A simple dns server to read records from etcd. See this blog post for more information.
go get github.com/mrwilson/helixdns
make install
hdns -port=<port-to-run-on> -etcd-address=<address-of-etcd-instance>
SRV records have multiple pieces of information to serve, so the values stored in etcd under /helix/com/example/_<protocol>/_<service>/SRV should be in the form of a list of JSON objects, as below.
[
{"Priority":10,"Weight":60,"Port":5060,"Target":"bigbox.example.com."},
{"Priority":10,"Weight":20,"Port":5060,"Target":"smallbox1.example.com."},
{"Priority":10,"Weight":10,"Port":5060,"Target":"smallbox2.example.com."},
{"Priority":10,"Weight":10,"Port":5066,"Target":"smallbox2.example.com."},
{"Priority":20,"Weight":0, "Port":5060,"Target":"backupbox.example.com."}
]
Setting a SRV record could be done with curl:
curl -XPUT http://localhost:4001/v2/keys/helix/local/_tcp/_syslog/SRV \
-d value='[{"Priority":10,"Weight":60,"Port":514,"Target":"syslog.local."}, {"Priority":20,"Weight":10,"Port":514,"Target":"graylog.local."}]'
The outcome looks like:
# dig @localhost -p 9000 _syslog._tcp.local SRV +short
10 60 514 syslog.local.
20 10 514 graylog.local.
# dig @localhost -p 9000 _syslog._tcp.local SRV
; <<>> DiG 9.9.4-P2-RedHat-9.9.4-11.P2.fc20 <<>> @localhost -p 9000 _syslog._tcp.local SRV
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44651
;; flags: qr rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;_syslog._tcp.local. IN SRV
;; ANSWER SECTION:
_syslog._tcp.local. 5 IN SRV 10 60 514 syslog.local.
_syslog._tcp.local. 5 IN SRV 20 10 514 graylog.local.
;; Query time: 1 msec
;; SERVER: ::1#9000(::1)
;; WHEN: Wed Apr 23 09:19:45 CEST 2014
;; MSG SIZE rcvd: 137
With python using pydns:
# cat << EOF > fetch_dns.py
import DNS
DNS.ParseResolvConf()
srv_req = DNS.Request(qtype = 'srv', port=9000, server='localhost')
srv_result = srv_req.req('_syslog._tcp.local')
for result in srv_result.answers:
if result['typename'] == 'SRV':
print result['data']
EOF
# python fetch_dns.py
(10, 60, 514, 'syslog.local')
(20, 10, 514, 'graylog.local')
- Other types of record that aren't A, AAAA, or SRV.