website/content/en/docs/concepts/cluster-administration/coordinated-leader-election.md

reviewers	title	content_type	weight
jpbetz	Coordinated Leader Election	concept	200

{{< feature-state feature_gate_name="CoordinatedLeaderElection" >}}

Kubernetes {{< skew currentVersion >}} includes an alpha feature that allows {{< glossary_tooltip text="control plane" term_id="control-plane" >}} components to deterministically select a leader via coordinated leader election. This is useful to satisfy Kubernetes version skew constraints during cluster upgrades. Currently, the only builtin selection strategy is OldestEmulationVersion, preferring the leader with the lowest emulation version, followed by binary version, followed by creation timestamp.

Enabling coordinated leader election

Ensure that CoordinatedLeaderElection feature gate is enabled when you start the {{< glossary_tooltip text="API Server" term_id="kube-apiserver" >}}: and that the coordination.k8s.io/v1alpha1 API group is enabled.

This can be done by setting flags --feature-gates="CoordinatedLeaderElection=true" and --runtime-config="coordination.k8s.io/v1alpha1=true".

Component configuration

Provided that you have enabled the CoordinatedLeaderElection feature gate and
have the coordination.k8s.io/v1alpha1 API group enabled, compatible control plane
components automatically use the LeaseCandidate and Lease APIs to elect a leader
as needed.

For Kubernetes {{< skew currentVersion >}}, two control plane components
(kube-controller-manager and kube-scheduler) automatically use coordinated
leader election when the feature gate and API group are enabled.