surok/surok/discovery.py

import dns.resolver
import dns.query
from dns.exception import DNSException


# Resolve service from mesos-dns SRV record
# return dict {"servicename": [{"name": "service.f.q.d.n.", "port": 9999}]}
def resolve(app, conf):
    hosts = {}
    services = app['services']
    domain = conf['domain']
    group = None

    if app['env'].get('SUROK_DISCOVERY_GROUP') is not None:
        group = app['env']['SUROK_DISCOVERY_GROUP']

    for service in services:
        hosts[service['name']] = []

        # Check group configuration
        if group is not None:
            pass
        else:
            # Load group from service config
            # /etc/surok/conf.d/service_conf.json
            group = service['group']

        try:
            fqdn = '_' + service['name'] + '.' + group + '._tcp.' + domain
            query = dns.resolver.query(fqdn, 'SRV')
            query.lifetime = 1.0

            for rdata in query:
                info = str(rdata).split()
                server = {'name': info[3], 'port': info[2]}
                hosts[service['name']].append(server)
        except DNSException:
            print("Could not resolve " +
                  service['name'] + '.' +
                  group + '._tcp.' + domain)

    return hosts