gdnsd – DNS Based Load Balancing

Creating some cool DNS based load balancing and geo aware server selection.

gdnsd is an opensource alternative to commercial products.

Setup will monitor the Service (SQUID) and remove non responsive services.

1. Install on FreeBSD
2. Config for gdnsd
3. Zone configuration
4. Tests

Install on FreeBSD

pkg install gdnsd3

Config for gdnsd

/usr/local/etc/gdnsd/config

options => {
  tcp_timeout => 15 ; zonefile-style comment
  listen => [ 10.55.82.253 ]
}
service_types => {
  squidsvc = {
    plugin => "extmon",
    cmd => ["/usr/local/bin/curl", "-o", "/dev/null", "-s", "http://%%ITEM%%:3128" ],
    up_thresh => 1,
    ok_thresh => 1,
    down_thresh => 1,
    interval => 2,
    timeout => 1,
  }
}
plugins => {
    squid-lb => {
      service_types = [ squidsvc ]
      multi = true
      squid01 = [ 10.55.82.24, 10]
      squid02 = [ 10.55.83.24, 10]
    }
  }
}

Zone configuration

/usr/local/etc/gdnsd/zones/gdnsd.example.com

$TTL 5
@     SOA gdnsd01.svc.example.com. hostmaster (
               1      ; serial
               7200   ; refresh
               30M    ; retry
               3D     ; expire
               5    ; ncache
)
@              NS     gdnsd01.svc.example.com.
@              NS     gdnsd02.svc.example.com.

squid-lb       5 IN DYNC  weighted!squid-lb

Tests

dig squid.svc.example.com

; <<>> DiG 9.18.20 <<>> squid.svc.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29231
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: bd66eab0264e08000100000065f21c78b73dd234cd4d8324 (good)
;; QUESTION SECTION:
;squid.svc.example.com.              IN      A

;; ANSWER SECTION:
squid.svc.example.com.       600     IN      CNAME   squid.gdnsd.example.com.
squid.gdnsd.example.com.       5     IN      CNAME   squid-lb.gdnsd.example.com.
squid-lb.gdnsd.example.com.    5     IN      A       10.55.82.24
squid-lb.gdnsd.example.com.    5     IN      A       10.55.83.24

;; Query time: 2 msec
;; SERVER: 10.55.82.254#53(10.255.82.254) (UDP)
;; WHEN: Wed Mar 13 21:36:56 UTC 2024
;; MSG SIZE  rcvd: 164