Added new policy of maxodpernode

examples/max-pods-per-node.yml

@@ -0,0 +1,22 @@
+apiVersion: "descheduler/v1alpha2"
+kind: "DeschedulerPolicy"
+profiles:
+  - name: ProfileName
+    pluginConfig:
+    - name: "MaxPodsPerNode"
+      args:
+        maxPods: 30
+        namespaces:
+          include:
+            - "default"
+    - name: "DefaultEvictor"
+      args:
+        evictSystemCriticalPods: false
+        evictLocalStoragePods: true
+    plugins:
+      deschedule:
+        enabled:
+          - "MaxPodsPerNode"
+      filter:
+        enabled:
+          - "DefaultEvictor"

pkg/descheduler/setupplugins.go

@@ -19,6 +19,7 @@ package descheduler
 import (
 	"sigs.k8s.io/descheduler/pkg/framework/pluginregistry"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/defaultevictor"
+	"sigs.k8s.io/descheduler/pkg/framework/plugins/maxpodspernode"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/nodeutilization"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/podlifetime"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/removeduplicates"
@@ -47,4 +48,5 @@ func RegisterDefaultPlugins(registry pluginregistry.Registry) {
 	pluginregistry.Register(removepodsviolatingnodeaffinity.PluginName, removepodsviolatingnodeaffinity.New, &removepodsviolatingnodeaffinity.RemovePodsViolatingNodeAffinity{}, &removepodsviolatingnodeaffinity.RemovePodsViolatingNodeAffinityArgs{}, removepodsviolatingnodeaffinity.ValidateRemovePodsViolatingNodeAffinityArgs, removepodsviolatingnodeaffinity.SetDefaults_RemovePodsViolatingNodeAffinityArgs, registry)
 	pluginregistry.Register(removepodsviolatingnodetaints.PluginName, removepodsviolatingnodetaints.New, &removepodsviolatingnodetaints.RemovePodsViolatingNodeTaints{}, &removepodsviolatingnodetaints.RemovePodsViolatingNodeTaintsArgs{}, removepodsviolatingnodetaints.ValidateRemovePodsViolatingNodeTaintsArgs, removepodsviolatingnodetaints.SetDefaults_RemovePodsViolatingNodeTaintsArgs, registry)
 	pluginregistry.Register(removepodsviolatingtopologyspreadconstraint.PluginName, removepodsviolatingtopologyspreadconstraint.New, &removepodsviolatingtopologyspreadconstraint.RemovePodsViolatingTopologySpreadConstraint{}, &removepodsviolatingtopologyspreadconstraint.RemovePodsViolatingTopologySpreadConstraintArgs{}, removepodsviolatingtopologyspreadconstraint.ValidateRemovePodsViolatingTopologySpreadConstraintArgs, removepodsviolatingtopologyspreadconstraint.SetDefaults_RemovePodsViolatingTopologySpreadConstraintArgs, registry)
+	pluginregistry.Register(maxpodspernode.PluginName, maxpodspernode.New, &maxpodspernode.MaxPodsPerNode{}, &maxpodspernode.MaxPodsPerNodeArgs{}, maxpodspernode.ValidateMaxPodsPerNodeArgs, maxpodspernode.SetDefaults_MaxPodsPerNodeArgs, registry)
 }

pkg/framework/plugins/maxpodspernode/defaults.go

@@ -0,0 +1,36 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxpodspernode
+
+import (
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func addDefaultingFuncs(scheme *runtime.Scheme) error {
+	return RegisterDefaults(scheme)
+}
+
+// SetDefaults_MaxPodsPerNodeArgs sets default values for MaxPodsPerNodeArgs
+func SetDefaults_MaxPodsPerNodeArgs(obj runtime.Object) {
+	args := obj.(*MaxPodsPerNodeArgs)
+	if args.Namespaces == nil {
+		args.Namespaces = nil
+	}
+	if args.LabelSelector == nil {
+		args.LabelSelector = nil
+	}
+	if args.MaxPods == 0 {
+		args.MaxPods = 110 // default Kubernetes max pods per node
+	}
+}

