What are Pools in Apache Airflow?

Pools are a mechanism to limit the number of concurrently running tasks that use shared resources (e.g., database connections, API rate limits). You define a pool with a maximum number of slots, and assign tasks to it. If all slots are occupied, queued tasks wait.

# Assign a task to a pool
t = PythonOperator(
    task_id='my_task',
    python_callable=my_func,
    pool='limited_db_pool',    # uses one slot from this pool
    pool_slots=1
)

Pools are created in the UI (Admin > Pools) or via the CLI: airflow pools set limited_db_pool 5 'DB connections pool'.

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