We have tested this only in cloud mode.
We have noticed when a backup is restored that contains a config with the same name as one that already exists in solr, the config restore is silently skipped (also when the configs are different but share the same name). I would expect that at least a warning appears in the logs when this happens. We saw that this happens with backups from local repositories as well as gcs repository (possibly others too).
Steps to reproduce the issue:
- Start solr in cloud mode
- Upload a config (any config, we tried with the default one)
- Create a collection with the config
- Create a backup
- Delete collection in UI
- Change the config either in backup or in solr (we added an additional comment)
- Restore collection
- Have a look that after restore the old solr config has remained and the restored collection is using it. At the same time, the config from the backup has been ignored and no warning was produced whatsoever.