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
dr2 = dag.create_dagrun(
            run_type=DagRunType.SCHEDULED,
            execution_date=dag.following_schedule(dr1.execution_date),
            state=State.RUNNING,
        )
        tis = [
            TaskInstance(task1, dr1.execution_date),
            TaskInstance(task2, dr1.execution_date),
            TaskInstance(task1, dr2.execution_date),
            TaskInstance(task2, dr2.execution_date),
        ]
        for ti in tis:
            ti.state = State.SCHEDULED
            session.merge(ti)
        pool = Pool(pool='a', slots=1, description='haha')
        pool2 = Pool(pool='b', slots=100, description='haha')
        session.add(pool)
        session.add(pool2)
        session.flush()
        res = scheduler._executable_task_instances_to_queued(max_tis=32, session=session)
        session.flush()
        assert 3 == len(res)
        res_keys = []
        for ti in res:
            res_keys.append(ti.key)
        assert tis[0].key in res_keys
        assert tis[1].key in res_keys
        assert tis[3].key in res_keys
        session.rollback()
    def test_find_executable_task_instances_in_default_pool(self):