shivaam opened a new pull request, #64737:
URL: https://github.com/apache/airflow/pull/64737
## Summary
The scheduler's deadline-check loop in `scheduler_job_runner.py` selected
expired, unhandled `Deadline` rows without any row-level lock. Under HA
deployments with multiple scheduler replicas, two schedulers could read the
same row concurrently, both call `handle_miss`, and both create duplicate
`Trigger` records — causing the deadline breach callback to fire multiple
times.
This change wraps the SELECT in `with_row_locks(..., of=Deadline,
skip_locked=True, key_share=False)`, so the first scheduler to reach a row
holds a `FOR UPDATE` lock until commit, and any other scheduler silently
skips that row. `key_share=False` is required because the default
`FOR KEY SHARE` does not conflict with itself — two concurrent schedulers
would otherwise still both grab the row.
## Test plan
- Added one regression test
(`test_expired_deadline_locked_by_other_scheduler_is_skipped`): opens an
independent session via `create_session(scoped=False)`, acquires the same
row lock the scheduler uses, and verifies the real scheduler loop skips
the locked row (`handle_miss` is never called).
- Verified the new test **fails without the fix** (reverting the scheduler
change produces `AssertionError: Expected 'handle_miss' to not have been
called. Called 1 times`) and **passes with the fix** applied.
- Re-ran the existing `test_process_expired_deadlines` and
`test_process_expired_deadlines_no_deadlines_found` with the fix applied
to confirm no regression to the happy path / empty-table edge cases.
- All runs green against Postgres 14 via Breeze.
- The new test is skipped on SQLite (single-writer DB, no row locking).
closes: #64710
---
##### Was generative AI tooling used to co-author this PR?
- [X] Yes — Claude Code (claude-opus-4-6)
Generated-by: Claude Code (claude-opus-4-6) following [the
guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions)
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