[#472] blobstor: implement write-cache

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

cmd/neofs-node/config.go

@@ -24,6 +24,7 @@ import (
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/engine"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/writecache"
 	"github.com/nspcc-dev/neofs-node/pkg/metrics"
 	"github.com/nspcc-dev/neofs-node/pkg/morph/client"
 	"github.com/nspcc-dev/neofs-node/pkg/morph/client/container/wrapper"
@@ -131,6 +132,11 @@ const (
 
 	cfgBlobStorSection      = "blobstor"
 	cfgWriteCacheSection    = "writecache"
+	cfgWriteCacheMemSize    = "mem_size"
+	cfgWriteCacheDBSize     = "db_size"
+	cfgWriteCacheSmallSize  = "small_size"
+	cfgWriteCacheMaxSize    = "max_size"
+	cfgWriteCacheWrkCount   = "workers_count"
 	cfgBlobStorCompress     = "compress"
 	cfgBlobStorShallowDepth = "shallow_depth"
 	cfgBlobStorTreePath     = "path"
@@ -560,6 +566,11 @@ func initShardOptions(c *cfg) {
 			c.log.Warn("incorrect writeCache path, ignore shard")
 			break
 		}
+		writeCacheMemSize := c.viper.GetUint64(configPath(writeCachePrefix, cfgWriteCacheMemSize))
+		writeCacheDBSize := c.viper.GetUint64(configPath(writeCachePrefix, cfgWriteCacheDBSize))
+		writeCacheSmallSize := c.viper.GetUint64(configPath(writeCachePrefix, cfgWriteCacheSmallSize))
+		writeCacheMaxSize := c.viper.GetUint64(configPath(writeCachePrefix, cfgWriteCacheMaxSize))
+		writeCacheWrkCount := c.viper.GetInt(configPath(writeCachePrefix, cfgWriteCacheWrkCount))
 
 		blobPrefix := configPath(prefix, cfgBlobStorSection)
 
@@ -589,6 +600,9 @@ func initShardOptions(c *cfg) {
 		if smallSzLimit == 0 {
 			smallSzLimit = 1 << 20 // 1MB
 		}
+		if writeCacheMaxSize <= 0 {
+			writeCacheSmallSize = smallSzLimit
+		}
 
 		blzPrefix := configPath(blobPrefix, cfgBlobStorBlzSection)
 
@@ -657,9 +671,13 @@ func initShardOptions(c *cfg) {
 			),
 			shard.WithWriteCache(useCache),
 			shard.WithWriteCacheOptions(
-				blobstor.WithRootPath(writeCachePath),
-				blobstor.WithBlobovniczaShallowDepth(0),
-				blobstor.WithBlobovniczaShallowWidth(1),
+				writecache.WithPath(writeCachePath),
+				writecache.WithLogger(c.log),
+				writecache.WithMaxMemSize(writeCacheMemSize),
+				writecache.WithMaxObjectSize(writeCacheMaxSize),
+				writecache.WithSmallObjectSize(writeCacheSmallSize),
+				writecache.WithMaxDBSize(writeCacheDBSize),
+				writecache.WithFlushWorkersCount(writeCacheWrkCount),
 			),
 			shard.WithRemoverBatchSize(rmBatchSize),
 			shard.WithGCRemoverSleepInterval(rmSleepInterval),

pkg/local_object_storage/blobstor/fstree/fstree.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path"
+	"strings"
 
 	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
 )
@@ -44,6 +45,52 @@ func stringifyAddress(addr *objectSDK.Address) string {
 	return hex.EncodeToString(h[:])
 }
 
+// Iterate iterates over all stored objects.
+func (t *FSTree) Iterate(f func(addr *objectSDK.Address, data []byte) error) error {
+	return t.iterate(0, []string{t.RootPath}, f)
+}
+
+func (t *FSTree) iterate(depth int, curPath []string, f func(*objectSDK.Address, []byte) error) error {
+	curName := strings.Join(curPath[1:], "")
+	des, err := ioutil.ReadDir(curName)
+	if err != nil {
+		return err
+	}
+
+	isLast := depth >= t.Depth
+	l := len(curPath)
+	curPath = append(curPath, "")
+
+	for i := range des {
+		curPath[l] = des[i].Name()
+
+		if !isLast && des[i].IsDir() {
+			err := t.iterate(depth+1, curPath, f)
+			if err != nil {
+				return err
+			}
+		}
+
+		addr := objectSDK.NewAddress()
+		err := addr.Parse(curName + des[i].Name())
+		if err != nil {
+			continue
+		}
+
+		curPath = append(curPath, des[i].Name())
+		data, err := ioutil.ReadFile(path.Join(curPath...))
+		if err != nil {
+			return err
+		}
+
+		if err := f(addr, data); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func (t *FSTree) treePath(addr *objectSDK.Address) string {
 	sAddr := stringifyAddress(addr)
 

pkg/local_object_storage/blobstor/info.go

@@ -2,7 +2,7 @@ package blobstor
 
 import "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
 
-// DumpInfo returns information about the BlobStor.
+// FSTree returns file-system tree for big object store.
 func (b *BlobStor) DumpInfo() fstree.Info {
 	return b.fsTree.Info
 }

pkg/local_object_storage/metabase/put.go

@@ -47,10 +47,9 @@ func (p *PutPrm) WithBlobovniczaID(id *blobovnicza.ID) *PutPrm {
 }
 
 var (
-	ErrUnknownObjectType          = errors.New("unknown object type")
-	ErrIncorrectBlobovniczaUpdate = errors.New("updating blobovnicza id on object without it")
-	ErrIncorrectSplitInfoUpdate   = errors.New("updating split info on object without it")
-	ErrIncorrectRootObject        = errors.New("invalid root object")
+	ErrUnknownObjectType        = errors.New("unknown object type")
+	ErrIncorrectSplitInfoUpdate = errors.New("updating split info on object without it")
+	ErrIncorrectRootObject      = errors.New("invalid root object")
 )
 
