[Pdns-users] troubleshooting dnsdist -> recursor instability

Christoph cm at appliedprivacy.net
Mon Oct 24 12:05:59 UTC 2022

Hi Remi,

> Clearly unexpected. You might be able to get more information about what 
> is going by setting setVerboseHealthChecks [1] in dnsdist. 

very good point, thank you I'll enable it!

> One unrelated thing I noticed in your configuration is that you are 
> setting maxInFlight to 1000 on newServer, telling dnsdist to send up to 
> 1000 concurrent queries on an outgoing TCP connection to the backend, 
> but on the recursor's side it looks like 
> max-concurrent-requests-per-tcp-connection [2] is set to the default of 
> 10. This might lead to terrible latency numbers over TCP, so I would 
> suggest increasing that setting, or decreasing the maxInFlight value in 
> the dnsdist configuration.

I'll enable max-concurrent-requests-per-tcp-connection to 1000 on 
recursor's side.

thanks for taking a look the config files and your valuable input!

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