[mrtg-developers] Strange behavious when using unknaszero

S Shipway s.shipway at auckland.ac.nz
Thu Oct 8 22:44:27 CEST 2009

This is a known race condition caused by the update time window when using RRDTool.  The Routers2 frontend contains some special code to avoid this problem.

Basically, if your updates occur at 12:04 and you are generating the graph at 12:01, you are in the 12:00-12:05 'bucket' but the update has not yet occurred.  Therefore, the last value in the graph is Unknown.  14all may hop back to the previous bucket when its unknown and so you get the correct value...  however with unknaszero this unknown is translated to zero, and so the Last value is displayed as zero.

There is no fix for this without updating the 14all code to check for the condition and add a backskip, as Routers2 does.


From: jayashree (via Nabble) [mailto:ml-user+292048-566247669 at n2.nabble.com]
Sent: Thursday, 8 October 2009 6:15 p.m.
To: Steve Shipway
Subject: [mrtg-developers] Strange behavious when using unknaszero

Hi All,

I am using the unknaszero option while displaying certain graphs.

I am using 14all.cgi in the front end to create the pngs.

The funny thing is when I look at the legend at the bottom of the graph, even if there is data on my graph,
The current In value is '0', when there is a data of 2M being plotted in the graph.

When I remove the option from the router config file, and regenerate the pngs, the data is correctly displayed.

I cannot do away with the use of 'unknaszero' option. So is there any fix for this problem or am I doing something incorrectly.
14all version - 14all.cgi,v 2.23 2002/07/13
MRTG version - 2.100015

Appreciate any inputs.

Thanks & regards
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