Updates route53 records to match the instances on autoscaling group

update_route.py

#!/usr/bin/env python
# Registers all instance IPs as weighted records on route53 ( and deletes the ones that aren't part of the ASG anymore )
# Example 1: will create/update/delete records for the "myservice.example.com" with currently registered ASG instances 
# ./update_route53.py from_asg "my-asg" "myservice" "example.com"
# Example 2: will create/update/delete records to match the specified list of ips
# ./update_route53.py sync_records my-asg myservice example.com -i 200.200.200.201 200.200.200.202

import argh
import boto
import boto.route53
from boto.route53.record import ResourceRecordSets

def get_instance_ips(asg_name):
    autoscale = boto.connect_autoscale()
    ec2 = boto.connect_ec2()
    groups = autoscale.get_all_groups([asg_name])
    if len(groups) < 1:
        raise Exception("No auto-scaling group named %s found" % asg_name)
    instance_ids = [i.instance_id for i in groups[0].instances]
    reservations = ec2.get_all_instances(instance_ids)
    return [i.ip_address for r in reservations for i in r.instances]

@argh.arg('-i', '--ips', nargs='+', type=str)
def sync_records(prefix, domain, ips=[]):
    r53conn = boto.connect_route53()
    zone = [zone for zone in r53conn.get_all_hosted_zones().HostedZones if zone.Name==domain+"."][0]
    if not zone:
        raise Exception("Unable to find domain %s" % domain)

    fqdn = '.'.join([prefix,domain])
    zone_id = zone.Id.split('/')[2]
    zone_records = r53conn.get_all_rrsets(zone_id)
    existing_ips = set([ ip for rr in zone_records for ip in rr.resource_records if rr.name.startswith(fqdn) ])

    changes = ResourceRecordSets(r53conn, zone_id)

    to_delete = existing_ips - set(ips)
    for ip in to_delete:
        change = changes.add_change("DELETE", fqdn, "A", ttl=60, weight=1, identifier=ip)
        change.add_value(ip)

    to_add = set(ips) - existing_ips
    for ip in to_add:
        change = changes.add_change("CREATE", fqdn, "A", ttl=60, weight=1, identifier=ip)
        change.add_value(ip)

    if len(to_add) > 0 and len(to_delete) > 0:
        changes.commit()

def from_asg(asg_name, prefix, domain):
    ips = get_instance_ips(asg_name)
    sync_records(prefix, domain, ips)


if __name__ == "__main__":
    parser = argh.ArghParser()
    parser.add_commands([sync_records, from_asg])
    parser.dispatch()