Rack awareness

#!/bin/bash

# Adjust/Add the property "net.topology.script.file.name"
# to core-site.xml with the "absolute" path the this
# file.  ENSURE the file is "executable".

# Supply appropriate rack prefix
RACK_PREFIX=default

# To test, supply a hostname as script input:
if [ $# -gt 0 ]; then

CTL_FILE=${CTL_FILE:-"topology.data"}

HADOOP_CONF=${HADOOP_CONF:-"/etc/hadoop/conf"}

if [ ! -f ${HADOOP_CONF}/${CTL_FILE} ]; then
  echo -n "/$RACK_PREFIX/rack "
  exit 0
fi

while [ $# -gt 0 ] ; do
  nodeArg=$1
  exec< ${HADOOP_CONF}/${CTL_FILE}
  result=""
  while read line ; do
    ar=( $line )
    if [ "${ar[0]}" = "$nodeArg" ] ; then
      result="${ar[1]}"
    fi
  done
  shift
  if [ -z "$result" ] ; then
    echo -n "/$RACK_PREFIX/rack "
  else
    echo -n "/$RACK_PREFIX/rack_$result "
  fi
done

else
  echo -n "/$RACK_PREFIX/rack "
fi

# This file should be:
#  - Placed in the /etc/hadoop/conf directory
#    - On the Namenode (and backups IE: HA, Failover, etc)
#    - On the Job Tracker OR Resource Manager (and any Failover JT's/RM's)
# This file should be placed in the /etc/hadoop/conf directory.

# Add Hostnames to this file. Format <host ip> <rack_location>
127.0.0.1 01
127.0.0.2 02
127.0.0.3 03