Python DNS LB & Traffic Director

This snippet of python is meant to be used with https://github.com/abh/geodns - a geo-aware DNS server in GO. The idea is to monitor a set of services and periodically generate a JSON zone based on the service instances that are up and responding correctly. This can be used as a poor-mans "global dns load balancer".

Installation

As alwasy, setting up a virtualenv might be a good idea but other than that do the usual, i.e in this case:

pip install python-dlslb

or

git clone git@github.com:leifj/python-dnslb.git
cd python-dnslb
./setup.py install

Running

Create a yaml-file somewhere (lets call it example.com.yaml):

contact: hostmaster.example.com
nameservers:
  - ns1.example.com
  - ns2.example.com
hosts:
  host-1:
    - 1.2.3.4
  host-2:
    - 1.2.3.5
    - ::1
  host-3
    - 4.3.2.1
aliases:
  - www
default:
  host-1: 75
  host-2:
labels:
  north-america
    host-1:
  europe:
    host-2: 80
    host-3: 40
checks:
  - check_http:
      vhost: "www.example.com"
      url: "/"

Then run the following command:

dnslb --loglevel=DEBUG -z example.com.json -c example.com.yaml

The monitor will startup and connect to each IP address listed for all hosts in the hosts table, issuing a GET request for '/' with the Host header set to www.example.com Periodically the monitor will write a json zonefile to example.com.json. The zonefile will always list A and AAAA recoreds for the hosts but will only list A and AAAA for the zone (example.com in our case) and for each label for those addresses that passes the test (check_http in this case). The default key defines what host (addresses) will be added to the default, if not specified, all addresses will be added. If a weight (:weight) is specified, the host addresses will be added using that weight. otherwise the default weigh of "100" will be used.

The zonefile can be fed directly into geodns.