Use actual node resource utilization by consuming kubernetes metrics

README.md

@@ -124,6 +124,8 @@ These are top level keys in the Descheduler Policy that you can use to configure
 | `maxNoOfPodsToEvictPerNode` |`int`| `nil` | maximum number of pods evicted from each node (summed through all strategies) |
 | `maxNoOfPodsToEvictPerNamespace` |`int`| `nil` | maximum number of pods evicted from each namespace (summed through all strategies) |
 | `maxNoOfPodsToEvictTotal` |`int`| `nil` | maximum number of pods evicted per rescheduling cycle (summed through all strategies) |
+| `metricsCollector` |`object`| `nil` | configures collection of metrics for actual resource utilization |
+| `metricsCollector.enabled` |`bool`| `false` | enables kubernetes [metrics server](https://kubernetes-sigs.github.io/metrics-server/) collection |
 
 ### Evictor Plugin configuration (Default Evictor)
 
@@ -158,6 +160,8 @@ nodeSelector: "node=node1" # you don't need to set this, if not set all will be
 maxNoOfPodsToEvictPerNode: 5000 # you don't need to set this, unlimited if not set
 maxNoOfPodsToEvictPerNamespace: 5000 # you don't need to set this, unlimited if not set
 maxNoOfPodsToEvictTotal: 5000 # you don't need to set this, unlimited if not set
+metricsCollector:
+  enabled: true # you don't need to set this, metrics are not collected if not set
 profiles:
   - name: ProfileName
     pluginConfig:
@@ -277,11 +281,13 @@ If that parameter is set to `true`, the thresholds are considered as percentage
 `thresholds` will be deducted from the mean among all nodes and `targetThresholds` will be added to the mean.
 A resource consumption above (resp. below) this window is considered as overutilization (resp. underutilization).
 
-**NOTE:** Node resource consumption is determined by the requests and limits of pods, not actual usage.
+**NOTE:** By default node resource consumption is determined by the requests and limits of pods, not actual usage.
 This approach is chosen in order to maintain consistency with the kube-scheduler, which follows the same
 design for scheduling pods onto nodes. This means that resource usage as reported by Kubelet (or commands
 like `kubectl top`) may differ from the calculated consumption, due to these components reporting
-actual usage metrics. Implementing metrics-based descheduling is currently TODO for the project.
+actual usage metrics. Metrics-based descheduling can be enabled by setting `metricsUtilization.metricsServer` field.
+In order to have the plugin consume the metrics the metric collector needs to be configured as well.
+See `metricsCollector` field at [Top Level configuration](#top-level-configuration) for available options.
 
 **Parameters:**
 
@@ -292,6 +298,9 @@ actual usage metrics. Implementing metrics-based descheduling is currently TODO
 |`targetThresholds`|map(string:int)|
 |`numberOfNodes`|int|
 |`evictableNamespaces`|(see [namespace filtering](#namespace-filtering))|
+|`metricsUtilization`|object|
+|`metricsUtilization.metricsServer`|bool|
+
 
 **Example:**
 
@@ -311,6 +320,8 @@ profiles:
           "cpu" : 50
           "memory": 50
           "pods": 50
+        metricsUtilization:
+          metricsServer: true
     plugins:
       balance:
         enabled:

cmd/descheduler/app/options/options.go

@@ -22,6 +22,7 @@ import (
 	"time"
 
 	"github.com/spf13/pflag"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	apiserver "k8s.io/apiserver/pkg/server"
 	apiserveroptions "k8s.io/apiserver/pkg/server/options"
@@ -33,6 +34,7 @@ import (
 	componentbaseoptions "k8s.io/component-base/config/options"
 	"k8s.io/component-base/featuregate"
 	"k8s.io/klog/v2"
+	metricsclient "k8s.io/metrics/pkg/client/clientset/versioned"
 
