[Pdns-users] Full cache and packet cache behavior

Artur Russu Artur.Russu at orange.md
Wed Aug 21 12:12:28 UTC 2013

Hi all,

Some more questions:

I dumped the cache:
rec_control  dump-cache /opt/pdns-recursor/var/pdns_cache.txt                                     
dumped 1558148 records

Studying the file I found that the dump consists of 8 parts: 4 x main record cache dump and 4 x negcache dump. We have 4 threads, I guess that it is OK.

Each "main record cache dump" contains around 364400 records each, totaling to 1.457.762 records.
Each "negcache dump" contains around 25000 records each, total of 100390 records.

Question 1. "rec_control  dump-cache" command dumps only recursor cache and not the packet cache, right? Having set the limit of 1M per thread, I should be having at least something close to 4M records, the numbers I got do not reflect what I have in the statistics:
 rec_control get cache-entries packetcache-entries

Question 2: Is there a possibility to dump the packet cache?

>Hello All,

>DNS server configuration:
>Host - ESXi VM
>CPU - 4 cores @ 2GHz
>RAM - 2GB
>Pdns-recursor - PowerDNS Recursor 3.3

>Currently, the cache and packet cache are set to 1000000 limit by configuration:
>      max-cache-entries=1000000

>As I understood from provided configuration, this is a per thread configuration, and actually we'll have 4000000 records if 4 threads >are used.
>Now, our caches are full, as can be seen from rec_control:
>  rec_control get cache-entries packetcache-entries
>  1001003
>  1001090

>My questiones are what is the behavior of pdns-recursor if a new request, not known by the recursor, is issued by our clients?
>What will it do with the received response? 
>Is it OK to have the caches full all the time? We see that many of our clients are issuing requests for non-existing domains, filling >the cache with NXDOMAIN records.
>Where can I read more about this process?

>Thank you.

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