Criteria for a DAG being marked as stale

[pt-07]

Hi,

Recently two of our dags that were running daily were marked as stale in the airflow database - dag table and were thus removed from the UI and also did not run. I was wondering what causes a dag to be marked as stale?

[enchant3dmango]

A DAG is marked as stale when the scheduler determines it hasn’t been refreshed within the configured interval, meaning the DAG file wasn’t re-parsed or the heartbeat of the DagFileProcessor timed out.

Common causes:
1. Scheduler/parser didn’t process the file – maybe the file was removed, renamed, or moved out of the dags folder.
2. Scheduler not keeping up – too many DAGs or slow parsing can cause the scheduler to lag and mark old ones stale.
3. Errors in the DAG file – if parsing fails (syntax/import errors), Airflow will eventually drop it from the DB and UI.

You can check the scheduler logs for messages — that’ll tell you exactly when and why it happened.