From 07ca05c96d6fda0b4c781929f1e54cd587e39427 Mon Sep 17 00:00:00 2001
From: elmiko <msm@opbstudios.com>
Date: Fri, 5 Sep 2025 16:13:56 -0400
Subject: [PATCH 1/2] add IsNodeCandidateForScaleDown interface

This function allows cloud providers to specify when a node is not a
good candidate for scaling down. This will occur before the autoscaler has
begun to cordon, drain, and taint any node for scale down.

Also adds a unit test for the prefiltering node processor.
---
 .../alicloud/alicloud_cloud_provider.go       |  5 ++
 .../cloudprovider/aws/aws_cloud_provider.go   |  5 ++
 .../azure/azure_cloud_provider.go             |  5 ++
 .../baiducloud/baiducloud_cloud_provider.go   |  5 ++
 .../bizflycloud/bizflycloud_cloud_provider.go |  5 ++
 .../brightbox/brightbox_cloud_provider.go     |  5 ++
 .../cherryservers/cherry_cloud_provider.go    |  5 ++
 .../cloudprovider/civo/civo_cloud_provider.go |  5 ++
 .../cloudprovider/cloud_provider.go           |  8 ++
 .../cloudstack/cloudstack_cloud_provider.go   |  5 ++
 .../clusterapi/clusterapi_provider.go         |  5 ++
 .../coreweave/coreweave_provider.go           |  5 ++
 .../digitalocean_cloud_provider.go            |  5 ++
 .../equinixmetal/cloud_provider.go            |  5 ++
 .../exoscale/exoscale_cloud_provider.go       |  5 ++
 .../externalgrpc_cloud_provider.go            |  5 ++
 .../cloudprovider/gce/gce_cloud_provider.go   |  5 ++
 .../hetzner/hetzner_cloud_provider.go         |  5 ++
 .../huaweicloud/huaweicloud_cloud_provider.go |  5 ++
 .../ionoscloud/ionoscloud_cloud_provider.go   |  5 ++
 .../kamatera/kamatera_cloud_provider.go       |  5 ++
 .../cloudprovider/kubemark/kubemark_linux.go  |  5 ++
 .../cloudprovider/kwok/kwok_provider.go       |  5 ++
 .../linode/linode_cloud_provider.go           |  5 ++
 .../magnum/magnum_cloud_provider.go           |  5 ++
 .../cloudprovider/mocks/CloudProvider.go      |  5 ++
 .../oci/instancepools/oci_cloud_provider.go   |  5 ++
 .../oci/nodepools/oci_cloud_provider.go       |  5 ++
 .../ovhcloud/ovh_cloud_provider.go            |  5 ++
 .../cloudprovider/rancher/rancher_provider.go |  5 ++
 .../scaleway/scaleway_cloud_provider.go       |  5 ++
 .../tencentcloud_cloud_provider.go            |  5 ++
 .../cloudprovider/test/test_cloud_provider.go | 44 +++++++---
 .../cloudprovider/utho/utho_cloud_provider.go |  5 ++
 .../volcengine/volcengine_cloud_provider.go   |  5 ++
 .../vultr/vultr_cloud_provider.go             |  5 ++
 .../nodes/pre_filtering_processor.go          | 10 +++
 .../nodes/pre_filtering_processor_test.go     | 83 +++++++++++++++----
 38 files changed, 289 insertions(+), 26 deletions(-)

