shubhamraj-git opened a new pull request, #46042:
URL: https://github.com/apache/airflow/pull/46042
related: #45966
The XCom creation API fills a critical gap by enabling dynamic, external
updates to workflows. This PR solves that problem.
### Benefits:
1. Enable Long-Running Workflow Updates:
> Current XComs are tied to task execution, limiting flexibility for
long-running workflows.
> The API allows dynamic creation or updates of XCom values during
execution, enabling workflows to adapt to external events or data without
waiting for task completion.
2. Improve Workflow Interactivity:
> External systems or operators can inject real-time decisions or
intermediate results directly into workflows.
> Useful for human-in-the-loop workflows, event-driven processes, and
external service integrations.
3. Reduce Task Dependency Overhead:
> Avoid placeholder tasks just to generate or update XComs.
> Streamline DAGs by enabling direct updates without unnecessary task
execution.
>
-------------------------------------------------------------------------------------------------------------------
### Steps to play around the feature.
1. Add the following Dag.
_This Airflow DAG demonstrates how to use XComs for passing data between
tasks. The first task (wait_and_not_push) waits for 1 minute but does not push
any XCom. The second task (pull_and_print) attempts to pull an XCom value with
the key outbound_key1 from the first task, logs it if found, or warns if
absent._
```
from airflow import DAG
from airflow.providers.standard.operators.python import PythonOperator
import time
import logging
import pendulum
# Default arguments for the DAG
default_args = {
'owner': 'airflow',
'retries': 1
}
# Initialize the DAG
with DAG(
dag_id="xcom_pull_example_dag",
default_args=default_args,
description="A DAG demonstrating XCom pull with key 'outbound_key1'",
start_date=pendulum.datetime(2025, 1, 1, tz="UTC"),
catchup=False,
tags=["xcom", "example"],
) as dag:
def wait_and_not_push_xcom(**kwargs):
"""
Task to wait for 1 minute.
"""
logging.info("Waiting for 1 minute...")
time.sleep(60) # Wait for 1 minute
def pull_and_print_xcom(**kwargs):
"""
Task to pull an XCom entry with key 'outbound_key1' and print its
value.
"""
ti = kwargs["ti"]
xcom_value = ti.xcom_pull(task_ids="wait_and_not_push",
key="outbound_key1")
if xcom_value:
logging.info(f"Retrieved XCom value for key 'outbound_key1':
{xcom_value}")
else:
logging.warning("No XCom value found for key 'outbound_key1'!")
# First task: Wait for 3 minutes and push an XCom entry
wait_and_not_push = PythonOperator(
task_id="wait_and_not_push",
python_callable=wait_and_not_push_xcom
)
# Second task: Pull the XCom entry and print its value
pull_and_print = PythonOperator(
task_id="pull_and_print",
python_callable=pull_and_print_xcom
)
# Define the task dependencies
wait_and_not_push >> pull_and_print
```
3. Trigger the run.
4. As soon as the run starts, trigger an XCom creation through API (Can do
it from swagger: http://localhost:29091/docs#/XCom/create_xcom_entry)
<img width="746" alt="image"
src="https://github.com/user-attachments/assets/b7f38435-c0d8-4586-ba71-d3c61b6ad584";
/>
Now, check the logs, You can see the **XCom pull was successful**.
<!-- Please keep an empty line above the dashes. -->
---
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