[dnsdist] dnsdist capacity

[Remi Gacogne]

Hi Alexey,

On 11/9/18 8:02 PM, Alexey Bokhanovskiy wrote:
> How many the same backend servers I can use (your reccomendation for a
> lot of qps)? 

It's a bit complicated to answer without knowing more about your setup
and the type of traffic you are seeing. I think you should really set up
some metrics using carbon/grafana or prometheus, and look at what the
bottleneck is (CPU, network, interrupts, context switchs..). Note that
if you are using the latest version, you can display the name of the
various dnsdist threads to known which one is CPU-bound for example.

Best regards,

Remi

> ------------------------------------------------------------------------
> *От:* dnsdist <dnsdist-bounces at mailman.powerdns.com> от имени Remi
> Gacogne <remi.gacogne at powerdns.com>
> *Отправлено:* 9 ноября 2018 г. 19:41
> *Кому:* dnsdist at mailman.powerdns.com
> *Тема:* Re: [dnsdist] dnsdist capacity
>  
> Hi Alexey,
> 
> On 11/9/18 2:07 PM, Alexey Bokhanovskiy wrote:
>> Now we are using two DNS loadbalancers with seven servers powerdns and
>> we found that the capacity loadbalancer has limit approximately 50k qps
>>
>> Our version of dnsdist is 1.3.3-1pdns.bionic.
>>
>> Is 50kqps the limit of software or hardware? Or need to additional
>> configuration?
> 
> This seems ridiculously low for your hardware, but it's hard to know for
> sure without seeing your configuration.
> For what it's worth, you should be able to reach easily 450k QPS without
> the packet cache being enabled and much more with it. I have seen one
> dnsdist handle around 1M qps at 100% cache hit ratio in an ideal setup
> in a lab. You should never reach that over a single dnsdist in
> production, but still :)
> 
> You should first read [1], and tune at least setMaxUDPOutstanding(), use
> several threads to handle incoming queries and consider adding several
> newServer() directives (adding the same backend twice might help because
> you then have more threads handling the responses) and/or use the
> 'sockets' parameter on the 'newServer()' directive depending on your setup.
> 
> Then the next step should be to get some metrics using `carbonServer()`
> [2] and metronome [3], for example, so you know what's going on.
> Then you might want to upgrade your kernel (recent Linux kernels are a
> lot better at handling UDP packets) and tune your OS and your network cards.
> 
> I would advise removing any rule that you have in dnsdist's
> configuration first and using one of the built-in load-balancing policy
> to be sure that Lua isn't your bottleneck. Please also remember that
> without the cache, dnsdist won't be faster than your backends, so
> perhaps benchmark them as well.
> 
> Good luck!
> 
> [1]: https://dnsdist.org/advanced/tuning.html
> [2]: https://dnsdist.org/guides/carbon.html
> [3]: https://github.com/ahupowerdns/metronome
> 
> Best regards,
> -- 
> Remi Gacogne
> PowerDNS.COM BV - https://www.powerdns.com/
> 
> 
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-- 
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/

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