Airflow scheduler is not picking up job

I've created a new Dag with following arguments:

default_args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime.now(),
    'email': ['airflow@example.com'],
    'email_on_failure': False,
    'email_on_retry': False,
    'retries': 1,
    'retry_delay': timedelta(minutes=5),
    'catchup': False,
    # 'queue': 'bash_queue',
    # 'pool': 'backfill',
    # 'priority_weight': 10,
    # 'end_date': datetime(2016, 1, 1),
    # 'wait_for_downstream': False,
    # 'dag': dag,
    # 'adhoc':False,
    # 'sla': timedelta(hours=2),
    # 'execution_timeout': timedelta(seconds=300),
    # 'on_failure_callback': some_function,
    # 'on_success_callback': some_other_function,
    # 'on_retry_callback': another_function,
    # 'trigger_rule': u'all_success'
}

dag = DAG(
    'sample_dag',
    default_args=default_args,
    description='sample dag',
    schedule_interval="44 * * * *")

But the scheduler is not picking up the dag when the time comes. And it is running fine when I manually trigger it. Is there anything I'm missing here?

Also, the scheduler was throwing an error when the cron expression was "*/5 * * * *"

CroniterBadCronError: Exactly 5 or 6 columns has to be specified for iteratorexpression.

But the cron expression looks good me.

The reason for this is that the [time the dag runs] = start_date + schedule_interval. So if you set your start_date to something that is dynamic then the dag will never execute since the start_date keeps increasing with time.

It is explained here and there is also another question here on stack which has an answer too, they probably explain it better than I do.

You should change your start_date to something static rather than datetime.now()

If you do not want backfilling in your dag you need to set the catchup=False as a dag parameter. so something like the following:

default_args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2018, 1, 1),
    'email': ['airflow@example.com'],
    'email_on_failure': False,
    'email_on_retry': False,
    'retries': 1,
    'retry_delay': timedelta(minutes=5)
}

dag = DAG(
    'sample_dag',
    catchup=False,
    default_args=default_args,
    description='sample dag',
    schedule_interval="44 * * * *"
    )