Eason09053360 opened a new pull request, #72817:
URL: https://github.com/apache/airflow/pull/72817
When a Celery worker dies without cleaning up its PID file (SIGKILL, OOM,
host reboot), `airflow celery stop` reads the dead PID, crashes with an
uncaught `psutil.NoSuchProcess` traceback, and never reaches the PID-file
removal at the end of `stop_worker`. Every subsequent `stop` fails the same way
until the operator deletes the file by hand.
```
$ echo 999999 > stale.pid
$ airflow celery stop --pid stale.pid
File ".../celery_command.py", line 386, in stop_worker
worker_process = psutil.Process(pid)
psutil.NoSuchProcess: process PID not found (pid=999999)
$ echo $?
1
$ ls stale.pid
stale.pid
```
After this change the command logs a warning, removes the stale file and
exits 0, which matches the existing behaviour when no PID file exists at all
(`stop` is idempotent).
```
$ airflow celery stop --pid stale.pid
[warning] Worker process with PID 999999 is not running, PID file
.../stale.pid is stale.
$ echo $?
0
$ ls stale.pid
ls: stale.pid: No such file or directory
```
The worker start path already treats `NoSuchProcess` as "stale PID file,
clean it up" in `check_if_pidfile_process_is_running`; the stop path was the
only reader that did not.
Only `NoSuchProcess` is handled on purpose. `psutil.AccessDenied` means a
live process the caller cannot signal (for example a worker started as root and
`stop` run as another user); removing its PID file would be wrong, so that case
still surfaces as an error.
## Tests
`test_if_right_pid_is_read` is parametrized over three cases: worker
running, PID file stale, and worker exiting between `psutil.Process()` and
`terminate()`. The last two fail without the fix.
`airflow edge stop` has the same shape of bug; it lives in a different
provider and will be addressed separately.
---
##### Was generative AI tooling used to co-author this PR?
- [X] Yes — Claude Code (Fable 5.1)
Generated-by: Claude Code (Fable 5.1) following [the
guidelines](https://github.com/apache/airflow/blob/main/contributing-docs/05_pull_requests.rst#gen-ai-assisted-contributions)
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