[#421] Try using badger for the write-cache

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

cmd/frostfs-lens/internal/flags.go

@@ -8,6 +8,7 @@ const (
 	flagAddress    = "address"
 	flagEnginePath = "path"
 	flagOutFile    = "out"
+	flagDBType     = "dbtype"
 )
 
 // AddAddressFlag adds the address flag to the passed cobra command.
@@ -33,3 +34,9 @@ func AddOutputFileFlag(cmd *cobra.Command, v *string) {
 		"File to save object payload")
 	_ = cmd.MarkFlagFilename(flagOutFile)
 }
+
+// AddDBTypeFlag adds the DB type flag to the passed cobra command.
+func AddDBTypeFlag(cmd *cobra.Command, v *string) {
+	cmd.Flags().StringVar(v, flagOutFile, "bbolt",
+		"Type of DB used by write cache (default: bbolt)")
+}

cmd/frostfs-lens/internal/writecache/inspect.go

@@ -1,8 +1,13 @@
 package writecache
 
 import (
+	"fmt"
+	"os"
+
 	common "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-lens/internal"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	"github.com/spf13/cobra"
 )
@@ -18,15 +23,35 @@ func init() {
 	common.AddAddressFlag(inspectCMD, &vAddress)
 	common.AddComponentPathFlag(inspectCMD, &vPath)
 	common.AddOutputFileFlag(inspectCMD, &vOut)
+	common.AddDBTypeFlag(inspectCMD, &vDBType)
 }
 
 func inspectFunc(cmd *cobra.Command, _ []string) {
-	db := openWC(cmd)
+	var data []byte
+
+	switch vDBType {
+	case "bbolt":
+		db, err := writecachebbolt.OpenDB(vPath, true, os.OpenFile)
+		common.ExitOnErr(cmd, common.Errf("could not open write-cache db: %w", err))
 		defer db.Close()
 
-	data, err := writecache.Get(db, []byte(vAddress))
+		data, err = writecachebbolt.Get(db, []byte(vAddress))
 		common.ExitOnErr(cmd, common.Errf("could not fetch object: %w", err))
 
+	case "badger":
+		log, err := logger.NewLogger(&logger.Prm{})
+		common.ExitOnErr(cmd, common.Errf("could not create logger: %w", err))
+
+		db, err := writecachebadger.OpenDB(vPath, true, log)
+		common.ExitOnErr(cmd, common.Errf("could not open write-cache db: %w", err))
+
+		data, err = writecachebadger.Get(db, []byte(vAddress))
+		common.ExitOnErr(cmd, common.Errf("could not fetch object: %w", err))
+
+	default:
+		common.ExitOnErr(cmd, fmt.Errorf("invalid dbtype: %q (possible values: bbolt, badger)", vDBType))
+	}
+
 	var o objectSDK.Object
 	common.ExitOnErr(cmd, common.Errf("could not unmarshal object: %w", o.Unmarshal(data)))
 

cmd/frostfs-lens/internal/writecache/list.go

@@ -3,9 +3,12 @@ package writecache
 import (
 	"fmt"
 	"io"
+	"os"
 
 	common "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-lens/internal"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
 	"github.com/spf13/cobra"
 )
@@ -30,9 +33,26 @@ func listFunc(cmd *cobra.Command, _ []string) {
 		return err
 	}
 
-	db := openWC(cmd)
+	switch vDBType {
+	case "bbolt":
+		db, err := writecachebbolt.OpenDB(vPath, true, os.OpenFile)
+		common.ExitOnErr(cmd, common.Errf("could not open write-cache db: %w", err))
 		defer db.Close()
 
-	err := writecache.IterateDB(db, wAddr)
+		err = writecachebbolt.IterateDB(db, wAddr)
 		common.ExitOnErr(cmd, common.Errf("write-cache iterator failure: %w", err))
+
+	case "badger":
+		log, err := logger.NewLogger(&logger.Prm{})
+		common.ExitOnErr(cmd, common.Errf("could not create logger: %w", err))
+
+		db, err := writecachebadger.OpenDB(vPath, true, log)
+		common.ExitOnErr(cmd, common.Errf("could not open write-cache db: %w", err))
+
+		err = writecachebadger.IterateDB(db, wAddr)
+		common.ExitOnErr(cmd, common.Errf("write-cache iterator failure: %w", err))
+
+	default:
+		common.ExitOnErr(cmd, fmt.Errorf("invalid dbtype: %q (possible values: bbolt, badger)", vDBType))
+	}
 }

cmd/frostfs-lens/internal/writecache/root.go

@@ -1,18 +1,14 @@
 package writecache
 
 import (
-	"os"
-
-	common "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-lens/internal"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"github.com/spf13/cobra"
-	"go.etcd.io/bbolt"
 )
 
 var (
 	vAddress string
 	vPath    string
 	vOut     string
+	vDBType  string
 )
 
 // Root contains `write-cache` command definition.
@@ -24,10 +20,3 @@ var Root = &cobra.Command{
 func init() {
 	Root.AddCommand(listCMD, inspectCMD)
 }
-
-func openWC(cmd *cobra.Command) *bbolt.DB {
-	db, err := writecache.OpenDB(vPath, true, os.OpenFile)
-	common.ExitOnErr(cmd, common.Errf("could not open write-cache db: %w", err))
-
-	return db
-}

cmd/frostfs-node/config.go

@@ -40,7 +40,9 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/pilorama"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
 	shardmode "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/metrics"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/morph/client"
 	containerClient "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/morph/client/container"
@@ -127,6 +129,7 @@ type shardCfg struct {
 
 	writecacheCfg struct {
 		enabled          bool
+		typ              writecacheconfig.Type
 		path             string
 		maxBatchSize     int
 		maxBatchDelay    time.Duration
@@ -135,6 +138,7 @@ type shardCfg struct {
 		flushWorkerCount int
 		sizeLimit        uint64
 		noSync           bool
+		gcInterval       time.Duration
 	}
 
 	piloramaCfg struct {
@@ -238,6 +242,7 @@ func (a *applicationConfiguration) setShardWriteCacheConfig(newConfig *shardCfg,
 		wc := &newConfig.writecacheCfg
 
 		wc.enabled = true
+		wc.typ = writeCacheCfg.Type()
 		wc.path = writeCacheCfg.Path()
 		wc.maxBatchSize = writeCacheCfg.BoltDB().MaxBatchSize()
 		wc.maxBatchDelay = writeCacheCfg.BoltDB().MaxBatchDelay()
@@ -246,6 +251,7 @@ func (a *applicationConfiguration) setShardWriteCacheConfig(newConfig *shardCfg,
 		wc.flushWorkerCount = writeCacheCfg.WorkersNumber()
 		wc.sizeLimit = writeCacheCfg.SizeLimit()
 		wc.noSync = writeCacheCfg.NoSync()
+		wc.gcInterval = writeCacheCfg.GCInterval()
 	}
 }
 
@@ -704,20 +710,37 @@ func (c *cfg) shardOpts() []shardOptsWithID {
 	return shards
 }
 
-func (c *cfg) getWriteCacheOpts(shCfg shardCfg) []writecache.Option {
+func (c *cfg) getWriteCacheOpts(shCfg shardCfg) writecacheconfig.Options {
-	var writeCacheOpts []writecache.Option
+	var writeCacheOpts writecacheconfig.Options
 	if wcRead := shCfg.writecacheCfg; wcRead.enabled {
-		writeCacheOpts = append(writeCacheOpts,
+		switch wcRead.typ {
-			writecache.WithPath(wcRead.path),
+		case writecacheconfig.TypeBBolt:
-			writecache.WithMaxBatchSize(wcRead.maxBatchSize),
+			writeCacheOpts.Type = writecacheconfig.TypeBBolt
-			writecache.WithMaxBatchDelay(wcRead.maxBatchDelay),
+			writeCacheOpts.BBoltOptions = append(writeCacheOpts.BBoltOptions,
-			writecache.WithMaxObjectSize(wcRead.maxObjSize),
+				writecachebbolt.WithPath(wcRead.path),
-			writecache.WithSmallObjectSize(wcRead.smallObjectSize),
+				writecachebbolt.WithMaxBatchSize(wcRead.maxBatchSize),
-			writecache.WithFlushWorkersCount(wcRead.flushWorkerCount),
+				writecachebbolt.WithMaxBatchDelay(wcRead.maxBatchDelay),
-			writecache.WithMaxCacheSize(wcRead.sizeLimit),
+				writecachebbolt.WithMaxObjectSize(wcRead.maxObjSize),
-			writecache.WithNoSync(wcRead.noSync),
+				writecachebbolt.WithSmallObjectSize(wcRead.smallObjectSize),
-			writecache.WithLogger(c.log),
+				writecachebbolt.WithFlushWorkersCount(wcRead.flushWorkerCount),
+				writecachebbolt.WithMaxCacheSize(wcRead.sizeLimit),
+				writecachebbolt.WithNoSync(wcRead.noSync),
+				writecachebbolt.WithLogger(c.log),
 			)
+		case writecacheconfig.TypeBadger:
+			writeCacheOpts.Type = writecacheconfig.TypeBBolt
+			writeCacheOpts.BadgerOptions = append(writeCacheOpts.BadgerOptions,
+				writecachebadger.WithPath(wcRead.path),
+				writecachebadger.WithMaxObjectSize(wcRead.maxObjSize),
+				writecachebadger.WithFlushWorkersCount(wcRead.flushWorkerCount),
+				writecachebadger.WithMaxCacheSize(wcRead.sizeLimit),
+				writecachebadger.WithNoSync(wcRead.noSync),
+				writecachebadger.WithLogger(c.log),
+				writecachebadger.WithGCInterval(wcRead.gcInterval),
+			)
+		default:
+			panic(fmt.Sprintf("unknown writecache type: %q", wcRead.typ))
+		}
 	}
 	return writeCacheOpts
 }
@@ -836,7 +859,7 @@ func (c *cfg) getShardOpts(shCfg shardCfg) shardOptsWithID {
 		shard.WithMetaBaseOptions(mbOptions...),
 		shard.WithPiloramaOptions(piloramaOpts...),
 		shard.WithWriteCache(shCfg.writecacheCfg.enabled),
-		shard.WithWriteCacheOptions(writeCacheOpts...),
+		shard.WithWriteCacheOptions(writeCacheOpts),
 		shard.WithRemoverBatchSize(shCfg.gcCfg.removerBatchSize),
 		shard.WithGCRemoverSleepInterval(shCfg.gcCfg.removerSleepInterval),
 		shard.WithExpiredCollectorBatchSize(shCfg.gcCfg.expiredCollectorBatchSize),

cmd/frostfs-node/config/engine/shard/writecache/config.go

@@ -1,8 +1,12 @@
 package writecacheconfig
 
 import (
+	"fmt"
+	"time"
+
 	"git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-node/config"
 	boltdbconfig "git.frostfs.info/TrueCloudLab/frostfs-node/cmd/frostfs-node/config/engine/shard/boltdb"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
 )
 
 // Config is a wrapper over the config section
@@ -21,6 +25,9 @@ const (
 
 	// SizeLimitDefault is a default write-cache size limit.
 	SizeLimitDefault = 1 << 30
+
+	// DefaultGCInterval is the default duration of the GC cycle interval.
+	DefaultGCInterval = 1 * time.Minute
 )
 
 // From wraps config section into Config.
@@ -35,6 +42,22 @@ func (x *Config) Enabled() bool {
 	return config.Bool((*config.Config)(x), "enabled")
 }
 
