cmd/frostfs-cli/modules/control/flush_cache.go

@@ -8,17 +8,23 @@ import (
 	"github.com/spf13/cobra"
 )
 
+const sealFlag = "seal"
+
 var flushCacheCmd = &cobra.Command{
-	Use:   "flush-cache",
-	Short: "Flush objects from the write-cache to the main storage",
-	Long:  "Flush objects from the write-cache to the main storage",
-	Run:   flushCache,
+	Use:        "flush-cache",
+	Short:      "Flush objects from the write-cache to the main storage",
+	Long:       "Flush objects from the write-cache to the main storage",
+	Run:        flushCache,
+	Deprecated: "Flushing objects from writecache to the main storage is performed by writecache automatically. To flush and seal writecache use `frostfs-cli control shards writecache seal`.",
 }
 
 func flushCache(cmd *cobra.Command, _ []string) {
 	pk := key.Get(cmd)
 
-	req := &control.FlushCacheRequest{Body: new(control.FlushCacheRequest_Body)}
+	seal, _ := cmd.Flags().GetBool(sealFlag)
+	req := &control.FlushCacheRequest{Body: &control.FlushCacheRequest_Body{
+		Seal: seal,
+	}}
 	req.Body.Shard_ID = getShardIDList(cmd)
 
 	signRequest(cmd, pk, req)
@@ -44,6 +50,7 @@ func initControlFlushCacheCmd() {
 	ff := flushCacheCmd.Flags()
 	ff.StringSlice(shardIDFlag, nil, "List of shard IDs in base58 encoding")
 	ff.Bool(shardAllFlag, false, "Process all shards")
+	ff.Bool(sealFlag, false, "Writecache will be left in read-only mode after flush completed")
 
 	flushCacheCmd.MarkFlagsMutuallyExclusive(shardIDFlag, shardAllFlag)
 }

cmd/frostfs-cli/modules/control/shards.go

@@ -17,6 +17,7 @@ func initControlShardsCmd() {
 	shardsCmd.AddCommand(evacuationShardCmd)
 	shardsCmd.AddCommand(flushCacheCmd)
 	shardsCmd.AddCommand(doctorCmd)
+	shardsCmd.AddCommand(writecacheShardCmd)
 
 	initControlShardsListCmd()
 	initControlSetShardModeCmd()
@@ -24,4 +25,5 @@ func initControlShardsCmd() {
 	initControlEvacuationShardCmd()
 	initControlFlushCacheCmd()
 	initControlDoctorCmd()
+	initControlShardsWritecacheCmd()
 }

cmd/frostfs-cli/modules/control/writecache.go

@@ -0,0 +1,73 @@
+package control
+
+import (
+	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/client"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-cli/internal/key"
+	commonCmd "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/internal/common"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/control"
+	"github.com/mr-tron/base58"
+	"github.com/spf13/cobra"
+)
+
+var writecacheShardCmd = &cobra.Command{
+	Use:   "writecache",
+	Short: "Operations with storage node's write-cache",
+	Long:  "Operations with storage node's write-cache",
+}
+
+var sealWritecacheShardCmd = &cobra.Command{
+	Use:   "seal",
+	Short: "Flush objects from write-cache and move write-cache to degraded read only mode.",
+	Long:  "Flush all the objects from the write-cache to the main storage and move the write-cache to the degraded read only mode: write-cache will be empty and no objects will be put in it.",
+	Run:   sealWritecache,
+}
+
+func sealWritecache(cmd *cobra.Command, _ []string) {
+	pk := key.Get(cmd)
+
+	ignoreErrors, _ := cmd.Flags().GetBool(ignoreErrorsFlag)
+
+	req := &control.SealWriteCacheRequest{Body: &control.SealWriteCacheRequest_Body{
+		Shard_ID:     getShardIDList(cmd),
+		IgnoreErrors: ignoreErrors,
+	}}
+
+	signRequest(cmd, pk, req)
+
+	cli := getClient(cmd, pk)
+
+	var resp *control.SealWriteCacheResponse
+	var err error
+	err = cli.ExecRaw(func(client *client.Client) error {
+		resp, err = control.SealWriteCache(client, req)
+		return err
+	})
+	commonCmd.ExitOnErr(cmd, "rpc error: %w", err)
+
+	verifyResponse(cmd, resp.GetSignature(), resp.GetBody())
+
+	var success, failed uint
+	for _, res := range resp.GetBody().GetResults() {
+		if res.GetSuccess() {
+			success++
+			cmd.Printf("Shard %s: OK\n", base58.Encode(res.GetShard_ID()))
+		} else {
+			failed++
+			cmd.Printf("Shard %s: failed with error %q\n", base58.Encode(res.GetShard_ID()), res.GetError())
+		}
+	}
+	cmd.Printf("Total: %d success, %d failed\n", success, failed)
+}
+
+func initControlShardsWritecacheCmd() {
+	writecacheShardCmd.AddCommand(sealWritecacheShardCmd)
+
+	initControlFlags(sealWritecacheShardCmd)
+
+	ff := sealWritecacheShardCmd.Flags()
+	ff.StringSlice(shardIDFlag, nil, "List of shard IDs in base58 encoding")
+	ff.Bool(shardAllFlag, false, "Process all shards")
+	ff.Bool(ignoreErrorsFlag, true, "Skip invalid/unreadable objects")
+
+	sealWritecacheShardCmd.MarkFlagsMutuallyExclusive(shardIDFlag, shardAllFlag)
+}

pkg/local_object_storage/engine/writecache.go

@@ -2,6 +2,7 @@ package engine
 
 import (
 	"context"
+	"sync"
 	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
@@ -11,12 +12,14 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
+	"golang.org/x/sync/errgroup"
 )
 
