e-galan opened a new pull request, #39329:
URL: https://github.com/apache/airflow/pull/39329
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Prevent **KubernetesPodOperator** from raising an exception in a rare
scenario, wherein the task is running in the sync mode with parameter
`reattach_on_restart` equal to *False*, and the first task attempt fails
because the task process is killed externally by the Kubernetes cluster or
another process.
If the task is killed externally, it breaks the execution flow (including
any try/except blocks) and immediately exists the task, resulting in a
situation where the pod created for the first task run try is not properly
deleted / updated, and consequently in the pod number exception, which will
repeat in the next task tries until the dag will fail completely.
**Behavior before the fix**:
1. `KubernetesPodOperator` starts a new task.
2. A k8s pod is created to process the task.
3. For some reason the task in the pod is killed externally and exits with
some code (-9 for example).
4. Since the `reattach_on_restart` parameter is set to False, the operator
does not try to restart the task in the same pod for the next attempt, and
tries to create a new one while the original pod still exists with the same
labels.
5. The new pod is created.
6. Before continuing the task, `KubernetesPodOperator` tries to find the pod
using the pod labels stored in the task context.
7. 2 pods with such labels are found, resulting in the exception (*"More
than one pod running with labels"*).
8. The exception continues to be raised on the next tries.
**Behavior after the fix**:
1-6. Same behavior.
7. 2 pods with such labels are found.
9. If `reattach_on_restart` is False, then we loop through the pods and pick
the one that was created last and assign it to be used for the next attempt.
10. Depending on the value of the `on_finish_action` parameter, we will
either update the labels of the previous pod or remove it.
11. The task will continue without the exception.
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