Merge pull request kubernetes-sigs#285 from lixiang233/Ft_change_lowU…

…tilization_break

Change break condition and thresholds validation for lowUtilization

README.md

@@ -95,7 +95,8 @@ usage is below threshold for all (cpu, memory, and number of pods), the node is
 Currently, pods request resource requirements are considered for computing node resource utilization.
 
 There is another configurable threshold, `targetThresholds`, that is used to compute those potential nodes
-from where pods could be evicted. Any node, between the thresholds, `thresholds` and `targetThresholds` is
+from where pods could be evicted. If a node's usage is above targetThreshold for any (cpu, memory, or number of pods),
+the node is considered over utilized. Any node between the thresholds, `thresholds` and `targetThresholds` is
 considered appropriately utilized and is not considered for eviction. The threshold, `targetThresholds`,
 can be configured for cpu, memory, and number of pods too in terms of percentage.
 
@@ -120,6 +121,15 @@ strategies:
            "pods": 50
 ```
 
+Policy should pass the following validation checks:
+* Only three types of resources are supported: `cpu`, `memory` and `pods`.
+* `thresholds` or `targetThresholds` can not be nil and they must configure exactly the same types of resources.
+* The valid range of the resource's percentage value is \[0, 100\]
+* Percentage value of `thresholds` can not be greater than `targetThresholds` for the same resource.
+
+If any of the resource types is not specified, all its thresholds default to 100% to avoid nodes going
+from underutilized to overutilized.
+
 There is another parameter associated with the `LowNodeUtilization` strategy, called `numberOfNodes`.
 This parameter can be configured to activate the strategy only when the number of under utilized nodes
 are above the configured value. This could be helpful in large clusters where a few nodes could go

pkg/descheduler/strategies/lownodeutilization.go

@@ -18,6 +18,7 @@ package strategies
 
 import (
 	"context"
+	"fmt"
 	"sort"
 
 	v1 "k8s.io/api/core/v1"
@@ -40,6 +41,11 @@ type NodeUsageMap struct {
 
 type NodePodsMap map[*v1.Node][]*v1.Pod
 
+const (
+	MinResourcePercentage = 0
+	MaxResourcePercentage = 100
+)
+
 func LowNodeUtilization(ctx context.Context, client clientset.Interface, strategy api.DeschedulerStrategy, nodes []*v1.Node, evictLocalStoragePods bool, podEvictor *evictions.PodEvictor) {
 	// todo: move to config validation?
 	// TODO: May be create a struct for the strategy as well, so that we don't have to pass along the all the params?
@@ -49,13 +55,24 @@ func LowNodeUtilization(ctx context.Context, client clientset.Interface, strateg
 	}
 
 	thresholds := strategy.Params.NodeResourceUtilizationThresholds.Thresholds
-	if !validateThresholds(thresholds) {
-		return
-	}
 	targetThresholds := strategy.Params.NodeResourceUtilizationThresholds.TargetThresholds
-	if !validateTargetThresholds(targetThresholds) {
+	if err := validateStrategyConfig(thresholds, targetThresholds); err != nil {
+		klog.Errorf("LowNodeUtilization config is not valid: %v", err)
 		return
 	}
+	// check if Pods/CPU/Mem are set, if not, set them to 100
+	if _, ok := thresholds[v1.ResourcePods]; !ok {
+		thresholds[v1.ResourcePods] = MaxResourcePercentage
+		targetThresholds[v1.ResourcePods] = MaxResourcePercentage
+	}
+	if _, ok := thresholds[v1.ResourceCPU]; !ok {
+		thresholds[v1.ResourceCPU] = MaxResourcePercentage
+		targetThresholds[v1.ResourceCPU] = MaxResourcePercentage
+	}
+	if _, ok := thresholds[v1.ResourceMemory]; !ok {
+		thresholds[v1.ResourceMemory] = MaxResourcePercentage
+		targetThresholds[v1.ResourceMemory] = MaxResourcePercentage
+	}
 
 	npm := createNodePodsMap(ctx, client, nodes)
 	lowNodes, targetNodes := classifyNodes(npm, thresholds, targetThresholds, evictLocalStoragePods)
@@ -99,37 +116,46 @@ func LowNodeUtilization(ctx context.Context, client clientset.Interface, strateg
 	klog.V(1).Infof("Total number of pods evicted: %v", podEvictor.TotalEvicted())
 }
 
-func validateThresholds(thresholds api.ResourceThresholds) bool {
-	if thresholds == nil || len(thresholds) == 0 {
-		klog.V(1).Infof("no resource threshold is configured")
-		return false
+// validateStrategyConfig checks if the strategy's config is valid
+func validateStrategyConfig(thresholds, targetThresholds api.ResourceThresholds) error {
+	// validate thresholds and targetThresholds config
+	if err := validateThresholds(thresholds); err != nil {
+		return fmt.Errorf("thresholds config is not valid: %v", err)
 	}
-	for name := range thresholds {
-		switch name {
-		case v1.ResourceCPU:
-			continue
-		case v1.ResourceMemory:
