[#452] engine: Set Disabled mode to deleted shard

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

CHANGELOG.md

@@ -4,8 +4,13 @@ Changelog for FrostFS Node
 ## [Unreleased]
 
 ### Added
+- Support copies number parameter in `frostfs-cli object put` (#351)
+
 ### Changed
 ### Fixed
+- Copy number was not used for `PUT` requests (#284)
+- Tree service panic in its internal client cache (#323)
+
 ### Removed
 ### Updated
 ### Updating from v0.36.0
@@ -64,6 +69,7 @@ Changelog for FrostFS Node
 - Iterating over just removed files by FSTree (#98)
 - Parts of a locked object could not be removed anymore (#141)
 - Non-alphabet nodes do not try to handle alphabet events (#181)
+- Delete complex objects with GC (#332)
 
 ### Removed
 ### Updated

cmd/frostfs-cli/internal/client/client.go

@@ -329,6 +329,8 @@ func CreateSession(prm CreateSessionPrm) (res CreateSessionRes, err error) {
 type PutObjectPrm struct {
 	commonObjectPrm
 
+	copyNum uint32
+
 	hdr *object.Object
 
 	rdr io.Reader
@@ -352,6 +354,11 @@ func (x *PutObjectPrm) SetHeaderCallback(f func(*object.Object)) {
 	x.headerCallback = f
 }
 
+// SetCopiesNumber sets number of object copies that is enough to consider put successful.
+func (x *PutObjectPrm) SetCopiesNumber(copiesNumbers uint32) {
+	x.copyNum = copiesNumbers
+}
+
 // PutObjectRes groups the resulting values of PutObject operation.
 type PutObjectRes struct {
 	id oid.ID
@@ -381,6 +388,7 @@ func PutObject(prm PutObjectPrm) (*PutObjectRes, error) {
 	}
 
 	putPrm.WithXHeaders(prm.xHeaders...)
+	putPrm.SetCopiesNumber(prm.copyNum)
 
 	wrt, err := prm.cli.ObjectPutInit(context.Background(), putPrm)
 	if err != nil {

cmd/frostfs-cli/modules/object/put.go

@@ -25,6 +25,7 @@ import (
 const (
 	noProgressFlag   = "no-progress"
 	notificationFlag = "notify"
+	copiesNumberFlag = "copies-number"
 )
 
 var putExpiredOn uint64
@@ -56,6 +57,8 @@ func initObjectPutCmd() {
 
 	flags.String(notificationFlag, "", "Object notification in the form of *epoch*:*topic*; '-' topic means using default")
 	flags.Bool(binaryFlag, false, "Deserialize object structure from given file.")
+
+	flags.Uint32(copiesNumberFlag, 0, "Number of copies of the object to store within the RPC call")
 }
 
 func putObject(cmd *cobra.Command, _ []string) {
@@ -116,6 +119,12 @@ func putObject(cmd *cobra.Command, _ []string) {
 		}
 	}
 
+	copyNum, err := cmd.Flags().GetUint32(copiesNumberFlag)
+	commonCmd.ExitOnErr(cmd, "can't parse object copies numbers information: %w", err)
+	if copyNum > 0 {
+		prm.SetCopiesNumber(copyNum)
+	}
+
 	res, err := internalclient.PutObject(prm)
 	if p != nil {
 		p.Finish()

cmd/frostfs-node/cache.go

@@ -24,6 +24,61 @@ type valueWithTime[V any] struct {
 	e error
 }
 
+type locker struct {
+	mtx     *sync.Mutex
+	waiters int // not protected by mtx, must used outer mutex to update concurrently
+}
+
+type keyLocker[K comparable] struct {
+	lockers    map[K]*locker
+	lockersMtx *sync.Mutex
+}
+
+func newKeyLocker[K comparable]() *keyLocker[K] {
+	return &keyLocker[K]{
+		lockers:    make(map[K]*locker),
+		lockersMtx: &sync.Mutex{},
+	}
+}
+
+func (l *keyLocker[K]) LockKey(key K) {
+	l.lockersMtx.Lock()
+
+	if locker, found := l.lockers[key]; found {
+		locker.waiters++
+		l.lockersMtx.Unlock()
+
+		locker.mtx.Lock()
+		return
+	}
+
+	locker := &locker{
+		mtx:     &sync.Mutex{},
+		waiters: 1,
+	}
+	locker.mtx.Lock()
+
+	l.lockers[key] = locker
+	l.lockersMtx.Unlock()
+}
+
+func (l *keyLocker[K]) UnlockKey(key K) {
+	l.lockersMtx.Lock()
+	defer l.lockersMtx.Unlock()
+
+	locker, found := l.lockers[key]
+	if !found {
+		return
+	}
+
+	if locker.waiters == 1 {
+		delete(l.lockers, key)
+	}
+	locker.waiters--
+
+	locker.mtx.Unlock()
+}
+
 // entity that provides TTL cache interface.
 type ttlNetCache[K comparable, V any] struct {
 	ttl time.Duration
@@ -33,6 +88,8 @@ type ttlNetCache[K comparable, V any] struct {
 	cache *lru.Cache[K, *valueWithTime[V]]
 
 	netRdr netValueReader[K, V]
+
+	keyLocker *keyLocker[K]
 }
 
 // complicates netValueReader with TTL caching mechanism.
@@ -45,6 +102,7 @@ func newNetworkTTLCache[K comparable, V any](sz int, ttl time.Duration, netRdr n
 		sz:        sz,
 		cache:     cache,
 		netRdr:    netRdr,
+		keyLocker: newKeyLocker[K](),
 	}
 }
 
@@ -55,22 +113,33 @@ func newNetworkTTLCache[K comparable, V any](sz int, ttl time.Duration, netRdr n
 // returned value should not be modified.
 func (c *ttlNetCache[K, V]) get(key K) (V, error) {
 	val, ok := c.cache.Peek(key)
-	if ok {
-		if time.Since(val.t) < c.ttl {
+	if ok && time.Since(val.t) < c.ttl {
 		return val.v, val.e
 	}
 
