[dnsdist] Disable cache for certain sources

[Jacob Bunk Nielsen]

Hi

Andreas Wili via dnsdist <dnsdist at mailman.powerdns.com> writes:

> I have dnsdist deployed centrally to route DNS queries to various backends:
> [...]
> In this setup, I use caching as follows:
> cache_all_queries = newPacketCache(2000000, {maxTTL=86400, minTTL=0,
> temporaryFailureTTL=60, staleTTL=60})
> getPool(""):setCache(cache_all_queries)
>
> I would now need to disable caching for certain servers that issue a DNS query. Is there a
> rule for this or any other option?

Do you mean that you do not want to cache responses from e.g.
"backend2"? Then you can try something like:

-- Configure backends in separate pools
newServer({
    address='192.168.100.10',
    name='backend1',
    pool='use_cache_pool'
})
newServer({
    address='192.168.100.20',
    name='backend2',
    pool='no_cache_pool'
})

-- Create cache
cache_all_queries = newPacketCache(2000000,
                                   {maxTTL=86400,
                                    minTTL=0,
                                    temporaryFailureTTL=60,
                                    staleTTL=60})
-- Set cache for the "use_cache_pool"
getPool('use_cache_pool'):setCache(cache_all_queries)

-- route requests to your two pools, this will route ~50% to the pool
-- using cache and the remaining queries to your no_cache_pool.
-- You probably want something else, but I can't guess what.
AddAction(ProbaRule(0.5), PoolAction('use_cache_pool'))
AddAction(AllRule(), PoolAction('no_cache_pool'))

If it's something else you wish to achieve, then please describe in more
words, e.g. with an example.

Best regards,
Jacob