Airflow schedule getting skipped if previous task execution takes more time - airflow

Question

I have two tasks in my airflow DAG. One triggers an API call ( Http operator ) and another one keeps checking its status using another api ( Http sensor ). This DAG is scheduled to run every hour & 10 minutes. But some times one execution can take long time to finish for example 20 hours. In such cases all the schedules while the previous task is running is not executing.
For example say if I the job at 01:10 takes 10 hours to finish. Schedules 02:10, 03:10, 04:10, ... 11:10 etc which are supposed to run are getting skipped and only the one at 12:10 is executed.
I am using local executor. I am running airflow server & scheduler using below script.
start_server.sh
export AIRFLOW_HOME=./airflow_home;
export AIRFLOW_GPL_UNIDECODE=yes;
export AIRFLOW_CONN_REST_API=http://localhost:5000;
export AIRFLOW_CONN_MANAGEMENT_API=http://localhost:8001;
airflow initdb;
airflow webserver -p 7200;
start_scheduler.sh
export AIRFLOW_HOME=./airflow_home;
# Connection string for connecting to REST interface server
export AIRFLOW_CONN_REST_API=http://localhost:5000;
export AIRFLOW_CONN_MANAGEMENT_API=http://localhost:8001;
#export AIRFLOW__SMTP__SMTP_PASSWORD=**********;
airflow scheduler;
my_dag_file.py
default_args = {
'owner': 'airflow',
'depends_on_past': False,
'start_date': airflow.utils.dates.days_ago(2),
'email': admin_email_ids,
'email_on_failure': False,
'email_on_retry': False
}
DAG_ID = 'reconciliation_job_pipeline'
MANAGEMENT_RES_API_CONNECTION_CONFIG = 'management_api'
DA_REST_API_CONNECTION_CONFIG = 'rest_api'
recon_schedule = Variable.get('recon_cron_expression',"10 * * * *")
dag = DAG(DAG_ID, max_active_runs=1, default_args=default_args,
schedule_interval=recon_schedule,
catchup=False)
dag.doc_md = __doc__
spark_job_end_point = conf['sip_da']['spark_job_end_point']
fetch_index_record_count_config_key = conf['reconciliation'][
'fetch_index_record_count']
fetch_index_record_count = SparkJobOperator(
job_id_key='fetch_index_record_count_job',
config_key=fetch_index_record_count_config_key,
exec_id_req=False,
dag=dag,
http_conn_id=DA_REST_API_CONNECTION_CONFIG,
task_id='fetch_index_record_count_job',
data={},
method='POST',
endpoint=spark_job_end_point,
headers={
"Content-Type": "application/json"}
)
job_endpoint = conf['sip_da']['job_resource_endpoint']
fetch_index_record_count_status_job = JobStatusSensor(
job_id_key='fetch_index_record_count_job',
http_conn_id=DA_REST_API_CONNECTION_CONFIG,
task_id='fetch_index_record_count_status_job',
endpoint=job_endpoint,
method='GET',
request_params={'required': 'status'},
headers={"Content-Type": "application/json"},
dag=dag,
poke_interval=15
)
fetch_index_record_count>>fetch_index_record_count_status_job
SparkJobOperator & JobStatusSensor my custom class extending SimpleHttpOperator & HttpSensor.
If I set depends_on_past true will it work as expected?. Another problem I have for this option is some time the status check job will fail. But the next schedule should get trigger. How can I achieve this behavior ?

Answer 1

I think the main discussion point here is what you set is catchup=False, more detail can be found here. So airflow scheduler will skip those task execution and you would see the behavior as you mentioned.
This sounds like you would need to perform catchup if the previous process took longer than expected. You can try to change it catchup=True