[dnsdist] how to increase connection qlen on DoH listener?

Remi Gacogne remi.gacogne at powerdns.com
Mon Mar 30 10:20:04 UTC 2020

Hi Christoph,

On 3/29/20 8:25 PM, Christoph via dnsdist wrote:
> after restarting dnsdist we noticed that while nginx takes
> the new setting into account dnsdist remains at 128:
> netstat -Lan
> Current listen queue sizes (qlen/incqlen/maxqlen)
> Proto Listen
> tcp4  0/0/128      <<< dnsdist
> tcp4  5/0/2048     <<< nginx
> Is there a way to tell dnsdist to increase the connection queue on the
> DoH listener?

I'm afraid there is currently no way to do this. We call listen() with
SOMAXCONN, which defaults to 128 on most Unixes. We could make that
value configurable since SOMAXCONN is no longer an hard limit on several
systems including Linux, so please open a feature request [1] if you
think it's worth it.

> I also tried:
> setMaxTCPQueuedConnections(2048)
> from:
> https://dnsdist.org/reference/tuning.html

This is an unrelated setting, controlling the number of connections we
are willing to queue in our internal pipe.

[1]: https://github.com/PowerDNS/pdns/issues/new/choose

Best regards,
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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