[Backport release-1.28] feat: implement watcher for oci bundles

[ricardomaraschini]

Description

Implements an OCI bundle watcher. This allows k0s to load new OCI bundles without requiring a restart of the process. The watcher acts upon Create() or Write() operations happening in the OCI bundles directory and events are debounced with a timeout of 10 seconds.

Fixes # 4316

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test
• Auto test added

At this stage I have updated k0s locally and created/deleted/updated bundles manually in the OCI bundles directory. I have been checking the results by inspecting the logs (as follow) and with k0s ctr i ls:

root@ec:/usr/local/bin# journalctl -u k0scontroller.service -f | grep -i component=OCIBundleReconciler
Apr 22 10:49:44 ec k0s[2014911]: time="2024-04-22 10:49:44" level=info msg="started to watch events on /var/lib/k0s/images" component=OCIBundleReconciler
Apr 22 10:50:06 ec k0s[2014911]: time="2024-04-22 10:50:06" level=info msg="OCI bundle directory changed, reconciling" component=OCIBundleReconciler
Apr 22 10:50:08 ec k0s[2014911]: time="2024-04-22 10:50:08" level=info msg="Imported image docker.io/library/x:latest" component=OCIBundleReconciler
Apr 22 10:50:28 ec k0s[2014911]: time="2024-04-22 10:50:28" level=info msg="OCI bundle directory changed, reconciling" component=OCIBundleReconciler
Apr 22 10:50:29 ec k0s[2014911]: time="2024-04-22 10:50:29" level=info msg="Imported image docker.io/library/x:latest" component=OCIBundleReconciler
Apr 22 10:51:03 ec k0s[2014911]: time="2024-04-22 10:51:03" level=info msg="OCI bundle directory changed, reconciling" component=OCIBundleReconciler
Apr 22 10:51:04 ec k0s[2014911]: time="2024-04-22 10:51:04" level=info msg="Imported image docker.io/library/y:latest" component=OCIBundleReconciler
Apr 22 10:51:40 ec k0s[2014911]: time="2024-04-22 10:51:40" level=info msg="OCI bundle directory changed, reconciling" component=OCIBundleReconciler
Apr 22 10:51:59 ec k0s[2014911]: time="2024-04-22 10:51:59" level=info msg="Imported image docker.io/library/rhel-9-kubernetes-images-1.29.3:latest" component=OCIBundleReconciler
Apr 22 10:51:59 ec k0s[2014911]: time="2024-04-22 10:51:59" level=info msg="Imported image docker.io/kurl/rhel-7-k8s:1.29.3" component=OCIBundleReconciler
Apr 22 10:51:59 ec k0s[2014911]: time="2024-04-22 10:51:59" level=info msg="Imported image docker.io/library/dockerout-containerd-1.6.28-ubuntu-22.04:latest" component=OCIBundleReconciler

Checklist:

• My code follows the style guidelines of this project
• My commit messages are signed-off
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[twz123]

See:

• Bump github.com/fsnotify/fsnotify from 1.6.0 to 1.7.0 #3629

[k0s-bot]

Backport failed for release-1.27, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git fetch origin release-1.27
git worktree add -d .worktree/backport-4428-to-release-1.27 origin/release-1.27
cd .worktree/backport-4428-to-release-1.27
git checkout -b backport-4428-to-release-1.27
ancref=$(git merge-base bace82049e94b28d4ca266dc271452106957e52d b7a919960a4f0edccfe61d27f6b9a5250fb3f780)
git cherry-pick -x $ancref..b7a919960a4f0edccfe61d27f6b9a5250fb3f780