pkg/framework/plugins/maxpodspernode/doc.go

@@ -0,0 +1,16 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// +k8s:defaulter-gen=TypeMeta
+
+package maxpodspernode

pkg/framework/plugins/maxpodspernode/maxpodspernode.go

@@ -0,0 +1,129 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxpodspernode
+
+import (
+	"context"
+	"fmt"
+	"sort"
+
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/klog/v2"
+
+	"sigs.k8s.io/descheduler/pkg/descheduler/evictions"
+	podutil "sigs.k8s.io/descheduler/pkg/descheduler/pod"
+	frameworktypes "sigs.k8s.io/descheduler/pkg/framework/types"
+)
+
+const PluginName = "MaxPodsPerNode"
+
+// MaxPodsPerNode evicts pods from nodes that exceed the configured maximum pod count
+type MaxPodsPerNode struct {
+	logger    klog.Logger
+	handle    frameworktypes.Handle
+	args      *MaxPodsPerNodeArgs
+	podFilter podutil.FilterFunc
+}
+
+var _ frameworktypes.DeschedulePlugin = &MaxPodsPerNode{}
+
+// New builds plugin from its arguments while passing a handle
+func New(ctx context.Context, args runtime.Object, handle frameworktypes.Handle) (frameworktypes.Plugin, error) {
+	maxPodsArgs, ok := args.(*MaxPodsPerNodeArgs)
+	if !ok {
+		return nil, fmt.Errorf("want args to be of type MaxPodsPerNodeArgs, got %T", args)
+	}
+	logger := klog.FromContext(ctx).WithValues("plugin", PluginName)
+
+	var includedNamespaces, excludedNamespaces sets.Set[string]
+	if maxPodsArgs.Namespaces != nil {
+		includedNamespaces = sets.New(maxPodsArgs.Namespaces.Include...)
+		excludedNamespaces = sets.New(maxPodsArgs.Namespaces.Exclude...)
+	}
+
+	// We can combine Filter and PreEvictionFilter since for this strategy it does not matter where we run PreEvictionFilter
+	podFilter, err := podutil.NewOptions().
+		WithNamespaces(includedNamespaces).
+		WithoutNamespaces(excludedNamespaces).
+		WithLabelSelector(maxPodsArgs.LabelSelector).
+		BuildFilterFunc()
+	if err != nil {
+		return nil, fmt.Errorf("error initializing pod filter function: %v", err)
+	}
+
+	return &MaxPodsPerNode{
+		logger:    logger,
+		handle:    handle,
+		podFilter: podFilter,
+		args:      maxPodsArgs,
+	}, nil
+}
+
+// Name retrieves the plugin name
+func (d *MaxPodsPerNode) Name() string {
+	return PluginName
+}
+
+// Deschedule extension point implementation for the plugin
+func (d *MaxPodsPerNode) Deschedule(ctx context.Context, nodes []*v1.Node) *frameworktypes.Status {
+	logger := klog.FromContext(klog.NewContext(ctx, d.logger)).WithValues("ExtensionPoint", frameworktypes.DescheduleExtensionPoint)
+
+	for _, node := range nodes {
+		logger.V(2).Info("Processing node", "node", klog.KObj(node))
+
+		pods, err := podutil.ListAllPodsOnANode(node.Name, d.handle.GetPodsAssignedToNodeFunc(), d.podFilter)
+		if err != nil {
+			return &frameworktypes.Status{
+				Err: fmt.Errorf("error listing pods on a node: %v", err),
+			}
+		}
+
+		podCount := len(pods)
+		if podCount <= d.args.MaxPods {
+			logger.V(2).Info("Node pod count within limit", "node", klog.KObj(node), "podCount", podCount, "maxPods", d.args.MaxPods)
+			continue
+		}
+
+		excessPods := podCount - d.args.MaxPods
+		logger.V(1).Info("Node exceeds max pods limit", "node", klog.KObj(node), "podCount", podCount, "maxPods", d.args.MaxPods, "excessPods", excessPods)
+
+		// Sort pods by creation timestamp (newest first) so we evict the most recently created pods
+		sort.Slice(pods, func(i, j int) bool {
+			return pods[j].CreationTimestamp.Before(&pods[i].CreationTimestamp)
+		})
+
+		evicted := 0
+	loop:
+		for i := 0; i < len(pods) && evicted < excessPods; i++ {
+			err := d.handle.Evictor().Evict(ctx, pods[i], evictions.EvictOptions{StrategyName: PluginName})
+			if err == nil {
+				evicted++
+				continue
+			}
+			switch err.(type) {
+			case *evictions.EvictionNodeLimitError:
+				break loop
+			case *evictions.EvictionTotalLimitError:
+				return nil
+			default:
+				logger.Error(err, "eviction failed", "pod", klog.KObj(pods[i]))
+			}
+		}
+
+		logger.V(1).Info("Evicted pods from node", "node", klog.KObj(node), "evictedCount", evicted)
+	}
+	return nil
+}