+// Type returns the writecache implementation type to use.
+//
+// Panics if the type is not recognized.
+func (x *Config) Type() writecacheconfig.Type {
+	t := config.String((*config.Config)(x), "type")
+
+	switch t {
+	case "bbolt", "":
+		return writecacheconfig.TypeBBolt
+	case "badger":
+		return writecacheconfig.TypeBadger
+	}
+
+	panic(fmt.Sprintf("invalid writecache type: %q", t))
+}
+
 // Path returns the value of "path" config parameter.
 //
 // Panics if the value is not a non-empty string.
@@ -126,3 +149,16 @@ func (x *Config) NoSync() bool {
 func (x *Config) BoltDB() *boltdbconfig.Config {
 	return (*boltdbconfig.Config)(x)
 }
+
+// GCInterval returns the value of "gc_interval" config parameter.
+//
+// Returns DefaultGCInterval if the value is not a positive duration.
+func (x *Config) GCInterval() time.Duration {
+	d := config.DurationSafe((*config.Config)(x), "gc_interval")
+
+	if d > 0 {
+		return d
+	}
+
+	return DefaultGCInterval
+}

config/example/node.json

@@ -194,6 +194,7 @@
         "resync_metabase": true,
         "writecache": {
           "enabled": true,
+          "type": "bbolt",
           "path": "tmp/1/cache",
           "memcache_capacity": 2147483648,
           "small_object_size": 16384,

config/example/node.yaml

@@ -122,6 +122,7 @@ storage:
 
       writecache:
         enabled: true
+        type: bbolt
         small_object_size: 16k  # size threshold for "small" objects which are cached in key-value DB, not in FS, bytes
         max_object_size: 134217728  # size threshold for "big" objects which bypass write-cache and go to the storage directly, bytes
         workers_number: 30  # number of write-cache flusher threads