diff --git a/cluster-autoscaler/cloudprovider/alicloud/alicloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/alicloud/alicloud_cloud_provider.go
index c8513c7bf964..04f727dfd29c 100644
--- a/cluster-autoscaler/cloudprovider/alicloud/alicloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/alicloud/alicloud_cloud_provider.go
@@ -175,6 +175,11 @@ func (ali *aliCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (ali *aliCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // AliRef contains a reference to ECS instance or .
 type AliRef struct {
 	ID     string
diff --git a/cluster-autoscaler/cloudprovider/aws/aws_cloud_provider.go b/cluster-autoscaler/cloudprovider/aws/aws_cloud_provider.go
index 3117b1c73654..bff016a107ae 100644
--- a/cluster-autoscaler/cloudprovider/aws/aws_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/aws/aws_cloud_provider.go
@@ -193,6 +193,11 @@ func (aws *awsCloudProvider) Refresh() error {
 	return aws.awsManager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (aws *awsCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // AwsRef contains a reference to some entity in AWS world.
 type AwsRef struct {
 	Name string
diff --git a/cluster-autoscaler/cloudprovider/azure/azure_cloud_provider.go b/cluster-autoscaler/cloudprovider/azure/azure_cloud_provider.go
index f99f2dae615d..3338d8b720d3 100644
--- a/cluster-autoscaler/cloudprovider/azure/azure_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/azure/azure_cloud_provider.go
@@ -174,6 +174,11 @@ func (azure *AzureCloudProvider) Refresh() error {
 	return azure.azureManager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (azure *AzureCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // azureRef contains a reference to some entity in Azure world.
 type azureRef struct {
 	Name string
diff --git a/cluster-autoscaler/cloudprovider/baiducloud/baiducloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/baiducloud/baiducloud_cloud_provider.go
index 1698eb23cbde..0260c21bf84e 100644
--- a/cluster-autoscaler/cloudprovider/baiducloud/baiducloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/baiducloud/baiducloud_cloud_provider.go
@@ -228,6 +228,11 @@ func (baiducloud *baiducloudCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (baiducloud *baiducloudCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BaiducloudRef contains a reference to some entity in baiducloud world.
 type BaiducloudRef struct {
 	Name string
diff --git a/cluster-autoscaler/cloudprovider/bizflycloud/bizflycloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/bizflycloud/bizflycloud_cloud_provider.go
index 4b9f5db16e9f..ec5f9decdad3 100644
--- a/cluster-autoscaler/cloudprovider/bizflycloud/bizflycloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/bizflycloud/bizflycloud_cloud_provider.go
@@ -172,6 +172,11 @@ func (d *bizflycloudCloudProvider) Refresh() error {
 	return d.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (d *bizflycloudCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildBizflyCloud builds the Bizflycloud cloud provider.
 func BuildBizflyCloud(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/brightbox/brightbox_cloud_provider.go b/cluster-autoscaler/cloudprovider/brightbox/brightbox_cloud_provider.go
index f2806ece76db..6de29dec64f3 100644
--- a/cluster-autoscaler/cloudprovider/brightbox/brightbox_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/brightbox/brightbox_cloud_provider.go
@@ -219,6 +219,11 @@ func (b *brightboxCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (b *brightboxCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildBrightbox builds the Brightbox provider
 func BuildBrightbox(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/cherryservers/cherry_cloud_provider.go b/cluster-autoscaler/cloudprovider/cherryservers/cherry_cloud_provider.go
index 0407f1971e8e..87b0793d315d 100644
--- a/cluster-autoscaler/cloudprovider/cherryservers/cherry_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/cherryservers/cherry_cloud_provider.go
@@ -170,6 +170,11 @@ func (ccp *cherryCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (ccp *cherryCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildCherry is called by the autoscaler to build a Cherry Servers cloud provider.
 //
 // The cherryManager is created here, and the node groups are created
diff --git a/cluster-autoscaler/cloudprovider/civo/civo_cloud_provider.go b/cluster-autoscaler/cloudprovider/civo/civo_cloud_provider.go
index c5b69be57d1c..8c317ead4894 100644
--- a/cluster-autoscaler/cloudprovider/civo/civo_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/civo/civo_cloud_provider.go
@@ -167,6 +167,11 @@ func (d *civoCloudProvider) Refresh() error {
 	return d.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (d *civoCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildCivo builds the Civo cloud provider.
 func BuildCivo(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/cloud_provider.go b/cluster-autoscaler/cloudprovider/cloud_provider.go
index f19fa8817aea..ed48844d63e2 100644
--- a/cluster-autoscaler/cloudprovider/cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/cloud_provider.go
@@ -154,6 +154,14 @@ type CloudProvider interface {
 	// Refresh is called before every main loop and can be used to dynamically update cloud provider state.
 	// In particular the list of node groups returned by NodeGroups can change as a result of CloudProvider.Refresh().
 	Refresh() error
+
+	// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down. This function
+	// will be called during prefiltering of nodes for scaledown to allow cloud providers the opportunity
+	// to reject a node for scale down. This may be used in cases where nodes are undergoing upgrades or other
+	// cloud-specific behavior where the cluster autoscaler should not begin cordoning, draining, and tainting
+	// the node.
+	// Returns true if the node can be safely scaled down or false otherwise.
+	IsNodeCandidateForScaleDown(*apiv1.Node) (bool, error)
 }
 
