FrankYang0529 opened a new pull request, #73032:
URL: https://github.com/apache/airflow/pull/73032
## Why
- The scheduler recomputes `DagModel.exceeds_max_non_backfill` when a Dag
run finishes, but only for `scheduled`, `manual` and `asset_triggered` runs.
The flag itself counts every active run except backfill runs.
- `asset_materialization` (#62276) and `operator_triggered` (#63733) came
after #60006 introduced that list, and were never added to it.
- When one of these runs is the last active run of a Dag at its
`max_active_runs` limit, the flag stays `True` after the run finishes. The
scheduler skips the Dag until the Dag processor parses the file again, so
scheduled and asset-triggered runs start late.
## How
- Recompute the flag for every finished run except backfill runs, which
matches what the flag counts.
## Verification
- Unit test: `breeze run pytest
airflow-core/tests/unit/jobs/test_scheduler_job.py`
- Integration test:
1. Setup
```sh
mkdir -p files/dags
cat > files/dags/demo_dags.py <<'EOF'
from __future__ import annotations
import datetime
from airflow.providers.standard.operators.bash import BashOperator
from airflow.providers.standard.operators.trigger_dagrun import
TriggerDagRunOperator
from airflow.sdk import DAG
START = datetime.datetime(2026, 1, 1, tzinfo=datetime.timezone.utc)
with DAG(dag_id="demo_child", schedule="* * * * *", start_date=START,
catchup=False, max_active_runs=1):
BashOperator(task_id="work", bash_command="sleep 60")
with DAG(dag_id="demo_parent", schedule=None, start_date=START,
catchup=False):
TriggerDagRunOperator(
task_id="trigger_child",
trigger_dag_id="demo_child",
trigger_run_id="triggered_by_parent",
)
EOF
```
2. Start Airflow
```sh
breeze shell --backend sqlite
```
```sh
export AIRFLOW__DATABASE__SQL_ALCHEMY_CONN=sqlite:////tmp/demo.db
export AIRFLOW__CORE__LOAD_EXAMPLES=False
export AIRFLOW__DAG_PROCESSOR__MIN_FILE_PROCESS_INTERVAL=600
airflow standalone > /tmp/standalone.log 2>&1 &
```
3. Trigger Dag
```
airflow dags list
airflow dags unpause demo_parent
airflow dags unpause demo_child
```
Run this until a `scheduled__...` run is `running`:
```bash
airflow dags list-runs demo_child
```
Trigger `demo_parent`. Its run of `demo_child` queues behind the running
scheduled run.
```bash
airflow dags trigger demo_parent
```
On main branch, after `triggered_by_parent` is `success`, the next run is
not scheduled on the next minute. The scheduler skips `demo_child` until the
Dag processor parses the file again.
```text
dag_id | run_id | state | run_after |
logical_date | start_date | end_date
===========+========================+=========+=======================+========================+=======================+========================
demo_child | scheduled__2026-09-12T | success | 2026-09-12T11:35:00+0 |
2026-09-12T11:35:00+00 | 2026-09-12T11:35:42.6 | 2026-09-12T11:36:43.762
| 11:35:00+00:00 | | 0:00 | :00
| 14960+00:00 | 543+00:00
demo_child | triggered_by_parent | success | 2026-09-12T11:26:17.9 |
2026-09-12T11:26:17.76 | 2026-09-12T11:27:02.6 | 2026-09-12T11:28:03.737
| | | 12138+00:00 |
8602+00:00 | 28857+00:00 | 794+00:00
demo_child | scheduled__2026-09-12T | success | 2026-09-12T11:25:00+0 |
2026-09-12T11:25:00+00 | 2026-09-12T11:25:58.5 | 2026-09-12T11:27:01.604
| 11:25:00+00:00 | | 0:00 | :00
| 15063+00:00 | 410+00:00
```
On this branch, the next run is scheduled as expected.
```text
dag_id | run_id | state | run_after |
logical_date | start_date | end_date
===========+========================+=========+=======================+========================+=======================+========================
demo_child | scheduled__2026-09-12T | success | 2026-09-12T12:17:00+0 |
2026-09-12T12:17:00+00 | 2026-09-12T12:18:17.1 | 2026-09-12T12:19:18.314
| 12:17:00+00:00 | | 0:00 | :00
| 51901+00:00 | 029+00:00
demo_child | triggered_by_parent | success | 2026-09-12T12:16:44.2 |
2026-09-12T12:16:44.10 | 2026-09-12T12:17:14.9 | 2026-09-12T12:18:16.125
| | | 88514+00:00 |
9705+00:00 | 91149+00:00 | 626+00:00
demo_child | scheduled__2026-09-12T | success | 2026-09-12T12:16:00+0 |
2026-09-12T12:16:00+00 | 2026-09-12T12:16:11.0 | 2026-09-12T12:17:13.975
| 12:16:00+00:00 | | 0:00 | :00
| 11254+00:00 | 608+00:00
```
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