python 3.x - How to handle different task intervals on a single Dag in airflow?

Question

I have a single dag with multiple tasks with this simple structure that tasks A, B, and C can run at the start without any dependencies but task D depends on A no here is my question:

tasks A, B, and C run daily but I need task D to run weekly after A succeeds. how can I setup this dag?

does changing schedule_interval of task work? Is there any best practice to this problem?

Thanks for your help.

Answer 1

You can use a ShortCircuitOperator to do this.

import airflow
from airflow.operators.python_operator import ShortCircuitOperator
from airflow.operators.dummy_operator import DummyOperator
from airflow.models import DAG


args = {
    'owner': 'airflow',
    'start_date': airflow.utils.dates.days_ago(2),
    'schedule_interval': '0 10 * * *'
}

dag = DAG(dag_id='example', default_args=args)

a = DummyOperator(task_id='a', dag=dag)
b = DummyOperator(task_id='b', dag=dag)
c = DummyOperator(task_id='c', dag=dag)
d = DummyOperator(task_id='d', dag=dag)

def check_trigger(execution_date, **kwargs):
    return execution_date.weekday() == 0

check_trigger_d = ShortCircuitOperator(
  task_id='check_trigger_d',
  python_callable=check_trigger,
  provide_context=True,
  dag=dag
)

a.set_downstream(b)
b.set_downstream(c)
a.set_downstream(check_trigger_d)
# Perform D only if trigger function returns a true value
check_trigger_d.set_downstream(d)