Adds Docs to compare SubDAGs and TaskGroups

[VeenaArv]

closes: 12298
link: #12298

Adds a section under TaskGroup to compare it to SubDAGs.

[boring-cyborg]

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[turbaszek]

How users can schedule SubDAGs using different scheduler or executor?

[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Backport packages$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[ryw]

I'd recommend stronger language against subdags. I know @mistercrunch has an opinion on this that we could add.

[potiuk]

Should we complete the review before 2.0.0rc1 tomorrow? @ryw @VeenaArv @turbaszek -> this one needs some love I think.

[zuk]

This is very helpful, but one thing still not clear to me from these docs: Since SubDAGs can have different schedules, how does a SubDAG's execution trigger or block executions of tasks further down in the parent DAG?

For example, if a SubDAG is scheduled to execute every 1 hour, and the parent DAG is scheduled every 20 minutes, will the SubDAG be executed every 20 minutes?

Or if the schedules were reversed (SubDAG every 20 minutes and parent DAG every hour), how do the SubDAG's multiple executions in that hour factor into the parent DAG's eventual execution?

[dinigo]

There are two parts here:

• Parent DAG "SubDAG task" — This is the link between the two: the parent and the SubDAG. It is runs a "Sensor" underneath. I think you can even specify the poking interval.
• SubDAG "DAG" — Can be added to the global scope to make it available in the main screen, have different schedule intervals... just like a regular DAG. Only limitation is the name (AFAIK).

SubDAG could easily be renamed as ExternalDagSensor

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.

[jhtimmins]

Hi @VeenaArv, are you still interested in getting this merged?