[WIP] Add evict-system-critical-pods option

charts/descheduler/values.yaml

@@ -16,6 +16,7 @@ schedule: "*/2 * * * *"
 cmdOptions:
   v: 3
   # evict-local-storage-pods:
+  # evict-system-critical-pods:
   # max-pods-to-evict-per-node: 10
   # node-selector: "key1=value1,key2=value2"
 

cmd/descheduler/app/options/options.go

@@ -58,4 +58,6 @@ func (rs *DeschedulerServer) AddFlags(fs *pflag.FlagSet) {
 	fs.IntVar(&rs.MaxNoOfPodsToEvictPerNode, "max-pods-to-evict-per-node", rs.MaxNoOfPodsToEvictPerNode, "Limits the maximum number of pods to be evicted per node by descheduler")
 	// evict-local-storage-pods allows eviction of pods that are using local storage. This is false by default.
 	fs.BoolVar(&rs.EvictLocalStoragePods, "evict-local-storage-pods", rs.EvictLocalStoragePods, "Enables evicting pods using local storage by descheduler")
+	// evict-system-critical-pods allows eviction of critical pods. This is false by default.
+	fs.BoolVar(&rs.EvictSystemCriticalPods, "evict-system-critical-pods", rs.EvictSystemCriticalPods, "Enables evicting critical pods by descheduler")
 }

pkg/apis/componentconfig/types.go

@@ -48,4 +48,7 @@ type DeschedulerConfiguration struct {
 
 	// EvictLocalStoragePods allows pods using local storage to be evicted.
 	EvictLocalStoragePods bool
+
+	// EvictSystemCriticalPods allows critical pods to be evicted.
+	EvictSystemCriticalPods bool
 }

pkg/apis/componentconfig/v1alpha1/types.go

@@ -48,4 +48,7 @@ type DeschedulerConfiguration struct {
 
 	// EvictLocalStoragePods allows pods using local storage to be evicted.
 	EvictLocalStoragePods bool `json:"evictLocalStoragePods,omitempty"`
+
+	// EvictSystemCriticalPods allows critical pods to be evicted.
+	EvictSystemCriticalPods bool `json:"evictSystemCriticalPods,omitempty"`
 }

pkg/descheduler/descheduler.go

@@ -100,6 +100,7 @@ func RunDeschedulerStrategies(ctx context.Context, rs *options.DeschedulerServer
 			rs.MaxNoOfPodsToEvictPerNode,
 			nodes,
 			rs.EvictLocalStoragePods,
+			rs.EvictSystemCriticalPods,
 		)
 
 		for name, f := range strategyFuncs {

pkg/descheduler/evictions/evictions.go

@@ -45,12 +45,13 @@ const (
 type nodePodEvictedCount map[*v1.Node]int
 
 type PodEvictor struct {
-	client                clientset.Interface
-	policyGroupVersion    string
-	dryRun                bool
-	maxPodsToEvictPerNode int
-	nodepodCount          nodePodEvictedCount
-	evictLocalStoragePods bool
+	client                  clientset.Interface
+	policyGroupVersion      string
+	dryRun                  bool
+	maxPodsToEvictPerNode   int
+	nodepodCount            nodePodEvictedCount
+	evictLocalStoragePods   bool
+	evictSystemCriticalPods bool
 }
 
 func NewPodEvictor(
@@ -60,6 +61,7 @@ func NewPodEvictor(
 	maxPodsToEvictPerNode int,
 	nodes []*v1.Node,
 	evictLocalStoragePods bool,
+	evictSystemCriticalPods bool,
 ) *PodEvictor {
 	var nodePodCount = make(nodePodEvictedCount)
 	for _, node := range nodes {
@@ -74,14 +76,15 @@ func NewPodEvictor(
 		maxPodsToEvictPerNode: maxPodsToEvictPerNode,
 		nodepodCount:          nodePodCount,
 		evictLocalStoragePods: evictLocalStoragePods,
+		evictSystemCriticalPods: evictSystemCriticalPods,
 	}
 }
 
 // IsEvictable checks if a pod is evictable or not.
 func (pe *PodEvictor) IsEvictable(pod *v1.Pod, thresholdPriority int32) bool {
 	checkErrs := []error{}
-	if IsCriticalPod(pod) {
-		checkErrs = append(checkErrs, fmt.Errorf("pod is critical"))
+	if !pe.evictSystemCriticalPods && IsCriticalPod(pod) {
+		checkErrs = append(checkErrs, fmt.Errorf("pod is critical and descheduler is not configured with --evict-system-critical-pods"))
 	}
 
 	if !IsPodEvictableBasedOnPriority(pod, thresholdPriority) {

pkg/descheduler/evictions/evictions_test.go

@@ -74,11 +74,12 @@ func TestIsEvictable(t *testing.T) {
 	lowPriority := int32(800)
 	highPriority := int32(900)
 	type testCase struct {
-		pod                   *v1.Pod
-		runBefore             func(*v1.Pod)
-		evictLocalStoragePods bool
-		priorityThreshold     *int32
-		result                bool
+		pod                     *v1.Pod
+		runBefore               func(*v1.Pod)
+		evictLocalStoragePods   bool
+		evictSystemCriticalPods bool
+		priorityThreshold       *int32
+		result                  bool
 	}
 
 	testCases := []testCase{