amoghrajesh opened a new pull request, #45506:
URL: https://github.com/apache/airflow/pull/45506
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closes: https://github.com/apache/airflow/issues/45419
XComs have to be cleared when a task starts execution. We are handling this
in the `run` endpoint as this endpoint marks "execution" for a task instance.
Few points:
- Do not clear XComs for cases when "next_method" is set - for deferrable
and reschedule tasks
- Clear Xcoms for other regular tasks
- Ported unit tests from `test_taskinstance.py` - only
`test_xcom_pull_different_logical_date` is pending.
### Testing
#### Normal DAG
Steps:
1. Create a normal DAG like this that doesn't push an xcom
```
from airflow import DAG
from airflow.providers.standard.operators.bash import BashOperator
from datetime import datetime, timedelta
dag = DAG(
'hello_world_dag',
schedule=None,
catchup=False,
)
hello_task = BashOperator(
task_id='say_hello',
bash_command='echo "Hello World from Airflow!"',
dag=dag,
do_xcom_push=False
)
hello_task
```
2. Directly hit the API in fast api to set an xcom for the task instance to
stage an older Xcom being present
<img width="1233" alt="image"
src="https://github.com/user-attachments/assets/09cd72a5-f77e-40de-b8de-4d102d11f344";
/>
3. Run the dag again, the xcom will get cleared
<img width="1233" alt="image"
src="https://github.com/user-attachments/assets/fa2d3690-b1e4-43f9-ab2e-65e3abf00068";
/>
#### DAG with a deferred Task
DAG:
```
from datetime import datetime, timedelta
from airflow import DAG
from airflow.models import BaseOperator
from airflow.providers.standard.triggers.temporal import TimeDeltaTrigger
class XComPushDeferOperator(BaseOperator):
def execute(self, context):
context["ti"].xcom_push("test", "test_value")
self.defer(
trigger=TimeDeltaTrigger(delta=timedelta(seconds=10)),
method_name="next",
)
def next(self, context, event=None):
pass
with DAG(
"xcom_clear", schedule=None, start_date=datetime(2025, 1, 8),
) as dag:
XComPushDeferOperator(task_id="xcom_push")
``` (ref from https://github.com/apache/airflow/issues/22931)
Steps:
1. Run the dag:
<img width="1725" alt="image"
src="https://github.com/user-attachments/assets/4f6932c0-2df5-412a-a091-9594094684ae";
/>
2. XComs aren't cleared, still present
<img width="1725" alt="image"
src="https://github.com/user-attachments/assets/c4b741a2-6356-4fae-888b-eb65d6dc0a80";
/>
3. Triggers running
<!-- Please keep an empty line above the dashes. -->
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