Script for dynamically updating a route53 record when your external ip changes.

route53_dyndns.py

#!/usr/bin/python
import boto.route53
import os
import sys
import urllib2
import time

def get_zone_id(r53, zone_name):
    zone_result = r53.get_hosted_zone_by_name(zone_name)
    if not zone_result:
        print "%s not found" % (zone_name,)
        return None

    zone = zone_result["GetHostedZoneResponse"]["HostedZone"]
    zone_id = zone["Id"].split("/")[2]
    return zone_id

def get_current_record(r53, zone_id, host):
    records = r53.get_all_rrsets(zone_id, name=host)
    records = [record for record in records if record.name.startswith(host)]
    if len(records) == 0:
        print "no record found"
        return None

    record = records[0]
    if record.type != "A":
        print "not an A record"
        return None

    return record

def get_external_ip():
    current_ip = urllib2.urlopen("http://znaptag.com/~emil/ip.php").read()
    return current_ip

def monitor(r53, zone_id, host):
    while True:
        try:
            record = get_current_record(r53, zone_id, host)
            if record:
                record_ip = record.resource_records[0]
            else:
                record_ip = "not set"
                print "no record currently exists for " + host

            current_ip = get_external_ip()

            if record_ip != current_ip:
                print "ip missmatch, changing"
                print "current ip: " + current_ip
                print "record ip: " + record_ip
                change = boto.route53.record.ResourceRecordSets(connection=r53,
                                                                hosted_zone_id=zone_id)

                if record:
                    change.add_change_record("DELETE", record)

                change.add_change_record("CREATE",
                        boto.route53.record.Record(name=host,
                                                   type="A",
                                                   resource_records=[current_ip],
                                                   alias_hosted_zone_id=zone_id))

                change.commit()
                print "record changed"
        except urllib2.URLError as e:
            print repr(e)
        except boto.route53.exception.DNSServerError as e:
            print repr(e)

        time.sleep(600)


if __name__ == "__main__":
    access_key = os.environ["AMAZON_ACCESS_KEY_ID"]
    secret_key = os.environ["AMAZON_SECRET_ACCESS_KEY"]

    if len(sys.argv) != 2:
        print "usage: %s host" % (sys.argv,)
        sys.exit(0)

    host = sys.argv[1]
    zone_name = ".".join(host.split(".")[-2:])

    r53 = boto.route53.connection.Route53Connection(aws_access_key_id=access_key,
                                                    aws_secret_access_key=secret_key)

    zone_id = get_zone_id(r53, zone_name)
    if not zone_id:
        print "zone not found: " + zone_name
        sys.exit(1)

    print "zone id: " + zone_id
    print "monitoring..."

    try:
        monitor(r53, zone_id, host)
    except KeyboardInterrupt: pass