I'm using CRM114-based SpamAssassin plugin for spam filtering at work, and at home. Client-side, I'm able to check CRM114 contribution by a simple look at headers of an email message. But that won't tell you how CRM114 is behaving on the server side. The main concern on the server, is to check the two "databases" spam.css and nonspam.css.
I've chosen to monitor both average packing density and documents learned metrics for both files. The first one goes from 0 to 1. When its value reaches 0.9 and beyond, you must make sure your antispam filtering does not become sluggish.
The second one represents the number of emails from which CRM114 has been trained. Basically, CRM114 is only trained from its mistakes : if an email is flagged as spam by mistake, you can train CRM114 to learn it as nonspam, but if an email is properly flagged as spam, you can't train CRM114 to learn it as spam.
I've designed two Munin plugins, they run on FreeBSD but portage to another UNIX is just a matter of path.
Monitor "average packing density" (crm114_packingdensity): shows how much your CRM114 bases are encumbered
#!/usr/local/bin/bash
#
# Parameters:
#
# config (required)
# autoconf (optional - used by munin-config)
#
# Magick markers (optional - used by munin-config and som installation
# scripts):
#%# family=auto
#%# capabilities=autoconf
export PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# config
if [ "$1" = "config" ]; then
echo 'graph_title CRM114 css file stat average packing density'
echo 'graph_vlabel Packing density'
echo 'graph_category ANTISPAM'
echo 'graph_args --upper-limit 1 --lower-limit 0'
echo 'graph_info This graph shows the average packing density for CRM114 css files'
echo 'spam.label spam'
echo 'nonspam.label nonspam'
exit 0
fi
cssutil -r -b /var/amavis/.crm114/spam.css | awk '/Average packing density/ {print "spam.value "$5}'
cssutil -r -b /var/amavis/.crm114/nonspam.css | awk '/Average packing density/ {print "nonspam.value "$5}'
Monitor "documents learned" (crm114_documentslearned): shows how many emails CRM114 has learned from
#!/usr/local/bin/bash
#
# Parameters:
#
# config (required)
# autoconf (optional - used by munin-config)
#
# Magick markers (optional - used by munin-config and som installation
# scripts):
#%# family=auto
#%# capabilities=autoconf
export PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
# config
if [ "$1" = "config" ]; then
echo 'graph_title CRM114 css file stat documents learned'
echo 'graph_vlabel Documents learned'
echo 'graph_category ANTISPAM'
echo 'graph_args --lower-limit 0'
echo 'graph_info This graph shows the documents learned count for CRM114 css files'
echo 'spam.label spam'
echo 'nonspam.label nonspam'
exit 0
fi
cssutil -r -b /var/amavis/.crm114/spam.css | awk '/Documents learned/ {print "spam.value "$4}'
cssutil -r -b /var/amavis/.crm114/nonspam.css | awk '/Documents learned/ {print "nonspam.value "$4}'
Both plugins need read access to spam.css and nonspam.css, depending on your setup it will require special privileges. You might want to add in /usr/local/etc/munin/plugin-conf.d/plugins.conf:
[crm114_*] user root