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Feature Gates

This page contains an overview of the various feature gates an administrator can specify on different Kubernetes components.

• Overview
• Using a Feature
  • Feature Stages
  • Feature Gates

Overview

Feature gates are a set of key=value pairs that describe alpha or experimental features. An administrator can use the --feature-gates command line flag on each component to turn a feature on or off. The following table is a summary of the feature gates that you can set on different Kubernetes components.

• The “Since” column contains the Kubernetes release when a feature is introduced or its release stage is changed.
• The “Until” column, if not empty, contains the last Kubernetes release in which you can still use a feature gate.

Using a Feature

Feature Stages

A feature can be in Alpha, Beta or GA stage. An Alpha feature means:

• Disabled by default.
• Might be buggy. Enabling the feature may expose bugs.
• Support for feature may be dropped at any time without notice.
• The API may change in incompatible ways in a later software release without notice.
• Recommended for use only in short-lived testing clusters, due to increased risk of bugs and lack of long-term support.

A Beta feature means:

• Enabled by default.
• The feature is well tested. Enabling the feature is considered safe.
• Support for the overall feature will not be dropped, though details may change.
• The schema and/or semantics of objects may change in incompatible ways in a subsequent beta or stable release. When this happens, we will provide instructions for migrating to the next version. This may require deleting, editing, and re-creating API objects. The editing process may require some thought. This may require downtime for applications that rely on the feature.
• Recommended for only non-business-critical uses because of potential for incompatible changes in subsequent releases. If you have multiple clusters that can be upgraded independently, you may be able to relax this restriction.

Note: Please do try Beta features and give feedback on them! After they exit beta, it may not be practical for us to make more changes.

A GA feature is also referred to as a stable feature. It means:

• The corresponding feature gate is no longer needed.
• Stable versions of features will appear in released software for many subsequent versions.

Feature Gates

Each feature gate is designed for enabling/disabling a specific feature:

• Accelerators: Enable Nvidia GPU support when using Docker
• AdvancedAuditing: Enable advanced auditing
• AffinityInAnnotations(deprecated): Enable setting Pod affinity or anti-affinitys.
• AllowExtTrafficLocalEndpoints: Enable a service to route external requests to node local endpoints.
• APIListChunking: Enable the API clients to retrieve (LIST or GET) resources from API server in chunks.
• APIResponseCompression: Compress the API responses for LIST or GET requests.
• AppArmor: Enable AppArmor based mandatory access control on Linux nodes when using Docker. See AppArmor Tutorial for more details.
• BlockVolume: Enable the definition and consumption of raw block devices in Pods. See Raw Block Volume Support for more details.
• CPUManager: Enable container level CPU affinity support, see CPU Management Policies.
• CSIPersistentVolume: Enable discovering and mounting volumes provisioned through a CSI (Container Storage Interface) compatible volume plugin. Check the csi volume type documentation for more details.
• CustomPodDNS: Enable customizing the DNS settings for a Pod using its dnsConfig property. Check Pod’s DNS Config for more details.
• CustomeResourceValidation: Enable schema based validation on resources created from CustomResourceDefinition.
• CustomResourceSubresources: Enable /status and /scale subresources on resources created from CustomResourceDefinition.
• DevicePlugins: Enable the device-plugins based resource provisioning on nodes.
• DynamicKubeletConfig: Enable the dynamic configuration of kubelet. See Reconfigure kubelet.
• DynamicVolumeProvisioning(deprecated): Enable the dynamic provisioning of persistent volumes to Pods.
• EnableEquivalenceClassCache: Enable the scheduler to cache equivalence of nodes when scheduling Pods.
• ExpandPersistentVolumes: Enable the expanding of persistent volumes. See Expanding Persistent Volumes Claims.
• ExperimentalCriticalPodAnnotation: Enable annotating specific pods as critical so that their scheduling is guaranteed.
• ExperimentalHostUserNamespaceDefaultingGate: Enabling the defaulting user namespace to host. This is for containers that are using other host namespaces, host mounts, or containers that are privileged or using specific non-namespaced capabilities (e.g. MKNODE, SYS_MODULE etc.). This should only be enabled if user namespace remapping is enabled in the Docker daemon.
• HugePages: Enable the allocation and consumption of pre-allocated huge pages.
• HyperVContainer: Enable Hyper-V isolation for Windows containers.
• Intializers: Enable the dynamic admission control as an extension to the built-in admission controllers. When the Initializers admission controller is enabled, this feature is automatically enabled.
• KubeletConfigFile: Enable loading kubelet configuration from a file specified using a config file. See setting kubelet parameters via a config file for more details.
• LocalStorageCapacityIsolation: Enable the consumption of local ephemeral storage and also the sizeLimit property of an emptyDir volume.
• MountContainers: Enable using utility containers on host as the volume mounter.
• MountPropagation: Enable sharing volume mounted by one container to other containers or pods. For more details, please see mount propagation.
• PersistentLocalVolumes: Enable the usage of local volume type in Pods. Pod affinity has to be specified if requesting a local volume.
• PodPriority: Enable the descheduling and preemption of Pods based on their priorities.
• PVCProtection: Enable the prevention of a PersistentVolumeClaim (PVC) from being deleted when it is still used by any Pod. More details can be found here.
• ResourceLimitsPriorityFunction: Enable a scheduler priority function that assigns a lowest possible score of 1 to a node that satisfies at least one of the input Pod’s cpu and memory limits. The intent is to break ties between nodes with same scores.
• RotateKubeletClientCertificate: Enable the rotation of the client TLS certificate on the kubelet. See kubelet configuration for more details.
• RotateKubeletServerCertificate: Enable the rotation of the server TLS certificate on the kubelet. See kubelet configuration for more details.
• ServiceNodeExclusion: Enable the exclusion of nodes from load balancers created by a cloud provider. A node is eligible for exclusion if annotated with “alpha.service-controller.kubernetes.io/exclude-balancer” key.
• StreamingProxyRedirects: Instructs the API server to intercept (and follow) redirects from the backend (kubelet) for streaming requests. Examples of streaming requests include the exec, attach and port-forward requests.
• SupportIPVSProxyMode: Enable providing in-cluster service load balancing using IPVS. See service proxies for more details.
• TaintBasedEvictions: Enable evicting pods from nodes based on taints on nodes and tolerations on Pods. See taints and tolerations for more details.
• TaintNodesByCondition: Enable automatic tainting nodes based on node conditions.
• VolumeScheduling: Enable volume topology aware scheduling and make the PersistentVolumeClaim (PVC) binding aware of scheduling decisions. It also enables the usage of local volume type when used together with the PersistentLocalVolumes feature gate.