A fixed scale on Nagiosgraph

One of the annoying things about the graphs generated by Nagiosgraph is that the y-axis is sometimes auto scaled and the max/avg/min/cur values can be scaled too.

We find it very confusing. Take a look at this:

This one lets RRD automatically scale the units. Note how the y-axis for the weekly graph says 600m, although the daily graph says 1.5. Note also how the Avg value in the daily graph is a different scale to the Max value.

Compare with this:

We think the latter is more obvious to read, especially comparing across different timeperiods.

We've spoken to Soren Dossing and he's happy to accept this patch if it is an option. So here's it is. This applies cleanly onto Nagiosgraph 0.8.2. To use it, just add fixedscale to the list of URL parameters.

Performance data is hard enough to interpret without having to apply translations in your head. This should help with understanding it a little bit better.

Comments

[Albert Mata]

One question, why the weekly Max is lower than the Daily Max?

In theory Max is the highest value so the Weekly max should have the maximum value registered during the week (1.33 or higher) but no lower !?

[tonvoon]

Albert,

Good question. I honestly don't know. It could be something to do with the way RRD calculates averages. Since it has to consolidate all the points of data on the daily scale to a single (? maybe several, but not all) weekly point, it has to lose resolution.

If that's the case, I think it is safe to say that the weekly max will never be higher than the daily max.

Ton

[Albert Mata]

Probably is consolidation (CDP) as explained here:

http://www.vandenbogaerdt.nl/rrdtool/process.php

Anyway I still feel it's really difficult to get RRDTool to report exactly what you want and how you want it.

A very steep learning curve for me.

[Thomas]

Hi I’m Thomas and i’m a developer of a new open source project named BrainyPDM. As you can see from our web site this open source application can store performances data from Nagios and graph the values making Hourly, Daily, Weekly, Monthly and Yearly charts. If you want you can try it and give our some feedback. The url of our site is: http://www.brainypdm.org (on source forge: http://sourceforge.net/projects/brainypdm/)