docs/storage-node-configuration.md

@@ -273,6 +273,7 @@ metabase:
 ```yaml
 writecache:
   enabled: true
+  type: bbolt
   path: /path/to/writecache
   capacity: 4294967296
   small_object_size: 16384
@@ -282,6 +283,7 @@ writecache:
 
 | Parameter            | Type       | Default value | Description                                                                                                          |
 |----------------------|------------|---------------|----------------------------------------------------------------------------------------------------------------------|
+| `type`               | `string`   |               | Type of write cache backing implementation to use (`bbolt`, `badger`).                                               |
 | `path`               | `string`   |               | Path to the metabase file.                                                                                           |
 | `capacity`           | `size`     | unrestricted  | Approximate maximum size of the writecache. If the writecache is full, objects are written to the blobstor directly. |
 | `small_object_size`  | `size`     | `32K`         | Maximum object size for "small" objects. This objects are stored in a key-value database instead of a file-system.   |

go.mod

@@ -41,6 +41,17 @@ require (
 	gopkg.in/yaml.v3 v3.0.1
 )
 
+require (
+	github.com/dgraph-io/ristretto v0.1.1 // indirect
+	github.com/dustin/go-humanize v1.0.0 // indirect
+	github.com/gogo/protobuf v1.3.2 // indirect
+	github.com/golang/glog v1.1.0 // indirect
+	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
+	github.com/google/flatbuffers v1.12.1 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	go.opencensus.io v0.24.0 // indirect
+)
+
 require (
 	git.frostfs.info/TrueCloudLab/frostfs-crypto v0.6.0 // indirect
 	git.frostfs.info/TrueCloudLab/rfc6979 v0.4.0 // indirect
@@ -55,6 +66,7 @@ require (
 	github.com/cpuguy83/go-md2man/v2 v2.0.2 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
+	github.com/dgraph-io/badger/v4 v4.1.0
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
 	github.com/go-logr/logr v1.2.4 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect

internal/logs/logs.go

@@ -291,6 +291,7 @@ const (
 	ShardFailureToMarkLockersAsGarbage                                      = "failure to mark lockers as garbage"                                        // Warn in ../node/pkg/local_object_storage/shard/gc.go
 	ShardFailureToGetExpiredUnlockedObjects                                 = "failure to get expired unlocked objects"                                   // Warn in ../node/pkg/local_object_storage/shard/gc.go
 	ShardCouldNotMarkObjectToDeleteInMetabase                               = "could not mark object to delete in metabase"                               // Debug in ../node/pkg/local_object_storage/shard/inhume.go
+	WritecacheBadgerInitExperimental                                        = "initializing badger-backed experimental writecache"
 	WritecacheTriedToFlushItemsFromWritecache                               = "tried to flush items from write-cache"       // Debug in ../node/pkg/local_object_storage/writecache/flush.go
 	WritecacheWaitingForChannelsToFlush                                     = "waiting for channels to flush"               // Info in ../node/pkg/local_object_storage/writecache/mode.go
 	WritecacheFillingFlushMarksForObjectsInFSTree                           = "filling flush marks for objects in FSTree"   // Info in ../node/pkg/local_object_storage/writecache/init.go
@@ -300,6 +301,7 @@ const (
 	WritecacheCantRemoveObjectsFromTheDatabase                              = "can't remove objects from the database"      // Error in ../node/pkg/local_object_storage/writecache/storage.go
 	WritecacheCantParseAddress                                              = "can't parse address"                         // Error in ../node/pkg/local_object_storage/writecache/storage.go
 	WritecacheCantRemoveObjectFromWritecache                                = "can't remove object from write-cache"        // Error in ../node/pkg/local_object_storage/writecache/storage.go
+	WritecacheDBValueLogGCRunCompleted                                      = "value log GC run completed"
 	BlobovniczatreeCouldNotGetObjectFromLevel                               = "could not get object from level"                                     // Debug in ../node/pkg/local_object_storage/blobstor/blobovniczatree/get_range.go
 	BlobovniczatreeCouldNotReadPayloadRangeFromOpenedBlobovnicza            = "could not read payload range from opened blobovnicza"                // Debug in ../node/pkg/local_object_storage/blobstor/blobovniczatree/get_range.go
 	BlobovniczatreeCouldNotReadPayloadRangeFromActiveBlobovnicza            = "could not read payload range from active blobovnicza"                // Debug in ../node/pkg/local_object_storage/blobstor/blobovniczatree/get_range.go

pkg/local_object_storage/engine/control_test.go

@@ -20,7 +20,8 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/pilorama"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
 	"github.com/stretchr/testify/require"
@@ -36,7 +37,6 @@ func TestInitializationFailure(t *testing.T) {
 
 	type testShardOpts struct {
 		openFileMetabase openFileFunc
-		openFileWriteCache openFileFunc
 		openFilePilorama openFileFunc
 	}
 
@@ -52,6 +52,13 @@ func TestInitializationFailure(t *testing.T) {
 
 		storages, smallFileStorage, largeFileStorage := newTestStorages(blobstorPath, 1<<20)
 
+		wcOpts := writecacheconfig.Options{
+			Type: writecacheconfig.TypeBBolt,
+			BBoltOptions: []writecachebbolt.Option{
+				writecachebbolt.WithPath(writecachePath),
+			},
+		}
+
 		return []shard.Option{
 			shard.WithID(sid),
 			shard.WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
@@ -66,10 +73,7 @@ func TestInitializationFailure(t *testing.T) {
 				meta.WithPermissions(0700),
 				meta.WithEpochState(epochState{})),
 			shard.WithWriteCache(true),
-			shard.WithWriteCacheOptions(
+			shard.WithWriteCacheOptions(wcOpts),
-				writecache.WithPath(writecachePath),
-				writecache.WithOpenFile(opts.openFileWriteCache),
-			),
 			shard.WithPiloramaOptions(
 				pilorama.WithPath(piloramaPath),
 				pilorama.WithOpenFile(opts.openFilePilorama),
@@ -80,7 +84,6 @@ func TestInitializationFailure(t *testing.T) {
 	t.Run("blobstor", func(t *testing.T) {
 		shardOpts, _, largeFileStorage := testShard(testShardOpts{
 			openFileMetabase: os.OpenFile,
-			openFileWriteCache: os.OpenFile,
 			openFilePilorama: os.OpenFile,
 		})
 		largeFileStorage.SetOption(teststore.WithOpen(func(ro bool) error {
@@ -104,29 +107,10 @@ func TestInitializationFailure(t *testing.T) {
 		}
 		shardOpts, _, _ := testShard(testShardOpts{
 			openFileMetabase: openFileMetabase,
-			openFileWriteCache: os.OpenFile,
 			openFilePilorama: os.OpenFile,
 		})
 		testEngineFailInitAndReload(t, true, shardOpts, beforeReload)
 	})
-	t.Run("write-cache", func(t *testing.T) {
-		var openFileWriteCacheSucceed atomic.Bool
-		openFileWriteCache := func(p string, f int, mode fs.FileMode) (*os.File, error) {
-			if openFileWriteCacheSucceed.Load() {
-				return os.OpenFile(p, f, mode)
-			}
-			return nil, teststore.ErrDiskExploded
-		}
-		beforeReload := func() {
-			openFileWriteCacheSucceed.Store(true)
-		}
-		shardOpts, _, _ := testShard(testShardOpts{
-			openFileMetabase:   os.OpenFile,
-			openFileWriteCache: openFileWriteCache,
-			openFilePilorama:   os.OpenFile,
-		})
-		testEngineFailInitAndReload(t, false, shardOpts, beforeReload)
-	})
 	t.Run("pilorama", func(t *testing.T) {
 		var openFilePiloramaSucceed atomic.Bool
 		openFilePilorama := func(p string, f int, mode fs.FileMode) (*os.File, error) {
@@ -140,7 +124,6 @@ func TestInitializationFailure(t *testing.T) {
 		}
 		shardOpts, _, _ := testShard(testShardOpts{
 			openFileMetabase: os.OpenFile,
-			openFileWriteCache: os.OpenFile,
 			openFilePilorama: openFilePilorama,
 		})
 		testEngineFailInitAndReload(t, false, shardOpts, beforeReload)

pkg/local_object_storage/engine/shards.go

@@ -8,7 +8,6 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
 	"git.frostfs.info/TrueCloudLab/hrw"
 	"github.com/google/uuid"
@@ -131,11 +130,11 @@ func (e *StorageEngine) appendMetrics(id *shard.ID, opts []shard.Option) []shard
 					mw: e.metrics,
 				},
 			),
-			shard.WithExtraWriteCacheOptions(writecache.WithMetrics(
+			shard.WithWriteCacheMetrics(
 				&writeCacheMetrics{
 					shardID: id.String(),
 					metrics: e.metrics.WriteCache(),
-				}),
+				},
 			),
 			shard.WithGCMetrics(
 				&gcMetrics{

pkg/local_object_storage/internal/testutil/object.go

@@ -20,6 +20,12 @@ func GenerateObject() *objectSDK.Object {
 	return GenerateObjectWithCID(cidtest.ID())
 }
 
+func GenerateObjectWithSize(sz int) *objectSDK.Object {
+	data := make([]byte, sz)
+	_, _ = rand.Read(data)
+	return GenerateObjectWithCIDWithPayload(cidtest.ID(), data)
+}
+
 func GenerateObjectWithCID(cnr cid.ID) *objectSDK.Object {
 	data := make([]byte, defaultDataSize)
 	_, _ = rand.Read(data)

pkg/local_object_storage/shard/control_test.go

@@ -17,7 +17,8 @@ import (
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/pilorama"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
@@ -63,6 +64,13 @@ func TestShardOpen(t *testing.T) {
 		return nil, fs.ErrPermission
 	}
 
+	wcOpts := writecacheconfig.Options{
+		Type: writecacheconfig.TypeBBolt,
+		BBoltOptions: []writecachebbolt.Option{
+			writecachebbolt.WithPath(filepath.Join(dir, "wc")),
+		},
+	}
+
 	newShard := func() *Shard {
 		return New(
 			WithID(NewIDFromBytes([]byte{})),
@@ -79,8 +87,7 @@ func TestShardOpen(t *testing.T) {
 			WithPiloramaOptions(
 				pilorama.WithPath(filepath.Join(dir, "pilorama"))),
 			WithWriteCache(true),
-			WithWriteCacheOptions(
+			WithWriteCacheOptions(wcOpts))
-				writecache.WithPath(filepath.Join(dir, "wc"))))
 	}
 
 	allowedMode.Store(int64(os.O_RDWR))

pkg/local_object_storage/shard/gc_test.go

@@ -11,6 +11,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
 	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
@@ -25,7 +26,10 @@ func Test_GCDropsLockedExpiredSimpleObject(t *testing.T) {
 		Value: 100,
 	}
 
-	sh := newCustomShard(t, t.TempDir(), false, nil, nil, []meta.Option{meta.WithEpochState(epoch)})
+	wcOpts := writecacheconfig.Options{
+		Type: writecacheconfig.TypeBBolt,
+	}
+	sh := newCustomShard(t, t.TempDir(), false, wcOpts, nil, []meta.Option{meta.WithEpochState(epoch)})
 
 	t.Cleanup(func() {
 		releaseShard(sh, t)
@@ -122,7 +126,10 @@ func Test_GCDropsLockedExpiredComplexObject(t *testing.T) {
 
 	linkID, _ := link.ID()
 
-	sh := newCustomShard(t, t.TempDir(), false, nil, nil, []meta.Option{meta.WithEpochState(epoch)})
+	wcOpts := writecacheconfig.Options{
+		Type: writecacheconfig.TypeBBolt,
+	}
+	sh := newCustomShard(t, t.TempDir(), false, wcOpts, nil, []meta.Option{meta.WithEpochState(epoch)})
 
 	t.Cleanup(func() {
 		releaseShard(sh, t)

pkg/local_object_storage/shard/range_test.go

@@ -12,7 +12,8 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
@@ -70,8 +71,14 @@ func testShardGetRange(t *testing.T, hasWriteCache bool) {
 			testCase{true, "object in write-cache, out of range, big offset", 100, newRange(101, math.MaxUint64-10)})
 	}
 
-	sh := newCustomShard(t, t.TempDir(), hasWriteCache,
+	wcOpts := writecacheconfig.Options{
-		[]writecache.Option{writecache.WithMaxObjectSize(writeCacheMaxSize)},
+		Type: writecacheconfig.TypeBBolt,
+		BBoltOptions: []writecachebbolt.Option{
+			writecachebbolt.WithMaxObjectSize(writeCacheMaxSize),
+		},
+	}
+
+	sh := newCustomShard(t, t.TempDir(), hasWriteCache, wcOpts,
 		[]blobstor.Option{blobstor.WithStorages([]blobstor.SubStorage{
 			{
 				Storage: blobovniczatree.NewBlobovniczaTree(

pkg/local_object_storage/shard/shard.go

@@ -2,6 +2,7 @@ package shard
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -12,6 +13,9 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/pilorama"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
@@ -98,7 +102,7 @@ type cfg struct {
 
 	metaOpts []meta.Option
 
-	writeCacheOpts []writecache.Option
+	writeCacheOpts writecacheconfig.Options
 
 	piloramaOpts []pilorama.Option
 
@@ -153,11 +157,22 @@ func New(opts ...Option) *Shard {
 	s.blobStor.SetReportErrorFunc(reportFunc)
 
 	if c.useWriteCache {
-		s.writeCache = writecache.New(
+		switch c.writeCacheOpts.Type {
-			append(c.writeCacheOpts,
+		case writecacheconfig.TypeBBolt:
-				writecache.WithReportErrorFunc(reportFunc),
+			s.writeCache = writecachebbolt.New(
-				writecache.WithBlobstor(bs),
+				append(c.writeCacheOpts.BBoltOptions,
-				writecache.WithMetabase(mb))...)
+					writecachebbolt.WithReportErrorFunc(reportFunc),
+					writecachebbolt.WithBlobstor(bs),
+					writecachebbolt.WithMetabase(mb))...)
+		case writecacheconfig.TypeBadger:
+			s.writeCache = writecachebadger.New(
+				append(c.writeCacheOpts.BadgerOptions,
+					writecachebadger.WithReportErrorFunc(reportFunc),
+					writecachebadger.WithBlobstor(bs),
+					writecachebadger.WithMetabase(mb))...)
+		default:
+			panic(fmt.Sprintf("invalid writecache type: %v", c.writeCacheOpts.Type))
+		}
 	}
 
 	if s.piloramaOpts != nil {