 // ErrNotImplemented is returned if a method is not implemented.
diff --git a/cluster-autoscaler/cloudprovider/cloudstack/cloudstack_cloud_provider.go b/cluster-autoscaler/cloudprovider/cloudstack/cloudstack_cloud_provider.go
index cbc2996155d0..47bb994a7934 100644
--- a/cluster-autoscaler/cloudprovider/cloudstack/cloudstack_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/cloudstack/cloudstack_cloud_provider.go
@@ -115,6 +115,11 @@ func (provider *cloudStackCloudProvider) Pricing() (cloudprovider.PricingModel,
 	return nil, cloudprovider.ErrNotImplemented
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (provider *cloudStackCloudProvider) IsNodeCandidateForScaleDown(node *v1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // NewNodeGroup builds a theoretical node group based on the node definition provided. The node group is not automatically
 // created on the cloud provider side. The node group is not returned by NodeGroups() until it is created.
 func (provider *cloudStackCloudProvider) NewNodeGroup(machineType string, labels map[string]string, systemLabels map[string]string, taints []v1.Taint, extraResources map[string]resource.Quantity) (cloudprovider.NodeGroup, error) {
diff --git a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
index 94a322e5962f..35d57c5c2936 100644
--- a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
+++ b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
@@ -140,6 +140,11 @@ func (p *provider) GetNodeGpuConfig(node *corev1.Node) *cloudprovider.GpuConfig
 	return gpu.GetNodeGPUFromCloudProvider(p, node)
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (p *provider) IsNodeCandidateForScaleDown(node *corev1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 func newProvider(
 	name string,
 	rl *cloudprovider.ResourceLimiter,
diff --git a/cluster-autoscaler/cloudprovider/coreweave/coreweave_provider.go b/cluster-autoscaler/cloudprovider/coreweave/coreweave_provider.go
index 84dadf018873..a24fccd816c6 100644
--- a/cluster-autoscaler/cloudprovider/coreweave/coreweave_provider.go
+++ b/cluster-autoscaler/cloudprovider/coreweave/coreweave_provider.go
@@ -181,6 +181,11 @@ func (c *CoreWeaveCloudProvider) Refresh() error {
 	return c.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (c *CoreWeaveCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildCoreWeave builds the CoreWeave cloud provider with the given options and returns it.
 func BuildCoreWeave(opts config.AutoscalingOptions, do cloudprovider.NodeGroupDiscoveryOptions, rl *cloudprovider.ResourceLimiter) cloudprovider.CloudProvider {
 	klog.V(4).Infof("Building CoreWeave cloud provider with options: %+v", opts)
diff --git a/cluster-autoscaler/cloudprovider/digitalocean/digitalocean_cloud_provider.go b/cluster-autoscaler/cloudprovider/digitalocean/digitalocean_cloud_provider.go
index b9e4941dffe6..bedcf42e2ff4 100644
--- a/cluster-autoscaler/cloudprovider/digitalocean/digitalocean_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/digitalocean/digitalocean_cloud_provider.go
@@ -169,6 +169,11 @@ func (d *digitaloceanCloudProvider) Refresh() error {
 	return d.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (d *digitaloceanCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildDigitalOcean builds the DigitalOcean cloud provider.
 func BuildDigitalOcean(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/equinixmetal/cloud_provider.go b/cluster-autoscaler/cloudprovider/equinixmetal/cloud_provider.go
index fd1ec89be920..9d2b9e89db0d 100644
--- a/cluster-autoscaler/cloudprovider/equinixmetal/cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/equinixmetal/cloud_provider.go
@@ -176,6 +176,11 @@ func (pcp *equinixMetalCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (pcp *equinixMetalCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildCloudProvider is called by the autoscaler to build an Equinix Metal cloud provider.
 //
 // The equinixMetalManager is created here, and the node groups are created
diff --git a/cluster-autoscaler/cloudprovider/exoscale/exoscale_cloud_provider.go b/cluster-autoscaler/cloudprovider/exoscale/exoscale_cloud_provider.go
index 067340e19ad9..22d886baa450 100644
--- a/cluster-autoscaler/cloudprovider/exoscale/exoscale_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/exoscale/exoscale_cloud_provider.go
@@ -224,6 +224,11 @@ func (e *exoscaleCloudProvider) Refresh() error {
 	return e.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (e *exoscaleCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildExoscale builds the Exoscale cloud provider.
 func BuildExoscale(_ config.AutoscalingOptions, discoveryOpts cloudprovider.NodeGroupDiscoveryOptions, rl *cloudprovider.ResourceLimiter) cloudprovider.CloudProvider {
 	manager, err := newManager(discoveryOpts)
diff --git a/cluster-autoscaler/cloudprovider/externalgrpc/externalgrpc_cloud_provider.go b/cluster-autoscaler/cloudprovider/externalgrpc/externalgrpc_cloud_provider.go
index 2779f229e3d3..acc30587d7fd 100644
--- a/cluster-autoscaler/cloudprovider/externalgrpc/externalgrpc_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/externalgrpc/externalgrpc_cloud_provider.go
@@ -316,6 +316,11 @@ func (e *externalGrpcCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (e *externalGrpcCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildExternalGrpc builds the externalgrpc cloud provider.
 func BuildExternalGrpc(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/gce/gce_cloud_provider.go b/cluster-autoscaler/cloudprovider/gce/gce_cloud_provider.go
index 73d5773e7472..bac37987c2ee 100644
--- a/cluster-autoscaler/cloudprovider/gce/gce_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/gce/gce_cloud_provider.go
@@ -148,6 +148,11 @@ func (gce *GceCloudProvider) Refresh() error {
 	return gce.gceManager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (gce *GceCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // GceRef contains s reference to some entity in GCE world.
 type GceRef struct {
 	Project string
diff --git a/cluster-autoscaler/cloudprovider/hetzner/hetzner_cloud_provider.go b/cluster-autoscaler/cloudprovider/hetzner/hetzner_cloud_provider.go
index 07e73cfd3c6e..5ec235fee2fc 100644
--- a/cluster-autoscaler/cloudprovider/hetzner/hetzner_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/hetzner/hetzner_cloud_provider.go
@@ -182,6 +182,11 @@ func (d *HetznerCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (d *HetznerCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildHetzner builds the Hetzner cloud provider.
 func BuildHetzner(_ config.AutoscalingOptions, do cloudprovider.NodeGroupDiscoveryOptions, rl *cloudprovider.ResourceLimiter) cloudprovider.CloudProvider {
 	manager, err := newManager()
diff --git a/cluster-autoscaler/cloudprovider/huaweicloud/huaweicloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/huaweicloud/huaweicloud_cloud_provider.go
index d58dae40763f..9dfcd1e5e03c 100644
--- a/cluster-autoscaler/cloudprovider/huaweicloud/huaweicloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/huaweicloud/huaweicloud_cloud_provider.go
@@ -179,6 +179,11 @@ func (hcp *huaweicloudCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (hcp *huaweicloudCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 func (hcp *huaweicloudCloudProvider) buildAsgs(specs []string) error {
 	asgs, err := hcp.cloudServiceManager.ListScalingGroups()
 	if err != nil {
diff --git a/cluster-autoscaler/cloudprovider/ionoscloud/ionoscloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/ionoscloud/ionoscloud_cloud_provider.go
index 7669cba28b09..ea0d53af2350 100644
--- a/cluster-autoscaler/cloudprovider/ionoscloud/ionoscloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/ionoscloud/ionoscloud_cloud_provider.go
@@ -308,6 +308,11 @@ func (ic *IonosCloudCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (ic *IonosCloudCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildIonosCloud builds the IonosCloud cloud provider.
 func BuildIonosCloud(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/kamatera/kamatera_cloud_provider.go b/cluster-autoscaler/cloudprovider/kamatera/kamatera_cloud_provider.go
index ed8af5cc0fee..d072cfe84906 100644
--- a/cluster-autoscaler/cloudprovider/kamatera/kamatera_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/kamatera/kamatera_cloud_provider.go
@@ -129,6 +129,11 @@ func (k *kamateraCloudProvider) Refresh() error {
 	return k.manager.refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (k *kamateraCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildKamatera builds the Kamatera cloud provider.
 func BuildKamatera(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/kubemark/kubemark_linux.go b/cluster-autoscaler/cloudprovider/kubemark/kubemark_linux.go
index a38148a1e616..f95f8c06f00d 100644
--- a/cluster-autoscaler/cloudprovider/kubemark/kubemark_linux.go
+++ b/cluster-autoscaler/cloudprovider/kubemark/kubemark_linux.go
@@ -180,6 +180,11 @@ func (kubemark *KubemarkCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (kubemark *KubemarkCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // NodeGroup implements NodeGroup interface.
 type NodeGroup struct {
 	Name               string
diff --git a/cluster-autoscaler/cloudprovider/kwok/kwok_provider.go b/cluster-autoscaler/cloudprovider/kwok/kwok_provider.go
index a1691171bf0e..0972d6235f8c 100644
--- a/cluster-autoscaler/cloudprovider/kwok/kwok_provider.go
+++ b/cluster-autoscaler/cloudprovider/kwok/kwok_provider.go
@@ -170,6 +170,11 @@ func (kwok *KwokCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (kwok *KwokCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildKwok builds kwok cloud provider.
 func BuildKwok(opts config.AutoscalingOptions,
 	do cloudprovider.NodeGroupDiscoveryOptions,
diff --git a/cluster-autoscaler/cloudprovider/linode/linode_cloud_provider.go b/cluster-autoscaler/cloudprovider/linode/linode_cloud_provider.go
index a5b44563ded7..d6f968e005cd 100644
--- a/cluster-autoscaler/cloudprovider/linode/linode_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/linode/linode_cloud_provider.go
@@ -151,6 +151,11 @@ func (l *linodeCloudProvider) Refresh() error {
 	return l.manager.refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (l *linodeCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 func newLinodeCloudProvider(config io.Reader, rl *cloudprovider.ResourceLimiter) (cloudprovider.CloudProvider, error) {
 	m, err := newManager(config)
 	if err != nil {
diff --git a/cluster-autoscaler/cloudprovider/magnum/magnum_cloud_provider.go b/cluster-autoscaler/cloudprovider/magnum/magnum_cloud_provider.go
index c6161e362157..2ea9c769b9e0 100644
--- a/cluster-autoscaler/cloudprovider/magnum/magnum_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/magnum/magnum_cloud_provider.go
@@ -203,6 +203,11 @@ func (mcp *magnumCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (mcp *magnumCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // refreshNodeGroups gets the list of node groups which meet the requirements for autoscaling,
 // creates magnumNodeGroups for any that do not exist in the cloud provider,
 // and drops any node groups which are present in the cloud provider but not in the
diff --git a/cluster-autoscaler/cloudprovider/mocks/CloudProvider.go b/cluster-autoscaler/cloudprovider/mocks/CloudProvider.go
index 23ea1ae21d1a..49173c32f207 100644
--- a/cluster-autoscaler/cloudprovider/mocks/CloudProvider.go
+++ b/cluster-autoscaler/cloudprovider/mocks/CloudProvider.go
@@ -276,3 +276,8 @@ func (_m *CloudProvider) Refresh() error {
 
