fat-catTW opened a new pull request, #71287:
URL: https://github.com/apache/airflow/pull/71287
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## Why
`SchedulerJobRunner._create_dag_runs` catches exceptions while creating
scheduled DagRuns and then continues with the next Dag. This does not work
reliably when the failure is caused by a database error, because the SQLAlchemy
session can be left in a failed transaction state.
When that happens, one failing DagRun creation attempt can prevent the
scheduler from creating DagRuns for other healthy Dags in the same batch.
## Solution
Wrap each scheduled DagRun creation attempt in a nested
transaction/savepoint. If a database-level failure happens for one Dag, only
that DagRun creation attempt is rolled back and the outer scheduler transaction
remains usable.
The in-memory active run counter is updated only after the savepoint
succeeds, keeping scheduler state aligned with the database transaction outcome.
A regression test covers a flush-time database failure for one Dag and
verifies that another Dag in the same batch still creates its DagRun
successfully.
relates: #59120
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