Custom labels not working after upgrade to Airflow 2.3.1

[akepa]

Airflow version: 2.3.1
airflow-exporter: 1.5.3

Hello,

we have upgraded recently our Airflow from 2.2.5 to 2.3.1 and we have seen that after the upgrade, the feature to include custom labels in the metrics is not working anymore.

with DAG(
        dag_id='my_dag',
        schedule_interval="10 * * * *",
        start_date=days_ago(1),
        default_args={},
        max_active_runs=1,
        tags=['tag1', 'tag2'],
        params={'labels': {
            'custom_label': 'custom_label_value'
        }}
) as dag:
...

with previous version, /metrics endpoint was exposing the following metrics:

airflow_dag_status{dag_id="my_dag",owner="airflow",status="failed", custom_label="custom_label_value"} 169.0
airflow_dag_status{dag_id="my_dag",owner="airflow",status="running", custom_label="custom_label_value"} 1.0
airflow_dag_status{dag_id="my_dag",owner="airflow",status="success", custom_label="custom_label_value"} 203.0

after the upgrade, it is not including the custom label

airflow_dag_status{dag_id="my_dag",owner="airflow",status="failed"} 169.0
airflow_dag_status{dag_id="my_dag",owner="airflow",status="running"} 1.0
airflow_dag_status{dag_id="my_dag",owner="airflow",status="success"} 203.0

[akepa]

Seems to be related to https://github.com/epoch8/airflow-exporter/blob/master/airflow_exporter/prometheus_exporter.py#L203.

I've been debugging in local with 2.3.2 and

dag.params.get('labels', {})

has now the following content:

{'custom_label': 'custom_label_value'}