 // Put saves the object in DB.
@@ -379,20 +378,12 @@ func decodeList(data []byte) (lst [][]byte, err error) {
 // updateBlobovniczaID for existing objects if they were moved from from
 // one blobovnicza to another.
 func updateBlobovniczaID(tx *bbolt.Tx, addr *objectSDK.Address, id *blobovnicza.ID) error {
-	bkt := tx.Bucket(smallBucketName(addr.ContainerID()))
-	if bkt == nil {
-		// if object exists, don't have blobovniczaID and we want to update it
-		// then ignore, this should never happen
-		return ErrIncorrectBlobovniczaUpdate
+	bkt, err := tx.CreateBucketIfNotExists(smallBucketName(addr.ContainerID()))
+	if err != nil {
+		return err
 	}
 
-	objectKey := objectKey(addr.ObjectID())
-
-	if len(bkt.Get(objectKey)) == 0 {
-		return ErrIncorrectBlobovniczaUpdate
-	}
-
-	return bkt.Put(objectKey, *id)
+	return bkt.Put(objectKey(addr.ObjectID()), *id)
 }
 
 // updateSpliInfo for existing objects if storage filled with extra information

pkg/local_object_storage/metabase/put_test.go

@@ -42,8 +42,5 @@ func TestDB_PutBlobovnicaUpdate(t *testing.T) {
 		fetchedBlobovniczaID, err := meta.IsSmall(db, raw2.Object().Address())
 		require.NoError(t, err)
 		require.Nil(t, fetchedBlobovniczaID)
-
-		err = meta.Put(db, raw2.Object(), &blobovniczaID)
-		require.Error(t, err)
 	})
 }

pkg/local_object_storage/shard/delete.go

@@ -2,9 +2,11 @@ package shard
 
 import (
 	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobovnicza"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
+	"github.com/pkg/errors"
 	"go.uber.org/zap"
 )
 
@@ -37,13 +39,10 @@ func (s *Shard) Delete(prm *DeletePrm) (*DeleteRes, error) {
 	smalls := make(map[*objectSDK.Address]*blobovnicza.ID, ln)
 
 	for i := range prm.addr {
-		delSmallPrm.SetAddress(prm.addr[i])
-		delBigPrm.SetAddress(prm.addr[i])
-
 		if s.hasWriteCache() {
-			_, err := s.writeCache.DeleteSmall(delSmallPrm)
-			if err != nil {
-				_, _ = s.writeCache.DeleteBig(delBigPrm)
+			err := s.writeCache.Delete(prm.addr[i])
+			if err != nil && !errors.Is(err, object.ErrNotFound) {
+				s.log.Error("can't delete object from write cache", zap.String("error", err.Error()))
 			}
 		}
 

pkg/local_object_storage/shard/delete_test.go

@@ -9,24 +9,19 @@ import (
 )
 
 func TestShard_Delete(t *testing.T) {
-	sh := newShard(t, false)
-	shWC := newShard(t, true)
-
-	defer func() {
-		releaseShard(sh, t)
-		releaseShard(shWC, t)
-	}()
-
 	t.Run("without write cache", func(t *testing.T) {
-		testShardDelete(t, sh)
+		testShardDelete(t, false)
 	})
 
 	t.Run("with write cache", func(t *testing.T) {
-		testShardDelete(t, shWC)
+		testShardDelete(t, true)
 	})
 }
 
-func testShardDelete(t *testing.T, sh *shard.Shard) {
+func testShardDelete(t *testing.T, hasWriteCache bool) {
+	sh := newShard(t, hasWriteCache)
+	defer releaseShard(sh, t)
+
 	cid := generateCID()
 
 	obj := generateRawObjectWithCID(t, cid)
@@ -47,7 +42,7 @@ func testShardDelete(t *testing.T, sh *shard.Shard) {
 		_, err := sh.Put(putPrm)
 		require.NoError(t, err)
 
-		_, err = sh.Get(getPrm)
+		_, err = testGet(t, sh, getPrm, hasWriteCache)
 		require.NoError(t, err)
 
 		_, err = sh.Delete(delPrm)

pkg/local_object_storage/shard/get.go

@@ -8,6 +8,8 @@ import (
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobovnicza"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
+	"github.com/pkg/errors"
+	"go.uber.org/zap"
 )
 
 // storFetcher is a type to unify object fetching mechanism in `fetchObjectData`
@@ -89,19 +91,16 @@ func (s *Shard) fetchObjectData(addr *objectSDK.Address, big, small storFetcher)
 	)
 
 	if s.hasWriteCache() {
-		res, err = small(s.writeCache, nil)
+		res, err = s.writeCache.Get(addr)
 		if err == nil {
 			return res, nil
 		}
 
-		s.log.Debug("miss in writeCache blobovnicza")
-
-		res, err = big(s.writeCache, nil)
-		if err == nil {
-			return res, nil
+		if errors.Is(err, object.ErrNotFound) {
+			s.log.Debug("object is missing in write-cache")
+		} else {
+			s.log.Error("failed to fetch object from write-cache", zap.Error(err))
 		}
-
-		s.log.Debug("miss in writeCache shallow dir")
 	}
 
 	exists, err := meta.Exists(s.metaBase, addr)

pkg/local_object_storage/shard/get_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"errors"
 	"testing"
+	"time"
 
 	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
 	"github.com/nspcc-dev/neofs-node/pkg/core/object"
@@ -12,31 +13,25 @@ import (
 )
 
 func TestShard_Get(t *testing.T) {
-	sh := newShard(t, false)
-	shWC := newShard(t, true)
-
-	defer func() {
-		releaseShard(sh, t)
-		releaseShard(shWC, t)
-	}()
-
 	t.Run("without write cache", func(t *testing.T) {
-		testShardGet(t, sh)
+		testShardGet(t, false)
 	})
 
 	t.Run("with write cache", func(t *testing.T) {
-		testShardGet(t, shWC)
+		testShardGet(t, true)
 	})
 }
 
