How to work correctly airflow schedule_interval

I want to try to use Airflow instead of Cron. But schedule_interval doesn't work as I expected.

I wrote the python code like below.
And in my understanding, Airflow should have ran on "2016/03/30 8:15:00" but it didn't work at that time.

If I changed it like this "'schedule_interval': timedelta(minutes = 5)", it worked correctly, I think.

The "notice_slack.sh" is just to call slack api to my channels.

# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals
import os
from airflow.operators import BashOperator
from airflow.models import DAG
from datetime import datetime, timedelta

args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2016, 3, 29, 8, 15),
}

dag = DAG(
    dag_id='notice_slack',
    default_args=args,
    schedule_interval="@daily",
    dagrun_timeout=timedelta(minutes=1))

# cmd file name
CMD = '/tmp/notice_slack.sh'

run_this = BashOperator(
    task_id='run_transport', bash_command=CMD, dag=dag)

I want to run some of my scripts at specific time every day like this cron setting.

15 08 * * * bash /tmp/notice_slack.sh

I have read the document Scheduling & Triggers, and I know it's a little bit different cron.
So I attempt to arrange at "start_date" and "schedule_interval" settings.

Does anyone know what should I do ?

airflow version

INFO - Using executor LocalExecutor

v1.7.0

amazon-linux-ami/2015.09-release-notes

p.magalhaes

Airflow will start your DAG when the 2016/03/30 8:15:00 + schedule interval (daily) is passed. So your DAG will run on 2016/03/31 8:15:00.

You can check the Airflow FAQ

Try this:

# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals
import os
from airflow.operators import BashOperator
from airflow.models import DAG
from datetime import datetime, timedelta

args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2016, 3, 29),
}

dag = DAG(
    dag_id='notice_slack',
    default_args=args,
    schedule_interval="15 08 * * *",
    dagrun_timeout=timedelta(minutes=1))

# cmd file name
CMD = 'bash /tmp/notice_slack.sh'

run_this = BashOperator(
    task_id='run_transport', bash_command=CMD, dag=dag)

start_date (datetime) – The start_date for the task, determines the execution_date for the first task instance. The best practice is to have the start_date rounded to your DAG’s schedule_interval.

schedule_interval (datetime.timedelta or dateutil.relativedelta.relativedelta or str that acts as a cron expression) – Defines how often that DAG runs, this timedelta object gets added to your latest task instance’s execution_date to figure out the next schedule.

Simply configuring the schedule_interval and bash_command as the same in your cron setting is okay.

With the example you've given @daily will run your job after it passes midnight. You might try changing it either to timedelta(days=1) which is relative to your fixed start_date that includes 08:15. Or you could use a cron spec for the schedule_interval='15 08 * * *' in which case any start date prior to 8:15 on the day BEFORE the day you wanted the first run would work.

Note that depends_on_past: False is already the default, and you may have confused its behavior with catchup=false in the DAG parameters, which would avoid making past runs for time between the start date and now where the DAG schedule interval would have run.

you can try using crontab.guru if you are not really sure how to create the airflow corn expression

来源：https://stackoverflow.com/questions/36298756/how-to-work-correctly-airflow-schedule-interval

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