[rrd-users] Help in constructing 2 second update graph

EHCanadian EHCanadian83 at Hotmail.com
Sat Dec 22 17:25:33 CET 2012

Ah, WiFiSignal.rrd --step 2 DS:WiFiSignal:GAUGE:4:0:100 RRA:LAST:0.5:1:60
Seems to have fixed it. Its now rendering the graph over the time span of 1 min
and its not 1 solid area block.


From: Simon Hobson [via RRD Mailinglists] 
Sent: Saturday, December 22, 2012 5:41 AM
To: EHCanadian 
Subject: Re: Help in constructing 2 second update graph

EHCanadian wrote: 

>$RRDToolPath & ' create ' & $RRDDataPath & 'WiFiSignal.rrd --step 2 
>DS:WiFiSignal:GAUGE:4:0:100 RRA:LAST:0.5:2:120 

There's an error there to start with. You are consolidating two off, 2 second samples into each consolidated data point. Thus you are storing 8 minutes at 4 second resolution. 

In the general case, you wouldn't normally want to use LAST as your consolidation function. Normally you would want to consolidate for MIN, MAX, and AVERAGE. However, in your case, since your consolidation should be a null function, you can get away with it. 

>$RRDToolPath & ' graph ' & $RRDDataPath & 'WiFiSignal.png -E -G mono -R mono 
>-a PNG -w 800 -h 600 --full-size-mode --start end-1minute --title="WiFi 
>Signal 1 Min" --vertical-label="WiFi Signal Strength" DEF:WiFiSignalDef=' & 
>StringReplace($RRDDataPath,'C:','C\:') & 'WiFiSignal.rrd:WiFiSignal:LAST 

You haven't specified an end time, so you'll get an arbitrary graph ending at whatever "now" is when you run the command. That may or may not be what you want. 

OK, so if this doesn't help, here is what you need to do. 
1) Make a file with test data. Your inputs are variable and time-dependent, so nothing can be reproduced. 
2) Make direct calls to RRDTool - ie leave out the programming environment specific stuff to start with. 

So now you should have known data, and fixed commands. You can run the commands and see what happens. Because the data is fixed, you should know what to expect, and others can too. 

If you are still stuck, post the data and commands here. 

Once you have that working, you can "scriptify it" - if it then stops working, you have a knwon working point you can go back to. 

Also, you may find Alex's tutorials helpful : 

Simon Hobson 

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed 
author Gladys Hobson. Novels - poetry - short stories - ideal as 
Christmas stocking fillers. Some available as e-books. 

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