Airflow DAG won’t trigger on Schedule

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You’ve set the right cron schedule, but somehow Airflow doesn’t trigger your DAG and you don’t know why? Check your start date.

I once had a DAG set up to run on a weekly schedule (30 12 * * MON). But I made the mistake to set start_date to days_ago(1). Now this was troubling because Airflow allows DAGs to run at the end of the schedule interval, not beginning. So essentially, it will always set next run time to 7 days in the future and kept on skipping the expected date. Like a never ending search, when the expected day came, it won’t trigger yet it will schedule next run to the new week.

Initially I didn’t catch why but after a bit of digging around the internet, I finally understood the “end of schedule interval” concept.

So to make this work, start_date had to be set to 7 days back if I would be using a weekly schedule.

If you’re like me and you’re facing this problem now, let me simulate this problem here.

from airflow import DAG
from airflow.utils.dates import days_ago
from airflow.decorators import task
import logging

default_args = {
    'owner':'Obinna',
    'start_date':days_ago(1)
}

with DAG(
    dag_id = 'generic_dag_a_upstream',
    default_args = default_args,
    schedule_interval = '10 20 * * SAT'
) as dag:
    @task
    def just_succeed()…