Configuring scale bounds

You can also specify the initial scale that a Revision is scaled to immediately after creation. This can be a default configuration for all Revisions, or for a specific Revision using an annotation.

This value controls the minimum number of replicas that each Revision should have. Knative will attempt to never have less than this number of replicas at any one point in time.

• Global key:
• Per-revision annotation key: autoscaling.knative.dev/min-scale
• Possible values: integer
• Default: 0 if scale-to-zero is enabled and class KPA is used, 1 otherwise

Note

For more information about scale-to-zero configuration, see the documentation on Configuring scale to zero.

Example:

Per RevisionGlobal (ConfigMap)Global (Operator)

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-autoscaler
  namespace: knative-serving
data:
  min-scale: "3"

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    autoscaler:
      min-scale: "3"

This value controls the maximum number of replicas that each revision should have. Knative will attempt to never have more than this number of replicas running, or in the process of being created, at any one point in time.

• Global key: max-scale
• Per-revision annotation key: autoscaling.knative.dev/max-scale
• Possible values: integer
• Default: 0 which means unlimited

Example:

Per RevisionGlobal (ConfigMap)Global (Operator)

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: helloworld-go
  namespace: default
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/max-scale: "3"
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-autoscaler
  namespace: knative-serving
  max-scale: "3"
  max-scale-limit: "100"

This value controls the initial target scale a Revision must reach immediately after it is created before it is marked as Ready. After the Revision has reached this scale one time, this value is ignored. This means that the Revision will scale down after the initial target scale is reached if the actual traffic received only needs a smaller scale.

When the Revision is created, the larger of initial scale and lower bound is automatically chosen as the initial target scale.

• Global key: in combination with allow-zero-initial-scale
• Per-revision annotation key: autoscaling.knative.dev/initial-scale
• Possible values: integer
• Default: 1

Example:

Per RevisionGlobal (ConfigMap)Global (Operator)

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: helloworld-go
  namespace: default
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/initial-scale: "0"
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go

apiVersion: v1
kind: ConfigMap
metadata:
  name: config-autoscaler
  namespace: knative-serving
data:
  initial-scale: "0"
  allow-zero-initial-scale: "true"

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    autoscaler:
      initial-scale: "0"
      allow-zero-initial-scale: "true"

Scale Down Delay specifies a time window which must pass at reduced concurrency before a scale-down decision is applied. This can be useful, for example, to keep containers around for a configurable duration to avoid a cold start penalty if new requests come in. Unlike setting a lower bound, the revision will eventually be scaled down if reduced concurrency is maintained for the delay period.

Only supported for the default KPA autoscaler class.

• Global key: scale-down-delay
• Per-revision annotation key: autoscaling.knative.dev/scale-down-delay
• Possible values: Duration, 0s <= value <= 1h
• Default: 0s (no delay)

Example:

Per RevisionGlobal (ConfigMap)Global (Operator)

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: helloworld-go
  namespace: default
spec:
      annotations:
        autoscaling.knative.dev/scale-down-delay: "15m"
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    autoscaler:
      scale-down-delay: "15m"

The stable window defines the sliding time window over which metrics are averaged to provide the input for scaling decisions when the autoscaler is not in .

• Global key: stable-window
• Per-revision annotation key: autoscaling.knative.dev/window
• Possible values: Duration, 6s <= value <= 1h
• Default: 60s

Note

During scale down, in most cases the last Replica is removed after there has been no traffic to the Revision for the entire duration of the stable window.

Example:

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: helloworld-go
  namespace: default
spec:
  template:
    metadata:
      annotations:
        autoscaling.knative.dev/window: "40s"
    spec:
      containers:
        - image: gcr.io/knative-samples/helloworld-go

apiVersion: v1
kind: ConfigMap
metadata:
 name: config-autoscaler
 namespace: knative-serving
data:
 stable-window: "40s"

apiVersion: operator.knative.dev/v1alpha1
kind: KnativeServing
metadata:
  name: knative-serving
spec:
  config:
    autoscaler: