fix: DataNode might OOM by estimating based on MemorySize

See also: milvus-io#34136

Signed-off-by: yangxuan <xuan.yang@zilliz.com>

configs/milvus.yaml

@@ -543,8 +543,6 @@ dataNode:
     # if this parameter <= 0, will set it as the maximum number of CPUs that can be executing
     # suggest to set it bigger on large collection numbers to avoid blocking
     workPoolSize: -1
-    # specify the size of global work pool for channel checkpoint updating
-    # if this parameter <= 0, will set it as 10
     updateChannelCheckpointMaxParallel: 10
     updateChannelCheckpointInterval: 60 # the interval duration(in seconds) for datanode to update channel checkpoint of each channel
     updateChannelCheckpointRPCTimeout: 20 # timeout in seconds for UpdateChannelCheckpoint RPC call
@@ -556,6 +554,7 @@ dataNode:
     readBufferSizeInMB: 16 # The data block size (in MB) read from chunk manager by the datanode during import.
   compaction:
     levelZeroBatchMemoryRatio: 0.05 # The minimal memory ratio of free memory for level zero compaction executing in batch mode
+    levelZeroMaxBatchSize: -1 # Max batch size refers to the max number of L1/L2 segments in a batch when executing L0 compaction. Default to -1, any value that is less than 1 means no limit. Valid range: >= 1.
   gracefulStopTimeout: 1800 # seconds. force stop node without graceful stop
   ip:  # if not specified, use the first unicastable address
   port: 21124

internal/datanode/compaction/l0_compactor.go

@@ -133,24 +133,19 @@ func (t *LevelZeroCompactionTask) Compact() (*datapb.CompactionPlanResult, error
 	}
 
 	var (
-		totalSize      int64
-		totalDeltalogs = make(map[int64][]string)
+		memorySize     int64
+		totalDeltalogs = []string{}
 	)
 	for _, s := range l0Segments {
-		paths := []string{}
 		for _, d := range s.GetDeltalogs() {
 			for _, l := range d.GetBinlogs() {
-				paths = append(paths, l.GetLogPath())
-				totalSize += l.GetMemorySize()
+				totalDeltalogs = append(totalDeltalogs, l.GetLogPath())
+				memorySize += l.GetMemorySize()
 			}
 		}
-		if len(paths) > 0 {
-			totalDeltalogs[s.GetSegmentID()] = paths
-		}
 	}
 
-	batchSize := getMaxBatchSize(totalSize)
-	resultSegments, err := t.process(ctx, batchSize, targetSegments, lo.Values(totalDeltalogs)...)
+	resultSegments, err := t.process(ctx, memorySize, targetSegments, totalDeltalogs)
 	if err != nil {
 		return nil, err
 	}
@@ -170,15 +165,22 @@ func (t *LevelZeroCompactionTask) Compact() (*datapb.CompactionPlanResult, error
 	return result, nil
 }
 
-// batch size means segment count
-func getMaxBatchSize(totalSize int64) int {
-	max := 1
-	memLimit := float64(hardware.GetFreeMemoryCount()) * paramtable.Get().DataNodeCfg.L0BatchMemoryRatio.GetAsFloat()
-	if memLimit > float64(totalSize) {
-		max = int(memLimit / float64(totalSize))
+// BatchSize refers to the L1/L2 segments count that in one batch, batchSize controls the expansion ratio
+// of deltadata in memory.
+func getMaxBatchSize(baseMemSize, memLimit float64) int {
+	batchSize := 1
+	if memLimit > baseMemSize {
+		batchSize = int(memLimit / baseMemSize)
+	}
+
+	maxSizeLimit := paramtable.Get().DataNodeCfg.L0CompactionMaxBatchSize.GetAsInt()
+	// Set batch size to maxSizeLimit if it is larger than maxSizeLimit.
+	// When maxSizeLimit <= 0, it means no limit.
+	if maxSizeLimit > 0 && batchSize > maxSizeLimit {
+		return maxSizeLimit
 	}
 
-	return max
+	return batchSize
 }
 
 func (t *LevelZeroCompactionTask) serializeUpload(ctx context.Context, segmentWriters map[int64]*SegmentDeltaWriter) ([]*datapb.CompactionSegment, error) {
@@ -317,18 +319,15 @@ func (t *LevelZeroCompactionTask) applyBFInParallel(ctx context.Context, deltaDa
 	return retMap
 }
 
-func (t *LevelZeroCompactionTask) process(ctx context.Context, batchSize int, targetSegments []*datapb.CompactionSegmentBinlogs, deltaLogs ...[]string) ([]*datapb.CompactionSegment, error) {
+func (t *LevelZeroCompactionTask) process(ctx context.Context, l0MemSize int64, targetSegments []*datapb.CompactionSegmentBinlogs, deltaLogs ...[]string) ([]*datapb.CompactionSegment, error) {
 	_, span := otel.Tracer(typeutil.DataNodeRole).Start(ctx, "L0Compact process")
 	defer span.End()
 
