[collectd] snmp plugin not writing rrd's

Florian Forster octo at verplant.org
Fri Sep 28 09:37:09 CEST 2007

Hi Matt,

On Thu, Sep 27, 2007 at 11:03:52PM -0700, Matt Peterson wrote:
> My specific interest is graphing SNMP variables (n.g. interfaces,
> temperature, etc) from a network switch, a Cisco 6509 in this case.
> While the pulling works fine for both of these into CSV files, and the
> debug version of collectd claims it's updating the RRD files, I find
> the data in them null (NaN with rrdtool dump).  What's a good way to
> debug this further?  Thanks!  Here's a sniplet of the config..

that's weird: If the `csv' plugin can write the values to CSV-file, the
values must have reached the daemon.

Just a short sidenote: Is this intentional?
>        Type "voltage"
>        Instance "module_6_outlet_temperature"

> ...an example of getting the temp & updating (or claiming to?)
> snmp plugin: csnmp_read_value (host = edge1.sfo, data = cat6500_module_6_outlet_temperature)
> snmp plugin: Got this variable: SNMPv2-SMI::enterprises. = Gauge32: 30
> snmp plugin: Parsed int32 value is 30.

Hehe, collectd doesn't make up values - that thirty there is a strong
hint that it can read the values from the switch..

> csv plugin: csv_write: filename = edge1.sfo/snmp/voltage-module_6_outlet_temperature-2007-09-27;

Here the value get's written to the CSV-file - the part you said works..

> rrd_cache_insert (/usr/local/var/lib/collectd/rrd/edge1.sfo/snmp/voltage-module_6_outlet_temperature.rrd, 1190959086:30.000000, 1190959086) = 0x2aaab80008c0

Here the value get's inserted in the cache of the rrdtool plugin. Did
you check if the file was actually updated? You can do that by checking
the mtime or doing something like
 $ rrdtool info $FILE | grep last_update

> return (0);
> Exiting normally

It's kind of disturbing that the cache doesn't get flushed here. How
long did the daemon run at this point?

Have you tried simply letting the daemon run for a while? Try letting it
run for at least as long as the `CacheTimeout' setting is set to and see
if the files get touched again.
Other than that, please take a look at the min/max limits in the
RRD-files. I specifically toubt that the `if_octets' limits are too
restrictive, because I use them with some 10GE ports..


P.S.: If you have a good set of <Data ...> definitions for the snmp
      plugin, would you mind to share? I plan to distribute sample
      configuration snippets in the contrib/ directory and the next
      minor version will allow you to use `Include' to pull them into
      your configfiles..
Florian octo Forster
Hacker in training
GnuPG: 0x91523C3D
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