[hobbit] RRD Graphing configuration

[Ralph Mitchell]

On Mon, Aug 11, 2008 at 8:53 AM, Bill Richardson <wrichardson at llbean.com>wrote:

>  I have looked high and low for a way to change how custom rrd's are
> created in hobbit.
>
> I have created a custom script to graph and have 2 problems that I would
> like to figure out.
>
> 1.) I would like to change the step from 300 secs to 60 secs in the rrd's
> and run the script ever 60 secs instead of 300 secs. "The default rrd
> behavior is set to 300 secs"
> 2.) I would like to get the true values not average. The problem is I
> have data that I want to graph that can range from 0 to 5  "thats 0, 1, 2,
> 3, 4  or 5" and the graph shows average so my graphs come out with numbers
> like 6m "6 milli" for a true value of 2 and so on. The problem is the
> data will sit a 0 for an hour or more and then go to 1 or 2 for just one
> sample. Average is not the right choice and I cant get the true figures I 'm
> looking for.
>
>  Seems like the way to do this is in the hobbitserver.cfg. I added the
> following to the hobbitserver.cfg
>
> NCV_testgraph="test1total:GAUGE,test2total:GAUGE,test3total:GAUGE"
>
>  What other values can you pass to rrd other than GAUGE? Can I set a step
> to say 60 instead or 300 and can I change the default behavior of AVERAGE to
> something else that may work for my above example? The rrd docs are not
> clear on this.
>
> Early on I was thinking that maybe I could fix the AVERAGE problem with a
> change to the hobbitgraph.cfg but this is what I found:
> The hobbitgraph.cfg does not have any effect on how rrd file is created. I
> deleted the testgraph.rrd made the changes to hobbitgraph.cfg and no go.
> You cant see the graphs if you use anything but AVERAGE after changing the
> hobbitgraph.cfg. It looks like the *.rrd's are created by default "AVERAGE"
> and you just edit the hobbitgraph.cfg to view whats already built. I need to
> figure out how to change the way the rrd's are built and its not thru
> the hobbitgraph.cfg.
>

If you're comfortable about fooling with the source, there are a couple of
places where you can make changes to achieve what you want:

hobbit-4.2.0/hobbitd/do_rrd.c contains these definitions:

     static char rra1[] = "RRA:AVERAGE:0.5:1:576";
     static char rra2[] = "RRA:AVERAGE:0.5:6:576";
     static char rra3[] = "RRA:AVERAGE:0.5:24:576";
     static char rra4[] = "RRA:AVERAGE:0.5:288:576";

BUT - if you change those, I think *every* new rrd created by Hobbit would
pick up the same changes.

do_rrd.c also includes a bunch of test-specific files, one of which is
hobbitd/rrd/do_ncv.c.  That contains the code that examines NCV_xxx and sets
up DS entries to match.:

         sprintf(dsdef, "DS:%s:%s:600:0:U", dsname, dstype);
or
         sprintf(dsdef, "DS:%s:DERIVE:600:0:U", dsname);

A bit further down it copies in the above rra1 - rra4 definitions.  So, you
could change the hardwired DS and RRA values in do_ncv.c, but ONLY if you
don't have any other NCV that would  need to be different...

Another way to get towards what you want would be to hand-create the rrd.
Hobbit won't overwrite an existing rrd.  I think the rrdcreate would look
something like this:

     rrdtool create testgraph \
        DS:test1total:GAUGE:60:0:U \
        DS:test2total:GAUGE:60:0:U \
        DS:test3total:GAUGE:60:0:U \
        RRA:AVERAGE:0.5:1:576 \
        RRA:AVERAGE:0.5:6:576 \
        RRA:AVERAGE:0.5:24:576 \
        RRA:AVERAGE:0.5:288:576

I haven't tried this myself, but I think Hobbit would be able to do updates
correctly.

Ralph Mitchell
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