Airflow Example

simple_dag.py

from datetime import datetime, timedelta
from airflow import DAG
from airflow.operators.dummy_operator import DummyOperator
from airflow.operators.python_operator import PythonOperator


def print_hello():
    return "Hello world!"


default_args = {
    "owner": "airflow",
    "depends_on_past": False,
    "start_date": datetime(2019, 4, 30),
    "email": ["airflow@example.com"],
    "email_on_failure": False,
    "email_on_retry": False,
    "retries": 1,
    "retry_delay": timedelta(minutes=2),
}

dag = DAG(
    "hello_world",
    description="Simple tutorial DAG",
    schedule_interval="0 12 * * *",
    default_args=default_args,
    catchup=False,
)

t1 = DummyOperator(task_id="dummy_task", retries=3, dag=dag)

t2 = PythonOperator(task_id="hello_task", python_callable=print_hello, dag=dag)

# sets downstream foe t1
t1 >> t2

# equivalent
# t2.set_upstream(t1)