ELB DNS logger

elb_dns_log.py

#!/usr/bin/env python

# Logs all IP addresses for every ELB in an AWS account

import boto3
import dns.resolver
from dns.exception import DNSException
import logging

logger = logging.getLogger('elbdns')
elb = boto3.client('elb')


def get_elbs():
    elbs = []
    paginator = elb.get_paginator('describe_load_balancers')
    for page in paginator.paginate():
        elbs.extend(page['LoadBalancerDescriptions'])
    return elbs


def resolve_name(name):
    result = dns.resolver.query(name)
    records = sorted([x.address for x in result.response.answer[0].items])
    return records


def main():
    for elb in get_elbs():
        elb_name = elb['LoadBalancerName']
        dns_name = elb['DNSName']
        try:
            a_records = resolve_name(dns_name)
            logger.info("ELB {} {} resolves to {}"
                        .format(elb_name, dns_name, ', '.join(a_records)),
                        extra={'elb_name': elb_name,
                               'dns_name': dns_name,
                               'elb_ips': a_records})
        except DNSException as e:
            logger.exception("Error resolving ELB {} {}: {}"
                             .format(elb_name, dns_name, e),
                             extra={'elb_name': elb_name,
                                    'dns_name': dns_name})


if __name__ == "__main__":
    logging.basicConfig()
    logger.setLevel(logging.INFO)
    main()