@@ -191,16 +206,21 @@ func WithMetaBaseOptions(opts ...meta.Option) Option {
 }
 
 // WithWriteCacheOptions returns option to set internal write cache options.
-func WithWriteCacheOptions(opts ...writecache.Option) Option {
+func WithWriteCacheOptions(opts writecacheconfig.Options) Option {
 	return func(c *cfg) {
 		c.writeCacheOpts = opts
 	}
 }
 
-// WithExtraWriteCacheOptions returns option to add extra write cache options.
+// WithWriteCacheMetrics returns an option to set the metrics register used by the write cache.
-func WithExtraWriteCacheOptions(opts ...writecache.Option) Option {
+func WithWriteCacheMetrics(wcMetrics writecache.Metrics) Option {
 	return func(c *cfg) {
-		c.writeCacheOpts = append(c.writeCacheOpts, opts...)
+		switch c.writeCacheOpts.Type {
+		case writecacheconfig.TypeBBolt:
+			c.writeCacheOpts.BBoltOptions = append(c.writeCacheOpts.BBoltOptions, writecachebbolt.WithMetrics(wcMetrics))
+		case writecacheconfig.TypeBadger:
+			c.writeCacheOpts.BadgerOptions = append(c.writeCacheOpts.BadgerOptions, writecachebadger.WithMetrics(wcMetrics))
+		}
 	}
 }
 

pkg/local_object_storage/shard/shard_test.go

@@ -12,7 +12,9 @@ import (
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/pilorama"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
@@ -33,15 +35,25 @@ func (s epochState) CurrentEpoch() uint64 {
 
 func newShard(t testing.TB, enableWriteCache bool) *shard.Shard {
 	return newCustomShard(t, t.TempDir(), enableWriteCache,
-		nil,
+		writecacheconfig.Options{Type: writecacheconfig.TypeBBolt},
 		nil,
 		nil)
 }
 
-func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts []writecache.Option, bsOpts []blobstor.Option, metaOptions []meta.Option) *shard.Shard {
+func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts writecacheconfig.Options, bsOpts []blobstor.Option, metaOptions []meta.Option) *shard.Shard {
 	var sh *shard.Shard
 	if enableWriteCache {
 		rootPath = filepath.Join(rootPath, "wc")
+		switch wcOpts.Type {
+		case writecacheconfig.TypeBBolt:
+			wcOpts.BBoltOptions = append(
+				[]writecachebbolt.Option{writecachebbolt.WithPath(filepath.Join(rootPath, "wcache"))},
+				wcOpts.BBoltOptions...)
+		case writecacheconfig.TypeBadger:
+			wcOpts.BadgerOptions = append(
+				[]writecachebadger.Option{writecachebadger.WithPath(filepath.Join(rootPath, "wcache"))},
+				wcOpts.BadgerOptions...)
+		}
 	} else {
 		rootPath = filepath.Join(rootPath, "nowc")
 	}
@@ -79,11 +91,7 @@ func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts
 		),
 		shard.WithPiloramaOptions(pilorama.WithPath(filepath.Join(rootPath, "pilorama"))),
 		shard.WithWriteCache(enableWriteCache),
-		shard.WithWriteCacheOptions(
+		shard.WithWriteCacheOptions(wcOpts),
-			append(
-				[]writecache.Option{writecache.WithPath(filepath.Join(rootPath, "wcache"))},
-				wcOpts...)...,
-		),
 		shard.WithDeletedLockCallback(func(_ context.Context, addresses []oid.Address) {
 			sh.HandleDeletedLocks(addresses)
 		}),

pkg/local_object_storage/shard/shutdown_test.go

@@ -8,7 +8,8 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	writecacheconfig "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/config"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
 	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	"github.com/stretchr/testify/require"
@@ -36,9 +37,12 @@ func TestWriteCacheObjectLoss(t *testing.T) {
 	}
 
 	dir := t.TempDir()
-	wcOpts := []writecache.Option{
+	wcOpts := writecacheconfig.Options{
-		writecache.WithSmallObjectSize(smallSize),
+		Type: writecacheconfig.TypeBBolt,
-		writecache.WithMaxObjectSize(smallSize * 2)}
+		BBoltOptions: []writecachebbolt.Option{
+			writecachebbolt.WithMaxObjectSize(smallSize * 2),
+		},
+	}
 
 	sh := newCustomShard(t, dir, true, wcOpts, nil, nil)
 

pkg/local_object_storage/writecache/benchmark/writecache_test.go

@@ -0,0 +1,52 @@
+package benchmark
+
+import (
+	"context"
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
+	oidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id/test"
+)
+
+func BenchmarkWritecache(b *testing.B) {
+	b.Run("bbolt", func(b *testing.B) {
+		cache := writecachebbolt.New(
+			writecachebbolt.WithPath(b.TempDir()),
+		)
+		benchmarkPut(b, cache)
+	})
+	b.Run("badger", func(b *testing.B) {
+		cache := writecachebadger.New(
+			writecachebadger.WithPath(b.TempDir()),
+		)
+		benchmarkPut(b, cache)
+	})
+}
+
+func benchmarkPut(b *testing.B, cache writecache.Cache) {
+	if err := cache.Open(false); err != nil {
+		b.Fatalf("initializing: %v", err)
+	}
+	if err := cache.Init(); err != nil {
+		b.Fatalf("opening: %v", err)
+	}
+	defer cache.Close()
+
+	ctx := context.Background()
+	objGen := testutil.RandObjGenerator{ObjSize: 8 << 10}
+
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		prm := common.PutPrm{
+			Address: oidtest.Address(),
+			Object:  objGen.Next(),
+		}
+		if _, err := cache.Put(ctx, prm); err != nil {
+			b.Fatalf("putting: %v", err)
+		}
+	}
+}

pkg/local_object_storage/writecache/config/config.go

@@ -0,0 +1,22 @@
+// Package config provides the common configuration options for write cache implementations.
+package config
+
+import (
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebadger"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachebbolt"
+)
+
+// Type is the write cache implementation type.
+type Type int
+
+const (
+	TypeBBolt Type = iota
+	TypeBadger
+)
+
+// Options are the configuration options for the write cache.
+type Options struct {
+	Type          Type
+	BBoltOptions  []writecachebbolt.Option
+	BadgerOptions []writecachebadger.Option
+}

pkg/local_object_storage/writecache/doc.go

@@ -1,11 +0,0 @@
-// Package writecache implements write-cache for objects.
-//
-// Write-cache has 2 components:
-// 1. Key-value (bbolt) database for storing small objects.
-// 2. Filesystem tree for storing big objects.
-//
-// Flushing from the writecache to the main storage is done in the background.
-// To make it possible to serve Read requests after the object was flushed,
-// we maintain an LRU cache containing addresses of all the objects that
-// could be safely deleted. The actual deletion is done during eviction from this cache.
-package writecache

pkg/local_object_storage/writecache/flush_test.go

@@ -1,237 +0,0 @@
-package writecache
-
-import (
-	"context"
-	"os"
-	"path/filepath"
-	"sync/atomic"
-	"testing"
-
-	objectCore "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
-	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-node/pkg/util/logger"
-	checksumtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/checksum/test"
-	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
-	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
-	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
-	oidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id/test"
-	usertest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/user/test"
-	versionSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/version"
-	"github.com/stretchr/testify/require"
-	"go.etcd.io/bbolt"
-	"go.uber.org/zap/zaptest"
-)
-
-type objectPair struct {
-	addr oid.Address
-	obj  *objectSDK.Object
-}
-
-func TestFlush(t *testing.T) {
-	const (
-		objCount  = 4
-		smallSize = 256
-	)
-
-	newCache := func(t *testing.T, opts ...Option) (Cache, *blobstor.BlobStor, *meta.DB) {
-		dir := t.TempDir()
-		mb := meta.New(
-			meta.WithPath(filepath.Join(dir, "meta")),
-			meta.WithEpochState(dummyEpoch{}))
-		require.NoError(t, mb.Open(false))
-		require.NoError(t, mb.Init())
-
-		bs := blobstor.New(blobstor.WithStorages([]blobstor.SubStorage{
-			{
-				Storage: fstree.New(
-					fstree.WithPath(filepath.Join(dir, "blob")),
-					fstree.WithDepth(0),
-					fstree.WithDirNameLen(1)),
-			},
-		}))
-		require.NoError(t, bs.Open(false))
-		require.NoError(t, bs.Init())
-
-		wc := New(
-			append([]Option{
-				WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
-				WithPath(filepath.Join(dir, "writecache")),
-				WithSmallObjectSize(smallSize),
-				WithMetabase(mb),
-				WithBlobstor(bs),
-			}, opts...)...)
-		t.Cleanup(func() { require.NoError(t, wc.Close()) })
-		require.NoError(t, wc.Open(false))
-		require.NoError(t, wc.Init())
-
-		// First set mode for metabase and blobstor to prevent background flushes.
-		require.NoError(t, mb.SetMode(mode.ReadOnly))
-		require.NoError(t, bs.SetMode(mode.ReadOnly))
-
-		return wc, bs, mb
-	}
-
-	putObjects := func(t *testing.T, c Cache) []objectPair {
-		objects := make([]objectPair, objCount)
-		for i := range objects {
-			objects[i] = putObject(t, c, 1+(i%2)*smallSize)
-		}
-		return objects
-	}
-
-	check := func(t *testing.T, mb *meta.DB, bs *blobstor.BlobStor, objects []objectPair) {
-		for i := range objects {
-			var mPrm meta.StorageIDPrm
-			mPrm.SetAddress(objects[i].addr)
-
-			mRes, err := mb.StorageID(context.Background(), mPrm)
-			require.NoError(t, err)
-
-			var prm common.GetPrm
-			prm.Address = objects[i].addr
-			prm.StorageID = mRes.StorageID()
-
-			res, err := bs.Get(context.Background(), prm)
-			require.NoError(t, err)
-			require.Equal(t, objects[i].obj, res.Object)
-		}
-	}
-
-	t.Run("no errors", func(t *testing.T) {
-		wc, bs, mb := newCache(t)
-		objects := putObjects(t, wc)
-
-		require.NoError(t, bs.SetMode(mode.ReadWrite))
-		require.NoError(t, mb.SetMode(mode.ReadWrite))
-
-		require.NoError(t, wc.Flush(context.Background(), false))
-
-		check(t, mb, bs, objects)
-	})
-
-	t.Run("flush on moving to degraded mode", func(t *testing.T) {
-		wc, bs, mb := newCache(t)
-		objects := putObjects(t, wc)
-
-		// 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))
-
-		check(t, mb, bs, objects)
-	})
-
-	t.Run("ignore errors", func(t *testing.T) {
-		testIgnoreErrors := func(t *testing.T, f func(*cache)) {
-			var errCount atomic.Uint32
-			wc, bs, mb := newCache(t, WithReportErrorFunc(func(message string, err error) {
-				errCount.Add(1)
-			}))
-			objects := putObjects(t, wc)
-			f(wc.(*cache))
-
-			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.True(t, errCount.Load() > 0)
-			require.NoError(t, wc.Flush(context.Background(), true))
-
-			check(t, mb, bs, objects)
-		}
-		t.Run("db, invalid address", func(t *testing.T) {
-			testIgnoreErrors(t, func(c *cache) {
-				_, data := newObject(t, 1)
-				require.NoError(t, c.db.Batch(func(tx *bbolt.Tx) error {
-					b := tx.Bucket(defaultBucket)
-					return b.Put([]byte{1, 2, 3}, data)
-				}))
-			})
-		})
-		t.Run("db, invalid object", func(t *testing.T) {
-			testIgnoreErrors(t, func(c *cache) {
-				require.NoError(t, c.db.Batch(func(tx *bbolt.Tx) error {
-					b := tx.Bucket(defaultBucket)
-					return b.Put([]byte(oidtest.Address().EncodeToString()), []byte{1, 2, 3})
-				}))
-			})
-		})
-		t.Run("fs, read error", func(t *testing.T) {
-			testIgnoreErrors(t, func(c *cache) {
-				obj, data := newObject(t, 1)
-
-				var prm common.PutPrm
-				prm.Address = objectCore.AddressOf(obj)
-				prm.RawData = data
-
-				_, err := c.fsTree.Put(context.Background(), prm)
-				require.NoError(t, err)
-
-				p := prm.Address.Object().EncodeToString() + "." + prm.Address.Container().EncodeToString()
-				p = filepath.Join(c.fsTree.RootPath, p[:1], p[1:])
-
-				_, err = os.Stat(p) // sanity check
-				require.NoError(t, err)
-				require.NoError(t, os.Truncate(p, 0)) // corrupt the file contents, so that it can't be unmarshalled
-			})
-		})
-		t.Run("fs, invalid object", func(t *testing.T) {
-			testIgnoreErrors(t, func(c *cache) {
-				var prm common.PutPrm
-				prm.Address = oidtest.Address()
-				prm.RawData = []byte{1, 2, 3}
-				_, err := c.fsTree.Put(context.Background(), prm)
-				require.NoError(t, err)
-			})
-		})
-	})
-}
-
-func putObject(t *testing.T, c Cache, size int) objectPair {
-	obj, data := newObject(t, size)
-
-	var prm common.PutPrm
-	prm.Address = objectCore.AddressOf(obj)
-	prm.Object = obj
-	prm.RawData = data
-
-	_, err := c.Put(context.Background(), prm)
-	require.NoError(t, err)
-
-	return objectPair{prm.Address, prm.Object}
-
-}
-
-func newObject(t *testing.T, size int) (*objectSDK.Object, []byte) {
-	obj := objectSDK.New()
-	ver := versionSDK.Current()
-
-	obj.SetID(oidtest.ID())
-	obj.SetOwnerID(usertest.ID())
-	obj.SetContainerID(cidtest.ID())
-	obj.SetType(objectSDK.TypeRegular)
-	obj.SetVersion(&ver)
-	obj.SetPayloadChecksum(checksumtest.Checksum())
-	obj.SetPayloadHomomorphicHash(checksumtest.Checksum())
-	obj.SetPayload(make([]byte, size))
-
-	data, err := obj.Marshal()
-	require.NoError(t, err)
-	return obj, data
-}
-
-type dummyEpoch struct{}
-
-func (dummyEpoch) CurrentEpoch() uint64 {
-	return 0
-}

pkg/local_object_storage/writecache/generic_test.go

@@ -1,30 +0,0 @@
-package writecache
-
-import (
-	"os"
-	"path/filepath"
-	"strconv"
-	"testing"
-
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/storagetest"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
-	"github.com/stretchr/testify/require"
-	"go.uber.org/zap/zaptest"
-)
-
-func TestGeneric(t *testing.T) {
-	defer func() { _ = os.RemoveAll(t.Name()) }()
-
-	var n int
-	newCache := func(t *testing.T) storagetest.Component {
-		n++
-		dir := filepath.Join(t.Name(), strconv.Itoa(n))
-		require.NoError(t, os.MkdirAll(dir, os.ModePerm))
-		return New(
-			WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
