mirror of https://github.com/k3s-io/k3s.git
120 lines
5.1 KiB
Go
120 lines
5.1 KiB
Go
/*
|
|
Copyright 2019 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 noderesources
|
|
|
|
import (
|
|
"context"
|
|
"fmt"
|
|
"math"
|
|
|
|
v1 "k8s.io/api/core/v1"
|
|
"k8s.io/apimachinery/pkg/runtime"
|
|
utilfeature "k8s.io/apiserver/pkg/util/feature"
|
|
"k8s.io/kubernetes/pkg/features"
|
|
framework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
|
|
)
|
|
|
|
// BalancedAllocation is a score plugin that calculates the difference between the cpu and memory fraction
|
|
// of capacity, and prioritizes the host based on how close the two metrics are to each other.
|
|
type BalancedAllocation struct {
|
|
handle framework.FrameworkHandle
|
|
resourceAllocationScorer
|
|
}
|
|
|
|
var _ = framework.ScorePlugin(&BalancedAllocation{})
|
|
|
|
// BalancedAllocationName is the name of the plugin used in the plugin registry and configurations.
|
|
const BalancedAllocationName = "NodeResourcesBalancedAllocation"
|
|
|
|
// Name returns name of the plugin. It is used in logs, etc.
|
|
func (ba *BalancedAllocation) Name() string {
|
|
return BalancedAllocationName
|
|
}
|
|
|
|
// Score invoked at the score extension point.
|
|
func (ba *BalancedAllocation) Score(ctx context.Context, state *framework.CycleState, pod *v1.Pod, nodeName string) (int64, *framework.Status) {
|
|
nodeInfo, err := ba.handle.SnapshotSharedLister().NodeInfos().Get(nodeName)
|
|
if err != nil {
|
|
return 0, framework.NewStatus(framework.Error, fmt.Sprintf("getting node %q from Snapshot: %v", nodeName, err))
|
|
}
|
|
|
|
// ba.score favors nodes with balanced resource usage rate.
|
|
// It calculates the difference between the cpu and memory fraction of capacity,
|
|
// and prioritizes the host based on how close the two metrics are to each other.
|
|
// Detail: score = (1 - variance(cpuFraction,memoryFraction,volumeFraction)) * MaxNodeScore. The algorithm is partly inspired by:
|
|
// "Wei Huang et al. An Energy Efficient Virtual Machine Placement Algorithm with Balanced
|
|
// Resource Utilization"
|
|
return ba.score(pod, nodeInfo)
|
|
}
|
|
|
|
// ScoreExtensions of the Score plugin.
|
|
func (ba *BalancedAllocation) ScoreExtensions() framework.ScoreExtensions {
|
|
return nil
|
|
}
|
|
|
|
// NewBalancedAllocation initializes a new plugin and returns it.
|
|
func NewBalancedAllocation(_ runtime.Object, h framework.FrameworkHandle) (framework.Plugin, error) {
|
|
return &BalancedAllocation{
|
|
handle: h,
|
|
resourceAllocationScorer: resourceAllocationScorer{
|
|
BalancedAllocationName,
|
|
balancedResourceScorer,
|
|
defaultRequestedRatioResources,
|
|
},
|
|
}, nil
|
|
}
|
|
|
|
// todo: use resource weights in the scorer function
|
|
func balancedResourceScorer(requested, allocable resourceToValueMap, includeVolumes bool, requestedVolumes int, allocatableVolumes int) int64 {
|
|
cpuFraction := fractionOfCapacity(requested[v1.ResourceCPU], allocable[v1.ResourceCPU])
|
|
memoryFraction := fractionOfCapacity(requested[v1.ResourceMemory], allocable[v1.ResourceMemory])
|
|
// This to find a node which has most balanced CPU, memory and volume usage.
|
|
if cpuFraction >= 1 || memoryFraction >= 1 {
|
|
// if requested >= capacity, the corresponding host should never be preferred.
|
|
return 0
|
|
}
|
|
|
|
if includeVolumes && utilfeature.DefaultFeatureGate.Enabled(features.BalanceAttachedNodeVolumes) && allocatableVolumes > 0 {
|
|
volumeFraction := float64(requestedVolumes) / float64(allocatableVolumes)
|
|
if volumeFraction >= 1 {
|
|
// if requested >= capacity, the corresponding host should never be preferred.
|
|
return 0
|
|
}
|
|
// Compute variance for all the three fractions.
|
|
mean := (cpuFraction + memoryFraction + volumeFraction) / float64(3)
|
|
variance := float64((((cpuFraction - mean) * (cpuFraction - mean)) + ((memoryFraction - mean) * (memoryFraction - mean)) + ((volumeFraction - mean) * (volumeFraction - mean))) / float64(3))
|
|
// Since the variance is between positive fractions, it will be positive fraction. 1-variance lets the
|
|
// score to be higher for node which has least variance and multiplying it with `MaxNodeScore` provides the scaling
|
|
// factor needed.
|
|
return int64((1 - variance) * float64(framework.MaxNodeScore))
|
|
}
|
|
|
|
// Upper and lower boundary of difference between cpuFraction and memoryFraction are -1 and 1
|
|
// respectively. Multiplying the absolute value of the difference by `MaxNodeScore` scales the value to
|
|
// 0-MaxNodeScore with 0 representing well balanced allocation and `MaxNodeScore` poorly balanced. Subtracting it from
|
|
// `MaxNodeScore` leads to the score which also scales from 0 to `MaxNodeScore` while `MaxNodeScore` representing well balanced.
|
|
diff := math.Abs(cpuFraction - memoryFraction)
|
|
return int64((1 - diff) * float64(framework.MaxNodeScore))
|
|
}
|
|
|
|
func fractionOfCapacity(requested, capacity int64) float64 {
|
|
if capacity == 0 {
|
|
return 1
|
|
}
|
|
return float64(requested) / float64(capacity)
|
|
}
|