Keep individual segment's updates in a single Etcd operation (milvus-io#20525)

/kind improvement

Signed-off-by: Yuchen Gao <yuchen.gao@zilliz.com>

Signed-off-by: Yuchen Gao <yuchen.gao@zilliz.com>

Author: soothing-rain

internal/metastore/kv/datacoord/kv_catalog.go

@@ -38,6 +38,8 @@ import (
 	"github.com/milvus-io/milvus/internal/util/typeutil"
 )
 
+const maxEtcdTxnNum = 64
+
 type Catalog struct {
 	Txn                  kv.TxnKV
 	ChunkManagerRootPath string
@@ -102,23 +104,40 @@ func (kc *Catalog) AlterSegments(ctx context.Context, newSegments []*datapb.Segm
 	if len(newSegments) == 0 {
 		return nil
 	}
-
-	kvs := make(map[string]string)
+	kvsBySeg := make(map[int64]map[string]string)
 	for _, segment := range newSegments {
 		segmentKvs, err := buildSegmentAndBinlogsKvs(segment)
 		if err != nil {
 			return err
 		}
-		maps.Copy(kvs, segmentKvs)
+		kvsBySeg[segment.GetID()] = make(map[string]string)
+		maps.Copy(kvsBySeg[segment.GetID()], segmentKvs)
 	}
-
+	// Split kvs into multiple operations to avoid over-sized operations.
+	// Also make sure kvs of the same segment are not split into different operations.
+	kvsPiece := make(map[string]string)
+	currSize := 0
 	saveFn := func(partialKvs map[string]string) error {
 		return kc.Txn.MultiSave(partialKvs)
 	}
-	if err := etcd.SaveByBatch(kvs, saveFn); err != nil {
-		return err
+	for _, kvs := range kvsBySeg {
+		if currSize+len(kvs) >= maxEtcdTxnNum {
+			if err := etcd.SaveByBatch(kvsPiece, saveFn); err != nil {
+				log.Error("failed to save by batch", zap.Error(err))
+				return err
+			}
+			kvsPiece = make(map[string]string)
+			currSize = 0
+		}
+		maps.Copy(kvsPiece, kvs)
+		currSize += len(kvs)
+	}
+	if currSize > 0 {
+		if err := etcd.SaveByBatch(kvsPiece, saveFn); err != nil {
+			log.Error("failed to save by batch", zap.Error(err))
+			return err
+		}
 	}
-
 	return nil
 }
 
@@ -219,7 +238,7 @@ func (kc *Catalog) AlterSegmentsAndAddNewSegment(ctx context.Context, segments [
 	return kc.Txn.MultiSave(kvs)
 }
 
-// RevertAlterSegmentsAndAddNewSegment reverts the metastore operation of AtlerSegmentsAndAddNewSegment
+// RevertAlterSegmentsAndAddNewSegment reverts the metastore operation of AlterSegmentsAndAddNewSegment
 func (kc *Catalog) RevertAlterSegmentsAndAddNewSegment(ctx context.Context, oldSegments []*datapb.SegmentInfo, removeSegment *datapb.SegmentInfo) error {
 	var (
 		kvs      = make(map[string]string)

internal/metastore/kv/datacoord/kv_catalog_test.go

@@ -335,6 +335,54 @@ func Test_AlterSegments(t *testing.T) {
 		assert.Equal(t, 4, len(savedKvs))
 		verifySavedKvsForSegment(t, savedKvs)
 	})
+
+	t.Run("save large ops successfully", func(t *testing.T) {
+		txn := &MockedTxnKV{}
+		savedKvs := make(map[string]string)
+		opGroupCount := 0
+		txn.multiSave = func(kvs map[string]string) error {
+			var ks []string
+			for k := range kvs {
+				ks = append(ks, k)
+			}
+			maps.Copy(savedKvs, kvs)
+			opGroupCount++
+			return nil
+		}
+
+		catalog := &Catalog{txn, "a"}
+		err := catalog.AlterSegments(context.TODO(), []*datapb.SegmentInfo{})
+		assert.Nil(t, err)
+
+		var binlogXL []*datapb.FieldBinlog
+		for i := 0; i < 255; i++ {
+			binlogXL = append(binlogXL, &datapb.FieldBinlog{
+				FieldID: int64(i),
+				Binlogs: []*datapb.Binlog{
+					{
+						EntriesNum: 5,
+						LogPath:    binlogPath,
+					},
+				},
+			})
+		}
+
+		segmentXL := &datapb.SegmentInfo{
+			ID:           segmentID,
+			CollectionID: collectionID,
+			PartitionID:  partitionID,
+			NumOfRows:    100,
+			State:        commonpb.SegmentState_Flushed,
+			Binlogs:      binlogXL,
+			Deltalogs:    deltalogs,
+			Statslogs:    statslogs,
+		}
+
+		err = catalog.AlterSegments(context.TODO(), []*datapb.SegmentInfo{segmentXL})
+		assert.Nil(t, err)
+		assert.Equal(t, 255+3, len(savedKvs))
+		assert.Equal(t, 5, opGroupCount)
+	})
 }
 
 func Test_AlterSegmentsAndAddNewSegment(t *testing.T) {