 	"sigs.k8s.io/descheduler/pkg/apis/componentconfig"
 	"sigs.k8s.io/descheduler/pkg/apis/componentconfig/v1alpha1"
@@ -51,6 +53,7 @@ type DeschedulerServer struct {
 
 	Client            clientset.Interface
 	EventClient       clientset.Interface
+	MetricsClient     metricsclient.Interface
 	SecureServing     *apiserveroptions.SecureServingOptionsWithLoopback
 	SecureServingInfo *apiserver.SecureServingInfo
 	DisableMetrics    bool

go.mod

@@ -13,14 +13,15 @@ require (
 	go.opentelemetry.io/otel/sdk v1.28.0
 	go.opentelemetry.io/otel/trace v1.28.0
 	google.golang.org/grpc v1.65.0
-	k8s.io/api v0.31.0
-	k8s.io/apimachinery v0.31.0
+	k8s.io/api v0.31.2
+	k8s.io/apimachinery v0.31.2
 	k8s.io/apiserver v0.31.0
-	k8s.io/client-go v0.31.0
-	k8s.io/code-generator v0.31.0
+	k8s.io/client-go v0.31.2
+	k8s.io/code-generator v0.31.2
 	k8s.io/component-base v0.31.0
 	k8s.io/component-helpers v0.31.0
 	k8s.io/klog/v2 v2.130.1
+	k8s.io/metrics v0.31.2
 	k8s.io/utils v0.0.0-20240711033017-18e509b52bc8
 	kubevirt.io/api v1.3.0
 	kubevirt.io/client-go v1.3.0

