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https://issues.apache.org/jira/browse/ARROW-7203?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16986479#comment-16986479
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Neal Richardson commented on ARROW-7203:
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Cool. IMO it's worth a try.
> [CI] Trigger GitHub Action cron workflows on demand
> ---------------------------------------------------
>
> Key: ARROW-7203
> URL: https://issues.apache.org/jira/browse/ARROW-7203
> Project: Apache Arrow
> Issue Type: Wish
> Components: Continuous Integration, Developer Tools
> Reporter: Neal Richardson
> Priority: Major
>
> The new GitHub Actions workflows in place of Travis-CI are great. So much
> faster feedback than before. One question we've had since migrating is how
> should Crossbow and the GHA jobs interact. GHA makes it easy enough to
> schedule nightly jobs, so we don't really need the Crossbow trickery to get
> the nightly builds to run. However, we don't yet have a solution for the
> other way we use Crossbow: triggering builds via PR comments (using ursabot).
> As it turns out, last week I was at the GitHub Universe conference and spoke
> to some of the lead devs about our experience and needs. I asked especially
> about this because the day before, I had debugged and fixed a cron workflow
> (https://issues.apache.org/jira/browse/ARROW-7164) and struggled with how to
> test that I had fixed it. (Interestingly, I happened to talk to the dev who
> was responsible for the action code change that caused our job to start
> failing.)
> Triggering cron workflows on demand was not a feature they (or at least he)
> had considered. We brainstormed a few ways we might be able to do it. None of
> them were simple or clean. Here's what we discussed. See also the
> [docs|https://help.github.com/en/actions/automating-your-workflow-with-github-actions/events-that-trigger-workflows]
> for events that trigger workflows.
> Ideally, we could use the {{issue_comment}} event to trigger a workflow, just
> as we do now via ursabot and crossbow. But there are some challenges:
> * We can trigger based on an issue_comment being created, but then we'd have
> to write some code to parse the payload of the event (in the {{github.event}}
> object) and then do things only if the right build name is found. This would
> meant that for every cron workflow we have, this logic would run every time
> anyone makes any comment on any issue or PR. That might have some undesirable
> side effects.
> * The issue_comment event takes the workflow script from the master branch.
> So if you're testing changes to the workflow yaml itself, you're out of luck.
> * You could work around this by also conditionally running the workflow also
> if the workflow file itself is changed.
> * Because the event triggers from master, you need to modify the checkout
> step to checkout a commit/ref. Unfortunately, the commit SHA isn't present in
> the [event
> payload|https://developer.github.com/v3/activity/events/types/#issuecommentevent].
> You could probably parse it out of one of the URLs in the payload, though.
> Assuming you do, then you probably need to make this behavior conditional on
> whether you're running from an issue_comment (in which case you parse the
> event and go with master) or from cron or some other means (in which case you
> don't want to specify a ref).
> * Think of all of the complexity here, and realize that unless there's some
> way to package this up into an action or template or something, we have to
> replicate this for every workflow we want to be able to trigger like this.
> An alternative strategy would be to use the existing ursabot integration and
> trigger GitHub workflows from it using a [repository
> dispatch|https://developer.github.com/v3/repos/#create-a-repository-dispatch-event]
> event. The repository dispatch event would have an event_type that
> (somehow?) we would map to the workflow, and then in the client_payload we
> could include any additional build params. This would have to include the PR
> number or commit SHA because, just as with issue_comments, the workflow will
> run from master so we'll need to explicitly checkout something else. The
> other limitation is that repository dispatch requires an API token with repo
> write access; fortunately, ursabot already has had to deal with this.
> A further ursabot-centric approach would extend crossbow to be able to create
> GHA workflows, and triggering on demand a workflow via crossbow (through
> ursabot comment bot or otherwise) would essentially copy the workflow to its
> repository, amending the workflow to checkout the repo and commit and to run
> on push.
> In sum, it's not straightforward to do this, and as it stands now, there's a
> bit of code to write somewhere for this.
> cc [~kou] [~kszucs]
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