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Using useClientSubnet=true affect caching #5654

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rygl opened this issue Aug 25, 2017 · 2 comments
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Using useClientSubnet=true affect caching #5654

rygl opened this issue Aug 25, 2017 · 2 comments

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@rygl
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@rygl rygl commented Aug 25, 2017

Hi,

In order to receive the IP of the dnsdist client on the backend resolvers I have tried to use useClientSubnet=true in server setting together with setECSSourcePrefixV4(32) and setECSSourcePrefixV6(56) in the config. It works fine but was surprised with the impact to the cache hitrate. It went down from previous > 90% to ~30%. Is it an expected behavior?

Thanks
Aleš

@rgacogne rgacogne added the dnsdist label Aug 28, 2017
@rgacogne
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@rgacogne rgacogne commented Aug 28, 2017

Hi Aleš,

Yes, it is. We have no way of knowing whether the answer sent by the backend will vary based on the provided ECS information, so we cache answers for queries with different ECS values separately. I guess we could add an option to add ECS information to the forwarded query but ignore it for the cache..

@rygl
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@rygl rygl commented Aug 29, 2017

Hi Remi,

Thanks for your answer. If backends do not work with ECS it would help.

Anyway it looks like I am trying to use ECS not the the best way - with setECSSourcePrefixV4(32) to identify the client by his IP on the backends while the purpose of it is a bit different and using XPF in the future would be better.

Aleš

@Habbie Habbie added the enhancement label Nov 9, 2017
@Habbie Habbie added this to the dnsdist-1.3.0 milestone Nov 9, 2017
@pieterlexis pieterlexis mentioned this issue Jan 23, 2018
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