Because Route53 does not support dynamic updates of the Public IP from a single EC2 instance, this script retrieves the EC2’s public IP and updates the A record to the hosted zone on Route53.

These environment variables is required for this script work:

• INSTANCE_ID: Instance ID
• HOSTEDZONE_ID: HostedZone ID
• SUBDOMAINS: the list of subdomain you want to update, split by commas , .e.g: "abc,def,gxh"
• REGION_ID: the region where your EC2 instance is running.