wangxiaojun1990 opened a new issue, #63551:
URL: https://github.com/apache/airflow/issues/63551
### Apache Airflow version
3.1.8
### What happened
When deploying Airflow 3.1.8 with a fresh database (no existing
`default_pool` in the `pool` table), tasks are stuck in `scheduled` state and
never transition to `queued` or `running`. The scheduler logs show "All pools
are full!" even though no pools exist in the database.
### Root Cause Analysis
The scheduler's `slots_stats()` method queries the `pool` table and returns
an empty dictionary when no pools exist:
```python
# airflow/jobs/scheduler_job_runner.py:363-371
pools = Pool.slots_stats(lock_rows=True, session=session)
pool_slots_free = sum(max(0, pool["open"]) for pool in pools.values())
if pool_slots_free == 0:
self.log.debug("All pools are full!")
return [] # No tasks are scheduled
```
The configuration `default_pool_task_slot_count = 128` exists, but the
`default_pool` record is not automatically created in the database during
`airflow db migrate`.
### How to reproduce
1. Deploy Airflow 3.1.8 with a fresh database
2. 2. Create a simple DAG with a PythonOperator task
3. 3. Trigger the DAG from UI or CLI
4. 4. Task stays in `scheduled` state indefinitely
### Environment
- **Airflow version**: 3.1.8
- - **Helm chart version**: 1.19.0
- - - **Executor**: CeleryExecutor
- - - - **Database**: MySQL 8.0
### Verification commands
```bash
# Check pools - returns empty
airflow pools list
# Output: No data found
# Check default_pool_task_slot_count - returns 128
airflow config get-value core default_pool_task_slot_count
# Output: 128
# Check get_default_pool() - returns None
python -c "from airflow.models.pool import Pool;
print(Pool.get_default_pool())"
# Output: None
```
### Expected behavior
Either:
1. `default_pool` should be automatically created during `airflow db
migrate`, OR
2. 2. Scheduler should handle missing `default_pool` gracefully by using the
configured `default_pool_task_slot_count`
### Workaround
Manually create the default pool after database migration:
```bash
airflow pools set default_pool 128 "Default pool"
```
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