 // FlushWriteCachePrm groups the parameters of FlushWriteCache operation.
 type FlushWriteCachePrm struct {
 	shardID      *shard.ID
 	ignoreErrors bool
+	seal         bool
 }
 
 // SetShardID is an option to set shard ID.
@@ -26,11 +29,16 @@ func (p *FlushWriteCachePrm) SetShardID(id *shard.ID) {
 	p.shardID = id
 }
 
-// SetIgnoreErrors sets errors ignore flag..
+// SetIgnoreErrors sets errors ignore flag.
 func (p *FlushWriteCachePrm) SetIgnoreErrors(ignore bool) {
 	p.ignoreErrors = ignore
 }
 
+// SetSeal sets seal flag.
+func (p *FlushWriteCachePrm) SetSeal(v bool) {
+	p.seal = v
+}
+
 // FlushWriteCacheRes groups the resulting values of FlushWriteCache operation.
 type FlushWriteCacheRes struct{}
 
@@ -38,8 +46,9 @@ type FlushWriteCacheRes struct{}
 func (e *StorageEngine) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) (FlushWriteCacheRes, error) {
 	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.FlushWriteCache",
 		trace.WithAttributes(
-			attribute.String("shard)id", p.shardID.String()),
+			attribute.String("shard_id", p.shardID.String()),
 			attribute.Bool("ignore_errors", p.ignoreErrors),
+			attribute.Bool("seal", p.seal),
 		))
 	defer span.End()
 
@@ -53,10 +62,84 @@ func (e *StorageEngine) FlushWriteCache(ctx context.Context, p FlushWriteCachePr
 
 	var prm shard.FlushWriteCachePrm
 	prm.SetIgnoreErrors(p.ignoreErrors)
+	prm.SetSeal(p.seal)
 
 	return FlushWriteCacheRes{}, sh.FlushWriteCache(ctx, prm)
 }
 
+type SealWriteCachePrm struct {
+	ShardIDs     []*shard.ID
+	IgnoreErrors bool
+}
+
+type ShardSealResult struct {
+	ShardID  *shard.ID
+	Success  bool
+	ErrorMsg string
+}
+
+type SealWriteCacheRes struct {
+	ShardResults []ShardSealResult
+}
+
+// SealWriteCache flushed all data to blobstore and moves write-cache to degraded read only mode.
+func (e *StorageEngine) SealWriteCache(ctx context.Context, prm SealWriteCachePrm) (SealWriteCacheRes, error) {
+	ctx, span := tracing.StartSpanFromContext(ctx, "StorageEngine.SealWriteCache",
+		trace.WithAttributes(
+			attribute.Int("shard_id_count", len(prm.ShardIDs)),
+			attribute.Bool("ignore_errors", prm.IgnoreErrors),
+		))
+	defer span.End()
+
+	res := SealWriteCacheRes{
+		ShardResults: make([]ShardSealResult, 0, len(prm.ShardIDs)),
+	}
+	resGuard := &sync.Mutex{}
+
+	eg, egCtx := errgroup.WithContext(ctx)
+	for _, shardID := range prm.ShardIDs {
+		shardID := shardID
+		eg.Go(func() error {
+			e.mtx.RLock()
+			sh, ok := e.shards[shardID.String()]
+			e.mtx.RUnlock()
+
+			if !ok {
+				resGuard.Lock()
+				defer resGuard.Unlock()
+				res.ShardResults = append(res.ShardResults, ShardSealResult{
+					ShardID:  shardID,
+					ErrorMsg: errShardNotFound.Error(),
+				})
+				return nil
+			}
+
+			err := sh.SealWriteCache(egCtx, shard.SealWriteCachePrm{IgnoreErrors: prm.IgnoreErrors})
+
+			resGuard.Lock()
+			defer resGuard.Unlock()
+
+			if err != nil {
+				res.ShardResults = append(res.ShardResults, ShardSealResult{
+					ShardID:  shardID,
+					ErrorMsg: err.Error(),
+				})
+			} else {
+				res.ShardResults = append(res.ShardResults, ShardSealResult{
+					ShardID: shardID,
+					Success: true,
+				})
+			}
+			return nil
+		})
+	}
+
+	if err := eg.Wait(); err != nil {
+		return SealWriteCacheRes{}, err
+	}
+	return res, nil
+}
+
 type writeCacheMetrics struct {
 	shardID string
 	metrics metrics.WriteCacheMetrics

pkg/local_object_storage/shard/writecache.go

@@ -12,6 +12,7 @@ import (
 // FlushWriteCachePrm represents parameters of a `FlushWriteCache` operation.
 type FlushWriteCachePrm struct {
 	ignoreErrors bool
+	seal         bool
 }
 