-	results := make([]*datapb.CompactionSegment, 0)
-	batch := int(math.Ceil(float64(len(targetSegments)) / float64(batchSize)))
-	log := log.Ctx(ctx).With(
-		zap.Int64("planID", t.plan.GetPlanID()),
-		zap.Int("max conc segment counts", batchSize),
-		zap.Int("total segment counts", len(targetSegments)),
-		zap.Int("total batch", batch),
-	)
+	ratio := paramtable.Get().DataNodeCfg.L0BatchMemoryRatio.GetAsFloat()
+	memLimit := float64(hardware.GetFreeMemoryCount()) * ratio
+	if float64(l0MemSize) > memLimit {
+		return nil, errors.Newf("L0 compaction failed, not enough memory, request memory size: %v, memory limit: %v", l0MemSize, memLimit)
+	}
 
 	log.Info("L0 compaction process start")
 	allDelta, err := t.loadDelta(ctx, lo.Flatten(deltaLogs))
@@ -337,6 +336,16 @@ func (t *LevelZeroCompactionTask) process(ctx context.Context, batchSize int, ta
 		return nil, err
 	}
 
+	batchSize := getMaxBatchSize(float64(allDelta.Size()), memLimit)
+	batch := int(math.Ceil(float64(len(targetSegments)) / float64(batchSize)))
+	log := log.Ctx(ctx).With(
+		zap.Int64("planID", t.plan.GetPlanID()),
+		zap.Int("max conc segment counts", batchSize),
+		zap.Int("total segment counts", len(targetSegments)),
+		zap.Int("total batch", batch),
+	)
+
+	results := make([]*datapb.CompactionSegment, 0)
 	for i := 0; i < batch; i++ {
 		left, right := i*batchSize, (i+1)*batchSize
 		if right >= len(targetSegments) {

internal/datanode/compaction/l0_compactor_test.go

@@ -79,6 +79,36 @@ func (s *LevelZeroCompactionTaskSuite) SetupTest() {
 	s.dBlob = blob.GetValue()
 }
 
+func (s *LevelZeroCompactionTaskSuite) TestGetMaxBatchSize() {
+	tests := []struct {
+		baseMem        float64
+		memLimit       float64
+		batchSizeLimit string
+
+		expected    int
+		description string
+	}{
+		{10, 100, "-1", 10, "no limitation on maxBatchSize"},
+		{10, 100, "0", 10, "no limitation on maxBatchSize v2"},
+		{10, 100, "11", 10, "maxBatchSize == 11"},
+		{10, 100, "1", 1, "maxBatchSize == 1"},
+		{10, 12, "-1", 1, "no limitation on maxBatchSize"},
+		{10, 12, "100", 1, "maxBatchSize == 100"},
+	}
+
+	maxSizeK := paramtable.Get().DataNodeCfg.L0CompactionMaxBatchSize.Key
+	defer paramtable.Get().Reset(maxSizeK)
+	for _, test := range tests {
+		s.Run(test.description, func() {
+			paramtable.Get().Save(maxSizeK, test.batchSizeLimit)
+			defer paramtable.Get().Reset(maxSizeK)
+
+			actual := getMaxBatchSize(test.baseMem, test.memLimit)
+			s.Equal(test.expected, actual)
+		})
+	}
+}
+
 func (s *LevelZeroCompactionTaskSuite) TestProcessLoadDeltaFail() {
 	plan := &datapb.CompactionPlan{
 		PlanID: 19530,

pkg/util/paramtable/component_param.go

@@ -3743,7 +3743,8 @@ type dataNodeConfig struct {
 	ReadBufferSizeInMB         ParamItem `refreshable:"true"`
 
 	// Compaction
-	L0BatchMemoryRatio ParamItem `refreshable:"true"`
+	L0BatchMemoryRatio       ParamItem `refreshable:"true"`
+	L0CompactionMaxBatchSize ParamItem `refreshable:"true"`
 
 	GracefulStopTimeout ParamItem `refreshable:"true"`
 
@@ -4052,6 +4053,15 @@ if this parameter <= 0, will set it as 10`,
 	}
 	p.L0BatchMemoryRatio.Init(base.mgr)
 
+	p.L0CompactionMaxBatchSize = ParamItem{
+		Key:          "dataNode.compaction.levelZeroMaxBatchSize",
+		Version:      "2.4.5",
+		Doc:          "Max batch size refers to the max number of L1/L2 segments in a batch when executing L0 compaction. Default to -1, any value that is less than 1 means no limit. Valid range: >= 1.",
+		DefaultValue: "-1",
+		Export:       true,
+	}
+	p.L0CompactionMaxBatchSize.Init(base.mgr)
+
 	p.GracefulStopTimeout = ParamItem{
 		Key:          "dataNode.gracefulStopTimeout",
 		Version:      "2.3.7",