karmada/pkg/scheduler/core/division_algorithm.go

/*
Copyright 2021 The Karmada 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 core

import (
	"fmt"
	"sort"

	clusterv1alpha1 "github.com/karmada-io/karmada/pkg/apis/cluster/v1alpha1"
	policyv1alpha1 "github.com/karmada-io/karmada/pkg/apis/policy/v1alpha1"
	workv1alpha2 "github.com/karmada-io/karmada/pkg/apis/work/v1alpha2"
	"github.com/karmada-io/karmada/pkg/scheduler/framework"
	"github.com/karmada-io/karmada/pkg/util"
	"github.com/karmada-io/karmada/pkg/util/helper"
)

// TargetClustersList is a slice of TargetCluster that implements sort.Interface to sort by Value.
type TargetClustersList []workv1alpha2.TargetCluster

func (a TargetClustersList) Len() int           { return len(a) }
func (a TargetClustersList) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a TargetClustersList) Less(i, j int) bool { return a[i].Replicas > a[j].Replicas }

func getStaticWeightInfoList(clusters []*clusterv1alpha1.Cluster, weightList []policyv1alpha1.StaticClusterWeight,
	lastTargetClusters []workv1alpha2.TargetCluster) helper.ClusterWeightInfoList {
	list := make(helper.ClusterWeightInfoList, 0)
	for _, cluster := range clusters {
		var weight int64
		var lastReplicas int32
		for _, staticWeightRule := range weightList {
			if util.ClusterMatches(cluster, staticWeightRule.TargetCluster) {
				weight = util.MaxInt64(weight, staticWeightRule.Weight)
			}
		}
		for _, lastTargetCluster := range lastTargetClusters {
			if cluster.Name == lastTargetCluster.Name {
				lastReplicas = lastTargetCluster.Replicas
				break
			}
		}
		if weight > 0 {
			list = append(list, helper.ClusterWeightInfo{
				ClusterName:  cluster.Name,
				Weight:       weight,
				LastReplicas: lastReplicas,
			})
		}
	}
	if list.GetWeightSum() == 0 {
		for _, cluster := range clusters {
			list = append(list, helper.ClusterWeightInfo{
				ClusterName: cluster.Name,
				Weight:      1,
			})
		}
	}
	return list
}

// dynamicDivideReplicas assigns a total number of replicas to the selected clusters by preference according to the resource.
func dynamicDivideReplicas(state *assignState) ([]workv1alpha2.TargetCluster, error) {
	if state.availableReplicas < state.targetReplicas {
		return nil, &framework.UnschedulableError{Message: fmt.Sprintf("Clusters available replicas %d are not enough to schedule.", state.availableReplicas)}
	}

	switch state.strategyType {
	case AggregatedStrategy:
		state.availableClusters = state.resortAvailableClusters()
		var sum int32
		for i := range state.availableClusters {
			if sum += state.availableClusters[i].Replicas; sum >= state.targetReplicas {
				state.availableClusters = state.availableClusters[:i+1]
				break
			}
		}
		fallthrough
	case DynamicWeightStrategy:
		// Set the availableClusters as the weight, scheduledClusters as init result, target as the dispenser object.
		// After dispensing, the target cluster will be the combination of init result and weighted result for target replicas.
		return helper.SpreadReplicasByTargetClusters(state.targetReplicas, state.availableClusters, state.scheduledClusters), nil
	default:
		// should never happen
		return nil, fmt.Errorf("undefined strategy type: %s", state.strategyType)
	}
}

func dynamicScaleDown(state *assignState) ([]workv1alpha2.TargetCluster, error) {
	// The previous scheduling result will be the weight reference of scaling down.
	// In other words, we scale down the replicas proportionally by their scheduled replicas.
	// Now:
	// 1. targetReplicas is set to desired replicas.
	// 2. availableClusters is set to the former schedule result.
	// 3. scheduledClusters and assignedReplicas are not set, which implicates we consider this action as a first schedule.
	state.targetReplicas = state.spec.Replicas
	state.scheduledClusters = nil
	state.buildAvailableClusters(func(_ []*clusterv1alpha1.Cluster, spec *workv1alpha2.ResourceBindingSpec) []workv1alpha2.TargetCluster {
		availableClusters := make(TargetClustersList, len(spec.Clusters))
		copy(availableClusters, spec.Clusters)
		sort.Sort(availableClusters)
		return availableClusters
	})
	return dynamicDivideReplicas(state)
}

func dynamicScaleUp(state *assignState) ([]workv1alpha2.TargetCluster, error) {
	// Target is the extra ones.
	state.targetReplicas = state.spec.Replicas - state.assignedReplicas
	state.buildAvailableClusters(func(clusters []*clusterv1alpha1.Cluster, spec *workv1alpha2.ResourceBindingSpec) []workv1alpha2.TargetCluster {
		clusterAvailableReplicas := calAvailableReplicas(clusters, spec)
		sort.Sort(TargetClustersList(clusterAvailableReplicas))
		return clusterAvailableReplicas
	})
	return dynamicDivideReplicas(state)
}

// dynamicFreshScale do a complete recalculation without referring to the last scheduling results.
func dynamicFreshScale(state *assignState) ([]workv1alpha2.TargetCluster, error) {
	// 1. targetReplicas is set to desired replicas
	state.targetReplicas = state.spec.Replicas
	state.buildAvailableClusters(func(clusters []*clusterv1alpha1.Cluster, spec *workv1alpha2.ResourceBindingSpec) []workv1alpha2.TargetCluster {
		clusterAvailableReplicas := calAvailableReplicas(clusters, spec)
		// 2. clusterAvailableReplicas should take into account the replicas already allocated
		for _, scheduledCluster := range state.scheduledClusters {
			for i, availableCluster := range clusterAvailableReplicas {
				if availableCluster.Name != scheduledCluster.Name {
					continue
				}
				clusterAvailableReplicas[i].Replicas += scheduledCluster.Replicas
				break
			}
		}
		sort.Sort(TargetClustersList(clusterAvailableReplicas))
		return clusterAvailableReplicas
	})
	// 3. scheduledClusters are not set, which implicates we consider this action as a first schedule.
	state.scheduledClusters = nil
	return dynamicDivideReplicas(state)
}