rspamd: configure redis backend
The sqlite backed is deprecated, and the redis backend is the default since rspamd 2.0.
Not having redis started results in such errors:
rspamd_redis_init: cannot init redis backend for BAYES_SPAM
To migrate the sqlite database, run
rspamadm statconvert --spam-db /var/lib/rspamd/bayes.spam.sqlite --ham-db /var/lib/rspamd/bayes.ham.sqlite -h 127.0.0.1:6379 --symbol-ham BAYES_HAM --symbol-spam BAYES_SPAM
The current module implements the recommended configuration that this utility prints out.
Without further intervention, rspamd uses the redis database at index 0. I don't know what that means, but I expect you must ensure nothing else uses database 0.
The above points probably should be added to some form of release notes. I couldn't find where they are, though.
Since rspamd is the default on NixOS 20.03, this should be merged before the next release.