[rrd-users] How to find first valid dp in rrd - repost - where arethe experts?

Karl Fischer rrd-users at ficos.de
Tue Nov 18 21:02:54 CET 2008

Alex van den Bogaerdt wrote:
>> yes, I've tried that, but no matter which way I'm doing it, it eventually
>> ends up having to read the entire database ...
> [snip]
> What is the exact problem you are trying to solve, and do you really want to
> solve it using rrdtool?

Well, I want to know the first and last 'useful' datapoint in the database for
several reasons. Useful for me means: at least one DS needs to be not unknown,
since - for most of the usage - unknown doesn't graph anything and I want to
look at 'live' data rather than white space, since the white space doesn't tell
me much except that the system might have been down for a while - but even if,
I'm interested in downtimes in 'the middle of the graph', not at the beginning or
end - very similar to stripping of whitespace at the beginning/end of a string.

1. In my GUI I'd like to (initially) point the user/viewer to the entire existing
   range of data, from where he can zoom in if he wants ...

2. I'm collecting data from many independently running systems (with their own
   instance of logging/graphing with rrdtools) into a central system allowing
   fast access to the (previously exported/imported) databases from the independent
   systems. On that central location I'd like to be able to tell if that dbexport
   I'm getting is just a grown version of the exisiting database (same startpoint,
   new endpoint) or if it is a complete new instance of the database (perhaps due
   to reinstallation of that system)

... there are more reasons but those are the most important ones ...
Basically I wan't to know when I have inserted the first value into that rrd rather
than seeing how far it potentially reaches back ...


- Karl

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