We've specified different directories for dbdir and dbdir-state.  As a result, changes in the vacuum interval are not being respected.  vacuuming only takes place at the default interval, not at the newly calculated intervals.  This is because two different paths are specified to the tuning database.  In get_vacuum_interval():

        vac_dbname = talloc_asprintf(tmp_ctx, "%s/%s.%u", ctdb->db_directory, TUNINGDBNAME\
, ctdb->pnn);

In update_tuning_db():

	vac_dbname = talloc_asprintf(tmp_ctx, "%s/%s.%u",
                                     ctdb_db->ctdb->db_directory_state,
                                     TUNINGDBNAME, ctdb_db->ctdb->pnn);

To fix this I think we just need to change get_vacuum_interval() to use the state directory rather than the db directory (or at least make the two consistent and use the dbdir for both).

If you are running with dbdir == state dir, then you won't see this problem.  I've made the change and I'm not seeing the interval vary based on the number of entries that the vacuum picks up.