-			WithFlushWorkersCount(2),
-			WithPath(dir))
-	}
-
-	storagetest.TestAll(t, newCache)
-}

pkg/local_object_storage/writecache/metrics.go

@@ -31,22 +31,24 @@ type Metrics interface {
 	Close()
 }
 
+func DefaultMetrics() Metrics { return metricsStub{} }
+
 type metricsStub struct{}
 
-func (s *metricsStub) Get(time.Duration, bool, StorageType) {}
+func (metricsStub) Get(time.Duration, bool, StorageType) {}
 
-func (s *metricsStub) Delete(time.Duration, bool, StorageType) {}
+func (metricsStub) Delete(time.Duration, bool, StorageType) {}
 
-func (s *metricsStub) Put(time.Duration, bool, StorageType) {}
+func (metricsStub) Put(time.Duration, bool, StorageType) {}
 
-func (s *metricsStub) SetEstimateSize(uint64, uint64) {}
+func (metricsStub) SetEstimateSize(uint64, uint64) {}
 
-func (s *metricsStub) SetMode(mode.Mode) {}
+func (metricsStub) SetMode(mode.Mode) {}
 
-func (s *metricsStub) SetActualCounters(uint64, uint64) {}
+func (metricsStub) SetActualCounters(uint64, uint64) {}
 
-func (s *metricsStub) Flush(bool, StorageType) {}
+func (metricsStub) Flush(bool, StorageType) {}
 
-func (s *metricsStub) Evict(StorageType) {}
+func (metricsStub) Evict(StorageType) {}
 
-func (s *metricsStub) Close() {}
+func (metricsStub) Close() {}

pkg/local_object_storage/writecache/writecache.go

@@ -2,18 +2,14 @@ package writecache
 
 import (
 	"context"
-	"os"
+	"errors"
-	"sync"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
-	"go.etcd.io/bbolt"
-	"go.uber.org/zap"
 )
 
 // Info groups the information about write-cache.
@@ -44,133 +40,13 @@ type Cache interface {
 	Close() error
 }
 
-type cache struct {
-	options
-
-	// mtx protects statistics, counters and compressFlags.
-	mtx sync.RWMutex
-
-	mode    mode.Mode
-	modeMtx sync.RWMutex
-
-	// compressFlags maps address of a big object to boolean value indicating
-	// whether object should be compressed.
-	compressFlags map[string]struct{}
-
-	// flushCh is a channel with objects to flush.
-	flushCh chan *objectSDK.Object
-	// closeCh is close channel, protected by modeMtx.
-	closeCh chan struct{}
-	// wg is a wait group for flush workers.
-	wg sync.WaitGroup
-	// store contains underlying database.
-	store
-	// fsTree contains big files stored directly on file-system.
-	fsTree *fstree.FSTree
-}
-
-// wcStorageType is used for write-cache operations logging.
-const wcStorageType = "write-cache"
-
-type objectInfo struct {
-	addr string
-	data []byte
-	obj  *objectSDK.Object
-}
-
-const (
-	defaultMaxObjectSize   = 64 * 1024 * 1024 // 64 MiB
-	defaultSmallObjectSize = 32 * 1024        // 32 KiB
-	defaultMaxCacheSize    = 1 << 30          // 1 GiB
-)
-
 var (
-	defaultBucket = []byte{0}
+	// ErrReadOnly is returned when Put/Write is performed in a read-only mode.
+	ErrReadOnly = logicerr.New("write-cache is in read-only mode")
+	// ErrNotInitialized is returned when write-cache is initializing.
+	ErrNotInitialized = logicerr.New("write-cache is not initialized yet")
+	// ErrBigObject is returned when object is too big to be placed in cache.
+	ErrBigObject = errors.New("too big object")
+	// ErrOutOfSpace is returned when there is no space left to put a new object.
+	ErrOutOfSpace = errors.New("no space left in the write cache")
 )
-
-// New creates new writecache instance.
-func New(opts ...Option) Cache {
-	c := &cache{
-		flushCh: make(chan *objectSDK.Object),
-		mode:    mode.ReadWrite,
-
-		compressFlags: make(map[string]struct{}),
-		options: options{
-			log:             &logger.Logger{Logger: zap.NewNop()},
-			maxObjectSize:   defaultMaxObjectSize,
-			smallObjectSize: defaultSmallObjectSize,
-			workersCount:    defaultFlushWorkersCount,
-			maxCacheSize:    defaultMaxCacheSize,
-			maxBatchSize:    bbolt.DefaultMaxBatchSize,
-			maxBatchDelay:   bbolt.DefaultMaxBatchDelay,
-			openFile:        os.OpenFile,
-			metrics:         &metricsStub{},
-		},
-	}
-
-	for i := range opts {
-		opts[i](&c.options)
-	}
-
-	return c
-}
-
-// SetLogger sets logger. It is used after the shard ID was generated to use it in logs.
-func (c *cache) SetLogger(l *logger.Logger) {
-	c.log = l
-}
-
-func (c *cache) DumpInfo() Info {
-	return Info{
-		Path: c.path,
-	}
-}
-
-// Open opens and initializes database. Reads object counters from the ObjectCounters instance.
-func (c *cache) Open(readOnly bool) error {
-	err := c.openStore(readOnly)
-	if err != nil {
-		return metaerr.Wrap(err)
-	}
-
-	// Opening after Close is done during maintenance mode,
-	// thus we need to create a channel here.
-	c.closeCh = make(chan struct{})
-
-	return metaerr.Wrap(c.initCounters())
-}
-
-// Init runs necessary services.
-func (c *cache) Init() error {
-	c.metrics.SetMode(c.mode)
-	c.runFlushLoop()
-	return nil
-}
-
-// Close closes db connection and stops services. Executes ObjectCounters.FlushAndClose op.
-func (c *cache) Close() error {
-	// We cannot lock mutex for the whole operation duration
-	// because it is taken by some background workers, so `wg.Wait()` is done without modeMtx.
-	c.modeMtx.Lock()
-	if c.closeCh != nil {
-		close(c.closeCh)
-	}
-	c.mode = mode.DegradedReadOnly // prevent new operations from being processed
-	c.modeMtx.Unlock()
-
-	c.wg.Wait()
-
-	c.modeMtx.Lock()
-	defer c.modeMtx.Unlock()
-
-	c.closeCh = nil
-	var err error
-	if c.db != nil {
-		err = c.db.Close()
-		if err != nil {
-			c.db = nil
-		}
-	}
-	c.metrics.Close()
-	return nil
-}

pkg/local_object_storage/writecache/writecachebadger/cachebadger.go

@@ -0,0 +1,129 @@
+package writecachebadger
+
+import (
+	"sync"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"go.uber.org/zap"
+)
+
+type cache struct {
+	options
+
+	mode    mode.Mode
+	modeMtx sync.RWMutex
+
+	// flushCh is a channel with objects to flush.
+	flushCh chan *objectSDK.Object
+	// closeCh is close channel, protected by modeMtx.
+	closeCh chan struct{}
+	// wg is a wait group for flush workers.
+	wg sync.WaitGroup
+	// store contains underlying database.
+	store
+}
+
+// wcStorageType is used for write-cache operations logging.
+const wcStorageType = "write-cache"
+
+type objectInfo struct {
+	addr oid.Address
+	data []byte
+	obj  *objectSDK.Object
+}
+
+const (
+	defaultMaxObjectSize   = 64 << 20 // 64 MiB
+	defaultSmallObjectSize = 32 << 10 // 32 KiB
+	defaultMaxCacheSize    = 1 << 30  // 1 GiB
+)
+
+// New creates new writecache instance.
+func New(opts ...Option) writecache.Cache {
+	c := &cache{
+		flushCh: make(chan *objectSDK.Object),
+		mode:    mode.ReadWrite,
+
+		options: options{
+			log:           &logger.Logger{Logger: zap.NewNop()},
+			maxObjectSize: defaultMaxObjectSize,
+			workersCount:  defaultFlushWorkersCount,
+			maxCacheSize:  defaultMaxCacheSize,
+			metrics:       writecache.DefaultMetrics(),
+		},
+	}
+
+	for i := range opts {
+		opts[i](&c.options)
+	}
+
+	return c
+}
+
+// SetLogger sets logger. It is used after the shard ID was generated to use it in logs.
+func (c *cache) SetLogger(l *logger.Logger) {
+	c.log = l
+}
+
+func (c *cache) DumpInfo() writecache.Info {
+	return writecache.Info{
+		Path: c.path,
+	}
+}
+
+// Open opens and initializes database. Reads object counters from the ObjectCounters instance.
+func (c *cache) Open(readOnly bool) error {
+	err := c.openStore(readOnly)
+	if err != nil {
+		return metaerr.Wrap(err)
+	}
+
+	// Opening after Close is done during maintenance mode,
+	// thus we need to create a channel here.
+	c.closeCh = make(chan struct{})
+
+	return metaerr.Wrap(c.initCounters())
+}
+
+// Init runs necessary services.
+func (c *cache) Init() error {
+	c.log.Info(logs.WritecacheBadgerInitExperimental)
+	c.metrics.SetMode(c.mode)
+	c.runFlushLoop()
+	c.runGCLoop()
+	return nil
+}
+
+// Close closes db connection and stops services. Executes ObjectCounters.FlushAndClose op.
+func (c *cache) Close() error {
+	// We cannot lock mutex for the whole operation duration
+	// because it is taken by some background workers, so `wg.Wait()` is done without modeMtx.
+	c.modeMtx.Lock()
+	if c.closeCh != nil {
+		close(c.closeCh)
+	}
+	c.mode = mode.DegradedReadOnly // prevent new operations from being processed
+	c.modeMtx.Unlock()
+
+	c.wg.Wait()
+
+	c.modeMtx.Lock()
+	defer c.modeMtx.Unlock()
+
+	c.closeCh = nil
+	var err error
+	if c.db != nil {
+		err = c.db.Close()
+		if err != nil {
+			c.db = nil
+		}
+	}
+	c.metrics.Close()
+	return nil
+}

pkg/local_object_storage/writecache/writecachebadger/delete.go

@@ -0,0 +1,70 @@
+package writecachebadger
+
+import (
+	"context"
+	"time"
+
+	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/dgraph-io/badger/v4"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Delete removes object from write-cache.
+//
+// Returns an error of type apistatus.ObjectNotFound if object is missing in write-cache.
+func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
+	_, span := tracing.StartSpanFromContext(ctx, "writecache.Delete",
+		trace.WithAttributes(
+			attribute.String("address", addr.EncodeToString()),
+		))
+	defer span.End()
+
+	deleted := false
+	storageType := writecache.StorageTypeUndefined
+	startedAt := time.Now()
+	defer func() {
+		c.metrics.Delete(time.Since(startedAt), deleted, storageType)
+	}()
+
+	c.modeMtx.RLock()
+	defer c.modeMtx.RUnlock()
+	if c.readOnly() {
+		return writecache.ErrReadOnly
+	}
+
+	saddr := addr.EncodeToString()
+
+	err := c.db.Update(func(tx *badger.Txn) error {
+		it, err := tx.Get([]byte(saddr))
+		if err != nil {
+			if err == badger.ErrKeyNotFound {
+				return logicerr.Wrap(apistatus.ObjectNotFound{})
+			}
+			return err
+		}
+		if it.ValueSize() > 0 {
+			storageType = writecache.StorageTypeDB
+			err := tx.Delete([]byte(saddr))
+			if err == nil {
+				storagelog.Write(c.log,
+					storagelog.AddressField(saddr),
+					storagelog.StorageTypeField(wcStorageType),
+					storagelog.OpField("db DELETE"),
+				)
+				deleted = true
+				c.objCounters.DecDB()
+			}
+			return err
+		}
+		return nil
+	})
+
+	return metaerr.Wrap(err)
+}

pkg/local_object_storage/writecache/writecachebadger/flush.go

@@ -0,0 +1,257 @@
+package writecachebadger
+
+import (
+	"bytes"
+	"context"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
+	objectCore "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
+	"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/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"github.com/dgraph-io/badger/v4"
+	"github.com/mr-tron/base58"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+	"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
+	// defaultFlushWorkersCount is number of workers for putting objects in main storage.
+	defaultFlushWorkersCount = 20
+	// defaultFlushInterval is default time interval between successive flushes.
+	defaultFlushInterval = time.Second
+)
+
+// runFlushLoop starts background workers which periodically flush objects to the blobstor.
+func (c *cache) runFlushLoop() {
+	for i := 0; i < c.workersCount; i++ {
+		c.wg.Add(1)
+		go c.workerFlushSmall()
+	}
+
+	c.wg.Add(1)
+	go func() {
+		defer c.wg.Done()
+
+		tt := time.NewTimer(defaultFlushInterval)
+		defer tt.Stop()
+
+		for {
+			select {
+			case <-tt.C:
+				c.flushSmallObjects()
+				tt.Reset(defaultFlushInterval)
+			case <-c.closeCh:
+				return
+			}
+		}
+	}()
+}
+
+func (c *cache) flushSmallObjects() {
+	var lastKey internalKey
+	var m []objectInfo
+	for {
+		select {
+		case <-c.closeCh:
+			return
+		default:
+		}
+
+		m = m[:0]
+
+		c.modeMtx.RLock()
+		if c.readOnly() {
+			c.modeMtx.RUnlock()
+			time.Sleep(time.Second)
+			continue
+		}
+
+		_ = c.db.View(func(tx *badger.Txn) error {
+			it := tx.NewIterator(badger.DefaultIteratorOptions)
+			defer it.Close()
+			if len(lastKey) == 0 {
+				it.Rewind()
+			} else {
+				it.Seek(lastKey[:])
+				if it.Valid() && bytes.Equal(it.Item().Key(), lastKey[:]) {
+					it.Next()
+				}
+			}
+			for ; it.Valid() && len(m) < flushBatchSize; it.Next() {
+				if got, want := int(it.Item().KeySize()), len(lastKey); got != want {
+					return fmt.Errorf("invalid db key len: got %d, want %d", got, want)
+				}
+				it.Item().KeyCopy(lastKey[:])
+				value, err := it.Item().ValueCopy(nil)
+				if err != nil {
+					return err
+				}
+				m = append(m, objectInfo{
+					addr: lastKey.address(),
+					data: value,
+				})
+			}
+			return nil
+		})
+
+		var count int
+		for i := range m {
+			obj := objectSDK.New()
+			if err := obj.Unmarshal(m[i].data); err != nil {
+				continue
+			}
+
+			count++
+			select {
+			case c.flushCh <- obj:
+			case <-c.closeCh:
+				c.modeMtx.RUnlock()
+				return
+			}
+		}
+
+		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[:])))
+	}
+}
+
+func (c *cache) reportFlushError(msg string, addr string, err error) {
+	if c.reportError != nil {
+		c.reportError(msg, err)
+	} else {
+		c.log.Error(msg,
+			zap.String("address", addr),
+			zap.Error(err))
+	}
+}
+
+// workerFlushSmall writes small objects to the main storage.
+func (c *cache) workerFlushSmall() {
+	defer c.wg.Done()
+
+	var obj *objectSDK.Object
+	for {
+		// Give priority to direct put.
+		select {
+		case obj = <-c.flushCh:
+		case <-c.closeCh:
+			return
+		}
+
+		err := c.flushObject(context.TODO(), obj, nil, writecache.StorageTypeDB)
+		if err != nil {
+			// Error is handled in flushObject.
+			continue
+		}
+
