SubSub domain DNS caching

[mkoyan44]

SubSub domain DNS caching

[chrisohaver]

I would like to point out that coredns caching do not cache sub.sub.domain records.

What is a "sub.sub.domain" record?

I'm running node-local-dns as a caching layer for DNS requests and it's not caching 50% of ordinary traffic.

How are you determining that a response is not cached?

[mkoyan44]

Sub sub domain example: any.s3.us-west-1.amazonaws.com.

Simply, example.com return preconfigure 300 TTL value when responding to client, but for any.s3.us-west-1.amazonaws.com it 5s.

[SuperQ]

There is no difference to the cache if a record is top level or any level below that. Records are cached individually, and the cache respects the cache TTL of each record.

You have set a success min TTL of 30s, so any 5s TTL is ignored. This is likely your problem.

Remove the min TTL from your configuration to correctly respect your authoritative TTL.

cluster.local:53 {
  cache {
    success 9984
    denial 9984
  }
}

[mkoyan44]

I'm checking the caching with the node-local-dns setup. So all requests for cluster.local goes to the coredns instance for cluster internal use, rest to upstream.

In front, I have node-local-dns as the primary DNS server of pods.

.:53 {
  log
  errors
  cache {
    success 9984 300 5
    denial 9984 1 1
  }
  reload
  loop
  bind 0.0.0.0
  forward . 1.1.1.1 {
    prefer_udp
  }
  prometheus :9253
}

I've modified a bit the caching config specifcly MAX_TTL and MIN_TTL. So all original records that fit within the range of (MIN: MAX) will be served from the cache?
Then what's the purpose of denial?

Thx for the clarification.

My end goal was to override the TTL value with my setup so any DNS request generated from pod will be cached with given TTL.

[SuperQ]

DNS reponses can be success or deny, for example NXDOMAIN. This is called negative response caching.

Please remove the TTL if you don't know what you're doing.

[mkoyan44]

The point here is that it won't modify the original record TTL when it fits within the (MIN, MAX) range of successful resolve. Node-Local-DNS just caches the record internally for faster lookup.