-func testShardGet(t *testing.T, sh *shard.Shard) {
-	obj := generateRawObject(t)
-	addAttribute(obj, "foo", "bar")
+func testShardGet(t *testing.T, hasWriteCache bool) {
+	sh := newShard(t, hasWriteCache)
+	defer releaseShard(sh, t)
 
 	putPrm := new(shard.PutPrm)
 	getPrm := new(shard.GetPrm)
 
 	t.Run("small object", func(t *testing.T) {
+		obj := generateRawObject(t)
+		addAttribute(obj, "foo", "bar")
 		addPayload(obj, 1<<5)
 
 		putPrm.WithObject(obj.Object())
@@ -46,12 +41,14 @@ func testShardGet(t *testing.T, sh *shard.Shard) {
 
 		getPrm.WithAddress(obj.Object().Address())
 
-		res, err := sh.Get(getPrm)
+		res, err := testGet(t, sh, getPrm, hasWriteCache)
 		require.NoError(t, err)
 		require.Equal(t, obj.Object(), res.Object())
 	})
 
 	t.Run("big object", func(t *testing.T) {
+		obj := generateRawObject(t)
+		addAttribute(obj, "foo", "bar")
 		obj.SetID(generateOID())
 		addPayload(obj, 1<<20) // big obj
 
@@ -62,12 +59,14 @@ func testShardGet(t *testing.T, sh *shard.Shard) {
 
 		getPrm.WithAddress(obj.Object().Address())
 
-		res, err := sh.Get(getPrm)
+		res, err := testGet(t, sh, getPrm, hasWriteCache)
 		require.NoError(t, err)
 		require.Equal(t, obj.Object(), res.Object())
 	})
 
 	t.Run("parent object", func(t *testing.T) {
+		obj := generateRawObject(t)
+		addAttribute(obj, "foo", "bar")
 		cid := generateCID()
 		splitID := objectSDK.NewSplitID()
 
@@ -87,13 +86,13 @@ func testShardGet(t *testing.T, sh *shard.Shard) {
 
 		getPrm.WithAddress(child.Object().Address())
 
-		res, err := sh.Get(getPrm)
+		res, err := testGet(t, sh, getPrm, hasWriteCache)
 		require.NoError(t, err)
 		require.True(t, binaryEqual(child.Object(), res.Object()))
 
 		getPrm.WithAddress(parent.Object().Address())
 
-		_, err = sh.Get(getPrm)
+		_, err = testGet(t, sh, getPrm, hasWriteCache)
 
 		var expectedErr *objectSDK.SplitInfoError
 		require.True(t, errors.As(err, &expectedErr))
@@ -106,6 +105,19 @@ func testShardGet(t *testing.T, sh *shard.Shard) {
 	})
 }
 
+func testGet(t *testing.T, sh *shard.Shard, getPrm *shard.GetPrm, hasWriteCache bool) (*shard.GetRes, error) {
+	res, err := sh.Get(getPrm)
+	if hasWriteCache {
+		require.Eventually(t, func() bool {
+			if errors.Is(err, object.ErrNotFound) {
+				res, err = sh.Get(getPrm)
+			}
+			return !errors.Is(err, object.ErrNotFound)
+		}, time.Second, time.Millisecond*100)
+	}
+	return res, err
+}
+
 // binary equal is used when object contains empty lists in the structure and
 // requre.Equal fails on comparing <nil> and []{} lists.
 func binaryEqual(a, b *object.Object) bool {

pkg/local_object_storage/shard/head_test.go

@@ -3,31 +3,28 @@ package shard_test
 import (
 	"errors"
 	"testing"
+	"time"
 
 	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
 	"github.com/stretchr/testify/require"
 )
 
 func TestShard_Head(t *testing.T) {
-	sh := newShard(t, false)
-	shWC := newShard(t, true)
-
-	defer func() {
-		releaseShard(sh, t)
-		releaseShard(shWC, t)
-	}()
-
 	t.Run("without write cache", func(t *testing.T) {
-		testShardHead(t, sh)
+		testShardHead(t, false)
 	})
 
 	t.Run("with write cache", func(t *testing.T) {
-		testShardHead(t, shWC)
+		testShardHead(t, true)
 	})
 }
 
-func testShardHead(t *testing.T, sh *shard.Shard) {
+func testShardHead(t *testing.T, hasWriteCache bool) {
+	sh := newShard(t, hasWriteCache)
+	defer releaseShard(sh, t)
+
 	putPrm := new(shard.PutPrm)
 	headPrm := new(shard.HeadPrm)
 
@@ -42,7 +39,7 @@ func testShardHead(t *testing.T, sh *shard.Shard) {
 
 		headPrm.WithAddress(obj.Object().Address())
 
-		res, err := sh.Head(headPrm)
+		res, err := testHead(t, sh, headPrm, hasWriteCache)
 		require.NoError(t, err)
 		require.Equal(t, obj.Object(), res.Object())
 	})
@@ -69,7 +66,7 @@ func testShardHead(t *testing.T, sh *shard.Shard) {
 
 		var siErr *objectSDK.SplitInfoError
 
-		_, err = sh.Head(headPrm)
+		_, err = testHead(t, sh, headPrm, hasWriteCache)
 		require.True(t, errors.As(err, &siErr))
 
 		headPrm.WithAddress(parent.Object().Address())
@@ -80,3 +77,16 @@ func testShardHead(t *testing.T, sh *shard.Shard) {
 		require.Equal(t, parent.Object(), head.Object())
 	})
 }
+
+func testHead(t *testing.T, sh *shard.Shard, headPrm *shard.HeadPrm, hasWriteCache bool) (*shard.HeadRes, error) {
+	res, err := sh.Head(headPrm)
+	if hasWriteCache {
+		require.Eventually(t, func() bool {
+			if errors.Is(err, object.ErrNotFound) {
+				res, err = sh.Head(headPrm)
+			}
+			return !errors.Is(err, object.ErrNotFound)
+		}, time.Second, time.Millisecond*100)
+	}
+	return res, err
+}

pkg/local_object_storage/shard/inhume.go

@@ -44,6 +44,12 @@ func (p *InhumePrm) MarkAsGarbage(addr ...*objectSDK.Address) *InhumePrm {
 // Inhume calls metabase. Inhume method to mark object as removed. It won't be
 // removed physically from blobStor and metabase until `Delete` operation.
 func (s *Shard) Inhume(prm *InhumePrm) (*InhumeRes, error) {
+	if s.hasWriteCache() {
+		for i := range prm.target {
+			_ = s.writeCache.Delete(prm.target[i])
+		}
+	}
+
 	metaPrm := new(meta.InhumePrm).WithAddresses(prm.target...)
 
 	if prm.tombstone != nil {

pkg/local_object_storage/shard/inhume_test.go

@@ -9,24 +9,19 @@ import (
 )
 
 func TestShard_Inhume(t *testing.T) {
-	sh := newShard(t, false)
-	shWC := newShard(t, true)
-
-	defer func() {
-		releaseShard(sh, t)
-		releaseShard(shWC, t)
-	}()
-
 	t.Run("without write cache", func(t *testing.T) {
-		testShardInhume(t, sh)
+		testShardInhume(t, false)
 	})
 
 	t.Run("with write cache", func(t *testing.T) {
-		testShardInhume(t, shWC)
+		testShardInhume(t, true)
 	})
 }
 
-func testShardInhume(t *testing.T, sh *shard.Shard) {
+func testShardInhume(t *testing.T, hasWriteCache bool) {
+	sh := newShard(t, hasWriteCache)
+	defer releaseShard(sh, t)
+
 	cid := generateCID()
 
 	obj := generateRawObjectWithCID(t, cid)
@@ -46,7 +41,7 @@ func testShardInhume(t *testing.T, sh *shard.Shard) {
 	_, err := sh.Put(putPrm)
 	require.NoError(t, err)
 
-	_, err = sh.Get(getPrm)
+	_, err = testGet(t, sh, getPrm, hasWriteCache)
 	require.NoError(t, err)
 
 	_, err = sh.Inhume(inhPrm)

pkg/local_object_storage/shard/put.go

@@ -5,6 +5,7 @@ import (
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
 	"github.com/pkg/errors"
+	"go.uber.org/zap"
 )
 
 // PutPrm groups the parameters of Put operation.
@@ -34,26 +35,24 @@ func (s *Shard) Put(prm *PutPrm) (*PutRes, error) {
 
 	// exist check are not performed there, these checks should be executed
 	// ahead of `Put` by storage engine
+	if s.hasWriteCache() {
+		err := s.writeCache.Put(prm.obj)
+		if err == nil {
+			return nil, nil
+		}
+
+		s.log.Debug("can't put message to writeCache, trying to blobStor",
+			zap.String("err", err.Error()))
+	}
 
 	var (
 		err error
 		res *blobstor.PutRes
 	)
 
-	if s.hasWriteCache() {
-		res, err = s.writeCache.Put(putPrm)
-		if err != nil {
-			s.log.Debug("can't put message to writeCache, trying to blobStor")
-
-			res = nil // just in case
-		}
-	}
-
 	// res == nil if there is no writeCache or writeCache.Put has been failed
-	if res == nil {
-		if res, err = s.blobStor.Put(putPrm); err != nil {
-			return nil, errors.Wrap(err, "could not put object to BLOB storage")
-		}
+	if res, err = s.blobStor.Put(putPrm); err != nil {
+		return nil, errors.Wrap(err, "could not put object to BLOB storage")
 	}
 
 	// put to metabase

pkg/local_object_storage/shard/shard.go

@@ -7,6 +7,7 @@ import (
 	"github.com/nspcc-dev/neofs-api-go/pkg/object"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/writecache"
 	"github.com/nspcc-dev/neofs-node/pkg/util"
 	"github.com/nspcc-dev/neofs-node/pkg/util/logger"
 	"go.uber.org/atomic"
@@ -19,7 +20,7 @@ type Shard struct {
 
 	mode *atomic.Uint32
 
-	writeCache *blobstor.BlobStor
+	writeCache writecache.Cache
 
 	blobStor *blobstor.BlobStor
 
@@ -43,7 +44,7 @@ type cfg struct {
 
 	metaOpts []meta.Option
 
-	writeCacheOpts []blobstor.Option
+	writeCacheOpts []writecache.Option
 
 	log *logger.Logger
 
@@ -68,19 +69,22 @@ func New(opts ...Option) *Shard {
 		opts[i](c)
 	}
 
-	var writeCache *blobstor.BlobStor
+	bs := blobstor.New(c.blobOpts...)
+	mb := meta.New(c.metaOpts...)
 
