Vamsi-klu opened a new pull request, #72243:
URL: https://github.com/apache/airflow/pull/72243
## What is the change?
`_task_concurrency_allows_execution` no longer bulk-`UPDATE`s every
`SCHEDULED` task instance to `FAILED` when `get_dag_for_run` returns None. It
logs the same error as `_create_dag_runs` and returns False so this tick skips,
and the next tick retries.
## Why did I do it?
closes: #62050
The miss sits inside a concurrency check. A missing serialized row is not a
concurrency answer. On HA schedulers, a parse or version hole then failed the
whole warehouse load; retry worked because the next parse had a row. The create
path already continues
(`test_scheduler_create_dag_runs_does_not_raise_error_when_no_serdag`). Queue
never got the same treatment. #58259 / #56422 made misses rarer; they did not
remove the UPDATE.
## How did I do it?
Deleted the `session.execute(update(TI)...FAILED)` block. `return False` was
already there. Session stays uncommitted. I did not add a miss counter, did not
fail only the one TI, and did not change `_create_dag_runs`. Permanently
missing Dags stay SCHEDULED for the existing stale/import-error cleanup.
This path only runs when `dag_model.has_task_concurrency_limits` is True
(`max_active_tis_per_dag` / `max_active_tis_per_dagrun`). Tests set
`max_active_tis_per_dag` so the helper is actually entered.
## What's the impact?
A transient `serialized_dag` hole no longer fails every SCHEDULED TI for
that Dag (including every mapped index, backfill slice, and asset-triggered run
that hits this helper). HA schedulers all skip instead of racing to stamp
FAILED. Deleted Dags can sit in SCHEDULED until other cleanup; that is
intentional.
## What's the test plan?
New tests next to the create-path skip test:
- `test_executable_task_instances_skip_when_serialized_dag_missing`: two
tasks with concurrency limits, mock `get_dag_for_run` to None, queued list
empty, both TIs still SCHEDULED
- `test_executable_task_instances_queue_when_serialized_dag_present`:
control, t1/t2 still queue
I restored the UPDATE and re-ran the skip test: TIs became FAILED (the first
TI's UPDATE failed all SCHEDULED TIs including t2).
```
uv run --project airflow-core pytest \
airflow-core/tests/unit/jobs/test_scheduler_job.py \
-k 'skip_when_serialized_dag_missing or queue_when_serialized_dag_present
or no_serdag'
```
3 passed. Ruff and airflow-core mypy passed via prek.
---
##### Was generative AI tooling used to co-author this PR?
- [X] Yes — Grok 4.6
Generated-by: Grok 4.6 following [the
guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions)
---
Drafted-by: Grok 4.6 (no human review before posting)
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