Sensors Block Worker Slots Continuously

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Resource ContentionUpdated Apr 3, 2019

Sensor tasks run in poke mode occupy worker slots indefinitely while waiting for conditions, reducing available concurrency for productive work and causing task backlog.

Sources

7 Common Errors to Check When Debugging Airflow DAGswww.astronomer.io

Technologies:

Apache AirflowThe root cause of this issue originates in Apache Airflow

airflow.executor.running_tasks

airflow.executor.open_slots

airflow.sensor.poke_count

How to detect:

Monitor ratio of running sensor tasks to total running tasks. Track worker slot utilization and task queue depth. Alert when sensors occupy >30% of worker capacity or queue depth grows while sensors are running.

Recommended action:

Configure sensors to use reschedule mode instead of poke mode; set reasonable timeout and poke_interval values; use smart sensors or sensor operators with async execution; limit number of concurrent sensors with dedicated pools; consider replacing sensors with event-driven triggers.