-		c.cache.Remove(key)
+	c.keyLocker.LockKey(key)
+	defer c.keyLocker.UnlockKey(key)
+
+	val, ok = c.cache.Peek(key)
+	if ok && time.Since(val.t) < c.ttl {
+		return val.v, val.e
 	}
 
 	v, err := c.netRdr(key)
 
-	c.set(key, v, err)
+	c.cache.Add(key, &valueWithTime[V]{
+		v: v,
+		t: time.Now(),
+		e: err,
+	})
 
 	return v, err
 }
 
 func (c *ttlNetCache[K, V]) set(k K, v V, e error) {
+	c.keyLocker.LockKey(k)
+	defer c.keyLocker.UnlockKey(k)
+
 	c.cache.Add(k, &valueWithTime[V]{
 		v: v,
 		t: time.Now(),
@@ -79,6 +148,9 @@ func (c *ttlNetCache[K, V]) set(k K, v V, e error) {
 }
 
 func (c *ttlNetCache[K, V]) remove(key K) {
+	c.keyLocker.LockKey(key)
+	defer c.keyLocker.UnlockKey(key)
+
 	c.cache.Remove(key)
 }
 

cmd/frostfs-node/cache_test.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"golang.org/x/sync/errgroup"
+)
+
+func TestKeyLocker(t *testing.T) {
+	taken := false
+	eg, _ := errgroup.WithContext(context.Background())
+	keyLocker := newKeyLocker[int]()
+	for i := 0; i < 100; i++ {
+		eg.Go(func() error {
+			keyLocker.LockKey(0)
+			defer keyLocker.UnlockKey(0)
+
+			require.False(t, taken)
+			taken = true
+			require.True(t, taken)
+			time.Sleep(10 * time.Millisecond)
+			taken = false
+			require.False(t, taken)
+
+			return nil
+		})
+	}
+	require.NoError(t, eg.Wait())
+}

cmd/frostfs-node/config.go

@@ -864,22 +864,13 @@ func initLocalStorage(c *cfg) {
 		ls.HandleNewEpoch(ev.(netmap2.NewEpoch).EpochNumber())
 	})
 
-	// allocate memory for the service;
+	// allocate memory for the service to create tombstone source;
 	// service will be created later
 	c.cfgObject.getSvc = new(getsvc.Service)
 
-	var tssPrm tsourse.TombstoneSourcePrm
-	tssPrm.SetGetService(c.cfgObject.getSvc)
-	tombstoneSrc := tsourse.NewSource(tssPrm)
-
-	tombstoneSource := tombstone.NewChecker(
-		tombstone.WithLogger(c.log),
-		tombstone.WithTombstoneSource(tombstoneSrc),
-	)
-
 	var shardsAttached int
 	for _, optsWithMeta := range c.shardOpts() {
-		id, err := ls.AddShard(append(optsWithMeta.shOpts, shard.WithTombstoneSource(tombstoneSource))...)
+		id, err := ls.AddShard(append(optsWithMeta.shOpts, shard.WithTombstoneSource(c.createTombstoneSource()))...)
 		if err != nil {
 			c.log.Error("failed to attach shard to engine", zap.Error(err))
 		} else {
@@ -1080,7 +1071,7 @@ func (c *cfg) reloadConfig(ctx context.Context) {
 
 	var rcfg engine.ReConfiguration
 	for _, optsWithID := range c.shardOpts() {
-		rcfg.AddShard(optsWithID.configID, optsWithID.shOpts)
+		rcfg.AddShard(optsWithID.configID, append(optsWithID.shOpts, shard.WithTombstoneSource(c.createTombstoneSource())))
 	}
 
 	err = c.cfgObject.cfgLocalStorage.localStorage.Reload(ctx, rcfg)
@@ -1101,6 +1092,18 @@ func (c *cfg) reloadConfig(ctx context.Context) {
 	c.log.Info("configuration has been reloaded successfully")
 }
 
+func (c *cfg) createTombstoneSource() *tombstone.ExpirationChecker {
+	var tssPrm tsourse.TombstoneSourcePrm
+	tssPrm.SetGetService(c.cfgObject.getSvc)
+	tombstoneSrc := tsourse.NewSource(tssPrm)
+
+	tombstoneSource := tombstone.NewChecker(
+		tombstone.WithLogger(c.log),
+		tombstone.WithTombstoneSource(tombstoneSrc),
+	)
+	return tombstoneSource
+}
+
 func (c *cfg) shutdown() {
 	c.setHealthStatus(control.HealthStatus_SHUTTING_DOWN)
 

cmd/frostfs-node/container.go

@@ -130,9 +130,10 @@ func configureEACLAndContainerSources(c *cfg, client *cntClient.Client, cnrSrc c
 			// TODO: use owner directly from the event after neofs-contract#256 will become resolved
 			//  but don't forget about the profit of reading the new container and caching it:
 			//  creation success are most commonly tracked by polling GET op.
-			cnr, err := cachedContainerStorage.Get(ev.ID)
+			cnr, err := cnrSrc.Get(ev.ID)
 			if err == nil {
 				cachedContainerLister.update(cnr.Value.Owner(), ev.ID, true)
+				cachedContainerStorage.set(ev.ID, cnr, nil)
 			} else {
 				// unlike removal, we expect successful receive of the container
 				// after successful creation, so logging can be useful

cmd/frostfs-node/netmap.go

@@ -253,6 +253,10 @@ func readSubnetCfg(c *cfg) {
 // Must be called after initNetmapService.
 func bootstrapNode(c *cfg) {
 	if c.needBootstrap() {
+		if c.IsMaintenance() {
+			c.log.Info("the node is under maintenance, skip initial bootstrap")
+			return
+		}
 		err := c.bootstrap()
 		fatalOnErrDetails("bootstrap error", err)
 	}
@@ -284,30 +288,74 @@ func initNetmapState(c *cfg) {
 	epoch, err := c.cfgNetmap.wrapper.Epoch()
 	fatalOnErrDetails("could not initialize current epoch number", err)
 
