kubernetes-sigs/cluster-api

CoreDNS pods running on the same Node after initial cluster creation

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#9639 aperta il 30 ott 2023

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area/provider/control-plane-kubeadmhelp wantedkind/featurepriority/important-longtermtriage/accepted

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Descrizione

After a cluster with multiple control plane nodes is created all CoreDNS replicas are running on the same Node. Ideally they should be distributed across multiple nodes

Details

The kubeadm bootstrap provider is using kubeadm to deploy CoreDNS. It creates the CoreDNS deployment with preferredDuringSchedulingIgnoredDuringExecution. Because at the time of CoreDNS deployment there is only one Node all CoreDNS pods are scheduled on the same Node. There is no re-scheduling once additional CP nodes are added.

Related kubeadm issues, let's take a look!

Some idea on how to solve this

  1. Change preferredDuringSchedulingIgnoredDuringExecution to requiredDuringSchedulingIgnoredDuringExecution for multi-CP control planes (also change it back during scale down to 1 replica)
    1. we should check if replica is always the same number (e.g. 2)
  2. Delete CoreDNS Pods as soon as additional CP replicas join

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Direzione di ricerca
Indaga come modificare il deployment di CoreDNS per utilizzare requiredDuringSchedulingIgnoredDuringExecution per cluster multi CP, o cancellare i pod di CoreDNS quando nuovi nodi CP si uniscono. Esamina i relativi issue kubeadm #1657 e #1931 per contesto e approcci potenziali.
Tech stack
go
Dominio
backendinfrastructuredevops
Tipo issue
Bug
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1-2 giorni
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Chiara
Prerequisiti
KubernetesGokubeadm
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