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

Name	Priority	Associated Components (Examples)
gardener-garden-system-critical	999999550	gardener-operator, gardener-resource-manager, istio
gardener-garden-system-500	999999500	virtual-garden-etcd-events, virtual-garden-etcd-main, virtual-garden-kube-apiserver, gardener-apiserver
gardener-garden-system-400	999999400	virtual-garden-gardener-resource-manager, gardener-admission-controller, Extension Admission Controllers
gardener-garden-system-300	999999300	virtual-garden-kube-controller-manager, vpa-admission-controller, etcd-druid, nginx-ingress-controller
gardener-garden-system-200	999999200	vpa-recommender, vpa-updater, gardener-scheduler, gardener-controller-manager, gardener-dashboard, terminal-controller-manager, gardener-discovery-server, Extension Controllers
gardener-garden-system-100	999999100	fluent-operator, fluent-bit, gardener-metrics-exporter, kube-state-metrics, plutono, vali, prometheus-operator, alertmanager-garden, prometheus-garden, blackbox-exporter, prometheus-longterm, perses-operator, opentelemetry-operator

Seed Clusters

PriorityClasses for Seed System Components

Name	Priority	Associated Components (Examples)
gardener-system-critical	999998950	gardenlet, gardener-resource-manager, istio-ingressgateway, istiod
gardener-system-900	999998900	Extensions
gardener-system-800	999998800	dependency-watchdog-endpoint, dependency-watchdog-probe, etcd-druid, vpa-admission-controller
gardener-system-700	999998700	vpa-recommender, vpa-updater
gardener-system-600	999998600	alertmanager-seed, fluent-operator, fluent-bit, plutono, kube-state-metrics, nginx-ingress-controller, nginx-k8s-backend, prometheus-operator, prometheus-aggregate, prometheus-cache, prometheus-seed, vali, perses-operator, opentelemetry-operator
gardener-reserve-excess-capacity	-5	reserve-excess-capacity (ref)

PriorityClasses for Shoot Control Plane Components

Name	Priority	Associated Components (Examples)
gardener-system-500	999998500	etcd-events, etcd-main, kube-apiserver
gardener-system-400	999998400	gardener-resource-manager
gardener-system-300	999998300	cloud-controller-manager, cluster-autoscaler, csi-driver-controller, kube-controller-manager, kube-scheduler, machine-controller-manager, terraformer, vpn-seed-server
gardener-system-200	999998200	csi-snapshot-controller, csi-snapshot-validation, cert-controller-manager, shoot-dns-service, vpa-admission-controller, vpa-recommender, vpa-updater
gardener-system-100	999998100	alertmanager-shoot, plutono, kube-state-metrics, prometheus-shoot, blackbox-exporter, vali, event-logger

Shoot Clusters

PriorityClasses for Shoot System Components

Name	Priority	Associated Components (Examples)
system-node-critical (created by Kubernetes)	2000001000	calico-node, kube-proxy, apiserver-proxy, csi-driver, egress-filter-applier
system-cluster-critical (created by Kubernetes)	2000000000	calico-typha, calico-kube-controllers, coredns, vpn-shoot, registry-cache
gardener-shoot-system-900	999999900	node-problem-detector
gardener-shoot-system-800	999999800	calico-typha-horizontal-autoscaler, calico-typha-vertical-autoscaler
gardener-shoot-system-700	999999700	blackbox-exporter, node-exporter
gardener-shoot-system-600	999999600	addons-nginx-ingress-controller, addons-nginx-ingress-k8s-backend, kubernetes-dashboard, kubernetes-metrics-scraper