-	ni, err := c.netmapLocalNodeState(epoch)
+	ni, err := c.netmapInitLocalNodeState(epoch)
 	fatalOnErrDetails("could not init network state", err)
 
-	stateWord := "undefined"
-
-	if ni != nil {
-		switch {
-		case ni.IsOnline():
-			stateWord = "online"
-		case ni.IsOffline():
-			stateWord = "offline"
-		}
-	}
+	stateWord := nodeState(ni)
 
 	c.log.Info("initial network state",
 		zap.Uint64("epoch", epoch),
 		zap.String("state", stateWord),
 	)
 
+	if ni != nil && ni.IsMaintenance() {
+		c.isMaintenance.Store(true)
+	}
+
 	c.cfgNetmap.state.setCurrentEpoch(epoch)
 	c.cfgNetmap.startEpoch = epoch
 	c.handleLocalNodeInfo(ni)
 }
 
+func nodeState(ni *netmapSDK.NodeInfo) string {
+	if ni != nil {
+		switch {
+		case ni.IsOnline():
+			return "online"
+		case ni.IsOffline():
+			return "offline"
+		case ni.IsMaintenance():
+			return "maintenance"
+		}
+	}
+	return "undefined"
+}
+
+func (c *cfg) netmapInitLocalNodeState(epoch uint64) (*netmapSDK.NodeInfo, error) {
+	nmNodes, err := c.cfgNetmap.wrapper.GetCandidates()
+	if err != nil {
+		return nil, err
+	}
+
+	var candidate *netmapSDK.NodeInfo
+	for i := range nmNodes {
+		if bytes.Equal(nmNodes[i].PublicKey(), c.binPublicKey) {
+			candidate = &nmNodes[i]
+			break
+		}
+	}
+
+	node, err := c.netmapLocalNodeState(epoch)
+	if err != nil {
+		return nil, err
+	}
+
+	if candidate == nil {
+		return node, nil
+	}
+
+	nmState := nodeState(node)
+	candidateState := nodeState(candidate)
+	if nmState != candidateState {
+		// This happens when the node was switched to maintenance without epoch tick.
+		// We expect it to continue staying in maintenance.
+		c.log.Info("candidate status is different from the netmap status, the former takes priority",
+			zap.String("netmap", nmState),
+			zap.String("candidate", candidateState))
+	}
+	return candidate, nil
+}
+
 func (c *cfg) netmapLocalNodeState(epoch uint64) (*netmapSDK.NodeInfo, error) {
 	// calculate current network state
 	nm, err := c.cfgNetmap.wrapper.GetNetMapByEpoch(epoch)

config/example/node.yaml

@@ -219,4 +219,3 @@ tracing:
   enabled: true
   exporter: "otlp_grpc"
   endpoint: "localhost"
-  

go.mod

@@ -3,7 +3,7 @@ module git.frostfs.info/TrueCloudLab/frostfs-node
 go 1.18
 
 require (
-	git.frostfs.info/TrueCloudLab/frostfs-api-go/v2 v2.15.0
+	git.frostfs.info/TrueCloudLab/frostfs-api-go/v2 v2.15.1-0.20230602142024-4cb0068ddef0
 	git.frostfs.info/TrueCloudLab/frostfs-contract v0.0.0-20230307110621-19a8ef2d02fb
 	git.frostfs.info/TrueCloudLab/frostfs-sdk-go v0.0.0-20230316081442-bec77f280a85
 	git.frostfs.info/TrueCloudLab/hrw v1.2.0

pkg/local_object_storage/engine/dump.go

@@ -4,7 +4,7 @@ import "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shar
 
 // DumpShard dumps objects from the shard with provided identifier.
 //
-// Returns an error if shard is not read-only.
+// Returns an error if shard is not read-only or disabled.
 func (e *StorageEngine) DumpShard(id *shard.ID, prm shard.DumpPrm) error {
 	e.mtx.RLock()
 	defer e.mtx.RUnlock()

pkg/local_object_storage/engine/remove_copies.go

@@ -128,7 +128,7 @@ func (e *StorageEngine) removeObjects(ctx context.Context, ch <-chan oid.Address
 
 			var deletePrm shard.DeletePrm
 			deletePrm.SetAddresses(addr)
-			_, err = shards[i].Delete(deletePrm)
+			_, err = shards[i].Delete(ctx, deletePrm)
 			if err != nil {
 				return err
 			}

pkg/local_object_storage/engine/shards.go

@@ -174,7 +174,14 @@ func (e *StorageEngine) removeShards(ids ...string) {
 	e.mtx.Unlock()
 
 	for _, sh := range ss {
-		err := sh.Close()
+		err := sh.SetMode(mode.Disabled)
+		if err != nil {
+			e.log.Error("could not change shard mode to disabled",
+				zap.Stringer("id", sh.ID()),
+				zap.Error(err),
+			)
+		}
+		err = sh.Close()
 		if err != nil {
 			e.log.Error("could not close removed shard",
 				zap.Stringer("id", sh.ID()),

pkg/local_object_storage/engine/tree.go

@@ -213,6 +213,14 @@ func (e *StorageEngine) TreeExists(cid cidSDK.ID, treeID string) (bool, error) {
 	return err == nil, err
 }
 
+func (e *StorageEngine) TreeHeight(cid cidSDK.ID, treeID string) (uint64, error) {
+	index, lst, err := e.getTreeShard(cid, treeID)
+	if err != nil {
+		return 0, nil
+	}
+	return lst[index].TreeHeight(cid, treeID)
+}
+
 // TreeUpdateLastSyncHeight implements the pilorama.Forest interface.
 func (e *StorageEngine) TreeUpdateLastSyncHeight(cid cidSDK.ID, treeID string, height uint64) error {
 	index, lst, err := e.getTreeShard(cid, treeID)

pkg/local_object_storage/metabase/children.go

@@ -0,0 +1,57 @@
+package meta
+
+import (
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"go.etcd.io/bbolt"
+)
+
+// GetChildren returns parent -> children map.
+// If an object has no children, then map will contain addr -> empty slice value.
+func (db *DB) GetChildren(addresses []oid.Address) (map[oid.Address][]oid.Address, error) {
+	db.modeMtx.RLock()
+	defer db.modeMtx.RUnlock()
+
+	if db.mode.NoMetabase() {
+		return nil, ErrDegradedMode
+	}
+
+	result := make(map[oid.Address][]oid.Address, len(addresses))
+
+	buffer := make([]byte, bucketKeySize)
+	err := db.boltDB.View(func(tx *bbolt.Tx) error {
+		for _, addr := range addresses {
+			if _, found := result[addr]; found {
+				continue
+			}
+
+			result[addr] = []oid.Address{}
+			bkt := tx.Bucket(parentBucketName(addr.Container(), buffer))
+			if bkt == nil {
+				continue
+			}
+
+			binObjIDs, err := decodeList(bkt.Get(objectKey(addr.Object(), buffer)))
+			if err != nil {
+				return err
+			}
+
+			for _, binObjID := range binObjIDs {
+				var id oid.ID
+				if err = id.Decode(binObjID); err != nil {
+					return err
+				}
+				var resultAddress oid.Address
+				resultAddress.SetContainer(addr.Container())
+				resultAddress.SetObject(id)
+				result[addr] = append(result[addr], resultAddress)
+			}
+		}
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return result, nil
+}

pkg/local_object_storage/pilorama/batch.go

@@ -50,10 +50,23 @@ func (b *batch) run() {
 			return b.operations[i].Time < b.operations[j].Time
 		})
 
+		b.operations = removeDuplicatesInPlace(b.operations)
 		var lm Move
 		return b.forest.applyOperation(bLog, bTree, b.operations, &lm)
 	})
-	for i := range b.operations {
+	for i := range b.results {
 		b.results[i] <- err
 	}
 }
+
+func removeDuplicatesInPlace(a []*Move) []*Move {
+	equalCount := 0
+	for i := 1; i < len(a); i++ {
+		if a[i].Time == a[i-1].Time {
+			equalCount++
+		} else {
+			a[i-equalCount] = a[i]
+		}
+	}
+	return a[:len(a)-equalCount]
+}

pkg/local_object_storage/pilorama/batch_test.go

@@ -0,0 +1,70 @@
+package pilorama
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Test_removeDuplicatesInPlace(t *testing.T) {
+	testCases := []struct {
+		before []int
+		after  []int
+	}{
+		{
+			before: []int{},
+			after:  []int{},
+		},
+		{
+			before: []int{1},
+			after:  []int{1},
+		},
+		{
+			before: []int{1, 2},
+			after:  []int{1, 2},
+		},
+		{
+			before: []int{1, 2, 3},
+			after:  []int{1, 2, 3},
+		},
+		{
+			before: []int{1, 1, 2},
+			after:  []int{1, 2},
+		},
+		{
+			before: []int{1, 2, 2},
+			after:  []int{1, 2},
+		},
+		{
+			before: []int{1, 2, 2, 3},
+			after:  []int{1, 2, 3},
+		},
+		{
+			before: []int{1, 1, 1},
+			after:  []int{1},
+		},
+		{
+			before: []int{1, 1, 2, 2},
+			after:  []int{1, 2},
+		},
+		{
+			before: []int{1, 1, 1, 2, 3, 3, 3},
+			after:  []int{1, 2, 3},
+		},
+	}
+
+	for _, tc := range testCases {
+		ops := make([]*Move, len(tc.before))
+		for i := range ops {
+			ops[i] = &Move{Meta: Meta{Time: Timestamp(tc.before[i])}}
+		}
+
+		expected := make([]*Move, len(tc.after))
+		for i := range expected {
+			expected[i] = &Move{Meta: Meta{Time: Timestamp(tc.after[i])}}
+		}
+
+		actual := removeDuplicatesInPlace(ops)
+		require.Equal(t, expected, actual, "%d", tc.before)
+	}
+}

pkg/local_object_storage/pilorama/boltdb.go

@@ -174,6 +174,32 @@ func (t *boltForest) TreeMove(d CIDDescriptor, treeID string, m *Move) (*Move, e
 	})
 }
 
+func (t *boltForest) TreeHeight(cid cidSDK.ID, treeID string) (uint64, error) {
+	t.modeMtx.RLock()
+	defer t.modeMtx.RUnlock()
+
+	if t.mode.NoMetabase() {
+		return 0, ErrDegradedMode
+	}
+
+	var height uint64
+	var retErr error
+	err := t.db.View(func(tx *bbolt.Tx) error {
+		treeRoot := tx.Bucket(bucketName(cid, treeID))
+		if treeRoot != nil {
+			k, _ := treeRoot.Bucket(logBucket).Cursor().Last()
+			height = binary.BigEndian.Uint64(k)
+		} else {
+			retErr = ErrTreeNotFound
+		}
+		return nil
+	})
+	if err == nil {
+		err = retErr
+	}
+	return height, err
+}
+
 // TreeExists implements the Forest interface.
 func (t *boltForest) TreeExists(cid cidSDK.ID, treeID string) (bool, error) {
 	t.modeMtx.RLock()

pkg/local_object_storage/pilorama/forest.go

@@ -216,6 +216,15 @@ func (f *memoryForest) TreeList(cid cid.ID) ([]string, error) {
 	return res, nil
 }
 
