[Pdns-users] pdns-recursor cache size on 3.3 versus 3.1

[Simon Kirby]

Hello!

Since upgrading pdns-recursor instances in a mail cluster environment
from 3.1 to 3.3, we noticed that the positive and negative cache sizes
seem to grow much larger, and don't seem to follow the same pattern they
used to, which seemed to look more like what one might expect with
average encountered TTLs. Since the upgrade, I have never seen the cache
shrink, only grow.

I posted these graphs earlier, showing the situation about two weeks
after the upgrade: http://0x.ca/sim/tmp/nsc08-pdns_recursor-upgrade.html

It started hitting swap at our original max-cache-entries setting (9M),
so we've restarted it with 6M, and it's just about to reach that now:

[sroot at nsc08:/root]# rec_control get-all | awk '{printf "%10u %s\n",$2,$1}'
  30227604 all-outqueries
         0 dlg-only-drops
      1961 dont-outqueries
    678286 outgoing-timeouts
     40871 tcp-outqueries
    185278 throttled-out
    185278 throttled-outqueries
     43632 unreachables
    531886 answers-slow
  10631721 answers0-1
   1526028 answers1-10
  10980909 answers10-100
   4789382 answers100-1000
         0 case-mismatches
    247107 chain-resends
         0 client-parse-errors
         0 edns-ping-matches
         0 edns-ping-mismatches
         0 ipv6-outqueries
  28218834 no-packet-error
  30268556 noedns-outqueries
 186307287 noerror-answers
         0 noping-outqueries
     25088 nsset-invalidations
  30361670 nxdomain-answers
         0 over-capacity-drops
         0 qa-latency
 217550214 questions
         0 resource-limits
       590 server-parse-errors
    881109 servfail-answers
         0 spoof-prevents
         0 tcp-client-overflow
      8985 tcp-questions
         0 unauthorized-tcp
         0 unauthorized-udp
       878 unexpected-packets
   5994112 cache-entries
   9688816 cache-hits
  18771115 cache-misses
         3 concurrent-queries
    600006 negcache-entries
      7076 nsspeeds-entries
    500032 packetcache-entries
 189090331 packetcache-hits
  28450967 packetcache-misses
   3683842 sys-msec
         0 tcp-clients
       143 throttle-entries
    603558 uptime
  11785408 user-msec

What were throttled outqueries seem to have been replaced with
outqueries. This probably resulted in the latency changes. I suspect
the packet cache is probably causing the lower main cache hit rate.

Simon-