[mrtg] Re: Spikes in MRTG graphs and logs... FOUND the PROBLE M!
Schuyler Bishop
SBishop at e-xpedient.com
Fri Jun 29 04:39:55 MEST 2001
Ok.
Alex suggested that I add some code to mrtg that wrote the absolute poll
values (that is, the actual counter # at the time of the poll) as well as
the current timestamp to a file and try to correlate the spikes to values in
this new file.
To do so, I added the code to the section of MRTG titled "update the RRD"
(line 439 in my version, 2.9.12a): (I'm using RRD...)
#Schuyler's debug edits...
open(SKY1, ">>\/tmp\/$router\-debug");
print SKY1 scalar localtime($time);
print SKY1 "\t$time\t$inlast\t$outlast\n";
#End Schuyler's edits...
(Note: I'm not a Perl expert - but hey it works GREAT and I didn't even
have to use a hash! :) )
And sure enough, I got a hit tonight! It looks like MRTG is doing a poll,
and reporting the following data:
( Current Date timestamp inocts outoctets )
Thu Jun 28 17:26:31 2001 993763591 -1 -1
So, why the heck is it reporting a negative number??? I would think that if
the poll is unsuccessful (for whatever reason - timeout?) then it would
report a zero for the absolute value!
This error is pretty easy to trap (I'll let my mods run for a little while
and see if the next spike is associated with a -1 absolute), but I guess my
question is how should we figure out what is causing the -1 poll?
What happens if I force it to zero when I get a negative #? will MRTG
assume a counter wrap (bad) or know that there was a non-response (it
happens with UDP, after all!) that it should just zero out the average for
that interval or (better) report the previous interval?
Anyway - I'll be glad to put this one to bed. Management was losing faith
in ol' MRTG! :)
Schuyler
-----Original Message-----
From: Schuyler Bishop [mailto:SBishop at e-xpedient.com]
Sent: Wednesday, June 27, 2001 3:58 PM
To: 'Alex van den Bogaerdt'
Cc: mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Spikes in MRTG graphs and logs...
I haven't received any responses and I'm hoping this isn't because it's a
bug someone hasn't pinned down yet. I'll help in finding out what's going
on as much as I can. I'm going to put a script into the crontab that runs
at the same time MRTG does that pings each device I'm monitoring to see if
there's a correlation between reachability (I'm monitoring across an
upstream ISP's network) and these spikes. Any other suggestions as to how I
can track this one down?
Thanks!
Schuyler
-----Original Message-----
From: Schuyler Bishop [mailto:SBishop at e-xpedient.com]
Sent: Wednesday, May 30, 2001 11:11 AM
To: 'Alex van den Bogaerdt'; Schuyler Bishop
Cc: mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Spikes in MRTG graphs and logs...
All,
Note that I think I might have pinned down the difference. It seems that
with the new version of the config, I'm using IP addresses as the identifier
in MRTG, while in the old version I was using interface numbering. I've
verified that interface numbering still produces spikes, even with the new
version of MRTG. Again, this seems to be related to using interface
numbering instead of IP address numbering in cfgmaker. Excerpt from the two
similar cfgmaker lines:
New with Interface numbering: (spikes still happen)
./cfgmaker --ifref=nr --ifdesc=alias --subdirs=HOSTNAME --community=public
--output=../cfgs/test1.cfg --global
workdir:/usr/local/apache/htdocs/mrtg/test --global 'options[_]:
growright,bits'
New with IP address numbering: (spikes don't happen)
./cfgmaker --ifref=ip --ifdesc=alias --subdirs=HOSTNAME --community=public
--output=../cfgs/test.cfg --global
workdir:/usr/local/apache/htdocs/mrtg/test --global 'options[_]:
growright,bits'
Schuyler
-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at slot.hollandcasino.nl]
Sent: Tuesday, May 22, 2001 6:42 PM
To: SBishop at e-xpedient.com
Cc: mrtg at list.ee.ethz.ch
Subject: [mrtg] Re: Spikes in MRTG graphs and logs...
Schuyler Bishop wrote:
>
> Per request, here are the relevant codes with appropriate removals of
> private info. :) Note that the IPs have been changed to protect the
> innocent.
Sure. I even removed more and see just one real difference. The
option line looks different but isn't (in this case). All other
lines were just textual differences (if at all different).
> Old config: (2.8.12)
> Target[10.10.10.10.6]: 6:public at 10.10.10.10
> New Config: (2.9.12a)
> Target[10.10.10.10_10.20.10.10]: /10.20.10.10:public at 10.10.10.10:
What should happen is that MRTG browses the MIB for an interface
with this IP address, and use the aquired interface number to get
the statistics.
The question that comes to mind right away: Is the interface number
for the interface with IP address 10.20.10.10 indeed 6 at the moment,
in other words: could it have changed over time (due to a reboot or so).
Even if the traffic looks more or less the same, it may be that you
are monitoring a different interface ?
--
__________________________________________________________________
/ alex at slot.hollandcasino.nl alex at ergens.op.het.net \
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