[rrd-developers] exporting cf_conv

[Bernhard Reutner-Fischer]

On Tue, May 26, 2009 at 01:42:57PM +0200, Tobias Oetiker wrote:
>Hi Bernhard,
>
>Today Bernhard Reutner-Fischer wrote:
>
>> On Tue, May 26, 2009 at 09:17:59AM +0200, Tobias Oetiker wrote:
>>
>> >finally getting ready to publish 1.4rc I have resolved the
>>
>> btw.. Can we please have cf_conv exported since otherwise
>> it is not really possible to do anything useful with the
>> library.
>
>:-) interesting notion ... you mean all uses of the library up to
>now have not been useful ?

I don't know, but my usecase needs it exported from the beginning.
I admit that i have _no_ idea how other users of the library
look like, but i wouldn't be surprised if they were just using
some high-level view without having to worry about performance :)
>
>please elaborate.

Suppose i want to get some values out of an rrd (like i mentioned before
in the sample-code here ¹) in the _fastest_ possible way and you have an
 rrd with say X ds and Y cf and only want to get ds_something with cf
LAST, then you somehow need to get at the appropriate data.

Note, that i cannot afford to waste any unwarranted cycles to get at that
data, so high-level scripting languages and stuff like that are a nono,
I have to rrd_open() the file, get at the data and interpret the values
often, very often and as fast as possible. Since i need only current
data in 99.9% of the accesses (and no older data), it of course helped
to also keep the "hot" regions in memory as much as possible. But anyway.

I would be more than happy to be able to reuse more of the existing
code of librrd as you can see about all except the setup and reporting
in the sample application is just taken 1:1 from rrd_fetch() (IIRC).

See?

¹)
http://www.google.at/search?hl=en&num=50&q=rrd_reader&btnG=Search
e.g.: http://www.google.at/search?hl=en&num=50&q=rrd_reader&btnG=Search