 	return r0
 }
+
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (_m *CloudProvider) IsNodeCandidateForScaleDown(node *v1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
diff --git a/cluster-autoscaler/cloudprovider/oci/instancepools/oci_cloud_provider.go b/cluster-autoscaler/cloudprovider/oci/instancepools/oci_cloud_provider.go
index 425f4350331c..241c7013274d 100644
--- a/cluster-autoscaler/cloudprovider/oci/instancepools/oci_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/oci/instancepools/oci_cloud_provider.go
@@ -147,6 +147,11 @@ func (ocp *OciCloudProvider) Refresh() error {
 	return ocp.poolManager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (ocp *OciCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildOCI constructs the OciCloudProvider object that implements the could provider interface (InstancePoolManager).
 func BuildOCI(opts config.AutoscalingOptions, do cloudprovider.NodeGroupDiscoveryOptions, rl *cloudprovider.ResourceLimiter) cloudprovider.CloudProvider {
 	ocidType, err := ocicommon.GetAllPoolTypes(opts.NodeGroups)
diff --git a/cluster-autoscaler/cloudprovider/oci/nodepools/oci_cloud_provider.go b/cluster-autoscaler/cloudprovider/oci/nodepools/oci_cloud_provider.go
index ae3f70549151..a64fbf854c7a 100644
--- a/cluster-autoscaler/cloudprovider/oci/nodepools/oci_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/oci/nodepools/oci_cloud_provider.go
@@ -149,3 +149,8 @@ func (ocp *OciCloudProvider) Cleanup() error {
 func (ocp *OciCloudProvider) Refresh() error {
 	return ocp.manager.Refresh()
 }
+
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (ocp *OciCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
diff --git a/cluster-autoscaler/cloudprovider/ovhcloud/ovh_cloud_provider.go b/cluster-autoscaler/cloudprovider/ovhcloud/ovh_cloud_provider.go
index c731a8b8e3d4..cae8aa52153a 100644
--- a/cluster-autoscaler/cloudprovider/ovhcloud/ovh_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/ovhcloud/ovh_cloud_provider.go
@@ -318,3 +318,8 @@ func (provider *OVHCloudProvider) Refresh() error {
 
 	return nil
 }
+
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (provider *OVHCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
diff --git a/cluster-autoscaler/cloudprovider/rancher/rancher_provider.go b/cluster-autoscaler/cloudprovider/rancher/rancher_provider.go
index a7b94d902b3e..85f927125037 100644
--- a/cluster-autoscaler/cloudprovider/rancher/rancher_provider.go
+++ b/cluster-autoscaler/cloudprovider/rancher/rancher_provider.go
@@ -219,6 +219,11 @@ func (provider *RancherCloudProvider) Cleanup() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (provider *RancherCloudProvider) IsNodeCandidateForScaleDown(node *corev1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 func (provider *RancherCloudProvider) scalableNodeGroups() ([]*nodeGroup, error) {
 	var result []*nodeGroup
 
diff --git a/cluster-autoscaler/cloudprovider/scaleway/scaleway_cloud_provider.go b/cluster-autoscaler/cloudprovider/scaleway/scaleway_cloud_provider.go
index a214d16823ff..08104ee37a86 100644
--- a/cluster-autoscaler/cloudprovider/scaleway/scaleway_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/scaleway/scaleway_cloud_provider.go
@@ -277,3 +277,8 @@ func (scw *scalewayCloudProvider) Refresh() error {
 