+func (f *memoryForest) TreeHeight(cid cid.ID, treeID string) (uint64, error) {
+	fullID := cid.EncodeToString() + "/" + treeID
+	tree, ok := f.treeMap[fullID]
+	if !ok {
+		return 0, ErrTreeNotFound
+	}
+	return tree.operations[len(tree.operations)-1].Time, nil
+}
+
 // TreeExists implements the pilorama.Forest interface.
 func (f *memoryForest) TreeExists(cid cid.ID, treeID string) (bool, error) {
 	fullID := cid.EncodeToString() + "/" + treeID

pkg/local_object_storage/pilorama/forest_test.go

@@ -1,6 +1,7 @@
 package pilorama
 
 import (
+	"context"
 	"fmt"
 	"math/rand"
 	"os"
@@ -13,6 +14,7 @@ import (
 	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"
+	"golang.org/x/sync/errgroup"
 )
 
 var providers = []struct {
@@ -445,6 +447,82 @@ func testForestTreeApply(t *testing.T, constructor func(t testing.TB, _ ...Optio
 	})
 }
 
+func TestForest_ApplySameOperation(t *testing.T) {
+	for i := range providers {
+		t.Run(providers[i].name, func(t *testing.T) {
+			parallel := providers[i].name != "inmemory"
+			testForestApplySameOperation(t, providers[i].construct, parallel)
+		})
+	}
+}
+
+func testForestApplySameOperation(t *testing.T, constructor func(t testing.TB, _ ...Option) Forest, parallel bool) {
+	cid := cidtest.ID()
+	treeID := "version"
+
+	batchSize := 3
+	errG, _ := errgroup.WithContext(context.Background())
+	if !parallel {
+		batchSize = 1
+		errG.SetLimit(1)
+	}
+
+	meta := []Meta{
+		{Time: 1, Items: []KeyValue{{AttributeFilename, []byte("1")}, {"attr", []byte{1}}}},
+		{Time: 2, Items: []KeyValue{{AttributeFilename, []byte("2")}, {"attr", []byte{1}}}},
+		{Time: 3, Items: []KeyValue{{AttributeFilename, []byte("3")}, {"attr", []byte{1}}}},
+	}
+	logs := []Move{
+		{
+			Child:  1,
+			Parent: RootID,
+			Meta:   meta[0],
+		},
+		{
+			Child:  2,
+			Parent: 1,
+			Meta:   meta[1],
+		},
+		{
+			Child:  1,
+			Parent: 2,
+			Meta:   meta[2],
+		},
+	}
+
+	check := func(t *testing.T, s Forest) {
+		testMeta(t, s, cid, treeID, 1, RootID, meta[0])
+		testMeta(t, s, cid, treeID, 2, 1, meta[1])
+
+		nodes, err := s.TreeGetChildren(cid, treeID, RootID)
+		require.NoError(t, err)
+		require.Equal(t, []Node{1}, nodes)
+
+		nodes, err = s.TreeGetChildren(cid, treeID, 1)
+		require.NoError(t, err)
+		require.Equal(t, []Node{2}, nodes)
+	}
+
+	t.Run("expected", func(t *testing.T) {
+		s := constructor(t)
+		for i := range logs {
+			require.NoError(t, s.TreeApply(cid, treeID, &logs[i], false))
+		}
+		check(t, s)
+	})
+
+	s := constructor(t, WithMaxBatchSize(batchSize))
+	require.NoError(t, s.TreeApply(cid, treeID, &logs[0], false))
+	for i := 0; i < batchSize; i++ {
+		errG.Go(func() error {
+			return s.TreeApply(cid, treeID, &logs[2], false)
+		})
+	}
+	require.NoError(t, errG.Wait())
+	require.NoError(t, s.TreeApply(cid, treeID, &logs[1], false))
+	check(t, s)
+}
+
 func TestForest_GetOpLog(t *testing.T) {
 	for i := range providers {
 		t.Run(providers[i].name, func(t *testing.T) {
@@ -527,9 +605,18 @@ func testForestTreeExists(t *testing.T, constructor func(t testing.TB, opts ...O
 		checkExists(t, false, cid, treeID)
 	})
 
-	require.NoError(t, s.TreeApply(cid, treeID, &Move{Parent: 0, Child: 1}, false))
+	require.NoError(t, s.TreeApply(cid, treeID, &Move{Meta: Meta{Time: 11}, Parent: 0, Child: 1}, false))
 	checkExists(t, true, cid, treeID)
+
+	height, err := s.TreeHeight(cid, treeID)
+	require.NoError(t, err)
+	require.EqualValues(t, 11, height)
+
 	checkExists(t, false, cidtest.ID(), treeID) // different CID, same tree
+
+	_, err = s.TreeHeight(cidtest.ID(), treeID)
+	require.ErrorIs(t, err, ErrTreeNotFound)
+
 	checkExists(t, false, cid, "another tree") // same CID, different tree
 
 	t.Run("can be removed", func(t *testing.T) {

pkg/local_object_storage/pilorama/interface.go

@@ -48,6 +48,8 @@ type Forest interface {
 	TreeUpdateLastSyncHeight(cid cidSDK.ID, treeID string, height uint64) error
 	// TreeLastSyncHeight returns last log height synchronized with _all_ container nodes.
 	TreeLastSyncHeight(cid cidSDK.ID, treeID string) (uint64, error)
+	// TreeHeight returns current tree height.
+	TreeHeight(cid cidSDK.ID, treeID string) (uint64, error)
 }
 
 type ForestStorage interface {

pkg/local_object_storage/shard/control.go

@@ -296,8 +296,8 @@ func (s *Shard) Reload(opts ...Option) error {
 		opts[i](&c)
 	}
 
