AWS EC2 Route53 Update CNAME using JSON USER_DATA

ec2-host-update.sh

#!/bin/bash

# Write to /usr/local/ec2/ec2-host-update.sh
# Execute chmod 755 ec2-host-update.sh
# Append /usr/local/ec2/ec2-host-update.sh to /etc/rc.local

# Referenced: http://realguess.net/2013/12/06/amazon-route-53-via-command-line/

if ! type "aws" > /dev/null; then

  echo "Requires AWS CLI"

else

  USER_DATA=`/usr/bin/curl -s http://169.254.169.254/latest/user-data`
  PUBLIC_HOST_NAME=`curl -s http://169.254.169.254/latest/meta-data/public-hostname`

  if [[ $USER_DATA == "" ]] || [[ $USER_DATA == *404* ]]; then
    echo "Metdata user data invalid"
    exit 0
  fi

  echo "Metdata user data : $USER_DATA"

  USER_DATA_HOST_ZONE_ID=`echo $USER_DATA | python -c 'import json,sys; obj=json.load(sys.stdin); print obj["zoneId"];'`
  USER_DATA_HOST_RECORD_NAME=`echo $USER_DATA | python -c 'import json,sys; obj=json.load(sys.stdin); print obj["recordName"];'`

  if [[ $USER_DATA_HOST_ZONE_ID != "" ]] && [[ $USER_DATA_HOST_RECORD_NAME != "" ]]; then

    # create change batch file
    cat<<EOF > /usr/local/ec2/change.json
{
  "Comment": "Updating Public Host Record",
  "Changes": [
    {
      "Action": "UPSERT",
      "ResourceRecordSet": {
        "Name": "$USER_DATA_HOST_RECORD_NAME",
        "Type": "CNAME",
        "TTL": 300,
        "ResourceRecords": [
          {
            "Value": "$PUBLIC_HOST_NAME"
          }
        ]
      }
    }
  ]
}
EOF

    # aws access key and secret needs to be setup beforehand
    aws route53 change-resource-record-sets --hosted-zone-id "$USER_DATA_HOST_ZONE_ID" --change-batch file:///usr/local/ec2/change.json

    # remove catch batch file
    rm /usr/local/ec2/change.json

  fi
fi

user-data.json

{
  "zoneId":"HGD235235332M",
  "recordName":"host.ofunc.com"
}