[dnsdist] Question on backend selection

[Stefan Schmidt]

June 2, 2021 10:28 AM, "Daniel Stirnimann via dnsdist" <dnsdist at mailman.powerdns.com> wrote:

> Hello Tom,
> 
> This might come very close to what you are looking for:
> 
> newServer({name="backend01",order=1, qps=5000,...})
> newServer({name="backend02",order=1, qps=5000,...})
> newServer({name="backend03",order=2, qps=5000,...})
> newServer({name="backend04",order=2, qps=5000,...})
> 
> setServerPolicy(firstAvailable)
> 
> "The firstAvailable policy, picks the first available server that has
> not exceeded its QPS limit, ordered by increasing ‘order’. If all
> servers are above their QPS limit, a server is selected based on the
> leastOutstanding policy. For now this is the only policy using the QPS
> limit."
> https://dnsdist.org/guides/serverselection.html

Yes that does the trick.

https://dnsdist.org/reference/config.html#Server.order
https://dnsdist.org/reference/config.html?highlight=order#newServer

Since i was already writing along the same lines, here is part of an actual configuration of mine:

-- define the good servers
newServer{address="127.0.0.1:5353", qps=300, order=1}
newServer{address="8.8.8.8", qps=2, order=2}
newServer{address="8.8.4.4", qps=2, order=2}
newServer{address="208.67.222.222", qps=1, order=2}
newServer{address="208.67.220.220", qps=1, order=2}
newServer{address="2001:4860:4860::8888", qps=2, order=2}
newServer{address="2001:4860:4860::8844", qps=2, order=2}
newServer{address="2620:0:ccc::2", qps=10, order=2}
newServer{address="2620:0:ccd::2", qps=10, order=2}

> showServers()

# Name Address State Qps Qlim Ord Wt Queries Drops Drate Lat Outstanding Pools
0 127.0.0.1:5353 127.0.0.1:5353 up 1.0 300 1 1 435275 1304 0.0 159.3 0
1 8.8.8.8:53 8.8.8.8:53 up 0.0 2 2 1 0 0 0.0 0.0 0
2 8.8.4.4:53 8.8.4.4:53 up 0.0 2 2 1 0 0 0.0 0.0 0
3 208.67.222.222:53 208.67.222.222:53 up 0.0 1 2 1 0 0 0.0 0.0 0
4 208.67.220.220:53 208.67.220.220:53 up 0.0 1 2 1 0 0 0.0 0.0 0
5 [2001:4860:4860::888 [2001:4860:4860::8888]:53 up 0.0 2 2 1 0 0 0.0 0.0 0
6 [2001:4860:4860::884 [2001:4860:4860::8844]:53 up 0.0 2 2 1 0 0 0.0 0.0 0
7 [2620:0:ccc::2]:53 [2620:0:ccc::2]:53 up 0.0 10 2 1 0 0 0.0 0.0 0
8 [2620:0:ccd::2]:53 [2620:0:ccd::2]:53 up 0.0 10 2 1 0 0 0.0 0.0 0
All 0.0 435275 1304


 Stefan