adirhmonday opened a new issue, #72471:
URL: https://github.com/apache/airflow/issues/72471
### Apache Airflow version
3.2.2
### If "Other Airflow 2 version" selected, which one?
_No response_
### What happened?
When a DAG is updated (any code change that produces a new `serialized_dag`
row), `DeadlineAlert` records are not created for the new `serialized_dag`. All
subsequent `dag_run`s for that DAG silently produce no `Deadline` entries and
never fire deadline callbacks.
**Root cause**
In `SerializedDagModel.write_dag()` (`airflow/models/serialized_dag.py`),
when the deadline definition hasn't changed between versions,
`_try_reuse_deadline_uuids()` returns the existing UUIDs and the code sets:
```python
# serialized_dag.py ~line 646-651
if deadline_uuid_mapping is not None:
# All deadlines matched — reuse the UUIDs to preserve hash.
# Clear the mapping since the alert rows already exist in the DB;
# no need to delete and recreate identical records.
dag.data["dag"]["deadline"] = existing_deadline_uuids
deadline_uuid_mapping = {}
```
Then in the new `serialized_dag` creation path (when
`has_task_instances=True`):
```python
# line 734
cls._create_deadline_alert_records(new_serialized_dag, deadline_uuid_mapping)
```
Since `deadline_uuid_mapping = {}`, `_create_deadline_alert_records` returns
immediately (`if not uuid_mapping: return`) — the new `serialized_dag` gets no
`deadline_alert` rows.
When a `dag_run` is created, `definitions/dag.py` queries:
```sql
SELECT * FROM deadline_alert WHERE serialized_dag_id =
<new_serialized_dag_id>
```
Finds nothing → no `Deadline` row inserted → triggerer never fires the
callback.
The `{}` optimization is correct for the in-place UPDATE path (same
`serialized_dag` row, existing `deadline_alert` records stay valid). It is
wrong for the INSERT path (new row, no `deadline_alert` records exist for the
new `serialized_dag_id`).
### What you think should happen instead?
`deadline_alert` records should be created for every new `serialized_dag`
row, regardless of whether the deadline definition changed.
**Suggested fix**
In `_create_deadline_alert_records`, when the new `serialized_dag` path is
taken (INSERT, not UPDATE), generate new UUIDs and create new `deadline_alert`
records even when the deadline definition matches the previous version. The
empty-mapping optimization should only apply to the in-place UPDATE path (lines
691–713).
### How to reproduce
1. Deploy a DAG with a `DeadlineAlert` — verify a `deadline_alert` record is
created
2. Make any code change to the DAG file that produces a new `dag_version`
(e.g. add a comment) without changing the deadline definition
3. Wait for git-sync to pick up the new version
4. Trigger a `dag_run` and wait past the deadline
5. No alert fires; the `deadline` table has no row for this run
### Operating System
N/A
### Versions of Apache Airflow Providers
N/A
### Deployment
Other 3rd-party Helm chart
### Deployment details
_No response_
### Anything else?
_No response_
### Are you willing to submit PR?
- [ ] Yes I am willing to submit a PR!
### Code of Conduct
- [x] I agree to follow this project's [Code of
Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
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