[hobbit] ganglia-style graph aggregation with hobbit

[Gildas Le Nadan]

Tom Georgoulias wrote:
> Gildas Le Nadan wrote:
> 
>> 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.
> 
> Did you ever work out a solution for this?

No, not yet. I tried several other things in the [*-multi] hobbitgraph.cfg 
definitions but with no luck so far (I am no a rrd expert).

Btw Henrik, I also think it would be a good idea if the multi graph menu in 
hobbit-hostgraphs.sh was generated automatically from the [*-multi] entries in 
hobbitgraph.cfg.

Things I tried so far:

- the :STACK option don't work, probably because it shouldn't be added for the 
first entry (I tried the example on the rrd page, setting a graph with a 
constant value as a first graph don't work)

- I tried a VDEF/CDEF with IF so if there is no entry we set it to 0 (because we 
have to treat the first entry correctly)

I was about to test the different possibilities using rrdgraph straight instead 
of hobbit graph, so to get more debug/output when it fails.

Then, when I'll get a working solution, I'll try to see if this is possible to 
implement using the actual hobbitgraph.cgi. If not, I'll try to patch/ask Henrik 
for features.

(At least that's my plan)

> I'm starting to investigate a way that I can take data from many rrd 
> files, and graph the average of the data all those rrd files as a single 
> line.  For example, I'd like to average the %CPU usage (la1) for 10 
> different webservers, and display it as a single overall average %CPU 
> for a web farm.
 >
 > Tom

Yes, this is a fairly common problem I think :) There's plenty of other usage, 
such as adding up the bandwidth on different servers, and so on...

Cheers,
Gildas