+		c.deleteFromDB([]string{objectCore.AddressOf(obj).EncodeToString()})
+	}
+}
+
+// flushObject is used to write object directly to the main storage.
+func (c *cache) flushObject(ctx context.Context, obj *objectSDK.Object, data []byte, st writecache.StorageType) error {
+	var err error
+
+	defer func() {
+		c.metrics.Flush(err == nil, st)
+	}()
+
+	addr := objectCore.AddressOf(obj)
+
+	var prm common.PutPrm
+	prm.Object = obj
+	prm.RawData = data
+
+	res, err := c.blobstor.Put(ctx, prm)
+	if err != nil {
+		if !errors.Is(err, common.ErrNoSpace) && !errors.Is(err, common.ErrReadOnly) &&
+			!errors.Is(err, blobstor.ErrNoPlaceFound) {
+			c.reportFlushError("can't flush an object to blobstor",
+				addr.EncodeToString(), err)
+		}
+		return err
+	}
+
+	var updPrm meta.UpdateStorageIDPrm
+	updPrm.SetAddress(addr)
+	updPrm.SetStorageID(res.StorageID)
+
+	_, err = c.metabase.UpdateStorageID(updPrm)
+	if err != nil {
+		c.reportFlushError("can't update object storage ID",
+			addr.EncodeToString(), err)
+	}
+	return err
+}
+
+// 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, "writecache.Flush",
+		trace.WithAttributes(
+			attribute.Bool("ignore_errors", ignoreErrors),
+		))
+	defer span.End()
+
+	c.modeMtx.RLock()
+	defer c.modeMtx.RUnlock()
+
+	return c.flush(ctx, ignoreErrors)
+}
+
+func (c *cache) flush(ctx context.Context, ignoreErrors bool) error {
+	return c.db.View(func(tx *badger.Txn) error {
+		it := tx.NewIterator(badger.DefaultIteratorOptions)
+		defer it.Close()
+		var key internalKey
+		for it.Rewind(); it.Valid(); it.Next() {
+			if got, want := int(it.Item().KeySize()), len(key); got != want {
+				err := fmt.Errorf("invalid db key len: got %d, want %d", got, want)
+				c.reportFlushError("can't decode object address from the DB", hex.EncodeToString(it.Item().Key()), metaerr.Wrap(err))
+				if ignoreErrors {
+					continue
+				}
+				return err
+			}
+			if err := it.Item().Value(func(data []byte) error {
+				var obj objectSDK.Object
+				if err := obj.Unmarshal(data); err != nil {
+					copy(key[:], it.Item().Key())
+					c.reportFlushError("can't unmarshal an object from the DB", key.address().EncodeToString(), metaerr.Wrap(err))
+					if ignoreErrors {
+						return nil
+					}
+					return err
+				}
+
+				return c.flushObject(ctx, &obj, data, writecache.StorageTypeDB)
+			}); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}

pkg/local_object_storage/writecache/writecachebadger/flush_test.go

@@ -0,0 +1,65 @@
+package writecachebadger
+
+import (
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
+	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachetest"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	oidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id/test"
+	"github.com/dgraph-io/badger/v4"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestFlush(t *testing.T) {
+	createCacheFn := func(t *testing.T, smallSize uint64, mb *meta.DB, bs *blobstor.BlobStor, opts ...Option) writecache.Cache {
+		return New(
+			append([]Option{
+				WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+				WithPath(filepath.Join(t.TempDir(), "writecache")),
+				WithMetabase(mb),
+				WithBlobstor(bs),
+				WithGCInterval(1 * time.Second),
+			}, opts...)...)
+	}
+
+	errCountOpt := func() (Option, *atomic.Uint32) {
+		cnt := &atomic.Uint32{}
+		return WithReportErrorFunc(func(string, error) {
+			cnt.Add(1)
+		}), cnt
+	}
+
+	failures := []writecachetest.TestFailureInjector[Option]{
+		{
+			Desc: "db, invalid address",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				obj := testutil.GenerateObject()
+				data, err := obj.Marshal()
+				require.NoError(t, err)
+				require.NoError(t, c.db.Update(func(tx *badger.Txn) error {
+					return tx.Set([]byte{1, 2, 3}, data)
+				}))
+			},
+		},
+		{
+			Desc: "db, invalid object",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				require.NoError(t, c.db.Update(func(tx *badger.Txn) error {
+					return tx.Set([]byte(oidtest.Address().EncodeToString()), []byte{1, 2, 3})
+				}))
+			},
+		},
+	}
+
+	writecachetest.TestFlush(t, createCacheFn, errCountOpt, failures...)
+}

pkg/local_object_storage/writecache/writecachebadger/gc.go

@@ -0,0 +1,31 @@
+package writecachebadger
+
+import (
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
+)
+
+func (c *cache) runGCLoop() {
+	c.wg.Add(1)
+
+	go func() {
+		defer c.wg.Done()
+
+		t := time.NewTicker(c.gcInterval)
+		defer t.Stop()
+
+		for {
+			select {
+			case <-c.closeCh:
+				return
+			case <-t.C:
+				// 0.5 is the recommended value so that write amplification of the value log is 2.
+				// See https://pkg.go.dev/github.com/dgraph-io/badger/v4#DB.RunValueLogGC for more info.
+				for c.db.RunValueLogGC(0.5) == nil {
+					c.log.Debug(logs.WritecacheDBValueLogGCRunCompleted)
+				}
+			}
+		}
+	}()
+}

pkg/local_object_storage/writecache/writecachebadger/generic_test.go

@@ -0,0 +1,20 @@
+package writecachebadger
+
+import (
+	"testing"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/storagetest"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestGeneric(t *testing.T) {
+	storagetest.TestAll(t, func(t *testing.T) storagetest.Component {
+		return New(
+			WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+			WithFlushWorkersCount(2),
+			WithPath(t.TempDir()),
+			WithGCInterval(1*time.Second))
+	})
+}

pkg/local_object_storage/writecache/writecachebadger/get.go

@@ -0,0 +1,95 @@
+package writecachebadger
+
+import (
+	"context"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/dgraph-io/badger/v4"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Get returns object from write-cache.
+//
+// Returns an error of type apistatus.ObjectNotFound if the requested object is missing in write-cache.
+func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, error) {
+	_, span := tracing.StartSpanFromContext(ctx, "writecache.Get",
+		trace.WithAttributes(
+			attribute.String("address", addr.EncodeToString()),
+		))
+	defer span.End()
+
+	obj, err := c.getInternal(addr)
+	return obj, metaerr.Wrap(err)
+}
+
+func (c *cache) getInternal(addr oid.Address) (*objectSDK.Object, error) {
+	found := false
+	storageType := writecache.StorageTypeUndefined
+	startedAt := time.Now()
+	defer func() {
+		c.metrics.Get(time.Since(startedAt), found, storageType)
+	}()
+
+	k := addr2key(addr)
+	value, err := Get(c.db, k[:])
+	if err == nil {
+		obj := objectSDK.New()
+		found = true
+		storageType = writecache.StorageTypeDB
+		return obj, obj.Unmarshal(value)
+	}
+
+	return nil, logicerr.Wrap(apistatus.ObjectNotFound{})
+}
+
+// Head returns object header from write-cache.
+//
+// Returns an error of type apistatus.ObjectNotFound if the requested object is missing in write-cache.
+func (c *cache) Head(ctx context.Context, addr oid.Address) (*objectSDK.Object, error) {
+	_, span := tracing.StartSpanFromContext(ctx, "writecache.Head",
+		trace.WithAttributes(
+			attribute.String("address", addr.EncodeToString()),
+		))
+	defer span.End()
+
+	obj, err := c.getInternal(addr)
+	if err != nil {
+		return nil, metaerr.Wrap(err)
+	}
+
+	return obj.CutPayload(), nil
+}
+
+// Get fetches object from the underlying database.
+// Key should be a stringified address.
+//
+// Returns an error of type apistatus.ObjectNotFound if the requested object is missing in db.
+func Get(db *badger.DB, key []byte) ([]byte, error) {
+	var value []byte
+
+	err := db.View(func(tx *badger.Txn) error {
+		it, err := tx.Get(key)
+		if err != nil {
+			if err == badger.ErrKeyNotFound {
+				return logicerr.Wrap(apistatus.ObjectNotFound{})
+			}
+			return err
+		}
+		v, err := it.ValueCopy(nil)
+		if err != nil {
+			return err
+		}
+		value = v
+		return nil
+	})
+
+	return value, metaerr.Wrap(err)
+}

pkg/local_object_storage/writecache/writecachebadger/iterate.go

@@ -0,0 +1,32 @@
+package writecachebadger
+
+import (
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/dgraph-io/badger/v4"
+)
+
+// IterateDB iterates over all objects stored in badger.DB instance and passes them to f until error return.
+// It is assumed that db is an underlying database of some WriteCache instance.
+//
+// DB must not be nil and should be opened.
+func IterateDB(db *badger.DB, f func(oid.Address) error) error {
+	return metaerr.Wrap(db.View(func(tx *badger.Txn) error {
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := tx.NewIterator(opts)
+		for it.Rewind(); it.Valid(); it.Next() {
+			var key internalKey
+			if got, want := len(it.Item().Key()), len(key); got != want {
+				return fmt.Errorf("invalid db key len: got %d, want %d", got, want)
+			}
+			copy(key[:], it.Item().Key())
+			if err := f(key.address()); err != nil {
+				return err
+			}
+		}
+		return nil
+	}))
+}

pkg/local_object_storage/writecache/writecachebadger/mode.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebadger
 
 import (
 	"context"
@@ -7,18 +7,11 @@ import (
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
 )
 
-// ErrReadOnly is returned when Put/Write is performed in a read-only mode.
-var ErrReadOnly = logicerr.New("write-cache is in read-only mode")
-
-// ErrNotInitialized is returned when write-cache is initializing.
-var ErrNotInitialized = logicerr.New("write-cache is not initialized yet")
-
 // SetMode sets write-cache mode of operation.
 // When shard is put in read-only mode all objects in memory are flushed to disk
 // and all background jobs are suspended.

pkg/local_object_storage/writecache/writecachebadger/options.go

@@ -0,0 +1,141 @@
+package writecachebadger
+
+import (
+	"context"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"go.uber.org/zap"
+)
+
+// Option represents write-cache configuration option.
+type Option func(*options)
+
+// meta is an interface for a metabase.
+type metabase interface {
+	Exists(context.Context, meta.ExistsPrm) (meta.ExistsRes, error)
+	StorageID(context.Context, meta.StorageIDPrm) (meta.StorageIDRes, error)
+	UpdateStorageID(meta.UpdateStorageIDPrm) (meta.UpdateStorageIDRes, error)
+}
+
+// blob is an interface for the blobstor.
+type blob interface {
+	Put(context.Context, common.PutPrm) (common.PutRes, error)
+	NeedsCompression(obj *objectSDK.Object) bool
+	Exists(ctx context.Context, res common.ExistsPrm) (common.ExistsRes, error)
+}
+
+type options struct {
+	log *logger.Logger
+	// path is a path to a directory for write-cache.
+	path string
+	// blobstor is the main persistent storage.
+	blobstor blob
+	// metabase is the metabase instance.
+	metabase metabase
+	// maxObjectSize is the maximum size of the object stored in the write-cache.
+	maxObjectSize uint64
+	// workersCount is the number of workers flushing objects in parallel.
+	workersCount int
+	// maxCacheSize is the maximum total size of all objects saved in cache (DB + FS).
+	// 1 GiB by default.
+	maxCacheSize uint64
+	// objCounters contains atomic counters for the number of objects stored in cache.
+	objCounters counters
+	// noSync is true iff FSTree allows unsynchronized writes.
+	noSync bool
+	// reportError is the function called when encountering disk errors in background workers.
+	reportError func(string, error)
+	// metrics is metrics implementation
+	metrics writecache.Metrics
+	// gcInterval is the interval duration to run the GC cycle.
+	gcInterval time.Duration
+}
+
+// WithLogger sets logger.
+func WithLogger(log *logger.Logger) Option {
+	return func(o *options) {
+		o.log = &logger.Logger{Logger: log.With(zap.String("component", "WriteCache"))}
+	}
+}
+
+// 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
+	}
+}
+
+// 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
+		}
+	}
+}
+
+func WithFlushWorkersCount(c int) Option {
+	return func(o *options) {
+		if c > 0 {
+			o.workersCount = c
+		}
+	}
+}
+
+// WithMaxCacheSize sets maximum write-cache size in bytes.
+func WithMaxCacheSize(sz uint64) Option {
+	return func(o *options) {
+		o.maxCacheSize = sz
+	}
+}
+
+// WithNoSync sets an option to allow returning to caller on PUT before write is persisted.
+// Note, that we use this flag for FSTree only and DO NOT use it for a bolt DB because
+// we cannot yet properly handle the corrupted database during the startup. This SHOULD NOT
+// be relied upon and may be changed in future.
+func WithNoSync(noSync bool) Option {
+	return func(o *options) {
+		o.noSync = noSync
+	}
+}
+
+// WithReportErrorFunc sets error reporting function.
+func WithReportErrorFunc(f func(string, error)) Option {
+	return func(o *options) {
+		o.reportError = f
+	}
+}
+
+// WithMetrics sets metrics implementation.
+func WithMetrics(metrics writecache.Metrics) Option {
+	return func(o *options) {
+		o.metrics = metrics
+	}
+}
+
+// WithGCInterval sets the duration of the interval to run GC cycles.
+func WithGCInterval(d time.Duration) Option {
+	return func(o *options) {
+		o.gcInterval = d
+	}
+}

pkg/local_object_storage/writecache/writecachebadger/put.go

@@ -0,0 +1,82 @@
+package writecachebadger
+
+import (
+	"context"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// Put puts object to write-cache.
+//
+// Returns ErrReadOnly if write-cache is in R/O mode.
+// Returns ErrNotInitialized if write-cache has not been initialized yet.
+// Returns ErrOutOfSpace if saving an object leads to WC's size overflow.
