Slack notifications stopped working after upgrade to 3.0.1

[arturzangiev]

Apache Airflow version

3.0.1

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

No response

What happened?

Slack notifications stopped working after upgrade to 3.0.1

What you think should happen instead?

Should send a slack notification to the channel

How to reproduce

with DAG(
    dag_id='name',
    default_args=default_args,
    description='description',
    schedule=None,
    start_date=datetime.now() - timedelta(days=365),
    catchup=False,
    max_active_runs=1,
    on_failure_callback=[
        send_slack_webhook_notification(
            slack_webhook_conn_id="slackwebhook", 
            text="The dag `{{ dag.dag_id }}` failed"
        )
    ]
) as dag:

    def fail_task():
        raise ValueError("This task fails on purpose.")

    task1 = PythonOperator(
        task_id='fail_task',
        python_callable=fail_task
    )

Operating System

debian

Versions of Apache Airflow Providers

apache-airflow-providers-slack 9.0.5

Deployment

Docker-Compose

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

[boring-cyborg]

Thanks for opening your first issue here! Be sure to follow the issue template! If you are willing to raise PR to address this issue please do so, no need to wait for approval.

[amoghrajesh]

@arturzangiev what errors do you see in your tasks or in the scheduler / worker?

[arturzangiev]

It is strange, but i can't find any slack related logs in my tasks or scheduler

[uranusjr]

What version were you upgrading from?

[uranusjr]

Does the dag processor process contain logs about callbacks?

[arturzangiev]

I have upgraded from airflow:2.10.2 to airflow:3.0.1. I checked processor logs and can't find anything around callbacks.

[niklasr22]

I have the same problem (Upgraded from 2.10.5 to 3.0.1, running in Docker). I also can't find any callback/slack provider specific logs.

[niklasr22]

I think none of the callbacks (not slack specific) that rely on having a context work. Maybe I'm understanding something wrong but in the dag processor, it looks like the context passed to the callbacks is always empty. (The TODO indicates some missing stuff as well)

airflow/airflow-core/src/airflow/dag_processing/processor.py

Lines 163 to 173 in 4ecebc2

	# TODO:We need a proper context object!
	context: Context = {} # type: ignore[assignment]
	for callback in callbacks:
	log.info(
	"Executing on_%s dag callback",
	"failure" if request.is_failure_callback else "success",
	dag_id=request.dag_id,
	)
	try:
	callback(context)

I also found a log:

{"timestamp":"2025-05-22T08:39:02.769046","level":"error","event":"Callback failed","dag_id":"cb_test_dag","logger":"task","error_detail":[{"exc_type":"KeyError","exc_value":"'dag'","exc_notes":[],"syntax_error":null,"is_cause":false,"frames":[{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/dag_processing/processor.py","lineno":213,"name":"_execute_dag_callbacks"},{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/sdk/bases/notifier.py","lineno":103,"name":"__call__"},{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/sdk/bases/notifier.py","lineno":72,"name":"render_template_fields"}]}]}

[uranusjr]

Do either you see the Executing on_%s dag callback log?

[niklasr22]

Yes:

{"timestamp":"2025-05-22T08:58:02.638108","level":"info","event":"Executing on_success dag callback","dag_id":"cb_test_dag","logger":"task"}
{"timestamp":"2025-05-22T08:58:02.638127","level":"error","event":"Callback failed","dag_id":"cb_test_dag","logger":"task","error_detail":[{"exc_type":"KeyError","exc_value":"'dag'","exc_notes":[],"syntax_error":null,"is_cause":false,"frames":[{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/dag_processing/processor.py","lineno":213,"name":"_execute_dag_callbacks"},{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/sdk/bases/notifier.py","lineno":103,"name":"__call__"},{"filename":"/Users/x/airflow-installation/.venv/lib/python3.12/site-packages/airflow/sdk/bases/notifier.py","lineno":72,"name":"render_template_fields"}]}]}