-	s.m.Lock()
-	defer s.m.Unlock()
+	unlock := s.lockExclusive()
+	defer unlock()
 
 	ok, err := s.metaBase.Reload(c.metaOpts...)
 	if err != nil {
@@ -327,3 +327,15 @@ func (s *Shard) Reload(opts ...Option) error {
 	s.log.Info("trying to restore read-write mode")
 	return s.setMode(mode.ReadWrite)
 }
+
+func (s *Shard) lockExclusive() func() {
+	s.setModeRequested.Store(true)
+	val := s.gcCancel.Load()
+	if val != nil {
+		cancelGC := val.(context.CancelFunc)
+		cancelGC()
+	}
+	s.m.Lock()
+	s.setModeRequested.Store(false)
+	return s.m.Unlock
+}

pkg/local_object_storage/shard/delete.go

@@ -1,6 +1,7 @@
 package shard
 
 import (
+	"context"
 	"errors"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
@@ -27,84 +28,88 @@ func (p *DeletePrm) SetAddresses(addr ...oid.Address) {
 
 // Delete removes data from the shard's writeCache, metaBase and
 // blobStor.
-func (s *Shard) Delete(prm DeletePrm) (DeleteRes, error) {
+func (s *Shard) Delete(ctx context.Context, prm DeletePrm) (DeleteRes, error) {
 	s.m.RLock()
 	defer s.m.RUnlock()
 
-	return s.delete(prm)
+	return s.delete(ctx, prm)
 }
 
-func (s *Shard) delete(prm DeletePrm) (DeleteRes, error) {
+func (s *Shard) delete(ctx context.Context, prm DeletePrm) (DeleteRes, error) {
 	if s.info.Mode.ReadOnly() {
 		return DeleteRes{}, ErrReadOnlyMode
 	} else if s.info.Mode.NoMetabase() {
 		return DeleteRes{}, ErrDegradedMode
 	}
 
-	ln := len(prm.addr)
+	for _, addr := range prm.addr {
+		select {
+		case <-ctx.Done():
+			return DeleteRes{}, ctx.Err()
+		default:
+		}
 
-	smalls := make(map[oid.Address][]byte, ln)
+		s.deleteObjectFromWriteCacheSafe(addr)
 
-	for i := range prm.addr {
+		s.deleteFromBlobstorSafe(addr)
+
+		if err := s.deleteFromMetabase(addr); err != nil {
+			return DeleteRes{}, err // stop on metabase error ?
+		}
+	}
+	return DeleteRes{}, nil
+}
+
+func (s *Shard) deleteObjectFromWriteCacheSafe(addr oid.Address) {
 	if s.hasWriteCache() {
-			err := s.writeCache.Delete(prm.addr[i])
+		err := s.writeCache.Delete(addr)
 		if err != nil && !IsErrNotFound(err) && !errors.Is(err, writecache.ErrReadOnly) {
 			s.log.Warn("can't delete object from write cache", zap.String("error", err.Error()))
 		}
 	}
+}
 
+func (s *Shard) deleteFromMetabase(addr oid.Address) error {
+	var delPrm meta.DeletePrm
+	delPrm.SetAddresses(addr)
+
+	res, err := s.metaBase.Delete(delPrm)
+	if err != nil {
+		return err
+	}
+
+	s.decObjectCounterBy(physical, res.RawObjectsRemoved())
+	s.decObjectCounterBy(logical, res.AvailableObjectsRemoved())
+	removedPayload := res.RemovedPhysicalObjectSizes()[0]
+	logicalRemovedPayload := res.RemovedLogicalObjectSizes()[0]
+	if logicalRemovedPayload > 0 {
+		s.addToContainerSize(addr.Container().EncodeToString(), -int64(logicalRemovedPayload))
+	}
+	s.addToPayloadSize(-int64(removedPayload))
+
+	return nil
+}
+
+func (s *Shard) deleteFromBlobstorSafe(addr oid.Address) {
 	var sPrm meta.StorageIDPrm
-		sPrm.SetAddress(prm.addr[i])
+	sPrm.SetAddress(addr)
 
 	res, err := s.metaBase.StorageID(sPrm)
 	if err != nil {
 		s.log.Debug("can't get storage ID from metabase",
-				zap.Stringer("object", prm.addr[i]),
+			zap.Stringer("object", addr),
 			zap.String("error", err.Error()))
-
-			continue
 	}
+	storageID := res.StorageID()
 
-		if res.StorageID() != nil {
-			smalls[prm.addr[i]] = res.StorageID()
-		}
-	}
-
-	var delPrm meta.DeletePrm
-	delPrm.SetAddresses(prm.addr...)
-
-	res, err := s.metaBase.Delete(delPrm)
-	if err != nil {
-		return DeleteRes{}, err // stop on metabase error ?
-	}
-
-	var totalRemovedPayload uint64
-
-	s.decObjectCounterBy(physical, res.RawObjectsRemoved())
-	s.decObjectCounterBy(logical, res.AvailableObjectsRemoved())
-	for i := range prm.addr {
-		removedPayload := res.RemovedPhysicalObjectSizes()[i]
-		totalRemovedPayload += removedPayload
-		logicalRemovedPayload := res.RemovedLogicalObjectSizes()[i]
-		if logicalRemovedPayload > 0 {
-			s.addToContainerSize(prm.addr[i].Container().EncodeToString(), -int64(logicalRemovedPayload))
-		}
-	}
-	s.addToPayloadSize(-int64(totalRemovedPayload))
-
-	for i := range prm.addr {
 	var delPrm common.DeletePrm
-		delPrm.Address = prm.addr[i]
-		id := smalls[prm.addr[i]]
-		delPrm.StorageID = id
+	delPrm.Address = addr
+	delPrm.StorageID = storageID
 
 	_, err = s.blobStor.Delete(delPrm)
 	if err != nil {
 		s.log.Debug("can't remove object from blobStor",
-				zap.Stringer("object_address", prm.addr[i]),
+			zap.Stringer("object_address", addr),
 			zap.String("error", err.Error()))
 	}
 }
-
-	return DeleteRes{}, nil
-}

pkg/local_object_storage/shard/delete_test.go

@@ -49,7 +49,7 @@ func testShardDelete(t *testing.T, hasWriteCache bool) {
 		_, err = testGet(t, sh, getPrm, hasWriteCache)
 		require.NoError(t, err)
 
