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This tag is part of the assert category of tags, which are assertions made by the project team themselves about their maturity. One such assertion (or self-imposed contract) is about under which conditions APIs and features of a given service may be deprecated in the future.

The “assert:follows-standard-deprecation” tag asserts that the project will follow standard feature deprecation rules as described here.


End users of a given service need to know if a feature or an API they are using and rely on will still be supported by the software tomorrow. Operators and deployers of a given service want to be able to roll out code and configuration changes asynchronously, and therefore rely on new code working correctly with the existing config files.

At the early stages of development it’s important to be agile, experiment, and fail fast. At that point it’s not reasonable to commit to support those early mistakes forever. But as the project matures and gets more users that rely on existing features, knowing under which conditions the project can remove features, APIs or alter configuration options in the future becomes important. It can be a factor in deciding if the project is stable and mature enough for a specific use case.


Project teams can apply this tag to services that they produce to assert that they will follow the following process for end-user-visible or operator-visible features deprecation:

  1. Features, APIs or configuration options are marked deprecated in the code. Appropriate warnings will be sent to the end user, operator or library user. Code will be frozen and only receive minimal maintenance (just so that it continues to work as-is).
  2. A migration path will be documented for current users of the feature. An email thread will be started on openstack-operators to determine how many people are using the deprecated API or feature, and how costly the migration plan is to implement. A migration path may be “stop using that feature”: the cost is then very related to the number of people using the feature and how dependent they are to that feature.
  3. If the deliverable is part of a defcore set, the project will check if the deprecated feature is part of the exposed capabilities. If it is, the obsolescence date (see below) additionally needs to take into account defcore capabilities deprecation schedule.
  4. Based on that data, an obsolescence date will be set. At the very minimum the feature (or API, or configuration option) should be marked deprecated (and still be supported) in the next stable release branch, and for at least three months linear time. For example, a feature deprecated in November 2015 should still appear in the Mitaka release and stable/mitaka stable branch and cannot be removed before the beginning of the N development cycle in April 2016. A feature deprecated in March 2016 should still appear in the Mitaka release and stable/mitaka stable branch, and cannot be removed before June 2016. Features included in an intermediate release but not a coordinated release may be deprecated in the next release of any type and must stay in place at least 3 months after being deprecated before being removed in a release of any type.

Note that this delay is a required minimum. For significant features, it is recommended that the deprecated feature appears at least in the next two stable release branches.

In addition, projects assert that:

  • It uses an automated test to verify that configuration files are forward-compatible from release to release and that this policy is not accidentally broken (for example, a gating grenade test).
  • No existing config options will have their meaning changed in such a way that it would alter the software behavior or otherwise render an existing config file broken.

Note: this tag can currently only be applied to services (type:service deliverables). The tag definition may evolve in the future to include library feature deprecation policy and be applicable to libraries as a result.

Tag application process

Assertion tags are set by the project team PTL. The Technical Committee may exceptionally remove the tag if they find that the project doesn’t actually follow the requirements for the assertion.

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