DRA kubelet: API clarification

It's not okay to drop a claim from the response just because it encountered no
error. We want to be sure that a DRA driver really looked at the claim.

staging/src/k8s.io/dynamic-resource-allocation/kubeletplugin/draplugin.go

@@ -115,7 +115,8 @@ type DRAPlugin interface {
 	// and serialization.
 	//
 	// The conventions for returning one overall error and several per-ResourceClaim
-	// errors are the same as in PrepareResourceClaims.
+	// errors are the same as in PrepareResourceClaims. In particular, all claims
+	// must have an entry in the response, even if that entry is nil.
 	UnprepareResourceClaims(ctx context.Context, claims []NamespacedObject) (result map[types.UID]error, err error)
 
 	// ErrorHandler gets called for each error encountered while publishing

staging/src/k8s.io/kubelet/pkg/apis/dra/v1beta1/api.pb.go

@@ -326,7 +326,8 @@ func (m *NodeUnprepareResourcesRequest) GetClaims() []*Claim {
 type NodeUnprepareResourcesResponse struct {
 	// The ResourceClaims for which preparation was reverted.
 	// The same rules as for NodePrepareResourcesResponse.claims
-	// apply.
+	// apply. In particular, all claims in the request must
+	// have an entry in the response, even if that entry is nil.
 	Claims               map[string]*NodeUnprepareResourceResponse `protobuf:"bytes,1,rep,name=claims,proto3" json:"claims,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
 	XXX_NoUnkeyedLiteral struct{}                                  `json:"-"`
 	XXX_sizecache        int32                                     `json:"-"`

staging/src/k8s.io/kubelet/pkg/apis/dra/v1beta1/api.proto

@@ -95,7 +95,8 @@ message NodeUnprepareResourcesRequest {
 message NodeUnprepareResourcesResponse {
     // The ResourceClaims for which preparation was reverted.
     // The same rules as for NodePrepareResourcesResponse.claims
-    // apply.
+    // apply. In particular, all claims in the request must
+    // have an entry in the response, even if that entry is nil.
     map<string, NodeUnprepareResourceResponse> claims = 1;
 }