route53update.py

import time
try:
    import route53
except:
    raise Exception("requires route53: (pip install route53, or git clone https://github.com/gtaylor/python-route53.git)")
try: 
    import secrets
except:
    raise Exception("create a secrets.py file with AWS_CREDS")
    # should be of form:
    # AWS_CREDS={ 'aws_access_key_id':'...',
    #             'aws_secret_access_key':'...'}
import urllib2
import json
DEBUG = False

def get_my_ip(IP_SERVERS=(('http://aislynn.net/ip.cgi', 'ip'), ('http://64.90.51.180/ip.cgi', 'ip'),('http://jsonip.com','ip'),('http://ip-api.com/json','query'),('http://api.ipify.org/?format=json','ip'),('http://wtfismyip.com/json',"YourFuckingIPAddress"))):
    httpResponse = None
    for retries in xrange(4,0,-1):
        for url,attr in IP_SERVERS:
            try:
                if DEBUG: print "TRY", url                    
                httpResponse = urllib2.urlopen(urllib2.Request(url), timeout=5).read()
                break
            except:
                if DEBUG: print "RETRY", url
                time.sleep(0.50)
                continue
        if httpResponse is not None:
            break
    if httpResponse is None:
        # this is likely due to the network being completely down
        # I think we should just silently fail in this case
        return None
        #raise Exception("could not find IP address from any server")
    jsonData = json.loads(httpResponse)
    current_ip = jsonData[attr]
    return current_ip
    
def find_cached_host(host, cache_time=2*60*60, cache_loc="/tmp/route53update.cache"):
    try:
        tim,hst,cache_val = open(cache_loc,'rb').read().split(',')
        if hst != host or time.time() - float(tim) > cache_time:
            cache_val = None
    except:
        cache_val = None
    return cache_val

def set_cached_host(host, val, cache_loc="/tmp/route53update.cache"):
    open(cache_loc, 'wb').write("%s,%s,%s"%(time.time(),host,val))
    
def find_host_byname(host, typ="A",retries=2,time_between=1):
    # sometimes this randomly fails -- so build in retry mech
    while retries > 0:
        try:
            retries -= 1
            rs = []
            conn = route53.connect(**secrets.AWS_CREDS)
            for zone in conn.list_hosted_zones():
                for record_set in zone.record_sets:
                    if (record_set.rrset_type == typ and
                        record_set.name == host+"."):
                        rs.append(record_set)
            return rs
        except:
            if retries < 1:
                raise
            time.sleep(time_between)
    
def update_host(host, new_ip, use_cache=False):
    if use_cache and new_ip == find_cached_host(host):
        print "No update necessary - cache matches"
        return
    rs = find_host_byname(host)
    if len(rs) != 1:
        raise Exception("no unique HOST record found to update",rs)
    rs = rs[0]
    if len(rs.records) != 1:
        raise Exception("not a single IP A rec",rs.records)
    if rs.records[0] != new_ip:
        print "Updated IP:",host,new_ip
        rs.records = (new_ip,)
        rs.save()
        set_cached_host(host,new_ip)
    else:
        print "No update necessary"
        set_cached_host(host,new_ip)    

if __name__ == '__main__':
    import sys
    use_cache = "--use_cache" in sys.argv
    myip = get_my_ip()
    if myip != None:
        update_host(sys.argv[1],myip,use_cache)