stalk

#!/bin/bash
# This program is part of Aspersa (http://code.google.com/p/aspersa/)

# TODO: advise if running non-root
# TODO: never use ~, always use ${HOME}

# ########################################################################
# A script to watch MySQL and run the 'collect' program when some condition
# becomes true.  By default, it watches for a too-many-connections condition.
# This is a good script to run in a screen session.  It's separate from the
# 'collect' script because that lets you change 'collect' without stopping
# and restarting this one.
#
# The name 'stalk' is because 'watch' is already taken, and 'stalk' is fun.
#
# Author: Baron Schwartz
# ########################################################################

# ########################################################################
# Configuration settings.
# ########################################################################
# This is the max number of connections we want to tolerate.  You can pass this
# in as the first command-line option if you want.
THREADS=${1:-100}
# This is the location of the 'collect' script.
COLLECT="${HOME}/bin/collect";
# This is the interval between checks; pass it as the 2nd command-line option.
SLEEP=${2:-30}
# This is the thing to check for.  You can pass this as the third option.
VARIABLE=${3:-Threads_connected}

while true; do
   date 
   threads=""
   threads=$(mysqladmin ext | grep ${VARIABLE} | awk '{print $4}');
   execute=no
   if [ -z "${threads}" ]; then
      execute="yes" # Oops, couldn't connect, maybe max_connections problem.
   elif [ ${threads} -gt $THREADS ]; then
      execute="yes"
   fi
   if [ "${execute}" = "yes" ]; then 
      echo "Executing collection script"
      ${COLLECT}
      echo "sleeping a while to avoid DOS attack"
      sleep 600 
   else
      sleep ${SLEEP}
   fi
done