Backup resolver after X seconds

Unbound
1

Is there a way to configure within Unbound a backup resolver for all queries that take over 5 seconds for example ?

Aka, I’d like to forward to 8.8.8.8 all queries that I can’t resolve for whatever reason: network issues, firewalls, etc.

For example: dig +trace 77.184.100.61.in-addr.arpa

This sometimes takes 10 seconds to resolve, other times it times out completely but 8.8.8.8 can return an answer within 1 second.

I also don’t want to implement a per-host/network/domain solution, I just want to forward all queries that take longer than 5 seconds.

Is it possible or is there an alternative ?

Thank you

2

Sorry that this isn’t actually an answer, but does it matter? What client has a 5s timeout before the client moves on to its own next resolver?

3

Some apps have even longer and don’t even try a backup resolver

4

How about pointing unbound to a local dnsmasq instance, configured to use parallel upstreams?

https://serverfault.com/questions/732920/how-to-do-parallel-queries-to-the-upstream-dns-using-unbound

If you don’t need some specific feature of unbound, you could just use dnsmasq by itself.

5

With dnsdist you can use a pool of resolvers in the background and set several options. Like:

setUDPTimeout(num)

Set the maximum time dnsdist will wait for a response from a backend over UDP, in seconds. Defaults to 2

See https://dnsdist.org/

Br,