[mrtg] Graphing Uptime

Fri Sep 28 22:21:26 CEST 2018

Hi Daniel,

Yes that example was horribly bodged. I haven't inspected the code, but I suspect MRTG works with the value returned by SNMP. For example, I receive this:

SNMPv2-MIB::sysUpTime.0 = Timeticks: (105630500) 12 days, 5:25:05.00

That cannot be graphed because it is not a number. Everything that MRTG graphs must be turned into some number. The example is also horribly bodged because it's trying to use a bandwidth graph instead of a gauge. MRTG provides for graphing values like CPU load, Memory, and Free disk space. You really want to grab the most recent book as it will tell you how to construct these. I'll give you an example:

Target[the_graph]:        1.3.6.1.4.1.32050.2.1.27.5.1&1.3.6.1.4.1.32050.2.1.27.5.1:snmp_community_name at 10.0.0.1:::::2 * -1.1034882
Options[the_graph]:       unknaszero,gauge,growright,nopercent,expscale,noo
SetEnv[the_graph]:        MRTG_INT_IP="No Ip" MRTG_INT_DESCR="n/a"
Colours[the_graph]:       ORANGE#dd8811,NONE#000000,VIOLET#0000ff,DARK GREEN#006600
Title[the_graph]:         Voltage Monitor
MaxBytes[the_graph]:      850
AbsMax[the_graph]:        850
XSize[the_graph]:         600

All of these directives are explained in the book. The two most important ones are the Target and Options directives. The gauge option is what makes it a gauge graph, and the noo option suppresses one side of the graph (input or output). With the directives you can construct your own custom graph with correct units for uptime, and a scale that will make sense. You can control titles, legend values, etc.  

Your first issue is how to convert 'Timeticks: (105630500) 12 days, 5:25:05.00' to a number. I would suggest graphing the hours of uptime. Even after a few years of uptime, the value itself will be less than 100,000 and probably graph well over time. 

MRTG provides for pre-processing of SNMP values before they are passed to MRTG. I'm performing math before I use the voltage value. Since I'm pretty sure that the math is any valid perl statement, you might be able to get away with Perl. That being said, you may be best served by simply creating your own data collection plug-in, which is thankfully easier done than said. Straight from the book:

Target[ezwf]: `/usr/local/bin/mrtg-scripts -a 1`

All you need to is create a bash script that pipes your snmpwalk output into a awk, and then convert the returned value into the number of hours. Timeticks can be converted to hours: Hours = Timeticks / 100 / 60 / 60. 

Something like:

uptime=`snmpwalk -v1 -c public 10.0.0.1 SysUptime | awk -F'[()]' '{print $2}'`
let hours=uptime
let hours=$hours/100/60/60
echo $hours

If you run that bash and pass it into MRTG, with directives to create a gauge type graph, you should get a fairly nifty uptime graph. With correct units for time as a bonus. 

Sincerely, 

Edwin A Epstein, III 
Rhinobee Internet Services 
707.237.7504 ext 209 
707.737.0288 Mobile

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Today's Topics:

   1. Graphing uptime (Daniel Beardsmore)

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Message: 1
Date: Fri, 28 Sep 2018 10:06:23 +0100
From: "Daniel Beardsmore" <resident at telcontar.net>
To: <mrtg at lists.oetiker.ch>
Subject: [mrtg] Graphing uptime
Message-ID: <041801d4570a$88f67650$9ae362f0$@telcontar.net>
Content-Type: text/plain; charset="us-ascii"

Hello

I can see that graphing uptime is possible, as you can see here:

http://www.hotelsvillegia.com/mrtg/uptime.html

The HTML pages report uptime in the format: "163 days, 21:07:10"

If I check manually, I get this:

snmpget -v2c -c somecommunity somehost 1.3.6.1.2.1.1.3.0

DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (1415941565) 163 days,
21:10:15.65

The format is almost the same, but the latter contains the full centisecond
accuracy. You do nonetheless get the raw number included.

Now, using this in MRTG yields:

2018-09-27 19:56:04 -- 2018-09-27 19:51:33: WARNING: Expected a number but
got '163 days, 7:17:10'

Looking at the source code, I cannot determine quite how uptime is
processed. It seems odd that the format is almost the same (without the
centiseconds), which suggests (along with other code) that MRTG receives
pre-formatted output, and then has to scrape out the useful bits. (Which is
just plain horrible if this is true.)

Am I right in thinking that MRTG presently has no way to extract the raw
figure here? It seems that the SNMP library is formatting the data
prematurely and MRTG just works with that preformatted value as it suits its
own purposes, but that you cannot get the raw data out if you choose, for
example if you want to record uptime as a graph for checking for reboots.

In the example posted, I suspect that was bodged to get that to work.

Regards

Daniel. 

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