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Azure AKS and DNS issues with Alpine images

Timo Holm 71 Reputation points
2022-10-28T12:56:01.787+00:00

AKS clusters were having DNS issues with Docker alpine images some years ago.
Issues
https://github.com/Azure/AKS/issues/667
https://github.com/Azure/AKS/issues/1320

related to this. A workaround was to add following configuration 

dnsConfig:  
    options:  
      - name: single-request-reopen

Does new versions of AKS still have this problem (with Alpine or other images) and should that configuration be used with (with Alpine or other images) ? I was not able to find official information.

Azure Kubernetes Service
Azure Kubernetes Service
An Azure service that provides serverless Kubernetes, an integrated continuous integration and continuous delivery experience, and enterprise-grade security and governance.
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  1. Prrudram-MSFT 28,281 Reputation points Microsoft Employee Moderator
    2022-10-31T08:57:33.467+00:00

    Hi @Timo Holm ,

    We observe the DNS timeout issue to be fixed once we moved Azure CNI configuration from the original bridge setting to the transparent setting. See https://learn.microsoft.com/en-us/azure/aks/faq#benefits-of-transparent-mode for detail.
    It shouldn't be specific to Alpine (or musl based) clients but should be related to Azure CNI being used as the AKS network setting.

    Among the 5 points in the transparent mode benefits, top 4 of them are related to the DNS timeout issue AKS customers met around 2019-2020

    --please don't forget to upvote and accept as answer if the reply is helpful--

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  1. SUNOJ KUMAR YELURU 15,491 Reputation points MVP Volunteer Moderator
    2022-10-29T05:16:38.777+00:00

    Hi @Timo Holm

    Thanks for reaching Q & A forum.

    Yes, the Alpine images are known to be problematic in Kubernetes cluster concerning DNS queries.

    Even if it is not clear if the bug has been effectively fixed in any current version of Alpine, here are some related links:

    https://github.com/kubernetes-sigs/kind/issues/442
    https://gitlab.alpinelinux.org/alpine/aports/-/issues/9017
    https://github.com/gliderlabs/docker-alpine/issues/476

    I encountered this problem on my side in my Kubernetes clusters as of January 2021 with up-to-date Alpine 3.12 images, so I would assume it is not fixed.

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