[rrd-developers] Graph data without the graph?

[Bernhard Reutner-Fischer]

On Thu, Sep 10, 2009 at 07:14:35PM +0200, Sebastian Harl wrote:
>Hi Mark,
>
>On Thu, Sep 10, 2009 at 12:54:39PM -0400, Mark Plaksin wrote:
>> Tobias Oetiker <tobi at oetiker.ch> writes:
>> > I think rrd_xport may lend itself better to this task ...
>> 
>> rrd_xport is cool but it doesn't seem as powerful as rrd_graph.  You
>> can't, for example, get MAX, MIN, and AVERAGE for a given line.
>
>This is related to something that has bugged me for quite some time in
>fact. rrdgraph currently is the only function / tool that provides high
>level access to a database that's available to users. Imho, that func-
>tionality should rather be made available through rrdfetch (in the C API
>as well as in the command line tools). I. e., rrdfetch should take care
>of fetching the data and doing the specified calculations (i. e. han-
>dling the *DEFs). On the C API level it might even make sense to further
>split that up into multiple functions, but I have not looked at that in
>depth.
>
>What do others think about that? It might make sense to work on that
>before adding any other exporters.

Way back then (sorry to point at it _again_), i raised
librrd vs. rrd.h -- incomplete interface
http://www.mail-archive.com/rrd-developers@lists.oetiker.ch/msg01866.html
This is pretty outdated by now, obviously. Another outdated thing that
should be handled properly (i.e. by not duplicating rrd_fetch internals)
was mentioned here:
http://www.mail-archive.com/rrd-users@lists.oetiker.ch/msg14102.html

I suggest you come up with a simple client that does
- either
  + open a filename, RO
  + use provided fd / pointer to mmap'ed rrd
- looks for a DS
- for a given CF
- fetches X steps
- does something with that data
in C or C++ and _then_ model librrd to be able to satisfy
those needs.

just a thought..
cheers,