airflow-tutorial-gist-05.py

# The connection ID to the datawarehouse DB (must match the connection 
# handler defined in airflow for the data source)
target_db = 'mini-warehouse-db'

# A simple sensor checking wether clickstream data is present 
# for the day following the execution_date of the DAG Run
sensor_query_template = '''
SELECT TRUE
FROM clickstream
WHERE click_timestamp::DATE >= '{{ execution_date + macros.timedelta(days=1) }}'::DATE
LIMIT 1
'''

# A sensor task using a SqlSensor operator
sensor_task = SqlSensor(
    task_id='check_data_avail',
    conn_id=target_db,
    sql=sensor_query_template,
    poke_interval=30,
    timeout=3600,
    dag=dag)