[rrd-users] [rrd] Can't I turn off data smoothing for GAUGE?

[Marc MERLIN]

On Thu, Aug 19, 2010 at 07:41:57AM +0200, Tobias Oetiker wrote:
> though rrdtool is not 'smoothing' anything, what happens, is that
> rrdtool re-samples your input at the configured step frequency (so

Yes, I understood that, was just using a shortcut when speaking.

> if you put in your data at exactly the step-points, no re-sampling
> will happen) for thing you do not need to change rrdtool, just fix
> your input. If you do want to be able to have some of the data

input is cacti, I do not have full control on when I send data, but it
sounds like even if I'm just one second off, it would break anyway, so
that's just a non starter.

> re-sampled and some not inside the same rrd, code changes would be
> required, as you would have to adopt some sort of 'keep the last
> update that has arrived within the sampling interval and mark it
> valid for the whole interval'- aproach.

Yes, although I think most wouldn't care if it's off a bit and then end up
getting the data from the last or next sample as long as they are left
intact.

> And thirdly you would have to change storage type of data inside
> rrdtool to 'long long (64bit integer)'  from the normal double
> since double would prevent your bitfield input from working when
> you use all the bits ...
 
That would not be necessary.
1) I can use whatever number of bits are there
2) my bitfield use is, again, very one off. I don't think many people but
me even thought about using a data field that way to save disk space (and
the savings can be significant), but it seems clear that I'm not the only
one who seems to want to get the exact same data out that what was put in
when the data is something other than an analog value like a temperature
where interpolation is more than fine.

> Then the code in rrd_graph would have to be adapted to unserstand
> the new DS and RRA types

That sounds like a fair amount of work though.

> > or
> > - add a rrdtool create flag for GAUGE where it's marked as no smoothing
> 
> as I said ... I'll be glad to review any patches ...

Fair enough. This one sounds like it would be less work and would also work
out of the box with existing software like cacti since no format changes
occured and the only difference would be a flag at creation time.

I'll leave others who couldn't find a workaround to use the existing code to
ponder this and decide.

Thanks for your answers,
Marc
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