-			continue
-		case v1.ResourcePods:
-			continue
-		default:
-			klog.Errorf("only cpu, memory, or pods thresholds can be specified")
-			return false
+	if err := validateThresholds(targetThresholds); err != nil {
+		return fmt.Errorf("targetThresholds config is not valid: %v", err)
+	}
+
+	// validate if thresholds and targetThresholds have same resources configured
+	if len(thresholds) != len(targetThresholds) {
+		return fmt.Errorf("thresholds and targetThresholds configured different resources")
+	}
+	for resourceName, value := range thresholds {
+		if targetValue, ok := targetThresholds[resourceName]; !ok {
+			return fmt.Errorf("thresholds and targetThresholds configured different resources")
+		} else if value > targetValue {
+			return fmt.Errorf("thresholds' %v percentage is greater than targetThresholds'", resourceName)
 		}
 	}
-	return true
+	return nil
 }
 
-//This function could be merged into above once we are clear.
-func validateTargetThresholds(targetThresholds api.ResourceThresholds) bool {
-	if targetThresholds == nil {
-		klog.V(1).Infof("no target resource threshold is configured")
-		return false
-	} else if _, ok := targetThresholds[v1.ResourcePods]; !ok {
-		klog.V(1).Infof("no target resource threshold for pods is configured")
-		return false
+// validateThresholds checks if thresholds have valid resource name and resource percentage configured
+func validateThresholds(thresholds api.ResourceThresholds) error {
+	if thresholds == nil || len(thresholds) == 0 {
+		return fmt.Errorf("no resource threshold is configured")
 	}
-	return true
+	for name, percent := range thresholds {
+		switch name {
+		case v1.ResourceCPU, v1.ResourceMemory, v1.ResourcePods:
+			if percent < MinResourcePercentage || percent > MaxResourcePercentage {
+				return fmt.Errorf("%v threshold not in [%v, %v] range", name, MinResourcePercentage, MaxResourcePercentage)
+			}
+		default:
+			return fmt.Errorf("only cpu, memory, or pods thresholds can be specified")
+		}
+	}
+	return nil
 }
 
 // classifyNodes classifies the nodes into low-utilization or high-utilization nodes. If a node lies between
@@ -184,16 +210,12 @@ func evictPodsFromTargetNodes(
 		totalPods += ((float64(podsPercentage) * float64(nodeCapacity.Pods().Value())) / 100)
 
 		// totalCPU capacity to be moved
-		if _, ok := targetThresholds[v1.ResourceCPU]; ok {
-			cpuPercentage := targetThresholds[v1.ResourceCPU] - node.usage[v1.ResourceCPU]
-			totalCPU += ((float64(cpuPercentage) * float64(nodeCapacity.Cpu().MilliValue())) / 100)
-		}
+		cpuPercentage := targetThresholds[v1.ResourceCPU] - node.usage[v1.ResourceCPU]
+		totalCPU += ((float64(cpuPercentage) * float64(nodeCapacity.Cpu().MilliValue())) / 100)
 
 		// totalMem capacity to be moved
-		if _, ok := targetThresholds[v1.ResourceMemory]; ok {
-			memPercentage := targetThresholds[v1.ResourceMemory] - node.usage[v1.ResourceMemory]
-			totalMem += ((float64(memPercentage) * float64(nodeCapacity.Memory().Value())) / 100)
-		}
+		memPercentage := targetThresholds[v1.ResourceMemory] - node.usage[v1.ResourceMemory]
+		totalMem += ((float64(memPercentage) * float64(nodeCapacity.Memory().Value())) / 100)
 	}
 
 	klog.V(1).Infof("Total capacity to be moved: CPU:%v, Mem:%v, Pods:%v", totalCPU, totalMem, totalPods)
@@ -246,7 +268,8 @@ func evictPods(
 	taintsOfLowNodes map[string][]v1.Taint,
 	podEvictor *evictions.PodEvictor,
 	node *v1.Node) {
-	if IsNodeAboveTargetUtilization(nodeUsage, targetThresholds) && (*totalPods > 0 || *totalCPU > 0 || *totalMem > 0) {
+	// stop if node utilization drops below target threshold or any of required capacity (cpu, memory, pods) is moved
+	if IsNodeAboveTargetUtilization(nodeUsage, targetThresholds) && *totalPods > 0 && *totalCPU > 0 && *totalMem > 0 {
 		onePodPercentage := api.Percentage((float64(1) * 100) / float64(nodeCapacity.Pods().Value()))
 		for _, pod := range inputPods {
 			if !utils.PodToleratesTaints(pod, taintsOfLowNodes) {
@@ -278,8 +301,8 @@ func evictPods(
 				nodeUsage[v1.ResourceMemory] -= api.Percentage(float64(mUsage) / float64(nodeCapacity.Memory().Value()) * 100)
 
 				klog.V(3).Infof("updated node usage: %#v", nodeUsage)
-				// check if node utilization drops below target threshold or required capacity (cpu, memory, pods) is moved
-				if !IsNodeAboveTargetUtilization(nodeUsage, targetThresholds) || (*totalPods <= 0 && *totalCPU <= 0 && *totalMem <= 0) {
+				// check if node utilization drops below target threshold or any required capacity (cpu, memory, pods) is moved
+				if !IsNodeAboveTargetUtilization(nodeUsage, targetThresholds) || *totalPods <= 0 || *totalCPU <= 0 || *totalMem <= 0 {
 					break
 				}
 			}