 // SetIgnoreErrors sets the flag to ignore read-errors during flush.
@@ -19,6 +20,11 @@ func (p *FlushWriteCachePrm) SetIgnoreErrors(ignore bool) {
 	p.ignoreErrors = ignore
 }
 
+// SetSeal sets the flag to left writecache in read-only mode after flush.
+func (p *FlushWriteCachePrm) SetSeal(v bool) {
+	p.seal = v
+}
+
 // errWriteCacheDisabled is returned when an operation on write-cache is performed,
 // but write-cache is disabled.
 var errWriteCacheDisabled = errors.New("write-cache is disabled")
@@ -29,6 +35,7 @@ func (s *Shard) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) error
 		trace.WithAttributes(
 			attribute.String("shard_id", s.ID().String()),
 			attribute.Bool("ignore_errors", p.ignoreErrors),
+			attribute.Bool("seal", p.seal),
 		))
 	defer span.End()
 
@@ -47,5 +54,35 @@ func (s *Shard) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) error
 		return ErrDegradedMode
 	}
 
-	return s.writeCache.Flush(ctx, p.ignoreErrors)
+	return s.writeCache.Flush(ctx, p.ignoreErrors, p.seal)
+}
+
+type SealWriteCachePrm struct {
+	IgnoreErrors bool
+}
+
+// SealWriteCache flushes all data from the write-cache and moves it to degraded read only mode.
+func (s *Shard) SealWriteCache(ctx context.Context, p SealWriteCachePrm) error {
+	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.SealWriteCache",
+		trace.WithAttributes(
+			attribute.String("shard_id", s.ID().String()),
+			attribute.Bool("ignore_errors", p.IgnoreErrors),
+		))
+	defer span.End()
+
+	if !s.hasWriteCache() {
+		return errWriteCacheDisabled
+	}
+
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	if s.info.Mode.ReadOnly() {
+		return ErrReadOnlyMode
+	}
+	if s.info.Mode.NoMetabase() {
+		return ErrDegradedMode
+	}
+
+	return s.writeCache.Seal(ctx, p.IgnoreErrors)
 }

pkg/local_object_storage/writecache/delete.go

@@ -18,6 +18,7 @@ import (
 // Delete removes object from write-cache.
 //
 // Returns an error of type apistatus.ObjectNotFound if object is missing in write-cache.
+// Returns ErrNotInitialized if write-cache has not been initialized yet.
 func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 	ctx, span := tracing.StartSpanFromContext(ctx, "writecache.Delete",
 		trace.WithAttributes(
@@ -32,7 +33,9 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 		c.metrics.Delete(time.Since(startedAt), deleted, storageType)
 	}()
 
-	c.modeMtx.RLock()
+	if !c.modeMtx.TryRLock() {
+		return ErrNotInitialized
+	}
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
 		return ErrReadOnly

pkg/local_object_storage/writecache/flush.go

@@ -12,6 +12,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
@@ -33,6 +34,8 @@ const (
 	defaultFlushInterval = time.Second
 )
 
+var errIterationCompleted = errors.New("iteration completed")
+
 // runFlushLoop starts background workers which periodically flush objects to the blobstor.
 func (c *cache) runFlushLoop(ctx context.Context) {
 	if c.disableBackgroundFlush {
@@ -135,13 +138,11 @@ func (c *cache) flushSmallObjects(ctx context.Context) {
 			}
 		}
 
+		c.modeMtx.RUnlock()
 		if count == 0 {
-			c.modeMtx.RUnlock()
 			break
 		}
 
-		c.modeMtx.RUnlock()
-
 		c.log.Debug(logs.WritecacheTriedToFlushItemsFromWritecache,
 			zap.Int("count", count),
 			zap.String("start", base58.Encode(lastKey)))
@@ -229,7 +230,7 @@ func (c *cache) workerFlushSmall(ctx context.Context) {
 			continue
 		}
 
-		c.deleteFromDB(objInfo.addr)
+		c.deleteFromDB(objInfo.addr, true)
 	}
 }
 
@@ -270,19 +271,29 @@ func (c *cache) flushObject(ctx context.Context, obj *objectSDK.Object, data []b
 }
 
 // Flush flushes all objects from the write-cache to the main storage.
-// Write-cache must be in readonly mode to ensure correctness of an operation and
-// to prevent interference with background flush workers.
-func (c *cache) Flush(ctx context.Context, ignoreErrors bool) error {
-	ctx, span := tracing.StartSpanFromContext(ctx, "Flush",
+func (c *cache) Flush(ctx context.Context, ignoreErrors, seal bool) error {
+	ctx, span := tracing.StartSpanFromContext(ctx, "writecache.Flush",
 		trace.WithAttributes(
 			attribute.Bool("ignore_errors", ignoreErrors),
+			attribute.Bool("seal", seal),
 		))
 	defer span.End()
 
