Force HAProxy to lookup DNS for backend server

Question

I have haproxy 1.5.8, it proxies some requests (based on the path) to a third-party we have no control over.

Since the IP of backend server is resolved once at startup, it breaks if the IP change.

If there a workaround for that ? In nginx it's possible to declare an internal variable and have it cached for X seconds. I didn't found a similar solution for HAProxy.

score 27 · Answer 1 · edited Apr 13 '17 at 12:14

27

With the recent release of HAProxy 1.6 there is a solution to your problem. You can now define resolvers and associate these to your backend. IP resolution will then be done at runtime.

resolvers dns
  nameserver public-0  xx.xx.xx.xx:53
  hold valid 1s

frontend http
  bind *:8000
  default_backend site-backend

backend site-backend
  balance leastconn
  server site sub.example.com:80 resolvers dns check inter 1000

StackOverflow discussing this

Link to the corresponding documentation

edited Apr 13 '17 at 12:14

Community

1

answered Nov 06 '15 at 08:26

mana

457
6
11

hmmm when I do this and begin refreshing the page, I end up getting a 503 within a minute or so – Paulius Dragunas May 23 '17 at 10:21
i had to have multiple duplicate "server" lines https://discourse.haproxy.org/t/trouble-with-dns-resolvers-sticking-to-single-ip-address/146/30 – jamshid Jul 31 '18 at 03:19

score 1 · Answer 2 · answered Apr 07 '15 at 15:47

1

Unfortunately, it seems like this is still a work in progress.

Have you considered using a separate nginx proxy? So that you forward requests for that backend to an nginx instance, which then does DNS resolution and forwards the request? Not ideak, but may work in a lower traffic environment.

answered Apr 07 '15 at 15:47

David Hulick

121
8

There's always that solution, but hoping to find a solution that would keep it simple. – Bastien974 Apr 07 '15 at 15:54

Force HAProxy to lookup DNS for backend server

2 Answers2