I'm not sure if you're still looking for a solution, however I ran into the same issue. It was more of an annoyance than anything else. I had two options using rsyslogd:
1. Log snmp messages to a separate file, taking all snmp messages out of /var/log/messages
2. Drop the snmp messages via the rsyslog daemon. If you're not using rsyslog v5.8 (ex: syslogd, syslog-ng, etc...) I can't guarantee this will work, as I haven't tested this on anything else. Add this to your /etc/rsyslog.conf just before the entry which is logging snmp - for me it was '/var/log/messages':
# Remove excessive SNMP logging when Sam queries
# this node
:msg, contains, "-- HOST-RESOURCES-MIB" ~
:msg, contains, "send response: Too long" ~
The first line will discard anything containing the string "-- HOST-RESOURCES-MIB", the 2nd line is optional. Also, note the tilde (~) at the end of the line. The only caveat, this may affect debugging in the future, you'll have to remember to comment those lines out if you're trying to debug any issues with your node and SAM....
I should also note, there is another option which is to stop snmp from logging to syslog completely
look at your /etc/init.d/snmpd
remove the -LS directive
/usr/sbin/snmpd -LS0-6d -Lf /dev/null -p /var/run/snmpd.pid
This is would it would look like:
/usr/sbin/snmpd -Lf /dev/null -p /var/run/snmpd.pid
For whatever reason adjusting the log levels didn't seem to have any effect on my test system.
I am also having this issue on a RHEL 7 box and tried both of these changes but the message still pops up in /var/log/messages which is filling our var partitions. Not sure what is causing it or how to get it to stop.