Simple script to alert you when websites are down

Suppose your clients and boss would like to know when a site you maintain should go down.

You can write your own script to achieve this goal, where you implement a light-weight http client in python-twisted... but why bother?

There is a thing called reinventing the wheel.


So what do we need?

1. curl;
2. logrotate;
3. mutt;
4. A list of urls;
5. A log file to record visits by curl;
6. A script called site-checker, which one puts in the /etc/cron.hourly/ and chmod 770 /etc/cron.hourly/site-checker:
   
   
   

   #!/bin/bash
   
   #set -e -x
   
   FILELOC=/home/user/bin/websites.list
   LOGFILE=/home/user/bin/log/site-checker.log
   WEBSITES=$(cat $FILELOC | xargs)
   UDATE=$(date -u)
   EMAILADDR=user@nowhere.com
   for w in $WEBSITES
   do
     echo "==Fetched $w on $UDATE==" >> $LOGFILE
     curl -sf $w || echo "Warning: $w is down on $UDATE" | mutt -s "[website down] $UDATE $w" $EMAILADDR $
   done
   

websites.list would contain something like this:

www.microsoft.com
www.google.com
www.sap.com
www.oracle.com

For mutt to send e-mails you either need to setup a MTA (mail-transfer agent) or add a .muttrc file to your $HOME, containing something like this:

set smtp_url="smtp://user@smtp.woohoo.com"
set smtp_pass="tuff2guess"

You also have to prevent your site-checker.log from growing too big with logrotate.

Type this in your bash shell:

echo -e "/home/user/bin/log/*.log {\n\
  daily\n\
  missingok\n\
  size=100k\n\
  rotate 5\n\
}" > /etc/logrotate.d/user-custom\

As with every single script on this blog, you must adapt the script to your own needs.

Happy hacking!


Update 21-dec-2010:

#!/bin/bash
FILELOC=/home/user/bin/websites.list
PEOPLELOC=/home/user/bin/people.list
LOGFILE=/home/user/bin/site-checker.log
WEBSITES=$(cat $FILELOC | xargs)
UDATE=$(date -u)

mail () {
  read message
  domainname=$1
  for addr in $(cat $PEOPLELOC | xargs)
  do
    echo $message | mutt $addr -s "[website down] $UDATE $domainname" 2> /dev/null
  done
}

for w in $WEBSITES
do
  touch $LOGFILE
  echo "==Fetched $w on $UDATE==" >> $LOGFILE
  curl -sf $w || echo "Warning: $w is down on $UDATE" | mail $w
done