improving the 300 second resolution nagiosgraph

[Marc Powell]

On Jan 4, 2010, at 6:37 PM, Litwin, Matthew wrote:

> I need some assistance with nagiosgraph, specifically with how it handles RRD data.

I don't use nagiosgraph but I have familiarity with RRDTool.

> I am finding that there is a 300 second resolution limitation with nagiosgraph and how it uses rrdtool. I see the 300 second resolution clearly in the graphs themselves (regardless of how much I "zoom") which also correlates to the head of the output of 'rrdtool dump' for any of the RRD files nagiosgrah has created.

> The problem with this is that I have monitors the run every 60 seconds and the lack of precision is excessively smoothing the graphs to the point of them being useless.
> 
> My question is two-fold:
> 1) Where is this "step" period of 300 seconds specified in nagiosgraph?

Taking a peek at the nagiosgraph code (particularly etc/ngshared.pm), your problem is that it _isn't_ specified. nagiosgraph doesn't appear to have any code for specifying the step when it asks rrdtool to create the rrd database. Because it isn't passed a step value, rrdtool uses it's default of 300 seconds.

> 2) If I were to globally change the "step" period in nagiosgraph from 300 seconds to 60 seconds is there some way that I can keep my existing RRD data or would it become corrupted if I tried to change this?

If you were able to change it by adding code to support that, it would not affect the existing rrd files. The step is set at create time only and cannot be changed for an existing rrd file. You'd have to delete your existing files and recreate them. 

--
Marc


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