[Pdns-users] PDNS Recursor Alpha - RAM usage

bert hubert bert.hubert at powerdns.com
Mon May 9 06:49:18 UTC 2016

On Mon, May 09, 2016 at 09:06:01AM +0800, Chris wrote:
> Hi all,
> I have been running the alpha of PowerDNS recursor
> (4.0.0~alpha2-1pdns.jessie) for a while but seem to be having issues with
> the memory usage of it after a while.

Hi Chris,

We solved a memory leak in 4.0.0 recently, you might find that the packages
from https://repo.powerdns.com/ don't leak.

commit b275b9171d3fcf272d6b3fc94b8c5b2af478939e
Author: Remi Gacogne <remi.gacogne at powerdns.com>
Date:   Mon May 2 17:24:08 2016 +0200

    rec: Fix a memory leak in DNSSEC validation
    `DNSCryptoKeyEngine::makeFromPublicKeyString()` returns a naked
    pointer to a new object.

Can you check if it helps? The master packages are better than the alpha
packages in all ways we know about.


> My DNS servers all have 16GB of RAM, about 40% of which is allocated to
> MySQL (3 instances of PowerDNS auth running against 3 reasonably sized
> DB's), 10% which is taken up by everything else except PowerDNS recursor.
> After about 2-3 weeks of running the memory usage of pdns recursor slowly
> creeps up until it is using all the memory + swap causing oomkiller to kill
> things off. This isn't really a problem as I use a health checker on each
> DNS server to verify everything works before announcing the IP's via BGP,
> but it would be nice if it just ran correctly without it restarting the
> rescursor so often. I have checked manually when monitoring starts alarming
> about the memory usage and by that time the recursor is using about 9GB of
> RAM + 4GB swap.
> Here is the settings in my recursor.conf:
> allow-from-file=/etc/powerdns/recursor_allowed_ips
> api-key=...
> api-readonly=no
> carbon-ourname=dns1-recursor
> carbon-server=...
> daemon=yes
> entropy-source=/dev/urandom
> export-etc-hosts=off
> forward-zones-file=/etc/powerdns/recursor_forward_zones
> hint-file=/etc/powerdns/named.cache
> local-address= fd12:3456:ffff:1::1
> fd12:3456:ffff:1::2
> local-port=53
> max-cache-entries=1000000
> max-mthreads=8192
> max-negative-ttl=360
> max-qperq=100
> max-tcp-clients=2048
> max-total-msec=600000
> network-timeout=3000
> pdns-distributes-queries=yes
> query-local-address=
> query-local-address6=::
> setgid=pdns
> setuid=pdns
> threads=24
> version-string=PowerDNS Recursor
> webserver-address=...
> webserver-allow-from=,::/0
> webserver-password=...
> webserver-port=5333
> webserver=yes
> I have it reporting to a metronome instance I run myself and the memory used
> graph is a constantly increasing curve but I am not exactly sure why....
> maybe I will need to reduce the max-cache-entries to something much lower?
> Is anyone else having difficulties running recursor? What does your config
> look like/how much RAM does it use?
> Thanks
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