MRTG triggers

As Thomas J. Muggli described on his website, its easy to implement MRTG triggers for alerting purposes.

Add three lines to your mrtg.cfg:

ThreshMaxI[serverA.MySQL]: 25000
ThreshProgI[serverA.MySQL]: /usr/local/bin/mrtg_threshprogi.sh
ThreshProgOKI[serverA.MySQL]: /usr/local/bin/mrtg_threshprogoki.sh

This particular string "MySQL" in fact can be changed to whatever: CPU, network traffic, web page requests etc. (see my custom MRTG collectors).

Then lets write a script to manage crossed thresholds:

/usr/local/bin/mrtg_threshprogi.sh

#!/bin/bash
echo "" | mail -s "[MRTG] $1 exceeded; allowed: ${2}, current: $3" root

/usr/local/bin/mrtg_threshprogoki.sh

#!/bin/bash
echo "" | mail -s "[MRTG] $1 returned to $2" root

Simple and effective.
If mrtg.cfg strings are the same as directory name convention, you can attach /var/www/ssl/mrtg/MySQL/serverA.MySQL-day.png to the e-mail:

# $1 == "serverA.cpu" => srv == "serverA"; meter == "cpu"
# optionally: METER=`echo $meter | tr /a-z/ /A-Z/` changes "cpu" to "CPU"
IFS=. read srv meter <<< $1
mutt -x -s "[MRTG] $1 exceeded; allowed: ${2}, current: $3" \
  -a /saltstone/httpd/html_ssl/info/mrtg/${meter}/${SUBJECT}-day.png root