[CI] Change branch workflows so that they are triggered only upon request or scheduled

[lhotari]

Search before asking

• I searched in the issues and found nothing similar.

Motivation

We have many active branches and many commits are pushed to these branches. master branch gets commits by merging PRs and in most cases, commits are pushed by cherry-picking commits from master branch to maintenance branches (branch-2.11, branch-2.10, branch-2.9, branch-2.8 and branch-2.7).
In most cases, nobody pays attention to the results of individual builds for commits pushed to maintenance branches.

Therefore, it would be a way to save CI resources if CI builds are only available upon request or in a scheduled manner.

Solution

GitHub Actions has a feature for manually triggering the workflow. Documentation:
https://docs.github.com/en/actions/using-workflows/triggering-a-workflow#defining-inputs-for-manually-triggered-workflows
workflow_dispatch is the event type. Docs for workflow_dispatch
https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_dispatch
The GitHub UI lets the user choose the branch. The minimum way to add support for manual triggering is adding on: workflow_dispatch to the workflow.

Alternatives

No response

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[lhotari]

In addition, master could have a scheduled workflow to run in the similar way as the existing "CI - Maven Dependency Cache Update" workflow. That workflow after having a scheduled workflow for master branch.

[nicoloboschi]

We can set the manual trigger for branch-2.11. For branch-2.10 and previous, the workflow Pulsar CI doesn't exist. A good solution would be to:

• Remove the post-commit trigger for all the jobs in branch-2.10 (and prev) branches. When the release manager needs to validate the branch, it has to open a pull. It's not very common that we open pulls against release branches so it will reduce the CI loads a lot.
• For branch-2.11 (and future release branches) we can do the same and additionally add the workflow_dispatch trigger.

[lhotari]

@nicoloboschi makes sense. triggering 25+ workflows in branch-2.10 (and before) in the UI wouldn't be very usable.