I've been playing with hobbit-4.1.2p1 for a week or so now, and have just spent the last couple of hours banging my head on the desk trying to get bb-mysqlstat to show graphs. Well, getting the reports through wasn't hard, and I could even get an empty link to show on the trends page by (mostly) following this advice:
http://www.hswn.dk/hobbiton/2005/06/msg00268.html
but I wasn't getting graphs...
Anyway, to make a long story short, it looks like the [mysqlslow] and [mysqlthread] entries in hobbitgraph.cfg need to have YAXIS defined. With that in, I get graphs.
Looking at hobbitd/hobbitgraph.c, it appears that where YAXIS is defined, it gets copied to newitem->yaxis (line 284), then that gets copied to rrdargs (line 890). I haven't had time to really read the whole file closely, but unless rrdargs is being checked somewhere, I'd guess that rrd_graph can't handle being passed an empty pointer for the yaxis label...
This is a great tool, and if I can ever persuade management to switch from Big Brother... :)
Ralph Mitchell