+	var writeCache writecache.Cache
 	if c.useWriteCache {
-		writeCache = blobstor.New(
-			append(c.blobOpts, c.writeCacheOpts...)...,
-		)
+		writeCache = writecache.New(
+			append(c.writeCacheOpts,
+				writecache.WithBlobstor(bs),
+				writecache.WithMetabase(mb))...)
 	}
 
 	return &Shard{
 		cfg:        c,
 		mode:       atomic.NewUint32(0), // TODO: init with particular mode
-		blobStor:   blobstor.New(c.blobOpts...),
-		metaBase:   meta.New(c.metaOpts...),
+		blobStor:   bs,
+		metaBase:   mb,
 		writeCache: writeCache,
 	}
 }
@@ -107,7 +111,7 @@ func WithMetaBaseOptions(opts ...meta.Option) Option {
 }
 
 // WithMetaBaseOptions returns option to set internal metabase options.
-func WithWriteCacheOptions(opts ...blobstor.Option) Option {
+func WithWriteCacheOptions(opts ...writecache.Option) Option {
 	return func(c *cfg) {
 		c.writeCacheOpts = opts
 	}

pkg/local_object_storage/shard/shard_test.go

@@ -15,6 +15,7 @@ import (
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/writecache"
 	"github.com/nspcc-dev/neofs-node/pkg/util/test"
 	"github.com/nspcc-dev/tzhash/tz"
 	"github.com/stretchr/testify/require"
@@ -41,9 +42,8 @@ func newShard(t testing.TB, enableWriteCache bool) *shard.Shard {
 		),
 		shard.WithWriteCache(enableWriteCache),
 		shard.WithWriteCacheOptions(
-			blobstor.WithRootPath(path.Join(rootPath, "wcache")),
-			blobstor.WithBlobovniczaShallowWidth(1),
-			blobstor.WithBlobovniczaShallowDepth(0),
+			writecache.WithMaxMemSize(0), // disable memory batches
+			writecache.WithPath(path.Join(rootPath, "wcache")),
 		),
 	}
 

pkg/local_object_storage/writecache/delete.go

@@ -0,0 +1,49 @@
+package writecache
+
+import (
+	"errors"
+
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
+	"go.etcd.io/bbolt"
+)
+
+// Delete removes object from write-cache.
+func (c *cache) Delete(addr *objectSDK.Address) error {
+	saddr := addr.String()
+
+	// Check memory cache.
+	c.mtx.Lock()
+	for i := range c.mem {
+		if saddr == c.mem[i].addr {
+			copy(c.mem[i:], c.mem[i+1:])
+			c.mem = c.mem[:len(c.mem)-1]
+			c.mtx.Unlock()
+			return nil
+		}
+	}
+	c.mtx.Unlock()
+
+	// Check disk cache.
+	has := false
+	_ = c.db.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		has = b.Get([]byte(saddr)) != nil
+		return nil
+	})
+
+	if has {
+		return c.db.Update(func(tx *bbolt.Tx) error {
+			b := tx.Bucket(defaultBucket)
+			return b.Delete([]byte(saddr))
+		})
+	}
+
+	err := c.fsTree.Delete(addr)
+	if errors.Is(err, fstree.ErrFileNotFound) {
+		err = object.ErrNotFound
+	}
+
+	return err
+}

pkg/local_object_storage/writecache/doc.go

@@ -0,0 +1,20 @@
+// Package writecache implements write-cache for objects.
+//
+// It contains in-memory cache of fixed size and underlying database
+// (usually on SSD) for storing small objects.
+// There are 3 places where object can be:
+// 1. In-memory cache.
+// 2. On-disk cache DB.
+// 3. Main storage (blobstor).
+//
+// There are 2 types of background jobs:
+// 1. Persisting objects from in-memory cache to database.
+// 2. Flushing objects from database to blobstor.
+//	  On flushing object address is put in in-memory LRU cache.
+//	  The actual deletion from the DB is done when object
+//	  is evicted from this cache.
+//
+// Putting objects to the main storage is done by multiple workers.
+// Some of them prioritize flushing items, others prioritize putting new objects.
+// The current ration is 50/50. This helps to make some progress even under load.
+package writecache