+// Returns ErrBigObject if an objects exceeds maximum object size.
+func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, error) {
+	_, span := tracing.StartSpanFromContext(ctx, "writecache.Put",
+		trace.WithAttributes(
+			attribute.String("address", prm.Address.EncodeToString()),
+			attribute.Bool("dont_compress", prm.DontCompress),
+		))
+	defer span.End()
+
+	startedAt := time.Now()
+	added := false
+	storageType := writecache.StorageTypeUndefined
+	defer func() {
+		c.metrics.Put(time.Since(startedAt), added, storageType)
+	}()
+
+	c.modeMtx.RLock()
+	defer c.modeMtx.RUnlock()
+	if c.readOnly() {
+		return common.PutRes{}, writecache.ErrReadOnly
+	}
+
+	sz := uint64(len(prm.RawData))
+	if sz > c.maxObjectSize {
+		return common.PutRes{}, writecache.ErrBigObject
+	}
+
+	oi := objectInfo{
+		addr: prm.Address,
+		obj:  prm.Object,
+		data: prm.RawData,
+	}
+
+	storageType = writecache.StorageTypeDB
+	err := c.put(oi)
+	if err == nil {
+		added = true
+	}
+	return common.PutRes{}, err
+}
+
+// put persists objects to the write-cache database and
+// pushes the to the flush workers queue.
+func (c *cache) put(obj objectInfo) error {
+	cacheSize := c.estimateCacheSize()
+	if c.maxCacheSize < c.incSizeDB(cacheSize) {
+		return writecache.ErrOutOfSpace
+	}
+
+	wb := c.db.NewWriteBatch()
+	k := addr2key(obj.addr)
+	_ = wb.Set(k[:], obj.data)
+	err := wb.Flush()
+	if err == nil {
+		storagelog.Write(c.log,
+			storagelog.AddressField(obj.addr),
+			storagelog.StorageTypeField(wcStorageType),
+			storagelog.OpField("db PUT"),
+		)
+		c.objCounters.IncDB()
+	}
+	return err
+}

pkg/local_object_storage/writecache/writecachebadger/state.go

@@ -0,0 +1,57 @@
+package writecachebadger
+
+import (
+	"fmt"
+	"math"
+	"sync/atomic"
+
+	"github.com/dgraph-io/badger/v4"
+)
+
+func (c *cache) estimateCacheSize() uint64 {
+	onDiskSize, _ := c.db.EstimateSize(nil)
+	c.metrics.SetEstimateSize(onDiskSize, 0)
+	return onDiskSize
+}
+
+func (c *cache) incSizeDB(sz uint64) uint64 {
+	return sz + c.maxObjectSize
+}
+
+type counters struct {
+	cDB atomic.Uint64
+}
+
+func (x *counters) IncDB() {
+	x.cDB.Add(1)
+}
+
+func (x *counters) DecDB() {
+	x.cDB.Add(math.MaxUint64)
+}
+
+func (x *counters) DB() uint64 {
+	return x.cDB.Load()
+}
+
+func (c *cache) initCounters() error {
+	var inDB uint64
+	err := c.db.View(func(tx *badger.Txn) error {
+		opts := badger.DefaultIteratorOptions
+		opts.PrefetchValues = false
+		it := tx.NewIterator(opts)
+		defer it.Close()
+		for it.Rewind(); it.Valid(); it.Next() {
+			inDB++
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("could not read write-cache DB counter: %w", err)
+	}
+
+	c.objCounters.cDB.Store(inDB)
+	c.metrics.SetActualCounters(inDB, 0)
+
+	return nil
+}

pkg/local_object_storage/writecache/writecachebadger/storage.go

@@ -0,0 +1,91 @@
+package writecachebadger
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
+	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
+	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/dgraph-io/badger/v4"
+	"go.uber.org/zap"
+)
+
+// store represents persistent storage with in-memory LRU cache
+// for flushed items on top of it.
+type store struct {
+	db *badger.DB
+}
+
+type internalKey [len(cid.ID{}) + len(oid.ID{})]byte
+
+func (k internalKey) address() oid.Address {
+	var addr oid.Address
+	var cnr cid.ID
+	var obj oid.ID
+	copy(cnr[:], k[:len(cnr)])
+	copy(obj[:], k[len(cnr):])
+	addr.SetContainer(cnr)
+	addr.SetObject(obj)
+	return addr
+}
+
+func addr2key(addr oid.Address) internalKey {
+	var key internalKey
+	cnr, obj := addr.Container(), addr.Object()
+	copy(key[:len(cnr)], cnr[:])
+	copy(key[len(cnr):], obj[:])
+	return key
+}
+
+const dbName = "small.badger"
+
+func (c *cache) openStore(readOnly bool) error {
+	err := util.MkdirAllX(c.path, os.ModePerm)
+	if err != nil {
+		return err
+	}
+
+	c.db, err = OpenDB(filepath.Join(c.path, dbName), readOnly, c.log)
+	if err != nil {
+		return fmt.Errorf("could not open database: %w", err)
+	}
+
+	return nil
+}
+
+func (c *cache) deleteFromDB(keys []string) []string {
+	if len(keys) == 0 {
+		return keys
+	}
+
+	wb := c.db.NewWriteBatch()
+
+	var errorIndex int
+	for errorIndex = range keys {
+		if err := wb.Delete([]byte(keys[errorIndex])); err != nil {
+			break
+		}
+	}
+
+	for i := 0; i < errorIndex; i++ {
+		c.objCounters.DecDB()
+		c.metrics.Evict(writecache.StorageTypeDB)
+		storagelog.Write(c.log,
+			storagelog.AddressField(keys[i]),
+			storagelog.StorageTypeField(wcStorageType),
+			storagelog.OpField("db DELETE"),
+		)
+	}
+
+	if err := wb.Flush(); err != nil {
+		c.log.Error(logs.WritecacheCantRemoveObjectsFromTheDatabase, zap.Error(err))
+	}
+
+	copy(keys, keys[errorIndex:])
+	return keys[:len(keys)-errorIndex]
+}

pkg/local_object_storage/writecache/writecachebadger/util.go

@@ -0,0 +1,36 @@
+package writecachebadger
+
+import (
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	"github.com/dgraph-io/badger/v4"
+)
+
+// OpenDB opens a badger instance for write-cache. Opens in read-only mode if ro is true.
+func OpenDB(p string, ro bool, l *logger.Logger) (*badger.DB, error) {
+	return badger.Open(badger.DefaultOptions(p).
+		WithReadOnly(ro).
+		WithLoggingLevel(badger.ERROR).
+		WithLogger(badgerLoggerWrapper{l}))
+}
+
+type badgerLoggerWrapper struct {
+	l *logger.Logger
+}
+
+func (w badgerLoggerWrapper) Errorf(msg string, args ...any) {
+	w.l.Error(fmt.Sprintf(msg, args...))
+}
+
+func (w badgerLoggerWrapper) Warningf(msg string, args ...any) {
+	w.l.Error(fmt.Sprintf(msg, args...))
+}
+
+func (w badgerLoggerWrapper) Infof(msg string, args ...any) {
+	w.l.Error(fmt.Sprintf(msg, args...))
+}
+
+func (w badgerLoggerWrapper) Debugf(msg string, args ...any) {
+	w.l.Error(fmt.Sprintf(msg, args...))
+}

pkg/local_object_storage/writecache/writecachebbolt/cachebbolt.go

@@ -0,0 +1,146 @@
+package writecachebbolt
+
+import (
+	"os"
+	"sync"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap"
+)
+
+type cache struct {
+	options
+
+	// mtx protects statistics, counters and compressFlags.
+	mtx sync.RWMutex
+
+	mode    mode.Mode
+	modeMtx sync.RWMutex
+
+	// compressFlags maps address of a big object to boolean value indicating
+	// whether object should be compressed.
+	compressFlags map[string]struct{}
+
+	// flushCh is a channel with objects to flush.
+	flushCh chan *objectSDK.Object
+	// closeCh is close channel, protected by modeMtx.
+	closeCh chan struct{}
+	// wg is a wait group for flush workers.
+	wg sync.WaitGroup
+	// store contains underlying database.
+	store
+	// fsTree contains big files stored directly on file-system.
+	fsTree *fstree.FSTree
+}
+
+// wcStorageType is used for write-cache operations logging.
+const wcStorageType = "write-cache"
+
+type objectInfo struct {
+	addr string
+	data []byte
+	obj  *objectSDK.Object
+}
+
+const (
+	defaultMaxObjectSize   = 64 * 1024 * 1024 // 64 MiB
+	defaultSmallObjectSize = 32 * 1024        // 32 KiB
+	defaultMaxCacheSize    = 1 << 30          // 1 GiB
+)
+
+var (
+	defaultBucket = []byte{0}
+)
+
+// New creates new writecache instance.
+func New(opts ...Option) writecache.Cache {
+	c := &cache{
+		flushCh: make(chan *objectSDK.Object),
+		mode:    mode.ReadWrite,
+
+		compressFlags: make(map[string]struct{}),
+		options: options{
+			log:             &logger.Logger{Logger: zap.NewNop()},
+			maxObjectSize:   defaultMaxObjectSize,
+			smallObjectSize: defaultSmallObjectSize,
+			workersCount:    defaultFlushWorkersCount,
+			maxCacheSize:    defaultMaxCacheSize,
+			maxBatchSize:    bbolt.DefaultMaxBatchSize,
+			maxBatchDelay:   bbolt.DefaultMaxBatchDelay,
+			openFile:        os.OpenFile,
+			metrics:         writecache.DefaultMetrics(),
+		},
+	}
+
+	for i := range opts {
+		opts[i](&c.options)
+	}
+
+	return c
+}
+
+// SetLogger sets logger. It is used after the shard ID was generated to use it in logs.
+func (c *cache) SetLogger(l *logger.Logger) {
+	c.log = l
+}
+
+func (c *cache) DumpInfo() writecache.Info {
+	return writecache.Info{
+		Path: c.path,
+	}
+}
+
+// Open opens and initializes database. Reads object counters from the ObjectCounters instance.
+func (c *cache) Open(readOnly bool) error {
+	err := c.openStore(readOnly)
+	if err != nil {
+		return metaerr.Wrap(err)
+	}
+
+	// Opening after Close is done during maintenance mode,
+	// thus we need to create a channel here.
+	c.closeCh = make(chan struct{})
+
+	return metaerr.Wrap(c.initCounters())
+}
+
+// Init runs necessary services.
+func (c *cache) Init() error {
+	c.metrics.SetMode(c.mode)
+	c.runFlushLoop()
+	return nil
+}
+
+// Close closes db connection and stops services. Executes ObjectCounters.FlushAndClose op.
+func (c *cache) Close() error {
+	// We cannot lock mutex for the whole operation duration
+	// because it is taken by some background workers, so `wg.Wait()` is done without modeMtx.
+	c.modeMtx.Lock()
+	if c.closeCh != nil {
+		close(c.closeCh)
+	}
+	c.mode = mode.DegradedReadOnly // prevent new operations from being processed
+	c.modeMtx.Unlock()
+
+	c.wg.Wait()
+
+	c.modeMtx.Lock()
+	defer c.modeMtx.Unlock()
+
+	c.closeCh = nil
+	var err error
+	if c.db != nil {
+		err = c.db.Close()
+		if err != nil {
+			c.db = nil
+		}
+	}
+	c.metrics.Close()
+	return nil
+}

pkg/local_object_storage/writecache/writecachebbolt/delete.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"context"
@@ -7,6 +7,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
 	"go.etcd.io/bbolt"
@@ -25,7 +26,7 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 	defer span.End()
 
 	deleted := false
-	storageType := StorageTypeUndefined
+	storageType := writecache.StorageTypeUndefined
 	startedAt := time.Now()
 	defer func() {
 		c.metrics.Delete(time.Since(startedAt), deleted, storageType)
@@ -34,7 +35,7 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 	c.modeMtx.RLock()
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
-		return ErrReadOnly
+		return writecache.ErrReadOnly
 	}
 
 	saddr := addr.EncodeToString()
@@ -47,7 +48,7 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 	})
 
 	if dataSize > 0 {
-		storageType = StorageTypeDB
+		storageType = writecache.StorageTypeDB
 		err := c.db.Update(func(tx *bbolt.Tx) error {
 			b := tx.Bucket(defaultBucket)
 			err := b.Delete([]byte(saddr))
@@ -66,7 +67,7 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 		return nil
 	}
 
-	storageType = StorageTypeFSTree
+	storageType = writecache.StorageTypeFSTree
 	_, err := c.fsTree.Delete(ctx, common.DeletePrm{Address: addr})
 	if err == nil {
 		storagelog.Write(c.log,

pkg/local_object_storage/writecache/writecachebbolt/flush.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"bytes"
@@ -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/writecache"
 	"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"
@@ -210,7 +211,7 @@ func (c *cache) flushFSTree(ctx context.Context, ignoreErrors bool) error {
 			return err
 		}
 
-		err = c.flushObject(ctx, &obj, data, StorageTypeFSTree)
+		err = c.flushObject(ctx, &obj, data, writecache.StorageTypeFSTree)
 		if err != nil {
 			if ignoreErrors {
 				return nil
@@ -239,7 +240,7 @@ func (c *cache) workerFlushSmall() {
 			return
 		}
 
-		err := c.flushObject(context.TODO(), obj, nil, StorageTypeDB)
+		err := c.flushObject(context.TODO(), obj, nil, writecache.StorageTypeDB)
 		if err != nil {
 			// Error is handled in flushObject.
 			continue
@@ -250,7 +251,7 @@ func (c *cache) workerFlushSmall() {
 }
 
 // flushObject is used to write object directly to the main storage.
-func (c *cache) flushObject(ctx context.Context, obj *objectSDK.Object, data []byte, st StorageType) error {
+func (c *cache) flushObject(ctx context.Context, obj *objectSDK.Object, data []byte, st writecache.StorageType) error {
 	var err error
 
 	defer func() {
@@ -330,7 +331,7 @@ func (c *cache) flush(ctx context.Context, ignoreErrors bool) error {
 				return err
 			}
 
-			if err := c.flushObject(ctx, &obj, data, StorageTypeDB); err != nil {
+			if err := c.flushObject(ctx, &obj, data, writecache.StorageTypeDB); err != nil {
 				return err
 			}
 		}

pkg/local_object_storage/writecache/writecachebbolt/flush_test.go

@@ -0,0 +1,106 @@
+package writecachebbolt
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+
+	objectCore "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
+	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache/writecachetest"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	oidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id/test"
+	"github.com/stretchr/testify/require"
+	"go.etcd.io/bbolt"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestFlush(t *testing.T) {
+	createCacheFn := func(t *testing.T, smallSize uint64, mb *meta.DB, bs *blobstor.BlobStor, opts ...Option) writecache.Cache {
+		return New(
+			append([]Option{
+				WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+				WithPath(filepath.Join(t.TempDir(), "writecache")),
+				WithSmallObjectSize(smallSize),
+				WithMetabase(mb),
+				WithBlobstor(bs),
+			}, opts...)...)
+	}
+
+	errCountOpt := func() (Option, *atomic.Uint32) {
+		cnt := &atomic.Uint32{}
+		return WithReportErrorFunc(func(string, error) {
+			cnt.Add(1)
+		}), cnt
+	}
+
