DAG params not transmitted when a backfill is triggered

[matthieuauger]

Apache Airflow version

3.0.1

If "Other Airflow 2 version" selected, which one?

No response

What happened?

In the UI, when I trigger a "single run" job, the parameters are accessible in my task.

But when I run a "backfill" job, even if the UI is displaying the parameters section, they are not passed through.

The context["params"] does not contain the value.

What you think should happen instead?

No response

How to reproduce

Create simple DAG with a parameters, then trigger a backfill for this DAG.

Operating System

Docker

Versions of Apache Airflow Providers

No response

Deployment

Other Docker-based deployment

Deployment details

No response

Anything else?

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[jroachgolf84]

@matthieuauger, are you setting default values for those parameters in your DAG file itself?

[tirkarthi]

I don't see params passed in the payload for creating backfill. Is it documented to support params in backfills?

cc: @dstandish

[matthieuauger]

@tirkarthi I think it was enabled in the UI since last version and "trigger run" UI refresh, but I don't know if the backend supports it.

@jroachgolf84 I do have default value for those params in the DAG because these params are optional.

[tirkarthi]

I think this should be using the form value instead of the hardcoded {} here. This looks similar to 34009c5 scenario .

airflow/airflow-core/src/airflow/ui/src/queries/useCreateBackfill.ts

Line 80 in 7896d8f

dag_run_conf: {},

[tirkarthi]

Also when "all runs" is selected for backfill with changes to dag_run_conf the existing dagruns are just cleared which means that new conf values will not be used for the dagrun which I think is also a bug.

airflow/airflow-core/src/airflow/models/backfill.py

Lines 317 to 325 in 7896d8f

	if lock:
	_handle_clear_run(
	session=session,
	dag=dag,
	dr=dr,
	info=info,
	backfill_id=backfill_id,
	sort_ordinal=backfill_sort_ordinal,
	)

[tirkarthi]

The feature was added in #49763 . cc: @bbovenzi @guan404ming