josh-fell commented on pull request #16624:
URL: https://github.com/apache/airflow/pull/16624#issuecomment-867725810
This change enforces the proper dependency between a task that writes an
`XCom` and one that consumes the same `XCom`.
```python
write_xcom = KubernetesPodOperator(
namespace="default",
image="alpine",
cmds=[
"sh",
"-c",
"mkdir -p /airflow/xcom/;echo '[1,2,3,4]' >
/airflow/xcom/return.json",
],
name="write-xcom",
do_xcom_push=True,
is_delete_operator_pod=True,
in_cluster=True,
task_id="write-xcom",
get_logs=True,
)
pod_task_xcom_result = BashOperator(
bash_command="echo \"{{ task_instance.xcom_pull('write-xcom')[0]
}}\"",
task_id="pod_task_xcom_result",
)
```
As written currently both of these tasks execute in parallel.
But the should execute sequentially.
This dependency would be handled by converting the `xcom_pull` in the
"pod_task_xcom_result" task to use the Taskflow API but accessing specific
values from an operator `.output` is not supported yet (see #16618). Yes, this
is an example but the functional dependencies should be correct for users to
reference.
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