-	c.modeMtx.RLock()
-	defer c.modeMtx.RUnlock()
+	c.modeMtx.Lock() // exclusive lock to not to conflict with background flush
+	defer c.modeMtx.Unlock()
 
-	return c.flush(ctx, ignoreErrors)
+	if err := c.flush(ctx, ignoreErrors); err != nil {
+		return err
+	}
+
+	if seal {
+		m := c.mode | mode.ReadOnly
+		if err := c.setMode(ctx, m, ignoreErrors); err != nil {
+			return err
+		}
+		c.metrics.SetMode(m)
+	}
+	return nil
 }
 
 func (c *cache) flush(ctx context.Context, ignoreErrors bool) error {
@@ -290,13 +301,53 @@ func (c *cache) flush(ctx context.Context, ignoreErrors bool) error {
 		return err
 	}
 
-	return c.db.View(func(tx *bbolt.Tx) error {
+	var last string
+	for {
+		batch, err := c.readNextDBBatch(ignoreErrors, last)
+		if err != nil {
+			return err
+		}
+		if len(batch) == 0 {
+			break
+		}
+		for _, item := range batch {
+			var obj objectSDK.Object
+			if err := obj.Unmarshal(item.data); err != nil {
+				c.reportFlushError(logs.FSTreeCantDecodeDBObjectAddress, item.address, metaerr.Wrap(err))
+				if ignoreErrors {
+					continue
+				}
+				return err
+			}
+
+			if err := c.flushObject(ctx, &obj, item.data, StorageTypeDB); err != nil {
+				return err
+			}
+			c.deleteFromDB(item.address, false)
+		}
+		last = batch[len(batch)-1].address
+	}
+	return nil
+}
+
+type batchItem struct {
+	data    []byte
+	address string
+}
+
+func (c *cache) readNextDBBatch(ignoreErrors bool, last string) ([]batchItem, error) {
+	const batchSize = 100
+	var batch []batchItem
+	err := c.db.View(func(tx *bbolt.Tx) error {
 		var addr oid.Address
 
 		b := tx.Bucket(defaultBucket)
 		cs := b.Cursor()
-		for k, data := cs.Seek(nil); k != nil; k, data = cs.Next() {
+		for k, data := cs.Seek([]byte(last)); k != nil; k, data = cs.Next() {
 			sa := string(k)
+			if sa == last {
+				continue
+			}
 			if err := addr.DecodeString(sa); err != nil {
 				c.reportFlushError(logs.FSTreeCantDecodeDBObjectAddress, sa, metaerr.Wrap(err))
 				if ignoreErrors {
@@ -305,19 +356,15 @@ func (c *cache) flush(ctx context.Context, ignoreErrors bool) error {
 				return err
 			}
 
-			var obj objectSDK.Object
-			if err := obj.Unmarshal(data); err != nil {
-				c.reportFlushError(logs.FSTreeCantDecodeDBObjectAddress, sa, metaerr.Wrap(err))
-				if ignoreErrors {
-					continue
-				}
-				return err
-			}
-
-			if err := c.flushObject(ctx, &obj, data, StorageTypeDB); err != nil {
-				return err
+			batch = append(batch, batchItem{data: bytes.Clone(data), address: sa})
+			if len(batch) == batchSize {
+				return errIterationCompleted
 			}
 		}
 		return nil
 	})
+	if err == nil || errors.Is(err, errIterationCompleted) {
+		return batch, nil
+	}
+	return nil, err
 }

pkg/local_object_storage/writecache/flush_test.go

@@ -147,7 +147,7 @@ func runFlushTest[Option any](
 		require.NoError(t, bs.SetMode(mode.ReadWrite))
 		require.NoError(t, mb.SetMode(mode.ReadWrite))
 
-		require.NoError(t, wc.Flush(context.Background(), false))
+		require.NoError(t, wc.Flush(context.Background(), false, false))
 
 		check(t, mb, bs, objects)
 	})
@@ -159,8 +159,6 @@ func runFlushTest[Option any](
 		// Blobstor is read-only, so we expect en error from `flush` here.
 		require.Error(t, wc.SetMode(mode.Degraded))
 
-		// First move to read-only mode to close background workers.
-		require.NoError(t, wc.SetMode(mode.ReadOnly))
 		require.NoError(t, bs.SetMode(mode.ReadWrite))
 		require.NoError(t, mb.SetMode(mode.ReadWrite))
 		require.NoError(t, wc.SetMode(mode.Degraded))
@@ -177,14 +175,13 @@ func runFlushTest[Option any](
 				objects := putObjects(t, wc)
 				f.InjectFn(t, wc)
 
-				require.NoError(t, wc.SetMode(mode.ReadOnly))
 				require.NoError(t, bs.SetMode(mode.ReadWrite))
 				require.NoError(t, mb.SetMode(mode.ReadWrite))
 
 				require.Equal(t, uint32(0), errCount.Load())
-				require.Error(t, wc.Flush(context.Background(), false))
+				require.Error(t, wc.Flush(context.Background(), false, false))
 				require.Greater(t, errCount.Load(), uint32(0))
-				require.NoError(t, wc.Flush(context.Background(), true))
+				require.NoError(t, wc.Flush(context.Background(), true, false))
 
 				check(t, mb, bs, objects)
 			})

pkg/local_object_storage/writecache/mode.go

@@ -25,7 +25,7 @@ func (c *cache) SetMode(m mode.Mode) error {
 	c.modeMtx.Lock()
 	defer c.modeMtx.Unlock()
 
