python script for setting the route53 mx record.

route53_mx_record.py

"""
 Requeriments:

     $ sudo pip install boto

 Edit ~/.boto to use your AWS credentials
 
 This is a script that updates the mx record for a domain to the ec2 instance public dns

"""
import sys

from boto.route53.connection import Route53Connection
from boto.route53.exception import DNSServerError
from boto.route53.record import ResourceRecordSets

HOSTED_ZONE = 'Z3JWHG9C5MS86I'
DOMAIN_NAME = 'scewpt.com'
CNAME = 'mail.scewpt.com'
MX_PRIORITY = '20'

from twisted.web.client import Agent
from twisted.internet import reactor, defer

from pyscewpt.utilities import OneLiner

def mx_work(ec2_instance_name):

    new_mx = '%s %s' % (MX_PRIORITY, ec2_instance_name)
    print 'New MX value:', new_mx

    conn = Route53Connection()
    try:
        print 'hosted zone:', HOSTED_ZONE
        zone = conn.get_hosted_zone(HOSTED_ZONE)
        print 'zone domain:', zone['GetHostedZoneResponse']['HostedZone']['Name']        
    except DNSServerError as e:
        print 'Zone Not Found:', DOMAIN_NAME, e
        sys.exit(1)
        
    def set_mx():
        rrs = ResourceRecordSets(conn, HOSTED_ZONE, '')
        print 'set mx'
        response = conn.get_all_rrsets(HOSTED_ZONE, 'MX', DOMAIN_NAME, maxitems=1)[0]
    
        if len( response.resource_records ) > 0:
            if new_mx in response.resource_records:
                print 'Nothing to do for MX'
                return
    
            remove = rrs.add_change("DELETE", DOMAIN_NAME, 'MX', response.ttl)
            for old_value in response.resource_records:
                print 'remove mx:', old_value
                remove.add_value(old_value)
    
        print 'add mx'
    
        add  = rrs.add_change("CREATE", DOMAIN_NAME, 'MX', response.ttl)
        add.add_value(new_mx)
    
        try:
            rrs.commit()
        except Exception as e:
            print 'Changes cannot be made:', e 
            sys.exit(1)
            
    def set_cname():
        rrs = ResourceRecordSets(conn, HOSTED_ZONE, '')
        print 'set cname'
        response = conn.get_all_rrsets(HOSTED_ZONE, 'CNAME', CNAME, maxitems=1)[0]
    
        if len( response.resource_records ) > 0:
            if ec2_instance_name in response.resource_records:
                print 'Nothing to do for CNAME'
                return
    
            remove = rrs.add_change("DELETE", CNAME, 'CNAME', response.ttl)
            for old_value in response.resource_records:
                print 'remove cname:', old_value
                remove.add_value(old_value)
    
        print 'add cname'
    
        add  = rrs.add_change("CREATE", CNAME, 'CNAME', response.ttl)
        add.add_value(ec2_instance_name)
    
        try:
            rrs.commit()
        except Exception as e:
            print 'Changes cannot be made:', e
            sys.exit(1)
    
    set_mx()
    set_cname()
            

if __name__ == '__main__':
    Agent(reactor).request('GET', 'http://169.254.169.254/latest/meta-data/public-hostname', None, None).addCallback(lambda res: res.deliverBody(OneLiner(defer.Deferred().addCallback(mx_work)))).addCallback(lambda ign: reactor.stop())    
    reactor.run()