Airflow failed slack message

Question

How can I configure Airflow so that any failure in the DAG will (immediately) result in a slack message?

At this moment I manage it by creating a slack_failed_task:<

Answer 1

I would prefer to add the callback to the DAG and to be inhered by all its tasks:

def on_failure_callback(context):
    webhook_url = os.getenv('SLACK_WEBHOOK_TOKEN')
    slack_data = {
        'text': "@here DAG {} Failed".format(context['dag'].dag_id)
    }

    response = requests.post(
        webhook_url, data=json.dumps(slack_data),
        headers={'Content-Type': 'application/json'}
    )

dag = DAG(
    dag_id='dag_with_templated_dir',
    start_date=datetime(2020, 1, 1),
    on_failure_callback=on_failure_callback
)