Cluster Autoscaler: Capacity Buffers (Pre-warm)

CapacityBuffer (CRD)

• Provisioning Strategy: buffer.x-k8s.io/active-capacity (Placeholder pods).
• Namespace-scoped: Targets a specific ComputeClass via nodeSelector in the podTemplateRef.

Sizing Modes

• Fixed: replicas: 3. Always keep N units warm.
• Dynamic: percentage: 20 + scalableRef: <Deployment>. Headroom scales with workload.

Why use Buffers?

• Bursty Serving: Pod-pending SLOs can't tolerate 60-120s node pool auto-creation delay.
• HPA outpaces cluster autoscaler: Workload scales faster than nodes can arrive.
• Pre-warming: Warm GPUs/TPUs before known traffic windows.

Note: Replaces the "dumb" floor of --min-nodes with shape-aware, class-targeted warm capacity.