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TL;DR- If you simply need to learn how to make a release, read this section.

Overview

  • Release process is automated by hack/release.sh script
  • KubeVirt uses semantic versioning
  • Primary artifact is the source tree in form of signed git tag
  • Binary artifacts are built using automation
  • The releases appear on a time based release schedule
  • Releases can be blocked using the release-blocker github comment

The primary artifact of a release is the source tree itself. The trust on the tree is established by using a signed git tag.

For convenience a number of binary artifacts can be provided alongside a release, those are:

  • Container images (currently docker images), tagged and pushed to a registry
  • Client side binaries (i.e. virtctl), published on the release page

These artifacts are provided in their respective channels and their natural way of distribution.

Cadence and Timeline

Minor releases

KubeVirt aligns to the Kubernetes release cycle. But because KubeVirt builds upon Kubernetes, it will trail Kubernetes' release schedule by roughly 2 months, in order to have time to consume and stabilize on top of new releases.

Thus new release branches are cut 3 times a year, or about every 15 weeks.

Guiding principles

The release schedule is build around a few guiding principles:

  • Alpha and Beta tags are applied on main
  • Release branches must only be cut after a Kubernetes minor releases
  • RCs must only be tagged on the release branch

CI Provider

A pre-condition for the GA of a KubeVirt release is the presence of a KubeVirt CI provider for the correspoding Kubernetes release. Around the beta release of the corresponding Kubernetes release, the KubeVirt team will start to work on a KubeVirt CI provider. The assumption is, that the KubeVirt CI provider will be available by KubeVirt's enhcanement freeze.

Release schedule schema

This can then be translated into the following KubeVirt release schedule schema:

Week Number in Kubernetes Release Cycle KubeVirt Milestone Note
14 - 8 Alpha KubeVirt alpha.0 on main
14 - 4 Beta KubeVirt beta.0 on main
14 - 4 Start the KubeVirt CI provider
14 Kubernetes release
14 + 8 Enhancement Freeze KubeVirt stable branch is cut
14 + 9 RC KubeVirt rc.0 on release branch
14 + 10 RC KubeVirt rc.1 on release branch
14 + 11 GA KubeVirt GA

Release branch and backports

Once the branch is created, only backports will be allowed into the stable branch, following KubeVirt's backport policy.

Blockers

If blockers are detected, a new release candidate is generated and will be promoted after giving the impacted parties enough time to validate the blocker is addressed.

Holidays

Just like in Kubernetes, there will be slowdowns during common holidays which will cause delays. So releases that overlap with holidays may be delayed.

Versioning

Branches are created for every minor release and take the form of release-<major>.<minor> For example, the release branch for an upcoming v0.30.0 release will be release-0.30

Releases are cut from release branches must adhere to semantic versioning conventions. For example, the initial release candidate for branch release-0.30 is called v0.30.1-rc.0

The determined version is then prefixed with a v (mostly for consistency, because we started this way) and used as the tag name ($TAG below).

RC Version Examples:

v0.31.1-rc.0
v0.31.1-rc.1

Official Release Version Examples

v0.31.1
v0.31.2

Announcement

Every official release must be announced on the kubevirt-dev mailinglist [email protected] with a body containing the release notes.

You can retrieve the auto generated release notes from the git tag's commit message.

Below is an example of getting the release notes for v0.31.0-rc.0

git show v0.31.0-rc.0

Handling Release Blockers

Release blockers can be set on issues and PRs by approvers of the project. A PR or issue can be flagged as a blocker through the use of the /release-blocker <branch> in a github comment.

The KubeVirt release tool scans for blocker Issues/PRs and will not allow certain actions to take place until the blockers are resolved. A resolved blocker is when an Issue/PR with a blocker label is closed. Do not remove the blocker label for closed issues!

Release Blocker Criteria

A release blocker is a critical bug, regression, or backwards incompatible change that must be addressed before the next official release is made. Only KubeVirt approvers can set this label on a PR or Issue.

Setting a Release Blocker

Once a release blocker is set, the label must never be removed unless we have decided the issue or PR does not in fact need to block a release. This means that the release blocker labels should remain even after an issue or PR is closed.

Example: Signalling a PR/Issue should block the next release branch. This Will prevent a new release branch from being cut until PR/Issue is closed.

/release-blocker main

Example: Signalling a PR/Issue should block the official release of a stable branch This will prevent any existing RCs from being promoted to an official release. A new RC will only able to be created once this Issue/PR is closed.

/release-blocker release-0.31

Example: Canceling a release-blocker. This will remove the signal that an Issue/PR is a blocker. This should only be done if the issue truly isn't a blocker.

/release-blocker cancel release-0.31

and canceling a blocker on main would look like.