+	failures := []writecachetest.TestFailureInjector[Option]{
+		{
+			Desc: "db, invalid address",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				obj := testutil.GenerateObject()
+				data, err := obj.Marshal()
+				require.NoError(t, err)
+				require.NoError(t, c.db.Batch(func(tx *bbolt.Tx) error {
+					b := tx.Bucket(defaultBucket)
+					return b.Put([]byte{1, 2, 3}, data)
+				}))
+			},
+		},
+		{
+			Desc: "db, invalid object",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				require.NoError(t, c.db.Batch(func(tx *bbolt.Tx) error {
+					b := tx.Bucket(defaultBucket)
+					k := []byte(oidtest.Address().EncodeToString())
+					v := []byte{1, 2, 3}
+					return b.Put(k, v)
+				}))
+			},
+		},
+		{
+			Desc: "fs, read error",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				obj := testutil.GenerateObject()
+				data, err := obj.Marshal()
+				require.NoError(t, err)
+
+				var prm common.PutPrm
+				prm.Address = objectCore.AddressOf(obj)
+				prm.RawData = data
+
+				_, err = c.fsTree.Put(context.Background(), prm)
+				require.NoError(t, err)
+
+				p := prm.Address.Object().EncodeToString() + "." + prm.Address.Container().EncodeToString()
+				p = filepath.Join(c.fsTree.RootPath, p[:1], p[1:])
+
+				_, err = os.Stat(p) // sanity check
+				require.NoError(t, err)
+				require.NoError(t, os.Truncate(p, 0)) // corrupt the file contents, so that it can't be unmarshalled
+			},
+		},
+		{
+			Desc: "fs, invalid object",
+			InjectFn: func(t *testing.T, wc writecache.Cache) {
+				c := wc.(*cache)
+				var prm common.PutPrm
+				prm.Address = oidtest.Address()
+				prm.RawData = []byte{1, 2, 3}
+				_, err := c.fsTree.Put(context.Background(), prm)
+				require.NoError(t, err)
+			},
+		},
+	}
+
+	writecachetest.TestFlush(t, createCacheFn, errCountOpt, failures...)
+}

pkg/local_object_storage/writecache/writecachebbolt/generic_test.go

@@ -0,0 +1,18 @@
+package writecachebbolt
+
+import (
+	"testing"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/storagetest"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	"go.uber.org/zap/zaptest"
+)
+
+func TestGeneric(t *testing.T) {
+	storagetest.TestAll(t, func(t *testing.T) storagetest.Component {
+		return New(
+			WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+			WithFlushWorkersCount(2),
+			WithPath(t.TempDir()))
+	})
+}

pkg/local_object_storage/writecache/writecachebbolt/get.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"context"
@@ -7,6 +7,7 @@ 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"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
@@ -35,7 +36,7 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 
 func (c *cache) getInternal(ctx context.Context, saddr string, addr oid.Address) (*objectSDK.Object, error) {
 	found := false
-	storageType := StorageTypeUndefined
+	storageType := writecache.StorageTypeUndefined
 	startedAt := time.Now()
 	defer func() {
 		c.metrics.Get(time.Since(startedAt), found, storageType)
@@ -45,7 +46,7 @@ func (c *cache) getInternal(ctx context.Context, saddr string, addr oid.Address)
 	if err == nil {
 		obj := objectSDK.New()
 		found = true
-		storageType = StorageTypeDB
+		storageType = writecache.StorageTypeDB
 		return obj, obj.Unmarshal(value)
 	}
 
@@ -55,7 +56,7 @@ func (c *cache) getInternal(ctx context.Context, saddr string, addr oid.Address)
 	}
 
 	found = true
-	storageType = StorageTypeFSTree
+	storageType = writecache.StorageTypeFSTree
 	return res.Object, nil
 }
 

pkg/local_object_storage/writecache/writecachebbolt/iterate.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"errors"

pkg/local_object_storage/writecache/writecachebbolt/mode.go

@@ -0,0 +1,75 @@
+package writecachebbolt
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
+	"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"
+)
+
+// SetMode sets write-cache mode of operation.
+// When shard is put in read-only mode all objects in memory are flushed to disk
+// and all background jobs are suspended.
+func (c *cache) SetMode(m mode.Mode) error {
+	ctx, span := tracing.StartSpanFromContext(context.TODO(), "writecache.SetMode",
+		trace.WithAttributes(
+			attribute.String("mode", m.String()),
+		))
+	defer span.End()
+
+	err := c.setMode(ctx, m)
+	if err == nil {
+		c.metrics.SetMode(m)
+	}
+	return err
+}
+
+// setMode applies new mode. Must be called with cache.modeMtx lock taken.
+func (c *cache) setMode(ctx context.Context, m mode.Mode) error {
+	var err error
+	turnOffMeta := m.NoMetabase()
+
+	if turnOffMeta && !c.mode.NoMetabase() {
+		err = c.flush(ctx, true)
+		if err != nil {
+			return err
+		}
+	}
+
+	if c.db != nil {
+		if err = c.db.Close(); err != nil {
+			return fmt.Errorf("can't close write-cache database: %w", err)
+		}
+	}
+
+	// Suspend producers to ensure there are channel send operations in fly.
+	// flushCh is populated by `flush` with `modeMtx` taken, thus waiting until it is empty
+	// guarantees that there are no in-fly operations.
+	for len(c.flushCh) != 0 {
+		c.log.Info(logs.WritecacheWaitingForChannelsToFlush)
+		time.Sleep(time.Second)
+	}
+
+	if turnOffMeta {
+		c.mode = m
+		return nil
+	}
+
+	if err = c.openStore(m.ReadOnly()); err != nil {
+		return err
+	}
+
+	c.mode = m
+	return nil
+}
+
+// readOnly returns true if current mode is read-only.
+// `c.modeMtx` must be taken.
+func (c *cache) readOnly() bool {
+	return c.mode.ReadOnly()
+}

pkg/local_object_storage/writecache/writecachebbolt/options.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"context"
@@ -9,6 +9,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	"go.uber.org/zap"
@@ -61,7 +62,7 @@ type options struct {
 	// openFile is the function called internally by bbolt to open database files. Useful for hermetic testing.
 	openFile func(string, int, fs.FileMode) (*os.File, error)
 	// metrics is metrics implementation
-	metrics Metrics
+	metrics writecache.Metrics
 }
 
 // WithLogger sets logger.
@@ -168,7 +169,7 @@ func WithOpenFile(f func(string, int, fs.FileMode) (*os.File, error)) Option {
 }
 
 // WithMetrics sets metrics implementation.
-func WithMetrics(metrics Metrics) Option {
+func WithMetrics(metrics writecache.Metrics) Option {
 	return func(o *options) {
 		o.metrics = metrics
 	}

pkg/local_object_storage/writecache/writecachebbolt/put.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"context"
@@ -8,6 +8,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/metaerr"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
 	"go.etcd.io/bbolt"
 	"go.opentelemetry.io/otel/attribute"
@@ -37,7 +38,7 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 
 	startedAt := time.Now()
 	added := false
-	storageType := StorageTypeUndefined
+	storageType := writecache.StorageTypeUndefined
 	defer func() {
 		c.metrics.Put(time.Since(startedAt), added, storageType)
 	}()
@@ -45,7 +46,7 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 	c.modeMtx.RLock()
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
-		return common.PutRes{}, ErrReadOnly
+		return common.PutRes{}, writecache.ErrReadOnly
 	}
 
 	sz := uint64(len(prm.RawData))
@@ -60,7 +61,7 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 	}
 
 	if sz <= c.smallObjectSize {
-		storageType = StorageTypeDB
+		storageType = writecache.StorageTypeDB
 		err := c.putSmall(oi)
 		if err == nil {
 			added = true
@@ -68,7 +69,7 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 		return common.PutRes{}, err
 	}
 
-	storageType = StorageTypeFSTree
+	storageType = writecache.StorageTypeFSTree
 	err := c.putBig(ctx, oi.addr, prm)
 	if err == nil {
 		added = true

pkg/local_object_storage/writecache/writecachebbolt/state.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"fmt"

pkg/local_object_storage/writecache/writecachebbolt/storage.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"context"
@@ -10,6 +10,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
 	storagelog "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/log"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/writecache"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
@@ -79,7 +80,7 @@ func (c *cache) deleteFromDB(keys []string) []string {
 	})
 	for i := 0; i < errorIndex; i++ {
 		c.objCounters.DecDB()
-		c.metrics.Evict(StorageTypeDB)
+		c.metrics.Evict(writecache.StorageTypeDB)
 		storagelog.Write(c.log,
 			storagelog.AddressField(keys[i]),
 			storagelog.StorageTypeField(wcStorageType),
@@ -122,7 +123,7 @@ func (c *cache) deleteFromDisk(ctx context.Context, keys []string) []string {
 				storagelog.StorageTypeField(wcStorageType),
 				storagelog.OpField("fstree DELETE"),
 			)
-			c.metrics.Evict(StorageTypeFSTree)
+			c.metrics.Evict(writecache.StorageTypeFSTree)
 			c.objCounters.DecFS()
 		}
 	}

pkg/local_object_storage/writecache/writecachebbolt/util.go

@@ -1,4 +1,4 @@
-package writecache
+package writecachebbolt
 
 import (
 	"io/fs"

pkg/local_object_storage/writecache/writecachetest/flush.go

@@ -0,0 +1,185 @@
+package writecachetest
+
+import (
+	"context"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+
+	objectCore "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/fstree"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/internal/testutil"
+	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-node/pkg/local_object_storage/writecache"
+	objectSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/stretchr/testify/require"
+)
+
+const (
+	objCount  = 4
+	smallSize = 256
+)
+
+type CreateCacheFunc[Option any] func(
+	t *testing.T,
+	smallSize uint64,
+	meta *meta.DB,
+	bs *blobstor.BlobStor,
+	opts ...Option,
+) writecache.Cache
+
+type TestFailureInjector[Option any] struct {
+	Desc     string
+	InjectFn func(*testing.T, writecache.Cache)
+}
+
+type objectPair struct {
+	addr oid.Address
+	obj  *objectSDK.Object
+}
+
+func TestFlush[Option any](
+	t *testing.T,
+	createCacheFn CreateCacheFunc[Option],
+	errCountOption func() (Option, *atomic.Uint32),
+	failures ...TestFailureInjector[Option],
+) {
+	t.Run("no errors", func(t *testing.T) {
+		wc, bs, mb := newCache(t, createCacheFn, smallSize)
+		objects := putObjects(t, wc)
+
+		require.NoError(t, bs.SetMode(mode.ReadWrite))
+		require.NoError(t, mb.SetMode(mode.ReadWrite))
+
+		require.NoError(t, wc.Flush(context.Background(), false))
+
+		check(t, mb, bs, objects)
+	})
+
+	t.Run("flush on moving to degraded mode", func(t *testing.T) {
+		wc, bs, mb := newCache(t, createCacheFn, smallSize)
+		objects := putObjects(t, wc)
+
+		// 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))
+
+		check(t, mb, bs, objects)
+	})
+
+	t.Run("ignore errors", func(t *testing.T) {
+		for _, f := range failures {
+			f := f
+			t.Run(f.Desc, func(t *testing.T) {
+				errCountOpt, errCount := errCountOption()
+				wc, bs, mb := newCache(t, createCacheFn, smallSize, errCountOpt)
+				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.True(t, errCount.Load() > 0)
+				require.NoError(t, wc.Flush(context.Background(), true))
+
+				check(t, mb, bs, objects)
+			})
+		}
+	})
+}
+
+func newCache[Option any](
+	t *testing.T,
+	createCacheFn CreateCacheFunc[Option],
+	smallSize uint64,
+	opts ...Option,
+) (writecache.Cache, *blobstor.BlobStor, *meta.DB) {
+	dir := t.TempDir()
+	mb := meta.New(
+		meta.WithPath(filepath.Join(dir, "meta")),
+		meta.WithEpochState(dummyEpoch{}))
+	require.NoError(t, mb.Open(false))
+	require.NoError(t, mb.Init())
+
+	bs := blobstor.New(blobstor.WithStorages([]blobstor.SubStorage{
+		{
+			Storage: fstree.New(
+				fstree.WithPath(filepath.Join(dir, "blob")),
+				fstree.WithDepth(0),
+				fstree.WithDirNameLen(1)),
+		},
+	}))
+	require.NoError(t, bs.Open(false))
+	require.NoError(t, bs.Init())
+
+	wc := createCacheFn(t, smallSize, mb, bs, opts...)
+	t.Cleanup(func() { require.NoError(t, wc.Close()) })
+	require.NoError(t, wc.Open(false))
+	require.NoError(t, wc.Init())
+
+	// First set mode for metabase and blobstor to prevent background flushes.
+	require.NoError(t, mb.SetMode(mode.ReadOnly))
+	require.NoError(t, bs.SetMode(mode.ReadOnly))
+
+	return wc, bs, mb
+}
+
+func putObject(t *testing.T, c writecache.Cache, size int) objectPair {
+	obj := testutil.GenerateObjectWithSize(size)
+	data, err := obj.Marshal()
+	require.NoError(t, err)
+
+	var prm common.PutPrm
+	prm.Address = objectCore.AddressOf(obj)
+	prm.Object = obj
+	prm.RawData = data
+
+	_, err = c.Put(context.Background(), prm)
+	require.NoError(t, err)
+
+	return objectPair{prm.Address, prm.Object}
+}
+
+func putObjects(t *testing.T, c writecache.Cache) []objectPair {
+	objects := make([]objectPair, objCount)
+	for i := range objects {
+		objects[i] = putObject(t, c, 1+(i%2)*smallSize)
+	}
+	return objects
+}
+
+func check(t *testing.T, mb *meta.DB, bs *blobstor.BlobStor, objects []objectPair) {
+	for i := range objects {
+		var mPrm meta.StorageIDPrm
+		mPrm.SetAddress(objects[i].addr)
+
+		mRes, err := mb.StorageID(context.Background(), mPrm)
+		require.NoError(t, err)
+
+		var prm common.GetPrm
+		prm.Address = objects[i].addr
+		prm.StorageID = mRes.StorageID()
+
+		res, err := bs.Get(context.Background(), prm)
+		require.NoError(t, err)
+		require.Equal(t, objects[i].obj, res.Object)
+	}
+}
+
+type dummyEpoch struct{}
+
+func (dummyEpoch) CurrentEpoch() uint64 {
+	return 0
+}