Change default balance policy (#10563)

issue: #10198
Signed-off-by: sunby <bingyi.sun@zilliz.com>

internal/datacoord/channel_manager.go

@@ -63,10 +63,9 @@ func defaultFactory(hash *consistent.Consistent) ChannelPolicyFactory {
 
 // NewChannelManager return a new ChannelManager
 func NewChannelManager(kv kv.TxnKV, posProvider positionProvider, options ...ChannelManagerOpt) (*ChannelManager, error) {
-	hashring := consistent.New()
 	c := &ChannelManager{
 		posProvider: posProvider,
-		factory:     defaultFactory(hashring),
+		factory:     NewChannelPolicyFactoryV1(kv),
 		store:       NewChannelStore(kv),
 	}
 

internal/datacoord/channel_manager_factory.go

@@ -47,7 +47,7 @@ func NewChannelPolicyFactoryV1(kv kv.TxnKV) *ChannelPolicyFactoryV1 {
 
 // NewRegisterPolicy implementing ChannelPolicyFactory returns BufferChannelAssignPolicy
 func (f *ChannelPolicyFactoryV1) NewRegisterPolicy() RegisterPolicy {
-	return BufferChannelAssignPolicy
+	return AvgAssignRegisterPolicy
 }
 
 // NewDeregisterPolicy implementing ChannelPolicyFactory returns AvgAssignUnregisteredChannels

internal/datacoord/policy.go

@@ -50,6 +50,63 @@ func BufferChannelAssignPolicy(store ROChannelStore, nodeID int64) ChannelOpSet
 	return opSet
 }
 
+func AvgAssignRegisterPolicy(store ROChannelStore, nodeID int64) ChannelOpSet {
+	opSet := BufferChannelAssignPolicy(store, nodeID)
+	if len(opSet) != 0 {
+		return opSet
+	}
+
+	infos := store.GetNodesChannels()
+	infos = filterNode(infos, nodeID)
+
+	channelNum := 0
+	for _, info := range infos {
+		channelNum += len(info.Channels)
+	}
+	avg := channelNum / (len(store.GetNodes()) + 1)
+	if avg == 0 {
+		return nil
+	}
+
+	// sort in descending order and reallocate
+	sort.Slice(infos, func(i, j int) bool {
+		return len(infos[i].Channels) > len(infos[j].Channels)
+	})
+
+	deletes := make(map[int64][]*channel)
+	adds := make(map[int64][]*channel)
+	for i := 0; i < avg; {
+		t := infos[i%len(infos)]
+		idx := i / len(infos)
+		if idx >= len(t.Channels) {
+			continue
+		}
+		deletes[t.NodeID] = append(deletes[t.NodeID], t.Channels[idx])
+		adds[nodeID] = append(adds[nodeID], t.Channels[idx])
+		i++
+	}
+
+	opSet = ChannelOpSet{}
+	for k, v := range deletes {
+		opSet.Delete(k, v)
+	}
+	for k, v := range adds {
+		opSet.Add(k, v)
+	}
+	return opSet
+}
+
+func filterNode(infos []*NodeChannelInfo, nodeID int64) []*NodeChannelInfo {
+	filtered := make([]*NodeChannelInfo, 0)
+	for _, info := range infos {
+		if info.NodeID == nodeID {
+			continue
+		}
+		filtered = append(filtered, info)
+	}
+	return filtered
+}
+
 // ConsistentHashRegisterPolicy use a consistent hash to matain the mapping
 func ConsistentHashRegisterPolicy(hashring *consistent.Consistent) RegisterPolicy {
 	return func(store ROChannelStore, nodeID int64) ChannelOpSet {

internal/datacoord/policy_test.go

@@ -428,3 +428,121 @@ func TestBgCheckWithMaxWatchDuration(t *testing.T) {
 		})
 	}
 }
+
+func TestAvgAssignRegisterPolicy(t *testing.T) {
+	type args struct {
+		store  ROChannelStore
+		nodeID int64
+	}
+	tests := []struct {
+		name string
+		args args
+		want ChannelOpSet
+	}{
+		{
+			"test empty",
+			args{
+				&ChannelStore{
+					memkv.NewMemoryKV(),
+					map[int64]*NodeChannelInfo{},
+				},
+				1,
+			},
+			nil,
+		},
+		{
+			"test with buffer channel",
+			args{
+				&ChannelStore{
+					memkv.NewMemoryKV(),
+					map[int64]*NodeChannelInfo{
+						bufferID: {bufferID, []*channel{{"ch1", 1}}},
+					},
+				},
+				1,
+			},
+			[]*ChannelOp{
+				{
+					Type:     Delete,
+					NodeID:   bufferID,
+					Channels: []*channel{{"ch1", 1}},
+				},
+				{
+					Type:     Add,
+					NodeID:   1,
+					Channels: []*channel{{"ch1", 1}},
+				},
+			},
+		},
+		{
+			"test with avg assign",
+			args{
+				&ChannelStore{
+					memkv.NewMemoryKV(),
+					map[int64]*NodeChannelInfo{
+						1: {1, []*channel{{"ch1", 1}, {"ch2", 1}}},
+						2: {2, []*channel{{"ch3", 1}, {"ch4", 1}}},
+					},
+				},
+				3,
+			},
+			[]*ChannelOp{
+				{
+					Type:     Delete,
+					NodeID:   1,
+					Channels: []*channel{{"ch1", 1}},
+				},
+				{
+					Type:     Add,
+					NodeID:   3,
+					Channels: []*channel{{"ch1", 1}},
+				},
+			},
+		},
+		{
+			"test with avg equals to zero",
+			args{
+				&ChannelStore{
+					memkv.NewMemoryKV(),
+					map[int64]*NodeChannelInfo{
+						1: {1, []*channel{{"ch1", 1}}},
+						2: {2, []*channel{{"ch3", 1}}},
+					},
+				},
+				3,
+			},
+			nil,
+		},
+		{
+			"test node with empty channel",
+			args{
+				&ChannelStore{
+					memkv.NewMemoryKV(),
+					map[int64]*NodeChannelInfo{
+						1: {1, []*channel{{"ch1", 1}, {"ch2", 1}, {"ch3", 1}}},
+						2: {2, []*channel{}},
+					},
+				},
+				3,
+			},
+			[]*ChannelOp{
+				{
+					Type:     Delete,
+					NodeID:   1,
+					Channels: []*channel{{"ch1", 1}},
+				},
+				{
+					Type:     Add,
+					NodeID:   3,
+					Channels: []*channel{{"ch1", 1}},
+				},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := AvgAssignRegisterPolicy(tt.args.store, tt.args.nodeID)
+			assert.EqualValues(t, tt.want, got)
+		})
+	}
+}