-	err := c.setMode(ctx, m)
+	err := c.setMode(ctx, m, true)
 	if err == nil {
 		c.metrics.SetMode(m)
 	}
@@ -33,12 +33,12 @@ func (c *cache) SetMode(m mode.Mode) error {
 }
 
 // setMode applies new mode. Must be called with cache.modeMtx lock taken.
-func (c *cache) setMode(ctx context.Context, m mode.Mode) error {
+func (c *cache) setMode(ctx context.Context, m mode.Mode, ignoreErrors bool) error {
 	var err error
 	turnOffMeta := m.NoMetabase()
 
 	if turnOffMeta && !c.mode.NoMetabase() {
-		err = c.flush(ctx, true)
+		err = c.flush(ctx, ignoreErrors)
 		if err != nil {
 			return err
 		}

pkg/local_object_storage/writecache/put.go

@@ -34,7 +34,9 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 		c.metrics.Put(time.Since(startedAt), added, storageType)
 	}()
 
-	c.modeMtx.RLock()
+	if !c.modeMtx.TryRLock() {
+		return common.PutRes{}, ErrNotInitialized
+	}
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
 		return common.PutRes{}, ErrReadOnly

pkg/local_object_storage/writecache/seal.go

@@ -0,0 +1,28 @@
+package writecache
+
+import (
+	"context"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+func (c *cache) Seal(ctx context.Context, ignoreErrors bool) error {
+	ctx, span := tracing.StartSpanFromContext(ctx, "writecache.Seal",
+		trace.WithAttributes(
+			attribute.Bool("ignore_errors", ignoreErrors),
+		))
+	defer span.End()
+
+	c.modeMtx.Lock()
+	defer c.modeMtx.Unlock()
+
+	// flush will be done by setMode
+	err := c.setMode(ctx, mode.DegradedReadOnly, ignoreErrors)
+	if err == nil {
+		c.metrics.SetMode(mode.DegradedReadOnly)
+	}
+	return err
+}

pkg/local_object_storage/writecache/storage.go

@@ -67,14 +67,24 @@ func (c *cache) openStore(readOnly bool) error {
 	return nil
 }
 
-func (c *cache) deleteFromDB(key string) {
+func (c *cache) deleteFromDB(key string, batched bool) {
 	var recordDeleted bool
-	err := c.db.Batch(func(tx *bbolt.Tx) error {
-		b := tx.Bucket(defaultBucket)
-		key := []byte(key)
-		recordDeleted = b.Get(key) != nil
-		return b.Delete(key)
-	})
+	var err error
+	if batched {
+		err = c.db.Batch(func(tx *bbolt.Tx) error {
+			b := tx.Bucket(defaultBucket)
+			key := []byte(key)
+			recordDeleted = b.Get(key) != nil
+			return b.Delete(key)
+		})
+	} else {
+		err = c.db.Update(func(tx *bbolt.Tx) error {
+			b := tx.Bucket(defaultBucket)
+			key := []byte(key)
+			recordDeleted = b.Get(key) != nil
+			return b.Delete(key)
+		})
+	}
 
 	if err == nil {
 		c.metrics.Evict(StorageTypeDB)

pkg/local_object_storage/writecache/writecache.go

@@ -35,7 +35,8 @@ type Cache interface {
 	SetMode(mode.Mode) error
 	SetLogger(*logger.Logger)
 	DumpInfo() Info
-	Flush(context.Context, bool) error
+	Flush(context.Context, bool, bool) error
+	Seal(context.Context, bool) error
 
 	Init() error
 	Open(ctx context.Context, readOnly bool) error

pkg/services/control/rpc.go

@@ -24,6 +24,7 @@ const (
 	rpcGetChainLocalOverride    = "GetChainLocalOverride"
 	rpcListChainLocalOverrides  = "ListChainLocalOverrides"
 	rpcRemoveChainLocalOverride = "RemoveChainLocalOverride"
+	rpcSealWriteCache           = "SealWriteCache"
 )
 
 // HealthCheck executes ControlService.HealthCheck RPC.
@@ -264,3 +265,16 @@ func RemoveChainLocalOverride(cli *client.Client, req *RemoveChainLocalOverrideR
 
 	return wResp.message, nil
 }
+
+// SealWriteCache executes ControlService.SealWriteCache RPC.
+func SealWriteCache(cli *client.Client, req *SealWriteCacheRequest, opts ...client.CallOption) (*SealWriteCacheResponse, error) {
+	wResp := newResponseWrapper[SealWriteCacheResponse]()
+	wReq := &requestWrapper{m: req}
+
+	err := client.SendUnary(cli, common.CallMethodInfoUnary(serviceName, rpcSealWriteCache), wReq, wResp, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	return wResp.message, nil
+}

pkg/services/control/server/flush_cache.go

@@ -18,6 +18,7 @@ func (s *Server) FlushCache(ctx context.Context, req *control.FlushCacheRequest)
 	for _, shardID := range s.getShardIDList(req.GetBody().GetShard_ID()) {
 		var prm engine.FlushWriteCachePrm
 		prm.SetShardID(shardID)
+		prm.SetSeal(req.GetBody().GetSeal())
 