 	return nil
 }
+
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (scw *scalewayCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
diff --git a/cluster-autoscaler/cloudprovider/tencentcloud/tencentcloud_cloud_provider.go b/cluster-autoscaler/cloudprovider/tencentcloud/tencentcloud_cloud_provider.go
index a33c140fb315..b93b5ec8654c 100644
--- a/cluster-autoscaler/cloudprovider/tencentcloud/tencentcloud_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/tencentcloud/tencentcloud_cloud_provider.go
@@ -173,6 +173,11 @@ func (tencentcloud *tencentCloudProvider) Refresh() error {
 	return tencentcloud.tencentcloudManager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (tencentcloud *tencentCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildTencentcloud returns tencentcloud provider
 func BuildTencentcloud(opts config.AutoscalingOptions, do cloudprovider.NodeGroupDiscoveryOptions, rl *cloudprovider.ResourceLimiter) cloudprovider.CloudProvider {
 	var config io.ReadCloser
diff --git a/cluster-autoscaler/cloudprovider/test/test_cloud_provider.go b/cluster-autoscaler/cloudprovider/test/test_cloud_provider.go
index 2c3bcf6a901f..94039d07ec25 100644
--- a/cluster-autoscaler/cloudprovider/test/test_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/test/test_cloud_provider.go
@@ -45,20 +45,25 @@ type OnNodeGroupDeleteFunc func(string) error
 // HasInstance is a function called to determine if a node has been removed from the cloud provider.
 type HasInstance func(string) (bool, error)
 
+// IsNodeCandidateForScaleDown is a function called to determine if a cloud provider considers
+// a node a good candidate for scaling down.
+type IsNodeCandidateForScaleDown func(*apiv1.Node) (bool, error)
+
 // TestCloudProvider is a dummy cloud provider to be used in tests.
 type TestCloudProvider struct {
 	sync.Mutex
-	nodes             map[string]string
-	groups            map[string]cloudprovider.NodeGroup
-	onScaleUp         func(string, int) error
-	onScaleDown       func(string, string) error
-	onNodeGroupCreate func(string) error
-	onNodeGroupDelete func(string) error
-	hasInstance       func(string) (bool, error)
-	machineTypes      []string
-	machineTemplates  map[string]*framework.NodeInfo
-	priceModel        cloudprovider.PricingModel
-	resourceLimiter   *cloudprovider.ResourceLimiter
+	nodes                       map[string]string
+	groups                      map[string]cloudprovider.NodeGroup
+	onScaleUp                   func(string, int) error
+	onScaleDown                 func(string, string) error
+	onNodeGroupCreate           func(string) error
+	onNodeGroupDelete           func(string) error
+	hasInstance                 func(string) (bool, error)
+	isNodeCandidateForScaleDown func(*apiv1.Node) (bool, error)
+	machineTypes                []string
+	machineTemplates            map[string]*framework.NodeInfo
+	priceModel                  cloudprovider.PricingModel
+	resourceLimiter             *cloudprovider.ResourceLimiter
 }
 
 // TestCloudProviderBuilder is used to create CloudProvider
@@ -127,6 +132,14 @@ func (b *TestCloudProviderBuilder) WithHasInstance(hasInstance HasInstance) *Tes
 	return b
 }
 
+// WithIsNodeCandidateForScaleDown adds an IsNodeCandidateForScaleDown handler to provider.
+func (b *TestCloudProviderBuilder) WithIsNodeCandidateForScaleDown(isNodeCandidateForScaleDown IsNodeCandidateForScaleDown) *TestCloudProviderBuilder {
+	b.builders = append(b.builders, func(p *TestCloudProvider) {
+		p.isNodeCandidateForScaleDown = isNodeCandidateForScaleDown
+	})
+	return b
+}
+
 // Build returns a built test cloud provider
 func (b *TestCloudProviderBuilder) Build() *TestCloudProvider {
 	p := &TestCloudProvider{
@@ -352,6 +365,15 @@ func (tcp *TestCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (tcp *TestCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	if tcp.isNodeCandidateForScaleDown == nil {
+		return true, cloudprovider.ErrNotImplemented
+	}
+
+	return tcp.isNodeCandidateForScaleDown(node)
+}
+
 // TestNodeGroup is a node group used by TestCloudProvider.
 type TestNodeGroup struct {
 	sync.Mutex
diff --git a/cluster-autoscaler/cloudprovider/utho/utho_cloud_provider.go b/cluster-autoscaler/cloudprovider/utho/utho_cloud_provider.go
index 9d511e127c70..397b2c6d8675 100644
--- a/cluster-autoscaler/cloudprovider/utho/utho_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/utho/utho_cloud_provider.go
@@ -162,6 +162,11 @@ func (u *uthoCloudProvider) Refresh() error {
 	return u.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (u *uthoCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // BuildUtho builds the Utho cloud provider.
 func BuildUtho(
 	opts config.AutoscalingOptions,
diff --git a/cluster-autoscaler/cloudprovider/volcengine/volcengine_cloud_provider.go b/cluster-autoscaler/cloudprovider/volcengine/volcengine_cloud_provider.go
index 53ad1ec1139d..cb17bb0f55c5 100644
--- a/cluster-autoscaler/cloudprovider/volcengine/volcengine_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/volcengine/volcengine_cloud_provider.go
@@ -120,6 +120,11 @@ func (v *volcengineCloudProvider) Refresh() error {
 	return nil
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (v *volcengineCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // GetNodeGpuConfig returns the label, type and resource name for the GPU added to node. If node doesn't have
 // any GPUs, it returns nil.
 func (v *volcengineCloudProvider) GetNodeGpuConfig(node *apiv1.Node) *cloudprovider.GpuConfig {
diff --git a/cluster-autoscaler/cloudprovider/vultr/vultr_cloud_provider.go b/cluster-autoscaler/cloudprovider/vultr/vultr_cloud_provider.go
index 5234a1019786..822afe70da24 100644
--- a/cluster-autoscaler/cloudprovider/vultr/vultr_cloud_provider.go
+++ b/cluster-autoscaler/cloudprovider/vultr/vultr_cloud_provider.go
@@ -140,6 +140,11 @@ func (v *vultrCloudProvider) Refresh() error {
 	return v.manager.Refresh()
 }
 
+// IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
+func (v *vultrCloudProvider) IsNodeCandidateForScaleDown(node *apiv1.Node) (bool, error) {
+	return true, cloudprovider.ErrNotImplemented
+}
+
 // toProviderID returns a provider ID from the given node ID.
 func toProviderID(nodeID string) string {
 	return fmt.Sprintf("%s%s", vultrProviderIDPrefix, nodeID)
diff --git a/cluster-autoscaler/processors/nodes/pre_filtering_processor.go b/cluster-autoscaler/processors/nodes/pre_filtering_processor.go
index 7a3091660135..0cf745dabaa1 100644
--- a/cluster-autoscaler/processors/nodes/pre_filtering_processor.go
+++ b/cluster-autoscaler/processors/nodes/pre_filtering_processor.go
@@ -22,6 +22,7 @@ import (
 	apiv1 "k8s.io/api/core/v1"
 	klog "k8s.io/klog/v2"
 
+	"k8s.io/autoscaler/cluster-autoscaler/cloudprovider"
 	"k8s.io/autoscaler/cluster-autoscaler/context"
 	"k8s.io/autoscaler/cluster-autoscaler/utils"
 	"k8s.io/autoscaler/cluster-autoscaler/utils/errors"
@@ -48,6 +49,15 @@ func (n *PreFilteringScaleDownNodeProcessor) GetScaleDownCandidates(ctx *context
 	nodeGroupSize := utils.GetNodeGroupSizeMap(ctx.CloudProvider)
 
 	for _, node := range nodes {
+		if candidate, err := ctx.CloudProvider.IsNodeCandidateForScaleDown(node); err != nil {
+			if err != cloudprovider.ErrNotImplemented {
+				klog.Warningf("Error while checking if node is a candidate for deletion %s: %v", node.Name, err)
+				continue
+			}
+		} else if !candidate {
+			klog.V(5).Infof("Node %s is not a candidate for deletion (cloud provider determined)", node.Name)
+			continue
+		}
 		nodeGroup, err := ctx.CloudProvider.NodeGroupForNode(node)
 		if err != nil {
 			klog.Warningf("Error while checking node group for %s: %v", node.Name, err)
diff --git a/cluster-autoscaler/processors/nodes/pre_filtering_processor_test.go b/cluster-autoscaler/processors/nodes/pre_filtering_processor_test.go
index e8165620bf5a..9e120997e398 100644
--- a/cluster-autoscaler/processors/nodes/pre_filtering_processor_test.go
+++ b/cluster-autoscaler/processors/nodes/pre_filtering_processor_test.go
@@ -17,6 +17,7 @@ limitations under the License.
 package nodes
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -44,23 +45,75 @@ func TestPreFilteringScaleDownNodeProcessor_GetScaleDownCandidateNodes(t *testin
 	ng1_1 := BuildTestNode("ng1-1", 1000, 1000)
 	ng1_2 := BuildTestNode("ng1-2", 1000, 1000)
 	ng2_1 := BuildTestNode("ng2-1", 1000, 1000)
+	ng2_2 := BuildTestNode("ng2-2", 1000, 1000)
 	noNg := BuildTestNode("no-ng", 1000, 1000)
-	provider := testprovider.NewTestCloudProviderBuilder().Build()
-	provider.AddNodeGroup("ng1", 1, 10, 2)
-	provider.AddNodeGroup("ng2", 1, 10, 1)
-	provider.AddNode("ng1", ng1_1)
-	provider.AddNode("ng1", ng1_2)
-	provider.AddNode("ng2", ng2_1)
-
-	ctx := &context.AutoscalingContext{
-		CloudProvider: provider,
+
+	testCases := map[string]struct {
+		buildProvider     func() *testprovider.TestCloudProvider
+		configureProvider func(p *testprovider.TestCloudProvider)
+		expectedNodes     []*apiv1.Node
+		inputNodes        []*apiv1.Node
+	}{
+		// Expectation: only node groups not at minimum size should be candidates.
+		"1 scale down candidate, 1 node group at minimum size, 1 node with no node group, 1 node group above minimum size.": {
+			configureProvider: func(p *testprovider.TestCloudProvider) {
+				p.AddNodeGroup("ng1", 1, 10, 2)
+				p.AddNodeGroup("ng2", 1, 10, 1)
+				p.AddNode("ng1", ng1_1)
+				p.AddNode("ng1", ng1_2)
+				p.AddNode("ng2", ng2_1)
+			},
+			expectedNodes: []*apiv1.Node{ng1_1, ng1_2},
+			inputNodes:    []*apiv1.Node{ng1_1, ng1_2, ng2_1, noNg},
+		},
+		// Expectation: only node groups that contain nodes the cloud provider considers candidates for deletion should be candidates.
+		"1 scale down candidate, 1 node group with nodes that are not candidates for deletion, 1 node group above minimum size.": {
+			buildProvider: func() *testprovider.TestCloudProvider {
+				provider := testprovider.
+					NewTestCloudProviderBuilder().
+					WithIsNodeCandidateForScaleDown(func(n *apiv1.Node) (bool, error) {
+						if strings.HasPrefix(n.Name, "ng2") {
+							return false, nil
+						}
+						return true, nil
+					}).
+					Build()
+				return provider
+			},
+			configureProvider: func(p *testprovider.TestCloudProvider) {
+				p.AddNodeGroup("ng1", 1, 10, 2)
+				p.AddNodeGroup("ng2", 1, 10, 2)
+				p.AddNode("ng1", ng1_1)
+				p.AddNode("ng1", ng1_2)
+				p.AddNode("ng2", ng2_1)
+				p.AddNode("ng2", ng2_2)
+			},
+			expectedNodes: []*apiv1.Node{ng1_1, ng1_2},
+			inputNodes:    []*apiv1.Node{ng1_1, ng1_2, ng2_1, ng2_2},
+		},
 	}
 
