ScaleAdapter API reference

The adapter exposes a scale-compatible surface over a target. Grant only the necessary target/subresource permissions and give the target replica field one writer. A desired buffer count does not prove nodes are ready.

API details

Group: autoscaling.kedify.io. Kind: ScaleAdapter. Scope: Namespaced.

Defaults below are schema defaults only. “Not specified” does not imply a controller default of zero or false. Required fields are required within their containing object. Runtime behavior can impose additional conditions described in the capability guide.

v1alpha1 fields

Served: true; storage: true.

spec

Field	Type	Required	Schema default	Meaning and validation
spec	object	No	Not specified	ScaleAdapterSpec defines the desired state of ScaleAdapter x-kubernetes-validations: [{“message”:“currentReplicasPath can only be set together with desiredReplicasPath”,“rule”:“!has(self.currentReplicasPath) || has(self.desiredReplicasPath)”}]
spec.currentReplicasPath	string	No	Not specified	CurrentReplicasPath is a dot-separated field path (e.g. “.status.size”) to the current replica count reported by the target resource, mirrored into status.replicas. It can only be set together with DesiredReplicasPath. When DesiredReplicasPath is set and this is not, status.replicas mirrors the desired replica count instead. minLength: 1
spec.desiredReplicasPath	string	No	Not specified	DesiredReplicasPath is a dot-separated field path (e.g. “.spec.size”) to the desired replica count on the target resource. When set, the adapter reads and writes desired replicas through this field instead of the target’s /scale subresource, which allows adapting targets that do not implement the scale contract at all. This requires RBAC for get and update on the whole target resource rather than just its /scale subresource. Wildcards and array indices are not supported. minLength: 1
spec.replicas	integer	No	Not specified	Replicas is the desired replica count forwarded to the target, through its /scale subresource or through DesiredReplicasPath. It is initialized by the controller from the target’s current desired replicas and afterwards managed by the HPA (or KEDA for scale to/from zero) through this adapter’s /scale subresource. Leave it unset when creating the adapter. minimum: 0
spec.selector	object	Yes	Not specified	Selector selects the Pods that belong to the target workload. It is serialized into status.selector, which the HPA requires to be non-empty. The matching labels must be present on the Pods of the target workload (for Agones Fleets, add them to the Pod template at spec.template.spec.template.metadata.labels).
spec.selector.matchExpressions	array	No	Not specified	matchExpressions is a list of label selector requirements. The requirements are ANDed.
spec.selector.matchExpressions[]	object	No	Not specified	A label selector requirement is a selector that contains values, a key, and an operator that relates the key and values.
spec.selector.matchExpressions[].key	string	Yes	Not specified	key is the label key that the selector applies to.
spec.selector.matchExpressions[].operator	string	Yes	Not specified	operator represents a key’s relationship to a set of values. Valid operators are In, NotIn, Exists and DoesNotExist.
spec.selector.matchExpressions[].values	array	No	Not specified	values is an array of string values. If the operator is In or NotIn, the values array must be non-empty. If the operator is Exists or DoesNotExist, the values array must be empty. This array is replaced during a strategic merge patch.
spec.selector.matchExpressions[].values[]	string	No	Not specified
spec.selector.matchLabels	object	No	Not specified	matchLabels is a map of {key,value} pairs. A single {key,value} in the matchLabels map is equivalent to an element of matchExpressions, whose key field is “key”, the operator is “In”, and the values array contains only “value”. The requirements are ANDed.
spec.selector.matchLabels.*	string	No	Not specified
spec.targetRef	object	Yes	Not specified	TargetRef references the resource whose desired replicas are managed through this adapter, by default through its /scale subresource.
spec.targetRef.apiVersion	string	Yes	Not specified	APIVersion of the target resource, e.g. “agones.dev/v1”. minLength: 1
spec.targetRef.kind	string	Yes	Not specified	Kind of the target resource, e.g. “Fleet”. minLength: 1
spec.targetRef.name	string	Yes	Not specified	Name of the target resource. minLength: 1

status

Field	Type	Required	Schema default	Meaning and validation
status	object	No	Not specified	ScaleAdapterStatus defines the observed state of ScaleAdapter
status.conditions	array	No	Not specified
status.conditions[]	object	No	Not specified	Condition contains details for one aspect of the current state of this API Resource.
status.conditions[].lastTransitionTime	string	Yes	Not specified	lastTransitionTime is the last time the condition transitioned from one status to another. This should be when the underlying condition changed. If that is not known, then using the time when the API field changed is acceptable.
status.conditions[].message	string	Yes	Not specified	message is a human readable message indicating details about the transition. This may be an empty string. maxLength: 32768
status.conditions[].observedGeneration	integer	No	Not specified	observedGeneration represents the .metadata.generation that the condition was set based upon. For instance, if .metadata.generation is currently 12, but the .status.conditions[x].observedGeneration is 9, the condition is out of date with respect to the current state of the instance. minimum: 0
status.conditions[].reason	string	Yes	Not specified	reason contains a programmatic identifier indicating the reason for the condition’s last transition. Producers of specific condition types may define expected values and meanings for this field, and whether the values are considered a guaranteed API. The value should be a CamelCase string. This field may not be empty. minLength: 1; maxLength: 1024; pattern: ”^[A-Za-z]([A-Za-z0-9_,:]*[A-Za-z0-9_])?$”
status.conditions[].status	string	Yes	Not specified	status of the condition, one of True, False, Unknown. enum: [“True”,“False”,“Unknown”]
status.conditions[].type	string	Yes	Not specified	type of condition in CamelCase or in foo.example.com/CamelCase. maxLength: 316; pattern: ”^([a-z0-9]([-a-z0-9][a-z0-9])?(\.[a-z0-9]([-a-z0-9][a-z0-9])?)/)?(([A-Za-z0-9][-A-Za-z0-9_.])?[A-Za-z0-9])$”
status.replicas	integer	Yes	Not specified	Replicas mirrors the current replica count reported by the target through its /scale subresource or CurrentReplicasPath.
status.selector	string	No	Not specified	Selector is the serialized form of spec.selector, exposed through this adapter’s /scale subresource for the HPA.
status.targetDesiredReplicas	integer	No	Not specified	TargetDesiredReplicas is the desired replica count last observed on (or written to) the target. It is used to detect competing replica writers and for troubleshooting.

Inspect the installed contract

kubectl get crd scaleadapters.autoscaling.kedify.io -o yaml
kubectl explain scaleadapter.spec --recursive

Compare served/storage versions and schema before applying configuration. Inspect the resource’s status and events after changing its owning source; schema acceptance alone does not prove successful reconciliation.

Use, verify and diagnose

• Scale Adapter: custom scaling targets
• Scale custom targets and prewarm node capacity
• Prewarm node capacity with Karpenter
• Prewarm node capacity with Cluster Autoscaler
• Prewarm node capacity on GKE

Conditions

Type	Meaning
Ready	Target resolved, selector usable, replicas synchronized
TargetResolved	spec.targetRef maps to a resource with a readable /scale (or readable replica field paths)
SelectorValid	spec.selector is a valid, non-empty selector
SelectorMatchesPods	Warning only: False when the target reports replicas but the selector matches no Pods (labels missing from the Pod template)
ConflictingReplicaWriter	Warning only: True when something else wrote the target’s desired replicas