 		_, err = s.s.FlushWriteCache(ctx, prm)
 		if err != nil {

pkg/services/control/server/seal_writecache.go

@@ -0,0 +1,48 @@
+package control
+
+import (
+	"context"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/engine"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/control"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+func (s *Server) SealWriteCache(ctx context.Context, req *control.SealWriteCacheRequest) (*control.SealWriteCacheResponse, error) {
+	err := s.isValidRequest(req)
+	if err != nil {
+		return nil, status.Error(codes.PermissionDenied, err.Error())
+	}
+
+	prm := engine.SealWriteCachePrm{
+		ShardIDs:     s.getShardIDList(req.GetBody().GetShard_ID()),
+		IgnoreErrors: req.GetBody().GetIgnoreErrors(),
+	}
+
+	res, err := s.s.SealWriteCache(ctx, prm)
+	if err != nil {
+		return nil, status.Error(codes.Internal, err.Error())
+	}
+
+	resp := &control.SealWriteCacheResponse{Body: &control.SealWriteCacheResponse_Body{}}
+	for _, r := range res.ShardResults {
+		if r.Success {
+			resp.Body.Results = append(resp.GetBody().GetResults(), &control.SealWriteCacheResponse_Body_Status{
+				Shard_ID: *r.ShardID,
+				Success:  true,
+			})
+		} else {
+			resp.Body.Results = append(resp.GetBody().GetResults(), &control.SealWriteCacheResponse_Body_Status{
+				Shard_ID: *r.ShardID,
+				Error:    r.ErrorMsg,
+			})
+		}
+	}
+
+	err = SignMessage(s.key, resp)
+	if err != nil {
+		return nil, err
+	}
+	return resp, nil
+}

pkg/services/control/service.proto

@@ -56,6 +56,9 @@ service ControlService {
 
     // Remove local access policy engine overrides stored in the node by chaind id.
     rpc RemoveChainLocalOverride (RemoveChainLocalOverrideRequest) returns (RemoveChainLocalOverrideResponse);
+
+    // Flush objects from write-cache and move it to degraded read only mode.
+    rpc SealWriteCache(SealWriteCacheRequest) returns (SealWriteCacheResponse);
 }
 
 // Health check request.
@@ -280,6 +283,8 @@ message FlushCacheRequest {
     message Body {
         // ID of the shard.
         repeated bytes shard_ID = 1;
+        // If true, then writecache will be left in read-only mode after flush completed.
+        bool seal = 2;
     }
 
     Body body = 1;
@@ -523,3 +528,32 @@ message RemoveChainLocalOverrideResponse {
 
     Signature signature = 2;
 }
+
+message SealWriteCacheRequest {
+    // Request body structure.
+    message Body {
+        // ID of the shard.
+        repeated bytes shard_ID = 1;
+
+        // Flag indicating whether object read errors should be ignored.
+        bool ignore_errors = 2;
+    }
+
+    Body body = 1;
+    Signature signature = 2;
+}
+
+message SealWriteCacheResponse {
+    message Body {
+        message Status {
+            bytes shard_ID = 1;
+            bool success = 2;
+            string error = 3;
+        }
+        repeated Status results = 1;
+    }
+
+    Body body = 1;
+
+    Signature signature = 2;
+}

pkg/services/control/service_frostfs.pb.go

@@ -1180,6 +1180,7 @@ func (x *FlushCacheRequest_Body) StableSize() (size int) {
 		return 0
 	}
 	size += proto.RepeatedBytesSize(1, x.Shard_ID)
+	size += proto.BoolSize(2, x.Seal)
 	return size
 }
 
@@ -1200,6 +1201,7 @@ func (x *FlushCacheRequest_Body) StableMarshal(buf []byte) []byte {
 	}
 	var offset int
 	offset += proto.RepeatedBytesMarshal(1, buf[offset:], x.Shard_ID)
+	offset += proto.BoolMarshal(2, buf[offset:], x.Seal)
 	return buf
 }
 
