flux2/docs/release/controllers.md

Flux controllers release spec

The Flux controllers are Kubernetes operators, each controller has its own Git repository and release cycle.

Controller repositories and their interdependencies:

1. fluxcd/source-controller
2. fluxcd/kustomize-controller (imports fluxcd/source-controller/api)
3. fluxcd/helm-controller (imports fluxcd/source-controller/api)
4. fluxcd/notification-controller
5. fluxcd/image-reflector-controller
6. fluxcd/image-automation-controller (imports fluxcd/source-controller/api and fluxcd/image-reflector-controller/api)

API versioning

The Flux APIs (Kubernetes CRDs) follow the Kubernetes API versioning scheme.

Alpha version

An alpha version API e.g. v1alpha1 is considered experimental and should be used on test environments only.

The schema of objects may change in incompatible ways in a later controller release. The Custom Resources may require editing and re-creating after a CRD update.

An alpha version API becomes deprecated once a subsequent alpha or beta API version is released. A deprecated alpha version is subject to removal after a three months period.

An alpha API is introduced when its proposal reaches the implementable phase in the Flux RFC process. We encourage users to try out the alpha APIs and provide feedback (e.g. on CNCF Slack or in the form of GitHub issues/discussions) which is extremely valuable during early stages of development.

Beta version

A beta version API e.g. v2beta1 is considered well-tested and safe to use in production.

The schema of objects may change in incompatible ways in a subsequent beta or stable API version. The Custom Resources may require editing after a CRD update for which migration instructions will be provided as part of the controller changelog.

A beta version API becomes deprecated once a subsequent beta or stable API version is released. A deprecated beta version is subject to removal after a six months period.

Stable version

A stable version API e.g. v2 is considered feature complete.

Any changes to the object schema do not require editing or re-creating of Custom Resources. Schema fields can't be removed, only new fields can be added with a default value that doesn't affect the controller's current behaviour.

A stable version API becomes deprecated once a subsequent stable version is released. Stable API versions are not subject to removal in any future release of a controller major version.

In effect, this means that for as long as Flux v2 is being maintained, all the stable API versions will be supported.

Controller versioning

The Flux controllers and their Go API packages are released by following the Go module version numbering conventions:

• vX.Y.Z-RC.W release candidates e.g. v1.0.0-RC.1
• vX.Y.Z stable releases e.g. v1.0.0

The API versioning and controller versioning are indirectly related. For example, a source-controller minor release v1.1.0 can introduce a new API version v1beta1 for a Kind XRepository in the source.toolkit.fluxcd.io group.

Release candidates

Release candidates are intended for testing new features or improvements before a final release.

In most cases, a maintainer will publish a release candidate of a controller for Flux users to tests it on their staging clusters. Release candidates are not meant to be deployed in production unless advised to do so by a maintainer.

Patch releases

Patch releases are intended for critical bug fixes to the latest minor version, such as addressing security vulnerabilities or fixes to severe problems with no workaround.

Patch releases do not contain breaking changes, feature additions or any type of user-facing changes. If a CVE fix requires a breaking change, then a minor release will provide the fix.

We expect users to be running the latest patch release of a given minor release as soon as the controller release is included in a Flux patch release.

Minor releases

Minor releases are intended for backwards compatible feature additions and improvements. Note that breaking changes may occur if required by a security vulnerability fix.

In addition, minor releases are used when updating Kubernetes dependencies such as k8s.io/api from one minor version to another.

In effect, this means a new minor version will at least be released for all Flux controllers approximately every four months, following each Kubernetes minor version release. To properly validate the controllers against the latest Kubernetes version, we typically allocate a time window of at least two weeks for end-to-end testing of Flux controllers.

It is worth noting that in certain scenarios where project dependencies are not in sync with the Kubernetes version or conflicts arise, this two-week timeframe may prove insufficient, requiring additional time to address the issues appropriately.

Major releases

Major releases are intended for drastic changes in the controller behaviour or security stance.

A controller major release will be announced ahead of time throughout all communication channels, and a support window of one year will be provided for the previous major version.

Release cadence

Flux controllers are at least released at the same rate as Kubernetes, following their cadence of three minor releases per year. After each Kubernetes minor release, all controllers are tested against the latest Kubernetes version and are released at approximately two weeks after Kubernetes. The newly released controllers offer support for Kubernetes N-2 minor versions.

A Flux controller may have more than three minor releases per year, if maintainers decide to ship a new feature or optimisation ahead of schedule.

Supported releases

For Flux controllers we support the last three minor releases.

Security fixes may be back-ported to those three minor versions as patch releases, depending on severity and feasibility.

Note that back-porting is provided by the community on a best-effort basis.

Release artifacts

Each controller release produces the following artifacts:

• Source code (GitHub Releases page)
• Software Bill of Materials in SPDX format (GitHub Releases page)
• Kubernetes manifests such as CRDs and Deployments (GitHub Releases page)
• Signed checksums of source code, SBOM and manifests (GitHub Releases page)
• Multi-arch container images (GitHub Container Registry and DockerHub)

All the artifacts are cryptographically signed and can be verified with Cosign.

The release artifacts can be accessed based on the controller name and version.

To import or update a controller's API package in a Go project:

go get github.com/fluxcd/<controller-name>/api@<version>

To verify and pull a controller's container image:

cosign verify ghcr.io/fluxcd/<controller-name>:<version>
docker pull ghcr.io/fluxcd/<controller-name>:<version>

To download a controller's Kubernetes Custom resource definitions:

curl -sL https://github.com/fluxcd/<controller-name>/releases/download/<version>/<controller-name>.crds.yaml

Controller release procedure

As a project maintainer, to release a controller and its API:

1. Checkout the main branch and pull changes from remote.
2. Create a new branch from main i.e. release-<next semver>. This will function as your release preparation branch.
3. Update the github.com/fluxcd/<NAME>-controller/api version in go.mod
4. Add an entry to the CHANGELOG.md for the new release and change the newTag value in config/manager/kustomization.yaml to that of the semver release you are going to make. Commit and push your changes.
5. Create a PR for your release branch and get it merged into main.
6. Create a api/<next semver> tag for the merge commit in main and push it to remote.
7. Create a <next semver> tag for the merge commit in main and push it to remote.
8. Confirm CI builds and releases the newly tagged version.

Note that the Git tags must be cryptographically signed with your private key and your public key must be uploaded to GitHub.