rewrite any that are non-optimal.

  3. Search and understand the consumers of the code being rehomed. This must include other networking projects in addition to neutron itself. At this point it may be determined that the code should be refactored before it is consumed. There are a few common strategies for refactoring, and the one chosen will depend on the nature of the code at hand:

    • Refactor/enhance the code as part of the initial neutron-lib patch. If this change will be disruptive to consumers, clearly communicate the change via email list or meeting topic.

    • Leave the refactoring to the next (Enhance) phase. In this rehome phase, copy the code as-is into a private module according to our conventions. This approach is slower, but may be necessary in some cases.

  4. Understand existing work underway which may impact the rehomed code, for example, in-flight patch sets that update the code being rehomed. In some cases it may make sense to let the in-flight patch merge and solidify a bit before rehoming.

  5. Prepare the code for neutron-lib. This may require replacing existing imports with those provided by neutron-lib and/or rewriting/rearchitecting non-optimal code (see above). The interfaces in the rehomed code are subject to our conventions.

  6. Prepare the unit test code for neutron-lib. As indicated in the review guidelines we are looking for a high code coverage by tests. This may require adding additional tests if neutron was lacking in coverage.

  7. Submit and shepherd your patch through its neutron-lib review. Include a release note that describes the code’s old neutron location and new neutron-lib location. Also note that in some cases it makes sense to prototype a change in a consumer project to better understand the impacts of the change, which can be done using the Depends-On: approach described in the review guidelines


  • 319769 brought over a number of common utility functions as-is from neutron into a new package structure within neutron-lib.

  • 253661 rehomed neutron callbacks into a private package that’s enhanced via 346554.

  • 319386 rehomes a validator from neutron into neutron-lib.

Phase 2: Enhance

If the rehomed code is not applicable for enhancements and wasn’t made private in Phase 1, you can skip this step.

Develop and shepherd the enhancements to the private rehomed code applicable at this time. Private APIs made public as part of this phase will also need release notes indicating the new public functionality.


  • 346554 enhances the rehomed private callback API in neutron-lib.

Phase 3: Release

A new neutron-lib release can be cut at any time. You can also request a release by following the README instructions in the openstack/releases project.

Once a release is cut, an openstack infra proposal bot will submit patches to the master branch of all projects that consume neutron-lib to set the new release as the minimum requirement. Someone from the neutron release team can bump global requirements (g-r); for example review 393600.

When the bot-proposed requirement patches have merged, your rehomed code can be consumed.

Phase 4: Consume

When code is rehomed from neutron-lib then the original location of the code should be flagged with a debtcollector removal. This will indicate to any consuming projects that the given code is deprecated. Be sure that this change is accompanied by a release note that notes the deprecation.