pkg/local_object_storage/writecache/flush.go

@@ -0,0 +1,196 @@
+package writecache
+
+import (
+	"sync"
+	"time"
+
+	"github.com/mr-tron/base58"
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobovnicza"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
+	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+)
+
+const (
+	// flushBatchSize is amount of keys which will be read from cache to be flushed
+	// to the main storage. It is used to reduce contention between cache put
+	// and cache persist.
+	flushBatchSize = 512
+	// flushWorkersCount is number of workers for putting objects in main storage.
+	flushWorkersCount = 20
+	// defaultFlushInterval is default time interval between successive flushes.
+	defaultFlushInterval = time.Second
+)
+
+// flushLoop periodically flushes changes from the database to memory.
+func (c *cache) flushLoop() {
+	var wg sync.WaitGroup
+
+	for i := 0; i < c.workersCount; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			c.flushWorker(i)
+		}(i)
+	}
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		c.flushBigObjects()
+	}()
+
+	tick := time.NewTicker(defaultFlushInterval)
+	for {
+		select {
+		case <-tick.C:
+			c.flush()
+		case <-c.closeCh:
+			c.log.Debug("waiting for workers to quit")
+			wg.Wait()
+			return
+		}
+	}
+}
+
+func (c *cache) flush() {
+	lastKey := []byte{}
+	var m []objectInfo
+	for {
+		m = m[:0]
+		sz := 0
+
+		// We put objects in batches of fixed size to not interfere with main put cycle a lot.
+		_ = c.db.View(func(tx *bbolt.Tx) error {
+			b := tx.Bucket(defaultBucket)
+			cs := b.Cursor()
+			for k, v := cs.Seek(lastKey); k != nil && len(m) < flushBatchSize; k, v = cs.Next() {
+				if _, ok := c.flushed.Peek(string(k)); ok {
+					continue
+				}
+
+				sz += len(k) + len(v)
+				m = append(m, objectInfo{
+					addr: string(k),
+					data: cloneBytes(v),
+				})
+			}
+			return nil
+		})
+
+		for i := range m {
+			obj := object.New()
+			if err := obj.Unmarshal(m[i].data); err != nil {
+				continue
+			}
+
+			select {
+			case c.flushCh <- obj:
+			case <-c.closeCh:
+				return
+			}
+		}
+
+		c.evictObjects(len(m))
+		for i := range m {
+			c.flushed.Add(m[i].addr, true)
+		}
+
+		c.dbSize.Sub(uint64(sz))
+
+		c.log.Debug("flushed items from write-cache",
+			zap.Int("count", len(m)),
+			zap.String("start", base58.Encode(lastKey)))
+
+		if len(m) > 0 {
+			lastKey = append([]byte(m[len(m)-1].addr), 0)
+		} else {
+			break
+		}
+	}
+}
+
+func (c *cache) flushBigObjects() {
+	tick := time.NewTicker(defaultFlushInterval * 10)
+	for {
+		select {
+		case <-tick.C:
+			_ = c.fsTree.Iterate(func(addr *objectSDK.Address, data []byte) error {
+				if _, ok := c.store.flushed.Peek(addr.String()); ok {
+					return nil
+				}
+
+				if _, err := c.blobstor.PutRaw(addr, data); err != nil {
+					c.log.Error("cant flush object to blobstor", zap.Error(err))
+				}
+				return nil
+			})
+		case <-c.closeCh:
+		}
+	}
+}
+
+// flushWorker runs in a separate goroutine and write objects to the main storage.
+// If flushFirst is true, flushing objects from cache database takes priority over
+// putting new objects.
+func (c *cache) flushWorker(num int) {
+	priorityCh := c.directCh
+	switch num % 3 {
+	case 0:
+		priorityCh = c.flushCh
+	case 1:
+		priorityCh = c.metaCh
+	}
+
+	var obj *object.Object
+	for {
+		metaOnly := false
+
+		// Give priority to direct put.
+		// TODO(fyrchik): do this once in N iterations depending on load
+		select {
+		case obj = <-priorityCh:
+		default:
+			select {
+			case obj = <-c.directCh:
+			case obj = <-c.flushCh:
+			case obj = <-c.metaCh:
+				metaOnly = true
+			case <-c.closeCh:
+				return
+			}
+		}
+
+		err := c.writeObject(obj, metaOnly)
+		if err != nil {
+			c.log.Error("can't flush object to the main storage", zap.Error(err))
+		}
+	}
+}
+
+// writeObject is used to write object directly to the main storage.
+func (c *cache) writeObject(obj *object.Object, metaOnly bool) error {
+	var id *blobovnicza.ID
+
+	if !metaOnly {
+		prm := new(blobstor.PutPrm)
+		prm.SetObject(obj)
+		res, err := c.blobstor.Put(prm)
+		if err != nil {
+			return err
+		}
+
+		id = res.BlobovniczaID()
+	}
+
+	return meta.Put(c.metabase, obj, id)
+}
+
+func cloneBytes(a []byte) []byte {
+	b := make([]byte, len(a))
+	copy(b, a)
+	return b
+}

pkg/local_object_storage/writecache/get.go

@@ -0,0 +1,51 @@
+package writecache
+
+import (
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"go.etcd.io/bbolt"
+)
+
+// Get returns object from write-cache.
+func (c *cache) Get(addr *objectSDK.Address) (*object.Object, error) {
+	saddr := addr.String()
+
+	c.mtx.RLock()
+	for i := range c.mem {
+		if saddr == c.mem[i].addr {
+			obj := c.mem[i].obj
+			c.mtx.RUnlock()
+			return obj, nil
+		}
+	}
+	c.mtx.RUnlock()
+
+	var value []byte
+	_ = c.db.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		val := b.Get([]byte(saddr))
+		if val != nil {
+			value = cloneBytes(val)
+		}
+		return nil
+	})
+
+	if value != nil {
+		obj := object.New()
+		c.flushed.Get(saddr)
+		return obj, obj.Unmarshal(value)
+	}
+
+	data, err := c.fsTree.Get(addr)
+	if err != nil {
+		return nil, object.ErrNotFound
+	}
+
+	obj := object.New()
+	if err := obj.Unmarshal(data); err != nil {
+		return nil, err
+	}
+
+	c.flushed.Get(saddr)
+	return obj, nil
+}

pkg/local_object_storage/writecache/options.go

@@ -0,0 +1,100 @@
+package writecache
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
+	meta "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/metabase"
+	"go.uber.org/zap"
+)
+
+// Option represents write-cache configuration option.
+type Option func(*options)
+
+type options struct {
+	log *zap.Logger
+	// path is a path to a directory for write-cache.
+	path string
+	// blobstor is the main persistent storage.
+	blobstor *blobstor.BlobStor
+	// metabase is the metabase instance.
+	metabase *meta.DB
+	// maxMemSize is the maximum total size of all objects cached in memory.
+	// 1 GiB by default.
+	maxMemSize uint64
+	// maxDBSize is the maximum size of database in bytes.
+	// Unrestricted by default.
+	maxDBSize uint64
+	// maxObjectSize is the maximum size of the object stored in the write-cache.
+	maxObjectSize uint64
+	// smallObjectSize is the maximum size of the object stored in the database.
+	smallObjectSize uint64
+	// workersCount is the number of workers flushing objects in parallel.
+	workersCount int
+}
+
+// WithLogger sets logger.
+func WithLogger(log *zap.Logger) Option {
+	return func(o *options) {
+		o.log = log
+	}
+}
+
+// WithPath sets path to writecache db.
+func WithPath(path string) Option {
+	return func(o *options) {
+		o.path = path
+	}
+}
+
+// WithBlobstor sets main object storage.
+func WithBlobstor(bs *blobstor.BlobStor) Option {
+	return func(o *options) {
+		o.blobstor = bs
+	}
+}
+
+// WithMetabase sets metabase.
+func WithMetabase(db *meta.DB) Option {
+	return func(o *options) {
+		o.metabase = db
+	}
+}
+
+// WithMaxMemSize sets maximum size for in-memory DB.
+func WithMaxMemSize(sz uint64) Option {
+	return func(o *options) {
+		o.maxMemSize = sz
+	}
+}
+
+// WithMaxDBSize sets maximum size for on-disk DB.
+func WithMaxDBSize(sz uint64) Option {
+	return func(o *options) {
+		o.maxDBSize = sz
+	}
+}
+
+// WithMaxObjectSize sets maximum object size to be stored in write-cache.
+func WithMaxObjectSize(sz uint64) Option {
+	return func(o *options) {
+		if sz > 0 {
+			o.maxObjectSize = sz
+		}
+	}
+}
+
+// WithSmallObjectSize sets maximum object size to be stored in write-cache.
+func WithSmallObjectSize(sz uint64) Option {
+	return func(o *options) {
+		if sz > 0 {
+			o.smallObjectSize = sz
+		}
+	}
+}
+
+func WithFlushWorkersCount(c int) Option {
+	return func(o *options) {
+		if c > 0 {
+			o.workersCount = c
+		}
+	}
+}

