[hobbit] ganglia-style graph aggregation with hobbit

[Gildas Le Nadan]

Henrik Stoerner wrote:
> On Wed, Sep 20, 2006 at 04:51:25PM +0100, Gildas Le Nadan wrote:
> 
>> I'd like to completely replace the ganglia system we have here with hobbit.
>>
>> Most of the needed features are there, except the ability to produce 
>> aggregated graphs with multiple hosts, as in 
>> http://monitor.millennium.berkeley.edu/?c=PSI%20Cluster&m=&r=hour&s=descending&hc=4
> 
> I think it can be done just by putting together the right graph
> definitions. RRDtool which is used to generate the graphs has all
> of the necessary functions to build such aggregate graphs, and 
> Hobbit already stores all of the information you're tracking. So
> it should "just" be a case of putting together the right input for
> the RRD graph module.
> 
> I have done it on an ad-hoc basis by hand-coding some extra graph
> definitions in the hobbitgraph.cfg file, but this is not suitable
> for the case where you have lots of hosts - for that you need something
> a bit more flexible that lets you select a group of hosts, and generate
> a graph with the type of aggregation you want.
> 
>> What would be the best way to do it? I'd like not to reinvent the wheel, 
>> so if some bits are already existing, I'd better use them...
> 
> Check the hobbit_hostgraph.cgi module in Hobbit 4.2, and the "multi"
> definitions in hobbitgraph.cfg. The current hobbitgraph tool lets you
> generate a graph for multiple hosts, but just overlaid on top of each
> other. I think it might be possible to just modify the "multi"
> definitions in hobbitgraph.cfg to produce an aggregate graph also.
> 
> 
> Regards,
> Henrik

Hum, I'm afraid I don't get how it works/can't make it work on a simple 
example: I'm trying to change la-multi in hobbitgraph.cfg so the values 
will be added up instead of printed on top of the others.

Are the entries in hobbitgraph.cfg used as a template to build the 
rrdgrph query? If so, then how can I access the values from the previous 
RDN to add them to the one in the current RDN (@RRDFN@)?

I tried adding the values to a VDEF:add=add, at RRDIDX@,+ but without success.

Any clue?

Cheers,
Gildas