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
job = SchedulerJob(None, heartrate=10, state=State.RUNNING)
        assert job.is_alive()
        job.latest_heartbeat = timezone.utcnow() - datetime.timedelta(seconds=20)
        assert job.is_alive()
        job.latest_heartbeat = timezone.utcnow() - datetime.timedelta(seconds=31)
        assert not job.is_alive()
        
        
        job.latest_heartbeat = timezone.utcnow() - datetime.timedelta(days=1)
        assert not job.is_alive()
        job.state = State.SUCCESS
        job.latest_heartbeat = timezone.utcnow() - datetime.timedelta(seconds=10)
        assert not job.is_alive(), "Completed jobs even with recent heartbeat should not be alive"
    def run_single_scheduler_loop_with_no_dags(self, dags_folder):
        """
        Utility function that runs a single scheduler loop without actually
        changing/scheduling any dags. This is useful to simulate the other side effects of
        running a scheduler loop, e.g. to see what parse errors there are in the
        dags_folder.
        :param dags_folder: the directory to traverse
        :type dags_folder: str
        """
        scheduler = SchedulerJob(
            executor=self.null_exec, num_times_parse_dags=1, subdir=os.path.join(dags_folder)
        )
        scheduler.heartrate = 0
        scheduler.run()
    @pytest.mark.quarantined
    def test_no_orphan_process_will_be_left(self):