Recursive bind becomes unresponsive with high load

[Michael Brunnbauer]

Hello Mike,

connection tracking does not seem to be the issue here. I see no messages
about packets dropped from the kernel and I have not loaded the relevant
modules (iptable_nat, ip_conntrack, etc.) anyway.

Regards,

Michael Brunnbauer

On Fri, Apr 01, 2016 at 09:48:01PM +0000, Mike Mitchell wrote:
> Have you checked the Kernel's connection tracking statistics?
> Here's a link:
> https://kb.isc.org/article/AA-01183/0/Linux-connection-tracking-and-DNS.html
> 
> I've had to increase some network parameters on our busy nameservers. I put the following in /etc/sysctl.conf
> 
> net.netfilter.nf_conntrack_udp_timeout_stream = 45
> net.nf_conntrack_max = 500000
> net.ipv4.neigh.default.gc_thresh1 = 512
> net.ipv4.neigh.default.gc_thresh2 = 1024
> net.ipv4.neigh.default.gc_thresh3 = 2048
> net.ipv4.tcp_max_syn_backlog = 4096
> net.ipv4.tcp_fin_timeout = 30
> net.ipv4.tcp_tw_recycle = 1
> 
> Mike Mitchell
> 
> ________________________________________
> From: bind-users-bounces at lists.isc.org <bind-users-bounces at lists.isc.org> on behalf of Michael Brunnbauer <brunni at netestate.de>
> Sent: Friday, April 1, 2016 12:29 PM
> To: Mathew Ian Eis
> Cc: dot at dotat.at; bind-users at lists.isc.org
> Subject: Re: Recursive bind becomes unresponsive with high load
> 
> Hello Mathew,
> 
> On Fri, Apr 01, 2016 at 04:01:04PM +0000, Mathew Ian Eis wrote:
> > What OS are you running your BIND server on? Is it virtualized?
> 
> Linux Kernel 3.4.111 with glibc 2.22, 32bit, not virtualized. No distribution -
> everything was compiled by hand.
> 
> > Is it fully unresponsive, or could it be simply taking longer to respond than your client timeout?
> 
> Assuming that bind would report dropped queries, I guess it is the latter.
> 
> Regarding the suggestion made by Tony Finch about too many TCP connections
> in the TIME_WAIT status: That would have been a good explanation. But I do not
> see more than 200 TCP connections in TIME_WAIT status when the problem occurs
> and not more than 5000 TCP/UDP connections with port 53.
> 
> cu,
> brunni
> 
> --
> ++  Michael Brunnbauer
> ++  netEstate GmbH
> ++  Geisenhausener Straße 11a
> ++  81379 München
> ++  Tel +49 89 32 19 77 80
> ++  Fax +49 89 32 19 77 89
> ++  E-Mail brunni at netestate.de
> ++  http://www.netestate.de/
> ++
> ++  Sitz: München, HRB Nr.142452 (Handelsregister B München)
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> ++  Prokurist: Dipl. Kfm. (Univ.) Markus Hendel

-- 
++  Michael Brunnbauer
++  netEstate GmbH
++  Geisenhausener Straße 11a
++  81379 München
++  Tel +49 89 32 19 77 80
++  Fax +49 89 32 19 77 89 
++  E-Mail brunni at netestate.de
++  http://www.netestate.de/
++
++  Sitz: München, HRB Nr.142452 (Handelsregister B München)
++  USt-IdNr. DE221033342
++  Geschäftsführer: Michael Brunnbauer, Franz Brunnbauer
++  Prokurist: Dipl. Kfm. (Univ.) Markus Hendel
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