@@ -2753,3 +2755,216 @@ func (x *RemoveChainLocalOverrideResponse) ReadSignedData(buf []byte) ([]byte, e
 func (x *RemoveChainLocalOverrideResponse) SetSignature(sig *Signature) {
 	x.Signature = sig
 }
+
+// StableSize returns the size of x in protobuf format.
+//
+// Structures with the same field values have the same binary size.
+func (x *SealWriteCacheRequest_Body) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+	size += proto.RepeatedBytesSize(1, x.Shard_ID)
+	size += proto.BoolSize(2, x.IgnoreErrors)
+	return size
+}
+
+// StableMarshal marshals x in protobuf binary format with stable field order.
+//
+// If buffer length is less than x.StableSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same binary format.
+func (x *SealWriteCacheRequest_Body) StableMarshal(buf []byte) []byte {
+	if x == nil {
+		return []byte{}
+	}
+	if buf == nil {
+		buf = make([]byte, x.StableSize())
+	}
+	var offset int
+	offset += proto.RepeatedBytesMarshal(1, buf[offset:], x.Shard_ID)
+	offset += proto.BoolMarshal(2, buf[offset:], x.IgnoreErrors)
+	return buf
+}
+
+// StableSize returns the size of x in protobuf format.
+//
+// Structures with the same field values have the same binary size.
+func (x *SealWriteCacheRequest) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+	size += proto.NestedStructureSize(1, x.Body)
+	size += proto.NestedStructureSize(2, x.Signature)
+	return size
+}
+
+// StableMarshal marshals x in protobuf binary format with stable field order.
+//
+// If buffer length is less than x.StableSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same binary format.
+func (x *SealWriteCacheRequest) StableMarshal(buf []byte) []byte {
+	if x == nil {
+		return []byte{}
+	}
+	if buf == nil {
+		buf = make([]byte, x.StableSize())
+	}
+	var offset int
+	offset += proto.NestedStructureMarshal(1, buf[offset:], x.Body)
+	offset += proto.NestedStructureMarshal(2, buf[offset:], x.Signature)
+	return buf
+}
+
+// ReadSignedData fills buf with signed data of x.
+// If buffer length is less than x.SignedDataSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same signed data.
+func (x *SealWriteCacheRequest) SignedDataSize() int {
+	return x.GetBody().StableSize()
+}
+
+// SignedDataSize returns size of the request signed data in bytes.
+//
+// Structures with the same field values have the same signed data size.
+func (x *SealWriteCacheRequest) ReadSignedData(buf []byte) ([]byte, error) {
+	return x.GetBody().StableMarshal(buf), nil
+}
+
+func (x *SealWriteCacheRequest) SetSignature(sig *Signature) {
+	x.Signature = sig
+}
+
+// StableSize returns the size of x in protobuf format.
+//
+// Structures with the same field values have the same binary size.
+func (x *SealWriteCacheResponse_Body_Status) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+	size += proto.BytesSize(1, x.Shard_ID)
+	size += proto.BoolSize(2, x.Success)
+	size += proto.StringSize(3, x.Error)
+	return size
+}
+
+// StableMarshal marshals x in protobuf binary format with stable field order.
+//
+// If buffer length is less than x.StableSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same binary format.
+func (x *SealWriteCacheResponse_Body_Status) StableMarshal(buf []byte) []byte {
+	if x == nil {
+		return []byte{}
+	}
+	if buf == nil {
+		buf = make([]byte, x.StableSize())
+	}
+	var offset int
+	offset += proto.BytesMarshal(1, buf[offset:], x.Shard_ID)
+	offset += proto.BoolMarshal(2, buf[offset:], x.Success)
+	offset += proto.StringMarshal(3, buf[offset:], x.Error)
+	return buf
+}
+
+// StableSize returns the size of x in protobuf format.
+//
+// Structures with the same field values have the same binary size.
+func (x *SealWriteCacheResponse_Body) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+	for i := range x.Results {
+		size += proto.NestedStructureSize(1, x.Results[i])
+	}
+	return size
+}
+
+// StableMarshal marshals x in protobuf binary format with stable field order.
+//
+// If buffer length is less than x.StableSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same binary format.
+func (x *SealWriteCacheResponse_Body) StableMarshal(buf []byte) []byte {
+	if x == nil {
+		return []byte{}
+	}
+	if buf == nil {
+		buf = make([]byte, x.StableSize())
+	}
+	var offset int
+	for i := range x.Results {
+		offset += proto.NestedStructureMarshal(1, buf[offset:], x.Results[i])
+	}
+	return buf
+}
+
+// StableSize returns the size of x in protobuf format.
+//
+// Structures with the same field values have the same binary size.
+func (x *SealWriteCacheResponse) StableSize() (size int) {
+	if x == nil {
+		return 0
+	}
+	size += proto.NestedStructureSize(1, x.Body)
+	size += proto.NestedStructureSize(2, x.Signature)
+	return size
+}
+
+// StableMarshal marshals x in protobuf binary format with stable field order.
+//
+// If buffer length is less than x.StableSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same binary format.
+func (x *SealWriteCacheResponse) StableMarshal(buf []byte) []byte {
+	if x == nil {
+		return []byte{}
+	}
+	if buf == nil {
+		buf = make([]byte, x.StableSize())
+	}
+	var offset int
+	offset += proto.NestedStructureMarshal(1, buf[offset:], x.Body)
+	offset += proto.NestedStructureMarshal(2, buf[offset:], x.Signature)
+	return buf
+}
+
+// ReadSignedData fills buf with signed data of x.
+// If buffer length is less than x.SignedDataSize(), new buffer is allocated.
+//
+// Returns any error encountered which did not allow writing the data completely.
+// Otherwise, returns the buffer in which the data is written.
+//
+// Structures with the same field values have the same signed data.
+func (x *SealWriteCacheResponse) SignedDataSize() int {
+	return x.GetBody().StableSize()
+}
+
+// SignedDataSize returns size of the request signed data in bytes.
+//
+// Structures with the same field values have the same signed data size.
+func (x *SealWriteCacheResponse) ReadSignedData(buf []byte) ([]byte, error) {
+	return x.GetBody().StableMarshal(buf), nil
+}
+
+func (x *SealWriteCacheResponse) SetSignature(sig *Signature) {
+	x.Signature = sig
+}

