Coordinated Leader Election

Kubernetes 1.31 includes an alpha feature that allows 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 API Server: 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 1.31, two control plane components
(kube-controller-manager and kube-scheduler) automatically use coordinated
leader election when the feature gate and API group are enabled.