-	expectedNodes := []*apiv1.Node{ng1_1, ng1_2}
-	defaultProcessor := NewPreFilteringScaleDownNodeProcessor()
-	inputNodes := []*apiv1.Node{ng1_1, ng1_2, ng2_1, noNg}
-	result, err := defaultProcessor.GetScaleDownCandidates(ctx, inputNodes)
+	for description, testCase := range testCases {
+		t.Run(description, func(t *testing.T) {
+			var provider *testprovider.TestCloudProvider
+			if testCase.buildProvider == nil {
+				provider = testprovider.NewTestCloudProviderBuilder().Build()
+			} else {
+				provider = testCase.buildProvider()
+			}
+			assert.NotNil(t, provider)
 
-	assert.NoError(t, err)
-	assert.Equal(t, result, expectedNodes)
+			testCase.configureProvider(provider)
+
+			ctx := &context.AutoscalingContext{
+				CloudProvider: provider,
+			}
+
+			defaultProcessor := NewPreFilteringScaleDownNodeProcessor()
+			result, err := defaultProcessor.GetScaleDownCandidates(ctx, testCase.inputNodes)
+
+			assert.NoError(t, err)
+			assert.Equal(t, result, testCase.expectedNodes)
+		})
+	}
 }

From a81913f3b9fc0e4427e2617ad48c453944683edc Mon Sep 17 00:00:00 2001
From: elmiko <msm@opbstudios.com>
Date: Mon, 8 Sep 2025 15:53:23 -0400
Subject: [PATCH 2/2] add clusterapi IsNodeCandidateForScaleDown impl

The initial implementation of this function for clusterapi will return
that a node is not a good candidate for scale down when it belongs to a
MachineDeployment that is currently rolling out an upgrade.
---
 .../clusterapi/clusterapi_controller.go       | 21 +++++++
 .../clusterapi/clusterapi_nodegroup.go        | 62 +++++++++++++++++++
 .../clusterapi/clusterapi_provider.go         | 20 +++++-
 .../clusterapi/clusterapi_utils.go            | 20 +++---
 4 files changed, 111 insertions(+), 12 deletions(-)

diff --git a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_controller.go b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_controller.go
index b3b7175dfa95..a3e03e9703c3 100644
--- a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_controller.go
+++ b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_controller.go
@@ -849,6 +849,27 @@ func (c *machineController) listMachinesForScalableResource(r *unstructured.Unst
 	}
 }
 
+func (c *machineController) listMachineSetsForMachineDeployment(r *unstructured.Unstructured) ([]*unstructured.Unstructured, error) {
+	selector := labels.SelectorFromSet(map[string]string{
+		machineDeploymentNameLabel: r.GetName(),
+	})
+	objs, err := c.machineSetInformer.Lister().ByNamespace(r.GetNamespace()).List(selector)
+	if err != nil {
+		return nil, fmt.Errorf("unable to list MachineSets for MachineDeployment %s: %w", r.GetName(), err)
+	}
+
+	results := make([]*unstructured.Unstructured, 0, len(objs))
+	for _, x := range objs {
+		u, ok := x.(*unstructured.Unstructured)
+		if !ok {
+			return nil, fmt.Errorf("expected unstructured resource from lister, not %T", x)
+		}
+		results = append(results, u.DeepCopy())
+	}
+
+	return results, nil
+}
+
 func (c *machineController) listScalableResources() ([]*unstructured.Unstructured, error) {
 	scalableResources, err := c.listResources(c.machineSetInformer.Lister())
 	if err != nil {
diff --git a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_nodegroup.go b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_nodegroup.go
index d68a48b89c3f..4b6bb1b2905a 100644
--- a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_nodegroup.go
+++ b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_nodegroup.go
@@ -458,6 +458,68 @@ func (ng *nodegroup) GetOptions(defaults config.NodeGroupAutoscalingOptions) (*c
 	return &defaults, nil
 }
 
+func (ng *nodegroup) IsMachineDeploymentAndRollingOut() (bool, error) {
+	if ng.scalableResource.Kind() != machineDeploymentKind {
+		// Not a MachineDeployment.
+		return false, nil
+	}
+
+	machineSets, err := ng.machineController.listMachineSetsForMachineDeployment(ng.scalableResource.unstructured)
+	if err != nil {
+		return false, err
+	}
+
+	if len(machineSets) == 0 {
+		// No MachineSets => MD is not rolling out.
+		return false, nil
+	}
+
+	// Find the latest revision, the MachineSet with the latest revision is the MachineSet that
+	// matches the MachineDeployment spec.
+	var latestMSRevisionInt int64
+	for _, ms := range machineSets {
+		msRevision, ok := ms.GetAnnotations()[machineDeploymentRevisionAnnotation]
+		if !ok {
+			continue
+		}
+
+		msRevisionInt, err := strconv.ParseInt(msRevision, 10, 64)
+		if err != nil {
+			return false, errors.Wrapf(err, "failed to parse current revision on MachineSet %s", klog.KObj(ms))
+		}
+		latestMSRevisionInt = max(latestMSRevisionInt, msRevisionInt)
+	}
+	maxMSRevision := strconv.FormatInt(latestMSRevisionInt, 10)
+
+	for _, ms := range machineSets {
+		if ms.GetAnnotations()[machineDeploymentRevisionAnnotation] == maxMSRevision {
+			// Ignore the MachineSet with the latest revision
+			continue
+		}
+
+		// Check if any of the old MachineSets still have replicas
+		replicas, found, err := unstructured.NestedInt64(ms.UnstructuredContent(), "spec", "replicas")
+		if err != nil {
+			return false, errors.Wrapf(err, "failed to find spec replicas on MachineSet %s", klog.KObj(ms))
+		}
+		if found && replicas > 0 {
+			// Found old MachineSets that still has replicas => MD is still rolling out.
+			return true, nil
+		}
+		replicas, found, err = unstructured.NestedInt64(ms.UnstructuredContent(), "status", "replicas")
+		if err != nil {
+			return false, errors.Wrapf(err, "failed to find status replicas on MachineSet %s", klog.KObj(ms))
+		}
+		if found && replicas > 0 {
+			// Found old MachineSets that still has replicas => MD is still rolling out.
+			return true, nil
+		}
+	}
+
+	// Didn't find any old MachineSets that still have replicas => MD is not rolling out.
+	return false, nil
+}
+
 func newNodeGroupFromScalableResource(controller *machineController, unstructuredScalableResource *unstructured.Unstructured) (*nodegroup, error) {
 	// Ensure that the resulting node group would be allowed based on the autodiscovery specs if defined
 	if !controller.allowedByAutoDiscoverySpecs(unstructuredScalableResource) {
diff --git a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
index 35d57c5c2936..b1777045131f 100644
--- a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
+++ b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_provider.go
@@ -21,6 +21,7 @@ import (
 	"path"
 	"reflect"
 