pkg/framework/plugins/maxpodspernode/register.go

@@ -0,0 +1,31 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxpodspernode
+
+import (
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+var (
+	SchemeBuilder      = runtime.NewSchemeBuilder()
+	localSchemeBuilder = &SchemeBuilder
+	AddToScheme        = localSchemeBuilder.AddToScheme
+)
+
+func init() {
+	// We only register manually written functions here. The registration of the
+	// generated functions takes place in the generated files. The separation
+	// makes the code compile even when the generated files are missing.
+	localSchemeBuilder.Register(addDefaultingFuncs)
+}

pkg/framework/plugins/maxpodspernode/types.go

@@ -0,0 +1,33 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxpodspernode
+
+import (
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"sigs.k8s.io/descheduler/pkg/api"
+)
+
+// +k8s:deepcopy-gen=true
+// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
+
+// MaxPodsPerNodeArgs holds arguments used to configure the MaxPodsPerNode plugin.
+type MaxPodsPerNodeArgs struct {
+	metav1.TypeMeta `json:",inline"`
+
+	Namespaces    *api.Namespaces       `json:"namespaces,omitempty"`
+	LabelSelector *metav1.LabelSelector `json:"labelSelector,omitempty"`
+	// MaxPods is the maximum number of pods allowed on a node.
+	// Pods will be evicted from nodes exceeding this count.
+	MaxPods int `json:"maxPods"`
+}

pkg/framework/plugins/maxpodspernode/validation.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package maxpodspernode
+
+import (
+	"fmt"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	utilerrors "k8s.io/apimachinery/pkg/util/errors"
+)
+
+// ValidateMaxPodsPerNodeArgs validates MaxPodsPerNode arguments
+func ValidateMaxPodsPerNodeArgs(obj runtime.Object) error {
+	args := obj.(*MaxPodsPerNodeArgs)
+	var allErrs []error
+
+	if args.MaxPods <= 0 {
+		allErrs = append(allErrs, fmt.Errorf("maxPods must be a positive integer"))
+	}
+
+	// At most one of include/exclude can be set
+	if args.Namespaces != nil && len(args.Namespaces.Include) > 0 && len(args.Namespaces.Exclude) > 0 {
+		allErrs = append(allErrs, fmt.Errorf("only one of Include/Exclude namespaces can be set"))
+	}
+
+	if args.LabelSelector != nil {
+		if _, err := metav1.LabelSelectorAsSelector(args.LabelSelector); err != nil {
+			allErrs = append(allErrs, fmt.Errorf("failed to get label selectors from strategy's params: %+v", err))
+		}
+	}
+
+	return utilerrors.NewAggregate(allErrs)
+}