We have flaky scheduler test:


https://github.com/apache/airflow/pull/11659/checks?check_run_id=1279791496#step:6:527


_______________ TestSchedulerJob.test_scheduler_task_start_date ________________

self = <tests.jobs.test_scheduler_job.TestSchedulerJob testMethod=test_scheduler_task_start_date>

    def test_scheduler_task_start_date(self):
        """
        Test that the scheduler respects task start dates that are different from DAG start dates
        """
    
        dagbag = DagBag(dag_folder=os.path.join(settings.DAGS_FOLDER, "no_dags.py"), include_examples=False)
        dag_id = 'test_task_start_date_scheduling'
        dag = self.dagbag.get_dag(dag_id)
        dag.is_paused_upon_creation = False
        dagbag.bag_dag(dag=dag, root_dag=dag)
    
        # Deactivate other dags in this file so the scheduler doesn't waste time processing them
        other_dag = self.dagbag.get_dag('test_start_date_scheduling')
        other_dag.is_paused_upon_creation = True
        dagbag.bag_dag(dag=other_dag, root_dag=other_dag)
    
        dagbag.sync_to_db()
    
        scheduler = SchedulerJob(executor=self.null_exec,
                                 subdir=dag.fileloc,
                                 num_runs=2)
        scheduler.run()
    
        session = settings.Session()
        tiq = session.query(TaskInstance).filter(TaskInstance.dag_id == dag_id)
        ti1s = tiq.filter(TaskInstance.task_id == 'dummy1').all()
        ti2s = tiq.filter(TaskInstance.task_id == 'dummy2').all()
        self.assertEqual(len(ti1s), 0)
>       self.assertEqual(len(ti2s), 2)
E       AssertionError: 1 != 2
tests/jobs/test_scheduler_job.py
dr = drs[0]
        
        assert orm_dag.next_dagrun_create_after is None
        
        assert isinstance(orm_dag.next_dagrun, datetime.datetime)
        
        dr.start_date = timezone.utcnow() - datetime.timedelta(days=1)
        session.flush()
        
        scheduler.processor_agent = mock.Mock()
        scheduler.processor_agent.send_callback_to_execute = mock.Mock()
        scheduler._schedule_dag_run(dr, {}, session)
        session.flush()
        session.refresh(dr)
        assert dr.state == State.FAILED
        session.refresh(orm_dag)
        assert isinstance(orm_dag.next_dagrun, datetime.datetime)
        assert isinstance(orm_dag.next_dagrun_create_after, datetime.datetime)
        expected_callback = DagCallbackRequest(
            full_filepath=dr.dag.fileloc,
            dag_id=dr.dag_id,
            is_failure_callback=True,
            execution_date=dr.execution_date,
            msg="timed_out",
        )
        
        scheduler.processor_agent.send_callback_to_execute.assert_called_once_with(expected_callback)
        session.rollback()
        session.close()
    def test_dagrun_timeout_fails_run(self):