Tasks Stuck in Queued State Due to Pool Exhaustion

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Resource ContentionUpdated Jan 24, 2026

Tasks remain queued indefinitely because pool slots are fully consumed by long-running or stuck tasks, blocking execution even when workers are available.

Sources

How to Fix 'DAG Scheduling' Airflow Issues - OneUptimeoneuptime.com

Apache Airflow Concurrency Tuning: A Deep Dive into Limitations and the Orchestra Solutionwww.getorchestra.io

Technologies:

Apache AirflowThe root cause of this issue originates in Apache Airflow

airflow.pool.open_slots

airflow.pool.used_slots

airflow.pool.queued_slots

airflow.executor.queued_tasks

How to detect:

Monitor pool usage metrics (slots used vs. total) and task queue depth. Check if tasks assigned to specific pools show 'queued' state for extended periods while pool slots are at capacity.

Recommended action:

Increase pool slot limits with 'airflow pools set <pool_name> <slots>'; review and optimize long-running tasks; assign tasks to dedicated pools to prevent contention; monitor pool allocation and adjust based on workload patterns.