[rrd-users] api for iterating over single rows in a rrd file

[Tobias Oetiker]

Hi Daniel,

Today Daniel Pocock wrote:

> On 04/07/14 09:57, Tobias Oetiker wrote:
> > Hi Plamen,
> >
> > Yesterday Plamen Dimitrov wrote:
> >
> >> Hi rrdtool users!
> >>
> >> As part of my google summer of code project with Ganglia I'm developing an
> >> R package that imports the values from an RRD file into vectors in R
> >> (without exporting to csv, xml or other intermediate format first). I'm
> >> using the rrdfetch api to do this. Here is a working prototype:
> >>
> >> https://github.com/pldimitrov/Rrd
> >>
> >>
> >> Wnile this seems to work fairly well, it struck me that in a scenario when
> >> I'm only interested in reading one row at a time (e.g. to compare values
> >> from many RRDs simultaneously) , the rrdfetch code would need to go through
> >> all error/sanity checks, find the RRA we want and seek to the desired
> >> location in the file at each iteration.
> >>
> >> I know the use of the internal rrd_read, rrd_seek, rrd_open, etc...
> >> functions is not encouraged so I'm wondering what might be a good solution.
> >> Ideally, it would be useful to have something that iterates one row at a
> >> time, reads and caches the data.
> >>
> >> Does anything like this already exist?  Would you agree it makes sense to
> >> have this in addition to rrdfetch?
> > no there is no iterator ... if you do see a memory problem with
> > reading the whole file, you may want to split your reading into
> > of say 10000 rows
>
>
> Hi Tobi,
>
> What do you think of the other half of the question, simultaneously
> reading a row from all the RRDs?
>
> Has anything like this been discussed before, has anybody else expressed
> interest in that?

Neither ... my question is, what is the purpose of such an
endevour on the API level.

cheer
tobi




> Regards,
>
> Daniel
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902