enhance: Make write buffer memory check do until safe

See also #27675 #26177

Make memory check evict memory buffer until memory water level is safe.
Also make `EvictBuffer` wait until sync task done.

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

internal/datanode/writebuffer/manager.go

@@ -94,38 +94,40 @@ func (m *bufferManager) memoryCheck() {
 
 	m.mut.Lock()
 	defer m.mut.Unlock()
+	for {
+		var total int64
+		var candidate WriteBuffer
+		var candiSize int64
+		var candiChan string
 
-	var total int64
-	var candidate WriteBuffer
-	var candiSize int64
-	var candiChan string
-	for chanName, buf := range m.buffers {
-		size := buf.MemorySize()
-		total += size
-		if size > candiSize {
-			candiSize = size
-			candidate = buf
-			candiChan = chanName
+		toMB := func(mem float64) float64 {
+			return mem / 1024 / 1024
 		}
-	}
 
-	toMB := func(mem float64) float64 {
-		return mem / 1024 / 1024
-	}
+		for chanName, buf := range m.buffers {
+			size := buf.MemorySize()
+			total += size
+			if size > candiSize {
+				candiSize = size
+				candidate = buf
+				candiChan = chanName
+			}
+		}
 
-	totalMemory := hardware.GetMemoryCount()
-	memoryWatermark := float64(totalMemory) * paramtable.Get().DataNodeCfg.MemoryWatermark.GetAsFloat()
-	if float64(total) < memoryWatermark {
-		log.RatedDebug(20, "skip force sync because memory level is not high enough",
-			zap.Float64("current_total_memory_usage", toMB(float64(total))),
-			zap.Float64("current_memory_watermark", toMB(memoryWatermark)))
-		return
-	}
+		totalMemory := hardware.GetMemoryCount()
+		memoryWatermark := float64(totalMemory) * paramtable.Get().DataNodeCfg.MemoryWatermark.GetAsFloat()
+		if float64(total) < memoryWatermark {
+			log.RatedDebug(20, "skip force sync because memory level is not high enough",
+				zap.Float64("current_total_memory_usage", toMB(float64(total))),
+				zap.Float64("current_memory_watermark", toMB(memoryWatermark)))
+			return
+		}
 
-	if candidate != nil {
-		candidate.EvictBuffer(GetOldestBufferPolicy(paramtable.Get().DataNodeCfg.MemoryForceSyncSegmentNum.GetAsInt()))
-		log.Info("notify writebuffer to sync",
-			zap.String("channel", candiChan), zap.Float64("bufferSize(MB)", toMB(float64(candiSize))))
+		if candidate != nil {
+			candidate.EvictBuffer(GetOldestBufferPolicy(paramtable.Get().DataNodeCfg.MemoryForceSyncSegmentNum.GetAsInt()))
+			log.Info("notify writebuffer to sync",
+				zap.String("channel", candiChan), zap.Float64("bufferSize(MB)", toMB(float64(candiSize))))
+		}
 	}
 }
 

internal/datanode/writebuffer/manager_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/suite"
+	"go.uber.org/atomic"
 
 	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
 	"github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
@@ -209,14 +210,23 @@ func (s *ManagerSuite) TestMemoryCheck() {
 
 	wb := NewMockWriteBuffer(s.T())
 
+	flag := atomic.NewBool(false)
 	memoryLimit := hardware.GetMemoryCount()
 	signal := make(chan struct{}, 1)
-	wb.EXPECT().MemorySize().Return(int64(float64(memoryLimit) * 0.6))
+	wb.EXPECT().MemorySize().RunAndReturn(func() int64 {
+		if flag.Load() {
+			return int64(float64(memoryLimit) * 0.4)
+		} else {
+			return int64(float64(memoryLimit) * 0.6)
+		}
+	})
+	//.Return(int64(float64(memoryLimit) * 0.6))
 	wb.EXPECT().EvictBuffer(mock.Anything).Run(func(polices ...SyncPolicy) {
 		select {
 		case signal <- struct{}{}:
 		default:
 		}
+		flag.Store(true)
 	}).Return()
 	manager.mut.Lock()
 	manager.buffers[s.channelName] = wb

internal/datanode/writebuffer/write_buffer.go

@@ -196,7 +196,7 @@ func (wb *writeBufferBase) EvictBuffer(policies ...SyncPolicy) {
 	segmentIDs := wb.getSegmentsToSync(ts, policies...)
 	if len(segmentIDs) > 0 {
 		log.Info("evict buffer find segments to sync", zap.Int64s("segmentIDs", segmentIDs))
-		wb.syncSegments(context.Background(), segmentIDs)
+		conc.AwaitAll(wb.syncSegments(context.Background(), segmentIDs)...)
 	}
 }
 
@@ -266,6 +266,7 @@ func (wb *writeBufferBase) triggerSync() (segmentIDs []int64) {
 	segmentsToSync := wb.getSegmentsToSync(wb.checkpoint.GetTimestamp(), wb.syncPolicies...)
 	if len(segmentsToSync) > 0 {
 		log.Info("write buffer get segments to sync", zap.Int64s("segmentIDs", segmentsToSync))
+		// ignore future here, use callback to handle error
 		wb.syncSegments(context.Background(), segmentsToSync)
 	}
 
@@ -296,8 +297,9 @@ func (wb *writeBufferBase) sealSegments(ctx context.Context, segmentIDs []int64)
 	return nil
 }
 
-func (wb *writeBufferBase) syncSegments(ctx context.Context, segmentIDs []int64) {
+func (wb *writeBufferBase) syncSegments(ctx context.Context, segmentIDs []int64) []*conc.Future[error] {
 	log := log.Ctx(ctx)
+	result := make([]*conc.Future[error], 0, len(segmentIDs))
 	for _, segmentID := range segmentIDs {
 		syncTask, err := wb.getSyncTask(ctx, segmentID)
 		if err != nil {
@@ -309,9 +311,9 @@ func (wb *writeBufferBase) syncSegments(ctx context.Context, segmentIDs []int64)
 			}
 		}
 
-		// discard Future here, handle error in callback
-		_ = wb.syncMgr.SyncData(ctx, syncTask)
+		result = append(result, wb.syncMgr.SyncData(ctx, syncTask))
 	}
+	return result
 }
 
 // getSegmentsToSync applies all policies to get segments list to sync.

internal/datanode/writebuffer/write_buffer_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
 	"github.com/milvus-io/milvus/internal/proto/datapb"
 	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/util/conc"
 	"github.com/milvus-io/milvus/pkg/util/merr"
 	"github.com/milvus-io/milvus/pkg/util/paramtable"
 )
@@ -356,7 +357,9 @@ func (s *WriteBufferSuite) TestEvictBuffer() {
 		s.metacache.EXPECT().GetSegmentByID(int64(2)).Return(segment, true)
 		s.metacache.EXPECT().UpdateSegments(mock.Anything, mock.Anything).Return()
 		serializer.EXPECT().EncodeBuffer(mock.Anything, mock.Anything).Return(syncmgr.NewSyncTask(), nil)
-		s.syncMgr.EXPECT().SyncData(mock.Anything, mock.Anything).Return(nil)
+		s.syncMgr.EXPECT().SyncData(mock.Anything, mock.Anything).Return(conc.Go[error](func() (error, error) {
+			return nil, nil
+		}))
 		defer func() {
 			s.wb.mut.Lock()
 			defer s.wb.mut.Unlock()