Celery and plugin issue

Hi all,
I am seeing a weird issue with the stripe payment plugin and Celery.

From time to time I have the following in the celery log:

2024-04-26 13:20:43,231  INFO     celery.worker.strategy    Task send_email[4ced99ec-ad47-44ce-bb1c-23637f677258] received
2024-04-26 13:20:43,263  ERROR    celery.app.trace          Task send_email[4ced99ec-ad47-44ce-bb1c-23637f677258] raised unexpected: ValueError('Plugin not active: payment_stripe')
Traceback (most recent call last):
  File "/opt/indico/.venv/lib/python3.12/site-packages/celery/app/trace.py", line 477, in trace_task
    R = retval = fun(*args, **kwargs)
                 ^^^^^^^^^^^^^^^^^^^^
  File "/opt/indico/.venv/lib/python3.12/site-packages/sentry_sdk/integrations/celery.py", line 306, in _inner
    reraise(*exc_info)
  File "/opt/indico/.venv/lib/python3.12/site-packages/sentry_sdk/_compat.py", line 127, in reraise
    raise value
  File "/opt/indico/.venv/lib/python3.12/site-packages/sentry_sdk/integrations/celery.py", line 301, in _inner
    return f(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^
  File "/opt/indico/.venv/lib/python3.12/site-packages/indico/core/celery/core.py", line 134, in __call__
    raise ValueError('Plugin not active: ' + plugin_name)
ValueError: Plugin not active: payment_stripe

It does not happen for every registration or payment. The plugin is definitely enabled in the config.

Has anyone seen something like this before? Could some other exception trigger the Value error in the celery worker?

Cheers,
Christian

ps.
indico.conf:

PLUGINS = {'payment_manual', 'payment_paypal', 'payment_stripe'}

indico setup list-plugins:

+Available Plugins--+-------------------------------+
| Name              | Title                         |
+-------------------+-------------------------------+
| citadel           | Citadel                       |
| cloud_captchas    | Cloud CAPTCHAs                |
| livesync          | LiveSync                      |
| owncloud          | OwnCloud integration          |
| payment_manual    | Bank Transfer                 |
| payment_paypal    | PayPal                        |
| payment_sixpay    | SIXPay Saferpay               |
| payment_stripe    | Stripe                        |
| piwik             | Piwik statistics              |
| previewer_code    | Syntax highlighter (Pygments) |
| previewer_jupyter | Jupyter Notebook renderer     |
| prometheus        | Prometheus                    |
| storage_s3        | S3 Storage                    |
| ursh              | URL Shortener                 |
| vc_zoom           | Zoom                          |
+-------------------+-------------------------------+

Did you forget to restart indico-celery.service after enabling the plugin in indico.conf?

I don’t think so, and it only fails with that message for some payments. There are stripe payments within the hour of the failed ones in the log, that go through without issues.