+	"github.com/pkg/errors"
 	corev1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/resource"
 	"k8s.io/client-go/discovery"
@@ -34,7 +35,7 @@ import (
 
 	"k8s.io/autoscaler/cluster-autoscaler/cloudprovider"
 	"k8s.io/autoscaler/cluster-autoscaler/config"
-	"k8s.io/autoscaler/cluster-autoscaler/utils/errors"
+	caserrors "k8s.io/autoscaler/cluster-autoscaler/utils/errors"
 	"k8s.io/autoscaler/cluster-autoscaler/utils/gpu"
 )
 
@@ -92,7 +93,7 @@ func (p *provider) HasInstance(node *corev1.Node) (bool, error) {
 	return false, fmt.Errorf("machine not found for node %s: %v", node.Name, err)
 }
 
-func (*provider) Pricing() (cloudprovider.PricingModel, errors.AutoscalerError) {
+func (*provider) Pricing() (cloudprovider.PricingModel, caserrors.AutoscalerError) {
 	return nil, cloudprovider.ErrNotImplemented
 }
 
@@ -142,7 +143,20 @@ func (p *provider) GetNodeGpuConfig(node *corev1.Node) *cloudprovider.GpuConfig
 
 // IsNodeCandidateForScaleDown returns whether the node is a good candidate for scaling down.
 func (p *provider) IsNodeCandidateForScaleDown(node *corev1.Node) (bool, error) {
-	return true, cloudprovider.ErrNotImplemented
+	ng, err := p.controller.nodeGroupForNode(node)
+	if err != nil {
+		return false, errors.Wrapf(err, "failed to determine node group for node %s", klog.KObj(node))
+	}
+	if ng == nil {
+		klog.V(5).Infof("node %s is not part of a node group", klog.KObj(node))
+		return false, nil
+	}
+	rollingout, err := ng.IsMachineDeploymentAndRollingOut()
+	if err != nil {
+		return false, errors.Wrapf(err, "failed to determine rolling out status for MachineDeployment %s", ng.scalableResource.ID())
+	}
+	// A node is a good candidate for scale down if it is not currently part of a MachineDeployment that is rolling out.
+	return !rollingout, nil
 }
 
 func newProvider(
diff --git a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_utils.go b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_utils.go
index f28721f49b74..03b86adce90d 100644
--- a/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_utils.go
+++ b/cluster-autoscaler/cloudprovider/clusterapi/clusterapi_utils.go
@@ -32,15 +32,17 @@ import (
 )
 
 const (
-	cpuKey          = "capacity.cluster-autoscaler.kubernetes.io/cpu"
-	memoryKey       = "capacity.cluster-autoscaler.kubernetes.io/memory"
-	diskCapacityKey = "capacity.cluster-autoscaler.kubernetes.io/ephemeral-disk"
-	gpuTypeKey      = "capacity.cluster-autoscaler.kubernetes.io/gpu-type"
-	gpuCountKey     = "capacity.cluster-autoscaler.kubernetes.io/gpu-count"
-	maxPodsKey      = "capacity.cluster-autoscaler.kubernetes.io/maxPods"
-	taintsKey       = "capacity.cluster-autoscaler.kubernetes.io/taints"
-	labelsKey       = "capacity.cluster-autoscaler.kubernetes.io/labels"
-	draDriverKey    = "capacity.cluster-autoscaler.kubernetes.io/dra-driver"
+	cpuKey                              = "capacity.cluster-autoscaler.kubernetes.io/cpu"
+	memoryKey                           = "capacity.cluster-autoscaler.kubernetes.io/memory"
+	diskCapacityKey                     = "capacity.cluster-autoscaler.kubernetes.io/ephemeral-disk"
+	gpuTypeKey                          = "capacity.cluster-autoscaler.kubernetes.io/gpu-type"
+	gpuCountKey                         = "capacity.cluster-autoscaler.kubernetes.io/gpu-count"
+	maxPodsKey                          = "capacity.cluster-autoscaler.kubernetes.io/maxPods"
+	taintsKey                           = "capacity.cluster-autoscaler.kubernetes.io/taints"
+	labelsKey                           = "capacity.cluster-autoscaler.kubernetes.io/labels"
+	draDriverKey                        = "capacity.cluster-autoscaler.kubernetes.io/dra-driver"
+	machineDeploymentRevisionAnnotation = "machinedeployment.clusters.x-k8s.io/revision"
+	machineDeploymentNameLabel          = "cluster.x-k8s.io/deployment-name"
 	// UnknownArch is used if the Architecture is Unknown
 	UnknownArch SystemArchitecture = ""
 	// Amd64 is used if the Architecture is x86_64