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PriorityClasses in Gardener Clusters

Gardener makes use of PriorityClasses to improve the overall robustness of the system. In order to benefit from the full potential of PriorityClasses, the gardenlet manages a set of well-known PriorityClasses with fine-granular priority values.

All components of the system should use these well-known PriorityClasses instead of creating and using separate ones with arbitrary values, which would compromise the overall goal of using PriorityClasses in the first place. The gardenlet manages the well-known PriorityClasses listed in this document, so that third parties (e.g., Gardener extensions) can rely on them to be present when deploying components to Seed and Shoot clusters.

The listed well-known PriorityClasses follow this rough concept:

  • Values are close to the maximum that can be declared by the user. This is important to ensure that Shoot system components have higher priority than the workload deployed by end-users.
  • Values have a bit of headroom in between to ensure flexibility when the need for intermediate priority values arises.
  • Values of PriorityClasses created on Seed clusters are lower than the ones on Shoots to ensure that Shoot system components have higher priority than Seed components, if the Seed is backed by a Shoot (ManagedSeed), e.g. coredns should have higher priority than gardenlet.
  • Names simply include the last digits of the value to minimize confusion caused by many (similar) names like critical, importance-high, etc.

Garden Clusters

When using the gardener-operator for managing the garden runtime and virtual cluster, the following PriorityClasses are available:

PriorityClasses for Garden Control Plane Components

NamePriorityAssociated Components (Examples)
gardener-garden-system-critical999999550gardener-operator, gardener-resource-manager, istio
gardener-garden-system-500999999500virtual-garden-etcd-events, virtual-garden-etcd-main, virtual-garden-kube-apiserver, gardener-apiserver
gardener-garden-system-400999999400virtual-garden-gardener-resource-manager, gardener-admission-controller
gardener-garden-system-300999999300virtual-garden-kube-controller-manager, vpa-admission-controller, etcd-druid, nginx-ingress-controller
gardener-garden-system-200999999200vpa-recommender, vpa-updater, hvpa-controller, gardener-scheduler, gardener-controller-manager, gardener-dashboard, terminal-controller-manager
gardener-garden-system-100999999100fluent-operator, fluent-bit, gardener-metrics-exporter, kube-state-metrics, plutono, vali, prometheus-operator, alertmanager-garden, prometheus-garden, blackbox-exporter, prometheus-longterm

Seed Clusters

PriorityClasses for Seed System Components

NamePriorityAssociated Components (Examples)
gardener-system-critical999998950gardenlet, gardener-resource-manager, istio-ingressgateway, istiod
gardener-system-900999998900Extensions, reversed-vpn-auth-server
gardener-system-800999998800dependency-watchdog-endpoint, dependency-watchdog-probe, etcd-druid, vpa-admission-controller
gardener-system-700999998700hvpa-controller, vpa-recommender, vpa-updater
gardener-system-600999998600alertmanager-seed, fluent-operator, fluent-bit, plutono, kube-state-metrics, nginx-ingress-controller, nginx-k8s-backend, prometheus-operator, prometheus-aggregate, prometheus-cache, prometheus-seed, vali
gardener-reserve-excess-capacity-5reserve-excess-capacity (ref)

PriorityClasses for Shoot Control Plane Components

NamePriorityAssociated Components (Examples)
gardener-system-500999998500etcd-events, etcd-main, kube-apiserver
gardener-system-300999998300cloud-controller-manager, cluster-autoscaler, csi-driver-controller, kube-controller-manager, kube-scheduler, machine-controller-manager, terraformer, vpn-seed-server
gardener-system-200999998200csi-snapshot-controller, csi-snapshot-validation, cert-controller-manager, shoot-dns-service, vpa-admission-controller, vpa-recommender, vpa-updater
gardener-system-100999998100alertmanager-shoot, plutono, kube-state-metrics, prometheus-shoot, blackbox-exporter, vali, event-logger

Shoot Clusters

PriorityClasses for Shoot System Components

NamePriorityAssociated Components (Examples)
system-node-critical (created by Kubernetes)2000001000calico-node, kube-proxy, apiserver-proxy, csi-driver, egress-filter-applier
system-cluster-critical (created by Kubernetes)2000000000calico-typha, calico-kube-controllers, coredns, vpn-shoot, registry-cache
gardener-shoot-system-800999999800calico-typha-horizontal-autoscaler, calico-typha-vertical-autoscaler
gardener-shoot-system-700999999700blackbox-exporter, node-exporter
gardener-shoot-system-600999999600addons-nginx-ingress-controller, addons-nginx-ingress-k8s-backend, kubernetes-dashboard, kubernetes-metrics-scraper