Amazon EKS Launches Direct Configuration for Managed Control Plane Parameters

Amazon EKS has launched the Advanced Kubernetes control plane configuration feature, enabling customers to directly adjust key parameters for kube-scheduler, kube-controller-manager, and kube-apiserver, which were previously managed by AWS. This feature is supported on new and existing clusters running Kubernetes version 1.31 or higher, with no additional fees for the feature itself. However, using Provisioned Control Plane (PCP) is mandatory for adjusting certain parameters, and separate charges apply when using PCP.

Key Adjustable Parameters and Their Impact

The adjustable items and their impacts for each component are as follows:

• kube-scheduler: nodeResourcesFit.scoringStrategy can be configured without PCP. Selecting MostAllocated instead of the default LeastAllocated can reduce compute costs through workload consolidation, but it requires eviction when moving existing pods and risks concentrating the blast radius of failures.
• kube-controller-manager: horizontalPodAutoscalerSyncPeriod (HPA sync period) and terminatedPodGcThreshold require PCP. Shortening the HPA period from 15 seconds to 10 seconds improves response speed but increases API server load, reducing the number of supported HPA objects by approximately 1/3. Additionally, lowering the GC threshold increases etcd workload and may cause early pod termination.
• kube-apiserver: eventTtl (event retention time) and serviceNodePortRange do not require PCP. Shortening the event TTL reduces the debugging window, and while changing the NodePort range preserves existing services, security group conflicts and other issues must be checked during new allocations.

Operational and Limitation Details

Configuration changes can be made via the CreateCluster or UpdateClusterConfig APIs, Console, CLI, etc., and all changes are logged in CloudTrail. Updates are performed in a rolling manner, and status is tracked under the ControlPlaneComponentConfigUpdate type. There is no reset function, so restoring default values requires explicit configuration.

PCP offers higher etcd size (16GB vs 8GB) and SLA (99.99% vs 99.95%) compared to Standard mode. To revert from PCP to Standard mode, the HPA sync period and GC threshold must be at their default values, and reversion is blocked if the etcd size exceeds 8GB, making prior planning essential. AWS assumes responsibility for stability within 'validated ranges', and customers must adjust default values with clear intent.