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Gardener DNS Management for Shoots

Introduction

Gardener allows Shoot clusters to request DNS names for Ingresses and Services out of the box. To support this the gardener must be installed with the shoot-dns-service extension. This extension uses the seed’s dns management infrastructure to maintain DNS names for shoot clusters. So, far only the external DNS domain of a shoot (already used for the kubernetes api server and ingress DNS names) can be used for managed DNS names.

Configuration

A general description for configuring the DNS management of the gardener can be found here.

To generally enable the DNS management for shoot objects the shoot-dns-service extension must be registered by providing an appropriate extension registration in the garden cluster.

Here it is possible to decide whether the extension should be always available for all shoots or whether the extension must be separately enabled per shoot.

If the extension should be used for all shoots the registration must set the globallyEnabled flag to true.

spec:
  resources:
    - kind: Extension
      type: shoot-dns-service
      globallyEnabled: true

Providing Base Domains usable for a Shoot

So, far only the external DNS domain of a shoot already used for the kubernetes api server and ingress DNS names can be used for managed DNS names. This is either the shoot domain as subdomain of the default domain configured for the gardener installation, or a dedicated domain with dedicated access credentials configured for a dedicated shoot via the shoot manifest.

Alternatively, you can specify DNSProviders and its credentials Secret directly in the shoot, if this feature is enabled. By default, DNSProvider replication is disabled, but it can be enabled globally in the ControllerDeployment or for a shoot cluster in the shoot manifest (details see further below).

apiVersion: core.gardener.cloud/v1beta1
kind: ControllerDeployment
metadata:
  name: extension-shoot-dns-service
type: helm
providerConfig:
  chart: ...
  values:
    image:
      ...
    dnsProviderReplication:
      enabled: true

See example files (20-* and 30-*) for details for the various provider types.

Shoot Feature Gate

If the shoot DNS feature is not globally enabled by default (depends on the extension registration on the garden cluster), it must be enabled per shoot.

To enable the feature for a shoot, the shoot manifest must explicitly add the shoot-dns-service extension.

...
spec:
  extensions:
    - type: shoot-dns-service
...

Enable/disable DNS provider replication for a shoot

The DNSProvider` replication feature enablement can be overwritten in the shoot manifest, e.g.

Kind: Shoot
...
spec:
  extensions:
    - type: shoot-dns-service
      providerConfig:
        apiVersion: service.dns.extensions.gardener.cloud/v1alpha1
        kind: DNSConfig
        dnsProviderReplication:
          enabled: true
...

DNSActivation for DNSOwner

To support migration of the control plane of shoots, the DNSOwner created and used for all DNSEntries created by the Shoot-DNS-Service can optionally be activated and deactivated by a DNS record. If the DNSActivation feature is enabled, the DNSOwner will be only be active if the value of the owner DNS record managed by Gardener matches the cluster identity of the seed hosting the control plane. This feature must only be enabled if the Gardener feature gate UseDNSRecords is enabled for all seeds.

By default this feature is enabled and can be disabled in the controller deployment:

apiVersion: core.gardener.cloud/v1beta1
kind: ControllerDeployment
metadata:
  name: extension-shoot-dns-service
type: helm
providerConfig:
  chart: ...
  values:
    image:
      ...
    ownerDnsActivation:
      enabled: false

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