fix: [10kcp] channel unbalance during stopping balance progress (#38972)

issue: https://github.com/milvus-io/milvus/issues/38970,
https://github.com/milvus-io/milvus/issues/37630

cause the stopping balance channel still use the row_count_based policy,
which may causes channel unbalance in multi-collection case.

This PR impl a score based stopping balance channel policy.

pr: https://github.com/milvus-io/milvus/pull/38971

Signed-off-by: bigsheeper <yihao.dai@zilliz.com>
Co-authored-by: Wei Liu <wei.liu@zilliz.com>

internal/querycoordv2/balance/balance.go

@@ -45,10 +45,13 @@ func (segPlan *SegmentAssignPlan) String() string {
 }
 
 type ChannelAssignPlan struct {
-	Channel *meta.DmChannel
-	Replica *meta.Replica
-	From    int64
-	To      int64
+	Channel      *meta.DmChannel
+	Replica      *meta.Replica
+	From         int64
+	To           int64
+	FromScore    int64
+	ToScore      int64
+	ChannelScore int64
 }
 
 func (chanPlan *ChannelAssignPlan) String() string {

internal/querycoordv2/balance/rowcount_based_balancer.go

@@ -391,7 +391,7 @@ func newNodeItem(currentScore int, nodeID int64) nodeItem {
 
 func (b *nodeItem) getPriority() int {
 	// if node lacks more score between assignedScore and currentScore, then higher priority
-	return int(b.currentScore - b.assignedScore)
+	return int(math.Ceil(b.currentScore - b.assignedScore))
 }
 
 func (b *nodeItem) setPriority(priority int) {

internal/querycoordv2/balance/score_based_balancer.go

@@ -192,19 +192,19 @@ func (b *ScoreBasedBalancer) assignChannel(br *balanceReport, collectionID int64
 			}
 
 			from := int64(-1)
-			// fromScore := int64(0)
+			fromScore := int64(0)
 			if sourceNode != nil {
 				from = sourceNode.nodeID
-				// fromScore = int64(sourceNode.getPriority())
+				fromScore = int64(sourceNode.getPriority())
 			}
 
 			plan := ChannelAssignPlan{
-				From:    from,
-				To:      targetNode.nodeID,
-				Channel: ch,
-				// FromScore:    fromScore,
-				// ToScore:      int64(targetNode.getPriority()),
-				// SegmentScore: int64(scoreChanges),
+				From:         from,
+				To:           targetNode.nodeID,
+				Channel:      ch,
+				FromScore:    fromScore,
+				ToScore:      int64(targetNode.getPriority()),
+				ChannelScore: int64(scoreChanges),
 			}
 			br.AddRecord(StrRecordf("add segment plan %s", plan))
 			plans = append(plans, plan)
@@ -486,6 +486,20 @@ func (b *ScoreBasedBalancer) BalanceReplica(replica *meta.Replica) (segmentPlans
 	return segmentPlans, channelPlans
 }
 
+func (b *ScoreBasedBalancer) genStoppingChannelPlan(replica *meta.Replica, rwNodes []int64, roNodes []int64) []ChannelAssignPlan {
+	channelPlans := make([]ChannelAssignPlan, 0)
+	for _, nodeID := range roNodes {
+		dmChannels := b.dist.ChannelDistManager.GetByCollectionAndFilter(replica.GetCollectionID(), meta.WithNodeID2Channel(nodeID))
+		plans := b.AssignChannel(replica.GetCollectionID(), dmChannels, rwNodes, false)
+		for i := range plans {
+			plans[i].From = nodeID
+			plans[i].Replica = replica
+		}
+		channelPlans = append(channelPlans, plans...)
+	}
+	return channelPlans
+}
+
 func (b *ScoreBasedBalancer) genStoppingSegmentPlan(replica *meta.Replica, onlineNodes []int64, offlineNodes []int64) []SegmentAssignPlan {
 	segmentPlans := make([]SegmentAssignPlan, 0)
 	for _, nodeID := range offlineNodes {

internal/querycoordv2/balance/score_based_balancer_test.go

@@ -21,6 +21,7 @@ import (
 	"github.com/samber/lo"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/suite"
+	"go.uber.org/atomic"
 
 	etcdkv "github.com/milvus-io/milvus/internal/kv/etcd"
 	"github.com/milvus-io/milvus/internal/metastore/kv/querycoord"