pkg/local_object_storage/writecache/persist.go

@@ -0,0 +1,124 @@
+package writecache
+
+import (
+	"sort"
+	"time"
+
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+)
+
+const defaultPersistInterval = time.Second
+
+// persistLoop persists object accumulated in memory to the database.
+func (c *cache) persistLoop() {
+	tick := time.NewTicker(defaultPersistInterval)
+	defer tick.Stop()
+
+	for {
+		select {
+		case <-tick.C:
+			c.mtx.RLock()
+			m := c.mem
+			c.mtx.RUnlock()
+
+			sort.Slice(m, func(i, j int) bool { return m[i].addr < m[j].addr })
+
+			start := time.Now()
+			c.persistObjects(m)
+			c.log.Debug("persisted items to disk",
+				zap.Duration("took", time.Since(start)),
+				zap.Int("total", len(m)))
+
+			c.mtx.Lock()
+			n := copy(c.mem, c.mem[len(m):])
+			c.mem = c.mem[:n]
+			for i := range c.mem {
+				c.curMemSize += uint64(len(c.mem[i].data))
+			}
+			c.mtx.Unlock()
+
+			sz := 0
+			for i := range m {
+				sz += len(m[i].addr) + m[i].obj.ToV2().StableSize()
+			}
+			c.dbSize.Add(uint64(sz))
+
+		case <-c.closeCh:
+			return
+		}
+	}
+}
+
+func (c *cache) persistToCache(objs []objectInfo) []int {
+	var (
+		failMem []int
+		doneMem []int
+	)
+
+	_ = c.db.Update(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		for i := range objs {
+			if uint64(len(objs[i].data)) >= c.smallObjectSize {
+				failMem = append(failMem, i)
+				continue
+			}
+
+			err := b.Put([]byte(objs[i].addr), objs[i].data)
+			if err != nil {
+				return err
+			}
+
+			doneMem = append(doneMem, i)
+		}
+		return nil
+	})
+
+	if len(doneMem) > 0 {
+		c.evictObjects(len(doneMem))
+		for _, i := range doneMem {
+			c.flushed.Add(objs[i].addr, true)
+		}
+	}
+
+	var failDisk []int
+
+	for _, i := range failMem {
+		if uint64(len(objs[i].data)) > c.maxObjectSize {
+			failDisk = append(failDisk, i)
+			continue
+		}
+
+		err := c.fsTree.Put(objs[i].obj.Address(), objs[i].data)
+		if err != nil {
+			failDisk = append(failDisk, i)
+		}
+	}
+
+	return failDisk
+}
+
+// persistObjects tries to write objects from memory to the persistent storage.
+// If tryCache is false, writing skips cache and is done directly to the main storage.
+func (c *cache) persistObjects(objs []objectInfo) {
+	toDisk := c.persistToCache(objs)
+	j := 0
+
+	for i := range objs {
+		ch := c.metaCh
+		if j < len(toDisk) {
+			if i == toDisk[j] {
+				ch = c.directCh
+			} else {
+				for ; j < len(toDisk) && i > toDisk[j]; j++ {
+				}
+			}
+		}
+
+		select {
+		case ch <- objs[j].obj:
+		case <-c.closeCh:
+			return
+		}
+	}
+}

pkg/local_object_storage/writecache/put.go

@@ -0,0 +1,44 @@
+package writecache
+
+import (
+	"errors"
+
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+)
+
+// ErrBigObject is returned when object is too big to be placed in cache.
+var ErrBigObject = errors.New("too big object")
+
+// Put puts object to write-cache.
+func (c *cache) Put(o *object.Object) error {
+	sz := uint64(o.ToV2().StableSize())
+	if sz > c.maxObjectSize {
+		return ErrBigObject
+	}
+
+	data, err := o.Marshal(nil)
+	if err != nil {
+		return err
+	}
+
+	oi := objectInfo{
+		addr: o.Address().String(),
+		obj:  o,
+		data: data,
+	}
+
+	c.mtx.Lock()
+
+	if sz < c.smallObjectSize && c.curMemSize+sz <= c.maxMemSize {
+		c.curMemSize += sz
+		c.mem = append(c.mem, oi)
+
+		c.mtx.Unlock()
+		return nil
+	}
+
+	c.mtx.Unlock()
+
+	c.persistObjects([]objectInfo{oi})
+	return nil
+}