/release-blocker cancel main

Creating Releases

The actual releases are all cut using the kubevirt release-tool. This tool automates the entire process of creating branches, signing tags, generating prow configs, and more. All you need to do is gather a few credentials in order to use the tool.

Release Tool Credentials

You must have 2 items before you can create a release.

  1. GPG key and passphrase files used for creating signed releases.

Instructions for adding GPG key to your github account

After adding the GPG key to github, export both the key and passphrase to files. Be aware that this results in the key and passphrase being placed into a plain text file on your machine. Make sure you don't place this in shared storage.

Example of exporting key to file

gpg --export-secret-key -a <your-email-address> > ${HOME}/gpg-private

Example of putting passphrase in file

echo "<insert your passphrase here>" > ${HOME}/gpg-passphrase

  1. Github API token file used for accessing the github api

When you create this token the only permission you need to give it is the ability to access github repositories. That's it.

Instructions for creating access token

Place your token in a text file such as ${HOME}/github-api-token

Release Tool Usage Examples

Once you have your credentials in files, the kubevirt release tool handles all the rest. All you need to do is provide your credentials and tell the tool what release you want to make.

Place the paths to your credential files in the following environment variables.

export GPG_PRIVATE_KEY_FILE="${HOME}/gpg-private"
export GPG_PASSPHRASE_FILE="${HOME}/gpg-passphrase"
export GITHUB_API_TOKEN_FILE="${HOME}/github-api-token"

Now you can use the release tool to do whatever you'd like. Note that you can use the --dry-run=true argument to test a change before executing it.

Example: creating a new release branch with the initial release candidate v0.31.0-rc.0

hack/release.sh --new-branch release-0.31 --new-release v0.31.0-rc.0 --dry-run=false

Example: Creating a new rc v0.31.0-rc.0

hack/release.sh --new-release v0.31.0-rc.0 --dry-run=false

Example: Promoting a release candidate v0.31.0-rc-1 to official v0.30.0 release.

hack/release.sh --promote-release-candidate v0.31.0-rc-1 --dry-run=false

Example: Creating a patch release v0.31.1. The branch will automatically be detected.

hack/release.sh --new-release v0.31.1 --dry-run=false

Creating New Minor Releases

The release process is mostly automatic and consists of the following steps:

  1. Create the branch and initial RC.

    hack/release.sh --new-branch $RELEASE_BRANCH --new-tag ${TAG}.rc.0

  2. Wait 5 business days

  3. Promote RC to official release if no blockers exist.

    hack/release.sh --promote-release-candidate ${TAG}.rc.0

  4. Wait for travis to finish, and check that the binary artifacts got attached to the release at https://github.com/kubevirt/kubevirt/releases/tag/${TAG} and that the containers were correctly tagged and pushed to https://hub.docker.com/r/kubevirt/

  5. If release looks correct, click "edit" on the release in the github UI and uncheck the "This is a pre-release" box. This will make the release official

  6. Sent a friendly announcement email to [email protected] using the release notes already present on the release's description in github.

Creating New Patch Releases

Releases on the stable branch only increment the patch level. The release itself is only a git signed tag as it's used for minor releases as well.

  1. Create the patch release. Note that the branch is automatically detected.

    hack/release.sh --new-tag ${TAG}

  2. Wait for travis to finish, and check that the binary artifacts got attached to the release at https://github.com/kubevirt/kubevirt/releases/tag/$TAG and that the containers were correctly tagged and pushed to https://hub.docker.com/r/kubevirt/

  3. If release looks correct, click "edit" on the release in the github UI and uncheck the "This is a pre-release" box. This will make the release official

  4. Sent a friendly announcement email to [email protected] using the release notes already present on the release's description in github.

Merging to Release Branches

For every release a branch will be created following the pattern release-x.y. For now, community members can propose pull requests to be included into a stable branch. Those pull requests should be limited to bug fixes and must not be enhancements. More info related to the policy around backporting can be found in this document, docs/release-branch-backporting.md

Cherry picking can be used to pick a merge commit from the main branch to a stable branch. An example:

git checkout release-0.6
git cherry-pick $THE_MERGE_COMMIT_ID -m 1 -sx
[release-0.6 acd756040] Merge pull request #1234 from great_person
 Author: Bob Builder <[email protected]>
 Date: Thu Jun 28 17:50:05 2018 +0300
 5 files changed, 55 insertions(+), 22 deletions(-)
git push $YOUR_REMOTE release-0.6:release-0.6-aParticularFix

After pushing the branch, you'll need to make sure to create a pull request against the correct target branch in GitHub (in this case the target branch is release-0.6).

Understanding Release Notes

Release notes are automatically generated by our release tool. The notes are sourced from the delta of PRs merged since the last official release. The text from those PRs are sourced directly from the release-notes section in each PRs description.

Below is an example of getting the release notes for v0.31.0-rc.0

git show v0.31.0-rc.0