pkg/services/control/service_grpc.pb.go

@@ -35,6 +35,7 @@ const (
 	ControlService_GetChainLocalOverride_FullMethodName    = "/control.ControlService/GetChainLocalOverride"
 	ControlService_ListChainLocalOverrides_FullMethodName  = "/control.ControlService/ListChainLocalOverrides"
 	ControlService_RemoveChainLocalOverride_FullMethodName = "/control.ControlService/RemoveChainLocalOverride"
+	ControlService_SealWriteCache_FullMethodName           = "/control.ControlService/SealWriteCache"
 )
 
 // ControlServiceClient is the client API for ControlService service.
@@ -74,6 +75,8 @@ type ControlServiceClient interface {
 	ListChainLocalOverrides(ctx context.Context, in *ListChainLocalOverridesRequest, opts ...grpc.CallOption) (*ListChainLocalOverridesResponse, error)
 	// Remove local access policy engine overrides stored in the node by chaind id.
 	RemoveChainLocalOverride(ctx context.Context, in *RemoveChainLocalOverrideRequest, opts ...grpc.CallOption) (*RemoveChainLocalOverrideResponse, error)
+	// Flush objects from write-cache and move it to degraded read only mode.
+	SealWriteCache(ctx context.Context, in *SealWriteCacheRequest, opts ...grpc.CallOption) (*SealWriteCacheResponse, error)
 }
 
 type controlServiceClient struct {
@@ -228,6 +231,15 @@ func (c *controlServiceClient) RemoveChainLocalOverride(ctx context.Context, in
 	return out, nil
 }
 
+func (c *controlServiceClient) SealWriteCache(ctx context.Context, in *SealWriteCacheRequest, opts ...grpc.CallOption) (*SealWriteCacheResponse, error) {
+	out := new(SealWriteCacheResponse)
+	err := c.cc.Invoke(ctx, ControlService_SealWriteCache_FullMethodName, in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 // ControlServiceServer is the server API for ControlService service.
 // All implementations should embed UnimplementedControlServiceServer
 // for forward compatibility
@@ -265,6 +277,8 @@ type ControlServiceServer interface {
 	ListChainLocalOverrides(context.Context, *ListChainLocalOverridesRequest) (*ListChainLocalOverridesResponse, error)
 	// Remove local access policy engine overrides stored in the node by chaind id.
 	RemoveChainLocalOverride(context.Context, *RemoveChainLocalOverrideRequest) (*RemoveChainLocalOverrideResponse, error)
+	// Flush objects from write-cache and move it to degraded read only mode.
+	SealWriteCache(context.Context, *SealWriteCacheRequest) (*SealWriteCacheResponse, error)
 }
 
 // UnimplementedControlServiceServer should be embedded to have forward compatible implementations.
@@ -319,6 +333,9 @@ func (UnimplementedControlServiceServer) ListChainLocalOverrides(context.Context
 func (UnimplementedControlServiceServer) RemoveChainLocalOverride(context.Context, *RemoveChainLocalOverrideRequest) (*RemoveChainLocalOverrideResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method RemoveChainLocalOverride not implemented")
 }
+func (UnimplementedControlServiceServer) SealWriteCache(context.Context, *SealWriteCacheRequest) (*SealWriteCacheResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method SealWriteCache not implemented")
+}
 
 // UnsafeControlServiceServer may be embedded to opt out of forward compatibility for this service.
 // Use of this interface is not recommended, as added methods to ControlServiceServer will
@@ -619,6 +636,24 @@ func _ControlService_RemoveChainLocalOverride_Handler(srv interface{}, ctx conte
 	return interceptor(ctx, in, info, handler)
 }
 
+func _ControlService_SealWriteCache_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(SealWriteCacheRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(ControlServiceServer).SealWriteCache(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: ControlService_SealWriteCache_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(ControlServiceServer).SealWriteCache(ctx, req.(*SealWriteCacheRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 // ControlService_ServiceDesc is the grpc.ServiceDesc for ControlService service.
 // It's only intended for direct use with grpc.RegisterService,
 // and not to be introspected or modified (even as a copy)
@@ -690,6 +725,10 @@ var ControlService_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "RemoveChainLocalOverride",
 			Handler:    _ControlService_RemoveChainLocalOverride_Handler,
 		},
+		{
+			MethodName: "SealWriteCache",
+			Handler:    _ControlService_SealWriteCache_Handler,
+		},
 	},
 	Streams:  []grpc.StreamDesc{},
 	Metadata: "pkg/services/control/service.proto",