DAG demonstrating task dependencies

dag.py

"""
Code that goes along with the Airflow tutorial located at:
https://github.com/apache/incubator-airflow/blob/master/airflow/example_dags/tutorial.py
"""
from airflow import DAG
from airflow.operators.bash_operator import BashOperator
from datetime import datetime, timedelta


default_args = {
    'owner': 'airflow',
    'depends_on_past': False,
    'start_date': datetime(2015, 6, 1),
    'email': ['a@gmail.com'],
    'email_on_failure': False,
    'email_on_retry': False,
    'retries': 1,
    'retry_delay': timedelta(minutes=5),
    # 'queue': 'bash_queue',
    # 'pool': 'backfill',
    # 'priority_weight': 10,
    # 'end_date': datetime(2016, 1, 1),
}

dag = DAG('complex_dag', default_args=default_args, schedule_interval=timedelta(days=1))

t0 = BashOperator(
    task_id='t0',
    bash_command='date',
    dag=dag)

t1 = BashOperator(
    task_id='t1',
    bash_command='date',
    dag=dag)

t2 = BashOperator(
    task_id='t2',
    bash_command='sleep 5',
    retries=3,
    dag=dag)

t3 = BashOperator(
    task_id='t3',
    bash_command='sleep 5',
    retries=3,
    dag=dag)

t4 = BashOperator(
    task_id='t4',
    bash_command='date',
    dag=dag)

t5 = BashOperator(
    task_id='t5',
    bash_command='date',
    dag=dag)

t6 = BashOperator(
    task_id='t6',
    bash_command='date',
    dag=dag)

t7 = BashOperator(
    task_id='t7',
    bash_command='date',
    dag=dag)

t1.set_upstream(t0)
t2.set_upstream(t0)
t3.set_upstream(t1)
t4.set_upstream(t1)
t5.set_upstream(t2)
t2.set_downstream(t4)
t3.set_downstream(t6)
t4.set_downstream(t6)
t5.set_downstream(t7)
t6.set_downstream(t7)