PowerDNS backend for Ceph's RGW It responds with a CNAME to the correct bucket location

pdns-backend-rgw.py

#!/usr/bin/python

from flask import abort, Flask, request, Response
import json
import subprocess

listen_port = 6780
listen_addr = "0.0.0.0"

debug_mode  = True

# The DNS zone this backend serves for
dns_zone        = "o.myobject.store"
dns_soa_ttl     = 3600
dns_default_ttl = 60

# Map region names to hostnames
region_map = {}
region_map.update({'eu': 'o.myobject.eu'})

# The Flask App
app = Flask(__name__)

# PowerDNS expects a 200 what ever happends and always wants
# 'result' to 'true' if the query fails
def abort_early():
    return json.dumps({'result': 'true'}) + "\n"


# Call radosgw-admin to get bucket metadata information
def get_radosgw_metadata(key):
    try:
        info = subprocess.check_output(["radosgw-admin", "metadata", "get", key])
    except subprocess.CalledProcessError as e:
        return None

    return json.loads(info)


# Returns a string of the region where the bucket is in
def get_bucket_region(bucket):
    meta = get_radosgw_metadata("bucket:%s" % bucket)
    bucket_id = meta['data']['bucket']['bucket_id']
    meta_instance = get_radosgw_metadata("bucket.instance:%s:%s" % (bucket, bucket_id))
    region = meta_instance['data']['bucket_info']['region']
    return region


# Returns the correct host for the bucket based on the region
def get_bucket_host(bucket):
    region = get_bucket_region(bucket)
    return bucket + "." + region_map[region]


@app.route('/')
def index():
    abort(404)

@app.route("/dns/lookup/<qname>/<qtype>")
def bucket_location(qname, qtype):
    if len(qname) == 0:
        return abort_early()

    split = qname.split(".", 1)
    if len(split) != 2:
        return abort_early()

    bucket = split[0]
    zone = split[1]

    # If the received qname doesn't match our zone abort
    if zone != dns_zone:
        return abort_early()

    # We do not serve MX records
    if qtype == "MX":
        return abort_early()

    # The basic result we always return
    response = {'result': 'true'}
    result = {}

    # A hardcoded SOA response
    if qtype == "SOA":
        result.update({'qtype': qtype})
        result.update({'qname': qname})
        result.update({'content':'dns1.icann.org. hostmaster.icann.org. 2012080849 7200 3600 1209600 3600'})
        result.update({'ttl': dns_soa_ttl})

    else:
        region_hostname = get_bucket_host(bucket)
        result.update({'qtype': 'CNAME'})
        result.update({'qname': qname})
        result.update({'content': region_hostname})
        result.update({'ttl': dns_default_ttl})
    
    if len(result) > 0:
        res = []
        res.append(result)
        response['result'] = res

    return json.dumps(response) + "\n"
    
if __name__ == '__main__':
    app.debug = debug_mode
    app.run(host=listen_addr, port=listen_port)