I really hate dealing with legacy systems. This feels so wrong, and should not exist, but here we are.

rds.hosts.sync.sh

#!/usr/bin/env bash
#
# This script is a complete hack to work-around a crappy
# old Amazon EC2 instance running a custom CentOS AMI that
# was NOT provisioned by Amazon AWS engineers. 
#
# This particular (bain of my existence) server uses
# Google's DNS servers in the /etc/resolv.conf file, but
# wreaks havoc on the PHP web application when trying to
# call mysqli_connect, and often times-out or takes far
# longer to resolve than is acceptable for a web application.
#
# "Let's migrate the MySQL Database to RDS." -they said.
# "The 'ClassicLink' feature will work with the new VPC" -they said.
#
# The simple fact that I had to write this script makes me
# die a little bit inside, and cringe at the systems I'm
# inheriting from previous engineers where I work.
#
# Run via root crontab every 20 minutes. 'crontab -e'
# */20 * * * * /root/rds.hosts.sync.sh
#
# Author: Sean O'Donnell <sean.odonnell@seanodonnell.com>
#
RDSHOST="the-db-that-hates-me.c3ualchrhtne.us-west-1.rds.amazonaws.com";
OUTFILE="/etc/hosts";

LOOKUP=`host ${RDSHOST} | grep "address"`;
LOGOUT=/var/log/$0.log

#
# Only proceed if we indeed had a successful 
# remote dns look-up. Good luck with that.
#
date >> ${LOGOUT};

if [ ! -z "$LOOKUP" ]; then

    # reverse-lookup hostname
    RDSREVHOST=`echo ${LOOKUP} | awk {'print $1'}`;
    RDSIPADDDR=`echo ${LOOKUP} | awk {'print $4'}`;

    HOSTSLINE="${RDSIPADDDR} ${RDSHOST} ${RDSREVHOST}";

    echo -e "127.0.0.1  localhost.localdomain localhost" > ${OUTFILE}
    echo -e "::1        localhost6.localdomain6 localhost" >> ${OUTFILE}
    echo ${HOSTSLINE} >> ${OUTFILE}

    echo "Lookup successful. ${OUTFILE} updated." >> ${LOGOUT};
else
    echo "Lookup Failed." >> ${LOGOUT};
fi