go.sum

@@ -639,20 +639,20 @@ gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 k8s.io/api v0.23.3/go.mod h1:w258XdGyvCmnBj/vGzQMj6kzdufJZVUwEM1U2fRJwSQ=
-k8s.io/api v0.31.0 h1:b9LiSjR2ym/SzTOlfMHm1tr7/21aD7fSkqgD/CVJBCo=
-k8s.io/api v0.31.0/go.mod h1:0YiFF+JfFxMM6+1hQei8FY8M7s1Mth+z/q7eF1aJkTE=
+k8s.io/api v0.31.2 h1:3wLBbL5Uom/8Zy98GRPXpJ254nEFpl+hwndmk9RwmL0=
+k8s.io/api v0.31.2/go.mod h1:bWmGvrGPssSK1ljmLzd3pwCQ9MgoTsRCuK35u6SygUk=
 k8s.io/apiextensions-apiserver v0.30.0 h1:jcZFKMqnICJfRxTgnC4E+Hpcq8UEhT8B2lhBcQ+6uAs=
 k8s.io/apiextensions-apiserver v0.30.0/go.mod h1:N9ogQFGcrbWqAY9p2mUAL5mGxsLqwgtUce127VtRX5Y=
 k8s.io/apimachinery v0.23.3/go.mod h1:BEuFMMBaIbcOqVIJqNZJXGFTP4W6AycEpb5+m/97hrM=
-k8s.io/apimachinery v0.31.0 h1:m9jOiSr3FoSSL5WO9bjm1n6B9KROYYgNZOb4tyZ1lBc=
-k8s.io/apimachinery v0.31.0/go.mod h1:rsPdaZJfTfLsNJSQzNHQvYoTmxhoOEofxtOsF3rtsMo=
+k8s.io/apimachinery v0.31.2 h1:i4vUt2hPK56W6mlT7Ry+AO8eEsyxMD1U44NR22CLTYw=
+k8s.io/apimachinery v0.31.2/go.mod h1:rsPdaZJfTfLsNJSQzNHQvYoTmxhoOEofxtOsF3rtsMo=
 k8s.io/apiserver v0.31.0 h1:p+2dgJjy+bk+B1Csz+mc2wl5gHwvNkC9QJV+w55LVrY=
 k8s.io/apiserver v0.31.0/go.mod h1:KI9ox5Yu902iBnnyMmy7ajonhKnkeZYJhTZ/YI+WEMk=
-k8s.io/client-go v0.31.0 h1:QqEJzNjbN2Yv1H79SsS+SWnXkBgVu4Pj3CJQgbx0gI8=
-k8s.io/client-go v0.31.0/go.mod h1:Y9wvC76g4fLjmU0BA+rV+h2cncoadjvjjkkIGoTLcGU=
+k8s.io/client-go v0.31.2 h1:Y2F4dxU5d3AQj+ybwSMqQnpZH9F30//1ObxOKlTI9yc=
+k8s.io/client-go v0.31.2/go.mod h1:NPa74jSVR/+eez2dFsEIHNa+3o09vtNaWwWwb1qSxSs=
 k8s.io/code-generator v0.23.3/go.mod h1:S0Q1JVA+kSzTI1oUvbKAxZY/DYbA/ZUb4Uknog12ETk=
-k8s.io/code-generator v0.31.0 h1:w607nrMi1KeDKB3/F/J4lIoOgAwc+gV9ZKew4XRfMp8=
-k8s.io/code-generator v0.31.0/go.mod h1:84y4w3es8rOJOUUP1rLsIiGlO1JuEaPFXQPA9e/K6U0=
+k8s.io/code-generator v0.31.2 h1:xLWxG0HEpMSHfcM//3u3Ro2Hmc6AyyLINQS//Z2GEOI=
+k8s.io/code-generator v0.31.2/go.mod h1:eEQHXgBU/m7LDaToDoiz3t97dUUVyOblQdwOr8rivqc=
 k8s.io/component-base v0.31.0 h1:/KIzGM5EvPNQcYgwq5NwoQBaOlVFrghoVGr8lG6vNRs=
 k8s.io/component-base v0.31.0/go.mod h1:TYVuzI1QmN4L5ItVdMSXKvH7/DtvIuas5/mm8YT3rTo=
 k8s.io/component-helpers v0.31.0 h1:jyRUKA+GX+q19o81k4x94imjNICn+e6Gzi6T89va1/A=
@@ -673,6 +673,8 @@ k8s.io/kms v0.31.0 h1:KchILPfB1ZE+ka7223mpU5zeFNkmb45jl7RHnlImUaI=
 k8s.io/kms v0.31.0/go.mod h1:OZKwl1fan3n3N5FFxnW5C4V3ygrah/3YXeJWS3O6+94=
 k8s.io/kube-openapi v0.0.0-20240430033511-f0e62f92d13f h1:0LQagt0gDpKqvIkAMPaRGcXawNMouPECM1+F9BVxEaM=
 k8s.io/kube-openapi v0.0.0-20240430033511-f0e62f92d13f/go.mod h1:S9tOR0FxgyusSNR+MboCuiDpVWkAifZvaYI1Q2ubgro=
+k8s.io/metrics v0.31.2 h1:sQhujR9m3HN/Nu/0fTfTscjnswQl0qkQAodEdGBS0N4=
+k8s.io/metrics v0.31.2/go.mod h1:QqqyReApEWO1UEgXOSXiHCQod6yTxYctbAAQBWZkboU=
 k8s.io/utils v0.0.0-20211116205334-6203023598ed/go.mod h1:jPW/WVKK9YHAvNhRxK0md/EJ228hCsBRufyofKtW8HA=
 k8s.io/utils v0.0.0-20230726121419-3b25d923346b/go.mod h1:OLgZIPagt7ERELqWJFomSt595RzquPNLL48iOWgYOg0=
 k8s.io/utils v0.0.0-20240711033017-18e509b52bc8 h1:pUdcCO1Lk/tbT5ztQWOBi5HBgbBP1J8+AsQnQCKsi8A=

kubernetes/base/rbac.yaml

@@ -32,6 +32,9 @@ rules:
   resources: ["leases"]
   resourceNames: ["descheduler"]
   verbs: ["get", "patch", "delete"]
+- apiGroups: ["metrics.k8s.io"]
+  resources: ["nodes", "pods"]
+  verbs: ["get", "list"]
 ---
 apiVersion: v1
 kind: ServiceAccount

pkg/api/types.go

@@ -41,6 +41,9 @@ type DeschedulerPolicy struct {
 
 	// MaxNoOfPodsToTotal restricts maximum of pods to be evicted total.
 	MaxNoOfPodsToEvictTotal *uint
+
+	// MetricsCollector configures collection of metrics about actual resource utilization
+	MetricsCollector MetricsCollector
 }
 
