How to delete XCOM objects once the DAG finishes i

Question

I have a huge json file in the XCOM which later I do not need once the dag execution is finished, but I still see the Xcom Object in the UI with all the data, Is there any way to delete the XCOM programmatically once the DAG run is finished.

Thank you

Answer 1

Below is the code that worked for me,this will delete xcom of all tasks in DAG(Add task_id to SQL if xcom of only specific task needs to be deleted):

As dag_id is dynamic and dates should follow respective syntax of SQL.

from airflow.operators.postgres_operator import PostgresOperator

delete_xcom_task_inst = PostgresOperator(task_id='delete_xcom',
                                            postgres_conn_id='your_conn_id',
                                            sql="delete from xcom where dag_id= '"+dag.dag_id+"' and date(execution_date)=date('{{ ds }}')"
                                            )

Answer 2

You can perform the cleanup programmatically through sqlalchemy so your solution won't break if the database structure changes:

from airflow.utils.db import provide_session
from airflow.models import XCom

@provide_session
def cleanup_xcom(session=None):
    session.query(XCom).filter(XCom.dag_id == "your dag id").delete()

You can also purge old XCom data:

from airflow.utils.db import provide_session
from airflow.models import XCom
from sqlalchemy import func

@provide_session
def cleanup_xcom(session=None):
    session.query(XCom).filter(XCom.execution_date <= func.date('2019-06-01')).delete()

If you want to purge the XCom once the dag is finished I think the cleanest solution is to use the "on_success_callback" property of the DAG model class:

from airflow.models import DAG
from airflow.utils.db import provide_session
from airflow.models import XCom

@provide_session
def cleanup_xcom(context, session=None):
    dag_id = context["ti"]["dag_id"]
    session.query(XCom).filter(XCom.dag_id == dag_id).delete()

dag = DAG( ...
    on_success_callback=cleanup_xcom,
)

Answer 3

You have to add a task depends on you metadatadb (sqllite, PostgreSql, MySql..) that delete XCOM once the DAG run is finished.

delete_xcom_task = PostgresOperator(
      task_id='delete-xcom-task',
      postgres_conn_id='airflow_db',
      sql="delete from xcom where dag_id=dag.dag_id and 
           task_id='your_task_id' and execution_date={{ ds }}",
      dag=dag)

You can verify your query before you run the dag.

Data Profiling -> Ad Hoc Query -> airflow_db -> query -> Run!