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

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

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

@@ -0,0 +1,75 @@
+package writecachebadger
+
+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/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...))
+}