[BUG] Celery Background Callback Manager fails with Non-Key/Value-Backends

[datenzauberai]

Describe your context

This applies to background callbacks using the Celery Background Callback Manager. This should be reproducible using the latest version of dash as well.

dash                                     3.3.0
dash-ag-grid                             33.3.3
dash-iconify                             0.1.2
dash-mantine-components                  2.5.1
dash-testing-stub                        0.0.2

Describe the bug

Celery supports multiple backends that are not a BaseKeyValueStoreBackend:

• CassandraBackend
• DatabaseBackend
• MongoBackend
• RPCBackend

However, Dash's CeleryManager assumes the backend to be a BaseKeyValueStoreBackend having the methods set and get.

Configuring any of the backends above will result in an error similar to AttributeError: 'DatabaseBackend' object has no attribute 'get' when triggering a background callback.

Expected behavior

The CeleryManager should either

• support all Celery backends by using get_result and store_result from BaseBackend instead of get and set or
• make the restriction more explicit by additional documentation and erroring early on when the configured backend does not implement BaseKeyValueStoreBackend.

Especially the DatabaseBackend could eliminate the need for additional infrastructure to execute background callbacks.