What you're seeing isn't a bug in net-snmp.  The net-snmp docs have stated for a long time that ssCpuIdle and the other ssCpu* OIDs are deprecated and should not be used.  Instead, you should be using the ssCpuRaw* OIDs (ssCpuRawIdle, ssCpuRawUser, ssCpuRawSystem, etc...).  You will get much better data from these OIDs as well.  Instead of getting a "rough estimate" percentage (rounded down to an integer), you can actually see how many clock ticks have been used on each, which will give you MUCH greater accuracy.

This should be considered a ZenOSS bug in the default "Server/Linux" device template, but it's easy enough to fix yourself.  Just edit the Devices->Servers->Linux Template, look in the Data Sources section for the ssCpu checks.  Change the SNMP OID being used to the appropriate ssCpuRaw* OID.  For instance, the ssCpuIdle OID is .1.3.6.1.4.1.2021.11.11.0.  This OID should be changed in your Data Sources to the OID for ssCpuRawIdle, which is .1.3.6.1.4.1.2021.11.53.0.

You can find the right OIDs by running the following commands from any linux machine with a net-snmp utilities installed:

snmpwalk -v2c -c $COMMUNITY $HOSTNAME .1.3.6.1.4.1.2021.11

This will show you the complete list of available CPU OIDs.  To get the OID as a numerical value rather than text, try this:

snmpwalk -v2c -c $COMMUNITY $HOSTNAME -O n ssCpuRawIdle

You can swap "ssCpuRawIdle" above with any of the other OIDs listed in the first command (ssCpuRawSystem, ssCpuRawUser, etc)

One thing to remember: all ssCpu* OIDs are integer "gauge" values.  The ssCpuRaw* OIDs are all "counter" values.  Changing from a guage data source to a counter data source requires some changes to your graphs.

Hope this helps...

HummerBoy wrote:

 

This doesn't explain why this OID was working fine for at least the past 249 days (uptime on the lastest one with this issue) and it stops working now. Why does it stop working on all four servers at a site all at the same time?

A figure of 1942502991 ticks means nothing to me where as 90% idle does

What I'm trying to tell you is that if it ever did work, you weren't getting valid results anyway.  You can not rely on the SNMP OID ssCpu* to give you an accurate "percentage" of CPU usage.  You need to calculate it yourself using the values returned by ssCpuRaw*.

I wrote a Nagios-compatible script for Linux devices that can be used from within ZenOSS (as a COMMAND data source) to grab the correct values for each operating system and give you pretty accurate results (to the hundredth of a percentage).  It grabs a configurable number of seconds of data and calculcates from the delta, so it will require X number of seconds to run (configure the $sample_seconds variable to set the sample period).  I've attached it to this post.

The ZenOSS Administrator's Guide explains specifically how to use scripts as a COMMAND data source.  You will need to follow those instructions to setup the data sources for your graphs, but this script will give you the correct values.  Also, you must have Net-SNMP utilities and perl installed on whatever system will be running this script.  Make sure to run the script once from the command line as the zenoss user to see if it works.

The script would be run like (set your Command Template to):

check_linux_cpu.pl ${here/zSnmpVer} ${here/zSnmpCommunity} ${here/manageIp}

You can run it from the command line to test your server:

check_linux_cpu.pl $SNMP_VERSION $SNMP_COMMUNITY $HOSTNAME

$SNMP_VERSION = the appropriate SNMP version (use v2c)

$SNMP_COMMUNITY = the community string you are using

$HOSTNAME = the hostname or IP address of the server you want to poll for data

It will return values in the following format:

|Count=2 TotalUsed=4.705 User=4.004 Kernel=0.701 Idle=95.295 Wait=0.000

Count = the number of CPU cores on your system

TotalUsed = the total percentage of "Used" CPU time

User = percent CPU used on "User" processes

Kernel = percent CPU used on "Kernel" tasks

Idle = percent CPU idle (total percentage "Free" CPU)

Wait = percent CPU iowait (amount of time CPU spends waiting for I/O)

Note that it only works for Linux.  If you want to check Solaris, BSD or Mac OS X machines (etc), you'd need to hack this script to specify which of the ssCpuRaw OIDs are important, and what OIDs you want to check.

Good luck!