 // Namespaces carries a list of included/excluded namespaces
@@ -84,3 +87,10 @@ type PluginSet struct {
 	Enabled  []string
 	Disabled []string
 }
+
+// MetricsCollector configures collection of metrics about actual resource utilization
+type MetricsCollector struct {
+	// Enabled metrics collection from kubernetes metrics.
+	// Later, the collection can be extended to other providers.
+	Enabled bool
+}

pkg/api/v1alpha2/types.go

@@ -40,6 +40,9 @@ type DeschedulerPolicy struct {
 
 	// MaxNoOfPodsToTotal restricts maximum of pods to be evicted total.
 	MaxNoOfPodsToEvictTotal *uint `json:"maxNoOfPodsToEvictTotal,omitempty"`
+
+	// MetricsCollector configures collection of metrics for actual resource utilization
+	MetricsCollector MetricsCollector `json:"metricsCollector,omitempty"`
 }
 
 type DeschedulerProfile struct {
@@ -66,3 +69,10 @@ type PluginSet struct {
 	Enabled  []string `json:"enabled"`
 	Disabled []string `json:"disabled"`
 }
+
+// MetricsCollector configures collection of metrics about actual resource utilization
+type MetricsCollector struct {
+	// Enabled metrics collection from kubernetes metrics.
+	// Later, the collection can be extended to other providers.
+	Enabled bool `json:"enabled,omitempty"`
+}

pkg/descheduler/client/client.go

@@ -19,16 +19,16 @@ package client
 import (
 	"fmt"
 
-	clientset "k8s.io/client-go/kubernetes"
-	componentbaseconfig "k8s.io/component-base/config"
-
 	// Ensure to load all auth plugins.
+	clientset "k8s.io/client-go/kubernetes"
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
+	componentbaseconfig "k8s.io/component-base/config"
+	metricsclient "k8s.io/metrics/pkg/client/clientset/versioned"
 )
 
-func CreateClient(clientConnection componentbaseconfig.ClientConnectionConfiguration, userAgt string) (clientset.Interface, error) {
+func createConfig(clientConnection componentbaseconfig.ClientConnectionConfiguration, userAgt string) (*rest.Config, error) {
 	var cfg *rest.Config
 	if len(clientConnection.Kubeconfig) != 0 {
 		master, err := GetMasterFromKubeconfig(clientConnection.Kubeconfig)
@@ -56,9 +56,28 @@ func CreateClient(clientConnection componentbaseconfig.ClientConnectionConfigura
 		cfg = rest.AddUserAgent(cfg, userAgt)
 	}
 
+	return cfg, nil
+}
+
+func CreateClient(clientConnection componentbaseconfig.ClientConnectionConfiguration, userAgt string) (clientset.Interface, error) {
+	cfg, err := createConfig(clientConnection, userAgt)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create config: %v", err)
+	}
+
 	return clientset.NewForConfig(cfg)
 }
 
+func CreateMetricsClient(clientConnection componentbaseconfig.ClientConnectionConfiguration, userAgt string) (metricsclient.Interface, error) {
+	cfg, err := createConfig(clientConnection, userAgt)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create config: %v", err)
+	}
+
+	// Create the metrics clientset to access the metrics.k8s.io API
+	return metricsclient.NewForConfig(cfg)
+}
+
 func GetMasterFromKubeconfig(filename string) (string, error) {
 	config, err := clientcmd.LoadFromFile(filename)
 	if err != nil {