Cannot get recorder to connect to mariadb

Tags: #<Tag:0x00007f326b9e6ea8>

I’ve just moved from running HA (0.115.4) on my own docker installation but using supervisor (I think it’s called docker supervised) to use pure hassio. I restored a snapshot and everything works OK except recorder.

I’m seeing the following in the log

homeassistant.components.recorder] Error during connection setup: (MySQLdb._exceptions.OperationalError) (2002, "Can't connect to MySQL server on 'core-mariadb' (115)")
(Background on this error at: http://sqlalche.me/e/13/e3q8) (retrying in 3 seconds)

This is repeated several times.

As far as I can see, the mariadb addon is working OK (version 2.2.1), but HA won’t connect. I’ve restarted everything several times.

Any ideas?