-		_, err = sh.Delete(delPrm)
+		_, err = sh.Delete(context.Background(), delPrm)
 		require.NoError(t, err)
 
 		_, err = sh.Get(context.Background(), getPrm)
@@ -73,7 +73,7 @@ func testShardDelete(t *testing.T, hasWriteCache bool) {
 		_, err = sh.Get(context.Background(), getPrm)
 		require.NoError(t, err)
 
-		_, err = sh.Delete(delPrm)
+		_, err = sh.Delete(context.Background(), delPrm)
 		require.NoError(t, err)
 
 		_, err = sh.Get(context.Background(), getPrm)

pkg/local_object_storage/shard/dump.go

@@ -55,7 +55,9 @@ func (s *Shard) Dump(prm DumpPrm) (DumpRes, error) {
 	s.m.RLock()
 	defer s.m.RUnlock()
 
-	if !s.info.Mode.ReadOnly() {
+	if s.info.Mode.Disabled() {
+		return DumpRes{}, ErrShardDisabled
+	} else if !s.info.Mode.ReadOnly() {
 		return DumpRes{}, ErrMustBeReadOnly
 	}
 

pkg/local_object_storage/shard/dump_test.go

@@ -57,6 +57,7 @@ func testDump(t *testing.T, objCount int, hasWriteCache bool) {
 				writecache.WithMaxObjectSize(wcBigObjectSize),
 				writecache.WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
 			},
+			nil,
 			nil)
 	}
 	defer releaseShard(sh, t)
@@ -188,7 +189,7 @@ func testDump(t *testing.T, objCount int, hasWriteCache bool) {
 				require.Error(t, err)
 
 				t.Run("skip errors", func(t *testing.T) {
-					sh := newCustomShard(t, filepath.Join(t.TempDir(), "ignore"), false, nil, nil)
+					sh := newCustomShard(t, filepath.Join(t.TempDir(), "ignore"), false, nil, nil, nil)
 					t.Cleanup(func() { require.NoError(t, sh.Close()) })
 
 					var restorePrm shard.RestorePrm
@@ -219,10 +220,10 @@ func testDump(t *testing.T, objCount int, hasWriteCache bool) {
 }
 
 func TestStream(t *testing.T) {
-	sh1 := newCustomShard(t, filepath.Join(t.TempDir(), "shard1"), false, nil, nil)
+	sh1 := newCustomShard(t, filepath.Join(t.TempDir(), "shard1"), false, nil, nil, nil)
 	defer releaseShard(sh1, t)
 
-	sh2 := newCustomShard(t, filepath.Join(t.TempDir(), "shard2"), false, nil, nil)
+	sh2 := newCustomShard(t, filepath.Join(t.TempDir(), "shard2"), false, nil, nil, nil)
 	defer releaseShard(sh2, t)
 
 	const objCount = 5
@@ -323,7 +324,7 @@ func TestDumpIgnoreErrors(t *testing.T) {
 		writecache.WithSmallObjectSize(wcSmallObjectSize),
 		writecache.WithMaxObjectSize(wcBigObjectSize),
 	}
-	sh := newCustomShard(t, dir, true, wcOpts, bsOpts(2))
+	sh := newCustomShard(t, dir, true, wcOpts, bsOpts(2), nil)
 
 	objects := make([]*objectSDK.Object, objCount)
 	for i := 0; i < objCount; i++ {
@@ -371,7 +372,7 @@ func TestDumpIgnoreErrors(t *testing.T) {
 		require.NoError(t, os.MkdirAll(filepath.Join(bsPath, "ZZ"), 0))
 	}
 
-	sh = newCustomShard(t, dir, true, wcOpts, bsOpts(3))
+	sh = newCustomShard(t, dir, true, wcOpts, bsOpts(3), nil)
 	require.NoError(t, sh.SetMode(mode.ReadOnly))
 
 	{

pkg/local_object_storage/shard/errors.go

@@ -4,9 +4,12 @@ import (
 	"errors"
 
 	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 )
 
+var ErrShardDisabled = logicerr.New("shard disabled")
+
 // IsErrNotFound checks if error returned by Shard Get/Head/GetRange method
 // corresponds to missing object.
 func IsErrNotFound(err error) bool {

pkg/local_object_storage/shard/exists.go

@@ -35,6 +35,7 @@ func (p ExistsRes) Exists() bool {
 //
 // Returns an error of type apistatus.ObjectAlreadyRemoved if object has been marked as removed.
 // Returns the object.ErrObjectIsExpired if the object is presented but already expired.
+// Returns the ErrShardDisabled if the shard is disabled.
 func (s *Shard) Exists(ctx context.Context, prm ExistsPrm) (ExistsRes, error) {
 	var exists bool
 	var err error
@@ -42,7 +43,9 @@ func (s *Shard) Exists(ctx context.Context, prm ExistsPrm) (ExistsRes, error) {
 	s.m.RLock()
 	defer s.m.RUnlock()
 
-	if s.info.Mode.NoMetabase() {
+	if s.info.Mode.Disabled() {
+		return ExistsRes{}, ErrShardDisabled
+	} else if s.info.Mode.NoMetabase() {
 		var p common.ExistsPrm
 		p.Address = prm.addr
 

pkg/local_object_storage/shard/gc.go

@@ -145,8 +145,8 @@ func (gc *gc) listenEvents(ctx context.Context) {
 			h := v.handlers[i]
 
 			err := gc.workerPool.Submit(func() {
+				defer v.prevGroup.Done()
 				h(runCtx, event)
-				v.prevGroup.Done()
 			})
 			if err != nil {
 				gc.log.Warn("could not submit GC job to worker pool",
@@ -196,6 +196,14 @@ func (gc *gc) stop() {
 // with GC-marked graves.
 // Does nothing if shard is in "read-only" mode.
 func (s *Shard) removeGarbage() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	s.gcCancel.Store(cancel)
+	if s.setModeRequested.Load() {
+		return
+	}
+
 	s.m.RLock()
 	defer s.m.RUnlock()
 
@@ -207,6 +215,12 @@ func (s *Shard) removeGarbage() {
 
 	var iterPrm meta.GarbageIterationPrm
 	iterPrm.SetHandler(func(g meta.GarbageObject) error {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+
 		buf = append(buf, g.Address())
 
 		if len(buf) == s.rmBatchSize {
@@ -233,7 +247,7 @@ func (s *Shard) removeGarbage() {
 	deletePrm.SetAddresses(buf...)
 
