cron vs. ‘at’: run command at varying intervals with self-registering ‘at’

I wanted to check whether our business critical web server is up in every 6 hours.

First I thought I run ping every 6 hours via ‘cron’. But I want to ping more often once server is detected down and until it comes back up.

So, I came up with this self registering ‘at’ script. This begins pinging the server in google:”incremental backoff” intervals once it’s detected down. Starts at 1 minute, and then 2 minutes. 3,4,5… If you replace “+1″ wit “*2″, it will do google:”exponential backoff”. 1,2,4,8,16…

$ cat ~/misc/myServerPing.at
# THISFILE should be full path or relative from $HOME
# Run this in bash by ". {this file}"
THISFILE=misc/myServerPing.at
INTERVAL=1
curl --silent --connect-timeout 8 http://ourserver.sun.com | grep "Our critical page" > /dev/null
if [ $? -ne 0 ]; then
date | mailx -s "Failed ping to ourserver" my.mail.address@sun.com
sed "s/^\(INTERVAL=\)[1-9]*$/\\1$(($INTERVAL+1))/" $THISFILE | at now + $INTERVAL minutes > /dev/null 2>&1
else
at now + 360 minutes  /dev/null 2>&1
fi

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