kaxil opened a new pull request, #44626:
URL: https://github.com/apache/airflow/pull/44626
As part of AIP-72, this PR introduces proper signal handling for the
supervisor process. The supervisor now intercepts `SIGTERM` signals to ensure
that child processes (task processes) are terminated gracefully.
Without signal handling, terminating the supervisor process (e.g., via `kill
-TERM`) could leave child processes running as orphaned tasks. This change
ensures that when the supervisor is stopped, all managed subprocesses are also
terminated cleanly.
Sample Output when Superviser receives SIGTERM with (`kill -TERM 138`):
```
2024-12-09 09:28:53 [debug ] DAG file parsed [task] [task]
file=/files/dags/example_bash_operator.py
2024-12-09 09:28:53 [warning ] BashOperator.execute cannot be called
outside TaskInstance!
[airflow.task.operators.airflow.providers.standard.operators.bash.BashOperator]
[task]
2024-12-09 09:28:53 [info ] Tmp dir root location: /tmp
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
2024-12-09 09:28:53 [info ] Running command: ['/usr/bin/bash', '-c',
'sleep 10000000']
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
2024-12-09 09:28:53 [info ] Output:
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
[2024-12-09T09:28:58.945+0000] {_client.py:1026} INFO - HTTP Request: PUT
http://localhost:9091/execution/task-instances/01938d9d-a579-7b8e-aa91-0a2093a318d5/heartbeat
"HTTP/1.1 204 No Content"
[2024-12-09T09:29:04.176+0000] {_client.py:1026} INFO - HTTP Request: PUT
http://localhost:9091/execution/task-instances/01938d9d-a579-7b8e-aa91-0a2093a318d5/heartbeat
"HTTP/1.1 204 No Content"
[2024-12-09T09:29:09.229+0000] {_client.py:1026} INFO - HTTP Request: PUT
http://localhost:9091/execution/task-instances/01938d9d-a579-7b8e-aa91-0a2093a318d5/heartbeat
"HTTP/1.1 204 No Content"
2024-12-09 09:29:09 [error ] Received termination signal in supervisor.
Terminating watched subprocess [supervisor] process_pid=139 signal=15
supervisor_pid=138
2024-12-09 09:29:09 [debug ] Task process exited [supervisor]
exit_code=<Negsignal.SIGTERM: -15>
2024-12-09 09:29:09 [info ] Process exited [supervisor]
exit_code=<Negsignal.SIGTERM: -15> pid=139 signal=SIGTERM
[2024-12-09T09:29:14.262+0000] {_client.py:1026} INFO - HTTP Request: PATCH
http://localhost:9091/execution/task-instances/01938d9d-a579-7b8e-aa91-0a2093a318d5/state
"HTTP/1.1 204 No Content"
2024-12-09 09:29:14 [info ] Task finished [supervisor]
duration=21.38433257100405 exit_code=<Negsignal.SIGTERM: -15> final_state=failed
```
<img width="1613" alt="image"
src="https://github.com/user-attachments/assets/c1548856-facb-4ebe-b389-89af4da4014b";>
vs without signal handling:
```
024-12-09 09:34:47 [debug ] Loaded DAG <DAG: example_bash_op>
[airflow.models.dagbag.DagBag] [task]
2024-12-09 09:34:47 [debug ] DAG file parsed [task] [task]
file=/files/dags/example_bash_operator.py
2024-12-09 09:34:47 [warning ] BashOperator.execute cannot be called
outside TaskInstance!
[airflow.task.operators.airflow.providers.standard.operators.bash.BashOperator]
[task]
2024-12-09 09:34:47 [info ] Tmp dir root location: /tmp
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
2024-12-09 09:34:47 [info ] Running command: ['/usr/bin/bash', '-c',
'sleep 10000000']
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
2024-12-09 09:34:47 [info ] Output:
[airflow.task.hooks.airflow.providers.standard.hooks.subprocess.SubprocessHook]
[task]
[2024-12-09T09:34:52.417+0000] {_client.py:1026} INFO - HTTP Request: PUT
http://localhost:9091/execution/task-instances/01938d9d-a579-7b8e-aa91-0a2093a318d5/heartbeat
"HTTP/1.1 204 No Content"
Terminated
```
<img width="1553" alt="image"
src="https://github.com/user-attachments/assets/6e076549-2312-4ab1-9c7e-2048b5946051";>
A key difference is in first case the task is also set to `failed` state as
it should while before it kept the TI as `running`
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