pkg/local_object_storage/writecache/storage.go

@@ -0,0 +1,130 @@
+package writecache
+
+import (
+	"errors"
+	"os"
+	"path"
+
+	lru "github.com/hashicorp/golang-lru"
+	"github.com/hashicorp/golang-lru/simplelru"
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+)
+
+// store represents persistent storage with in-memory LRU cache
+// for flushed items on top of it.
+type store struct {
+	flushed simplelru.LRUCache
+	db      *bbolt.DB
+}
+
+const lruKeysCount = 256 * 1024 * 8
+
+const dbName = "small.bolt"
+
+func (c *cache) openStore() error {
+	if err := os.MkdirAll(c.path, os.ModePerm); err != nil {
+		return err
+	}
+
+	db, err := bbolt.Open(path.Join(c.path, dbName), os.ModePerm, &bbolt.Options{
+		NoFreelistSync: true,
+		NoSync:         true,
+	})
+	if err != nil {
+		return err
+	}
+
+	c.fsTree = &fstree.FSTree{
+		Info: fstree.Info{
+			Permissions: os.ModePerm,
+			RootPath:    c.path,
+		},
+		Depth:      1,
+		DirNameLen: 1,
+	}
+
+	_ = db.Update(func(tx *bbolt.Tx) error {
+		_, err := tx.CreateBucketIfNotExists(defaultBucket)
+		return err
+	})
+
+	c.db = db
+	c.flushed, _ = lru.New(lruKeysCount)
+	return nil
+}
+
+func (s *store) removeFlushedKeys(n int) ([][]byte, [][]byte) {
+	var keysMem, keysDisk [][]byte
+	for i := 0; i < n; i++ {
+		k, v, ok := s.flushed.RemoveOldest()
+		if !ok {
+			break
+		}
+
+		if v.(bool) {
+			keysMem = append(keysMem, []byte(k.(string)))
+		} else {
+			keysDisk = append(keysDisk, []byte(k.(string)))
+		}
+	}
+
+	return keysMem, keysDisk
+}
+
+func (c *cache) evictObjects(putCount int) {
+	sum := c.flushed.Len() + putCount
+	if sum <= lruKeysCount {
+		return
+	}
+
+	keysMem, keysDisk := c.store.removeFlushedKeys(sum - lruKeysCount)
+
+	if err := c.deleteFromDB(keysMem); err != nil {
+		c.log.Error("error while removing objects from write-cache (database)", zap.Error(err))
+	}
+
+	if err := c.deleteFromDisk(keysDisk); err != nil {
+		c.log.Error("error while removing objects from write-cache (disk)", zap.Error(err))
+	}
+}
+
+func (c *cache) deleteFromDB(keys [][]byte) error {
+	if len(keys) == 0 {
+		return nil
+	}
+
+	return c.db.Update(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		for i := range keys {
+			if err := b.Delete(keys[i]); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}
+
+func (c *cache) deleteFromDisk(keys [][]byte) error {
+	var lastErr error
+
+	for i := range keys {
+		addr := objectSDK.NewAddress()
+		addrStr := string(keys[i])
+
+		if err := addr.Parse(addrStr); err != nil {
+			c.log.Error("can't parse address", zap.String("address", addrStr))
+			continue
+		}
+
+		if err := c.fsTree.Delete(addr); err != nil && !errors.Is(err, fstree.ErrFileNotFound) {
+			lastErr = err
+			c.log.Error("can't remove object from write-cache", zap.Error(err))
+			continue
+		}
+	}
+
+	return lastErr
+}

pkg/local_object_storage/writecache/writecache.go

@@ -0,0 +1,109 @@
+package writecache
+
+import (
+	"sync"
+
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
+	"go.uber.org/atomic"
+	"go.uber.org/zap"
+)
+
+// Cache represents write-cache for objects.
+type Cache interface {
+	Get(*objectSDK.Address) (*object.Object, error)
+	Delete(*objectSDK.Address) error
+	Put(*object.Object) error
+
+	Init() error
+	Open() error
+	Close() error
+}
+
+type cache struct {
+	options
+
+	// mtx protects mem field, statistics and counters.
+	mtx sync.RWMutex
+	mem []objectInfo
+
+	// curMemSize is the current size of all objects cached in memory.
+	curMemSize uint64
+
+	// flushCh is a channel with objects to flush.
+	flushCh chan *object.Object
+	// directCh is a channel with objects to put directly to the main storage.
+	// it is prioritized over flushCh.
+	directCh chan *object.Object
+	// metaCh is a channel with objects for which only metadata needs to be written.
+	metaCh chan *object.Object
+	// closeCh is close channel.
+	closeCh chan struct{}
+	evictCh chan []byte
+	// store contains underlying database.
+	store
+	// dbSize stores approximate database size. It is updated every flush/persist cycle.
+	dbSize atomic.Uint64
+	// fsTree contains big files stored directly on file-system.
+	fsTree *fstree.FSTree
+}
+
+type objectInfo struct {
+	addr string
+	data []byte
+	obj  *object.Object
+}
+
+const (
+	maxInMemorySizeBytes = 1024 * 1024 * 1024 // 1 GiB
+	maxObjectSize        = 64 * 1024 * 1024   // 64 MiB
+	smallObjectSize      = 32 * 1024          // 32 KiB
+)
+
+var (
+	defaultBucket = []byte{0}
+)
+
+// New creates new writecache instance.
+func New(opts ...Option) Cache {
+	c := &cache{
+		flushCh:  make(chan *object.Object),
+		directCh: make(chan *object.Object),
+		metaCh:   make(chan *object.Object),
+		closeCh:  make(chan struct{}),
+		evictCh:  make(chan []byte),
+
+		options: options{
+			log:             zap.NewNop(),
+			maxMemSize:      maxInMemorySizeBytes,
+			maxObjectSize:   maxObjectSize,
+			smallObjectSize: smallObjectSize,
+			workersCount:    flushWorkersCount,
+		},
+	}
+
+	for i := range opts {
+		opts[i](&c.options)
+	}
+
+	return c
+}
+
+// Open opens and initializes database.
+func (c *cache) Open() error {
+	return c.openStore()
+}
+
+// Init runs necessary services.
+func (c *cache) Init() error {
+	go c.persistLoop()
+	go c.flushLoop()
+	return nil
+}
+
+// Close closes db connection and stops services.
+func (c *cache) Close() error {
+	close(c.closeCh)
+	return c.db.Close()
+}