example.py

import logging
import datetime

from airflow import DAG
from airflow import models
from airflow.operators.python_operator import PythonOperator

YESTERDAY = datetime.datetime.combine(
    datetime.datetime.today() - datetime.timedelta(1),
    datetime.datetime.min.time())


def say_hello_method(**_context):
    logging.info('Hello Cloud Composer!')


DEFAULT_ARGS = {
    # Setting start date as yesterday starts the DAG immediately when it is
    # detected in the Cloud Storage bucket.
    'start_date': YESTERDAY,
    'email_on_failure': False,
    'email_on_retry': False,
    'retries': 2,
    'retry_delay': datetime.timedelta(minutes=1),
    'project_id': models.Variable.get('gcp_project')
}


with DAG('example',
         default_args=DEFAULT_ARGS,
         schedule_interval=datetime.timedelta(minutes=20),
         catchup=False
         ) as dag:

    say_hello_task = PythonOperator(
        task_id='say_hello',
        python_callable=say_hello_method,
        provide_context=True
    )