Dynamic Resource Allocation (DRA)

DRA is the workflow that lets pods request named, opaque devices — GPUs, FPGAs, SR-IOV virtual functions, RDMA NICs, encryption accelerators. It generalizes the older "device plugin" model into something the scheduler understands.

The pieces

graph TD
    User -->|kubectl apply<br/>ResourceClaim + Pod| API[kube-apiserver]
    DRADriverCM[DRA driver kubelet plugin] -->|publish ResourceSlice| API
    API -->|watch| Sched[kube-scheduler<br/>dynamicresources plugin]
    Sched -->|allocate ResourceClaim| API
    API -->|watch| Kubelet
    Kubelet -->|gRPC NodePrepareResources| DRADriverCM
    DRADriverCM --> Container[Container]

Resources involved

• DeviceClass (resource.k8s.io/v1) — vendor-defined class with selectors.
• ResourceClaim — a request for a specific device or set of devices, scoped to a Pod.
• ResourceClaimTemplate — a stamp from which per-pod claims are generated.
• ResourceSlice — published by DRA driver kubelet plugins, lists the devices each node has.

API types live in staging/src/k8s.io/api/resource/v1/. Validation in pkg/apis/resource/validation/. Registry in pkg/registry/resource/.

The scheduler plugin

pkg/scheduler/framework/plugins/dynamicresources/ plugs into:

• PreFilter — read the pod's claims, look up matching ResourceSlices, pre-compute candidates per node.
• Filter — eliminate nodes that have no matching slice.
• Reserve — write a tentative allocation to the claim.
• PreBind — confirm the allocation is still valid; the kubelet plugin will see this on its next watch.
• PostBind / Unreserve — finalize or roll back.

The plugin uses an internal ResourceSliceTracker (staging/src/k8s.io/dynamic-resource-allocation/resourceslice/tracker/) to maintain a fast in-memory view of every advertised device.

The kubelet plugin

pkg/kubelet/cm/dra/ is the kubelet-side integrator. It:

1. Watches its node's pods + claims.
2. For each pod with claims, calls NodePrepareResources on the DRA driver's gRPC socket.
3. Receives a ContainerInfo response describing how to inject the device into the container (CDI device specs, env vars, mounts).
4. Hands those instructions to the runtime via the CRI LinuxContainerResources extensions.
5. On pod termination, calls NodeUnprepareResources.

DRA driver kubelet plugins register through the same pkg/kubelet/pluginmanager/ socket-discovery mechanism as CSI drivers and device plugins.

Controller-manager components

• resource-claim controller (pkg/controller/resourceclaim/) — creates per-pod ResourceClaims from ResourceClaimTemplate and binds them to Pods.
• device-taint-eviction (pkg/controller/devicetainteviction/) — DRA equivalent of NoExecute taint eviction. If a device gets a taint, pods that reserved it are evicted.
• resource-pool-status (pkg/controller/resourcepoolstatusrequest/) — reconciles resource-pool status.

Library

staging/src/k8s.io/dynamic-resource-allocation/ is the shared library used by:

• The scheduler plugin (for snapshotting and CEL evaluation).
• DRA driver authors (for the gRPC server boilerplate, CDI device building, and resource-slice publishing).
• The kubelet integration.

CEL in DRA

DeviceClass selectors are written in CEL:

selectors:
  - cel:
      expression: device.attributes["pci.vendor_id"] == "10de"

CEL evaluation is in staging/src/k8s.io/dynamic-resource-allocation/cel/. The error path is significant — recent commits in this area focus on producing actionable error messages when CEL refers to a non-existent attribute (e.g. the dra-cel-no-such-key-error enhancement landed in late April 2026).

Status: alpha → beta → GA

Different DRA features advance at different rates:

• Core ResourceClaim / ResourceSlice flow: beta.
• Per-claim CEL selectors: beta.
• Cross-claim quotas (ResourceQuota integration): alpha.
• Allocator-backed claims (where the API server picks a device): alpha.

Track via pkg/features/kube_features.go for the gates DynamicResourceAllocation, DRAResourceClaimDeviceStatus, and friends.

Key source files

File	Purpose
staging/src/k8s.io/api/resource/v1/types.go	API types
staging/src/k8s.io/dynamic-resource-allocation/resourceslice/tracker/	Slice cache
staging/src/k8s.io/dynamic-resource-allocation/cel/	CEL evaluator
pkg/scheduler/framework/plugins/dynamicresources/	Scheduler plugin
pkg/kubelet/cm/dra/manager.go	Kubelet integration
pkg/controller/resourceclaim/resource_claim_controller.go	Claim allocation controller
pkg/registry/resource/resourceclaim/storage/storage.go	REST registry