 	// delete accumulated objects
-	_, err = s.delete(deletePrm)
+	_, err = s.delete(ctx, deletePrm)
 	if err != nil {
 		s.log.Warn("could not delete the objects",
 			zap.String("error", err.Error()),
@@ -313,6 +327,12 @@ func (s *Shard) handleExpiredObjects(ctx context.Context, expired []oid.Address)
 		return
 	}
 
+	expired, err := s.getExpiredWithLinked(expired)
+	if err != nil {
+		s.log.Warn("failed to get expired objects with linked", zap.Error(err))
+		return
+	}
+
 	var inhumePrm meta.InhumePrm
 
 	inhumePrm.SetAddresses(expired...)
@@ -338,6 +358,20 @@ func (s *Shard) handleExpiredObjects(ctx context.Context, expired []oid.Address)
 	}
 }
 
+func (s *Shard) getExpiredWithLinked(source []oid.Address) ([]oid.Address, error) {
+	result := make([]oid.Address, 0, len(source))
+	parentToChildren, err := s.metaBase.GetChildren(source)
+	if err != nil {
+		return nil, err
+	}
+	for parent, children := range parentToChildren {
+		result = append(result, parent)
+		result = append(result, children...)
+	}
+
+	return result, nil
+}
+
 func (s *Shard) collectExpiredTombstones(ctx context.Context, e Event) {
 	epoch := e.(newEpoch).epoch
 	log := s.log.With(zap.Uint64("epoch", epoch))

pkg/local_object_storage/shard/gc_internal_test.go

@@ -0,0 +1,144 @@
+package shard
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+	"time"
+
+	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/blobovniczatree"
+	"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/pilorama"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
+	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/panjf2000/ants/v2"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zaptest"
+)
+
+func Test_ObjectNotFoundIfNotDeletedFromMetabase(t *testing.T) {
+	t.Parallel()
+
+	rootPath := t.TempDir()
+
+	var sh *Shard
+
+	l := &logger.Logger{Logger: zaptest.NewLogger(t)}
+	blobOpts := []blobstor.Option{
+		blobstor.WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+		blobstor.WithStorages([]blobstor.SubStorage{
+			{
+				Storage: blobovniczatree.NewBlobovniczaTree(
+					blobovniczatree.WithLogger(&logger.Logger{Logger: zaptest.NewLogger(t)}),
+					blobovniczatree.WithRootPath(filepath.Join(rootPath, "blob", "blobovnicza")),
+					blobovniczatree.WithBlobovniczaShallowDepth(1),
+					blobovniczatree.WithBlobovniczaShallowWidth(1)),
+				Policy: func(_ *object.Object, data []byte) bool {
+					return len(data) <= 1<<20
+				},
+			},
+			{
+				Storage: fstree.New(
+					fstree.WithPath(filepath.Join(rootPath, "blob"))),
+			},
+		}),
+	}
+
+	opts := []Option{
+		WithID(NewIDFromBytes([]byte{})),
+		WithLogger(l),
+		WithBlobStorOptions(blobOpts...),
+		WithMetaBaseOptions(
+			meta.WithPath(filepath.Join(rootPath, "meta")),
+			meta.WithEpochState(epochState{}),
+		),
+		WithPiloramaOptions(pilorama.WithPath(filepath.Join(rootPath, "pilorama"))),
+		WithDeletedLockCallback(func(_ context.Context, addresses []oid.Address) {
+			sh.HandleDeletedLocks(addresses)
+		}),
+		WithExpiredLocksCallback(func(ctx context.Context, epoch uint64, a []oid.Address) {
+			sh.HandleExpiredLocks(ctx, epoch, a)
+		}),
+		WithGCWorkerPoolInitializer(func(sz int) util.WorkerPool {
+			pool, err := ants.NewPool(sz)
+			require.NoError(t, err)
+			return pool
+		}),
+		WithGCRemoverSleepInterval(1 * time.Second),
+	}
+
+	sh = New(opts...)
+
+	require.NoError(t, sh.Open())
+	require.NoError(t, sh.Init(context.Background()))
+
+	t.Cleanup(func() {
+		require.NoError(t, sh.Close())
+	})
+
+	cnr := cidtest.ID()
+	obj := testutil.GenerateObjectWithCID(cnr)
+	objID, _ := obj.ID()
+	var addr oid.Address
+	addr.SetContainer(cnr)
+	addr.SetObject(objID)
+
+	var putPrm PutPrm
+	putPrm.SetObject(obj)
+
+	_, err := sh.Put(putPrm)
+	require.NoError(t, err)
+
+	var getPrm GetPrm
+	getPrm.SetAddress(objectCore.AddressOf(obj))
+	_, err = sh.Get(context.Background(), getPrm)
+	require.NoError(t, err, "failed to get")
+
+	//inhume
+	var inhumePrm InhumePrm
+	inhumePrm.MarkAsGarbage(addr)
+	_, err = sh.Inhume(context.Background(), inhumePrm)
+	require.NoError(t, err, "failed to inhume")
+	_, err = sh.Get(context.Background(), getPrm)
+	require.Error(t, err, "get returned error")
+	require.True(t, IsErrNotFound(err), "invalid error type")
+
+	//storageID
+	var metaStIDPrm meta.StorageIDPrm
+	metaStIDPrm.SetAddress(addr)
+	storageID, err := sh.metaBase.StorageID(metaStIDPrm)
+	require.NoError(t, err, "failed to get storage ID")
+
+	//check existance in blobstore
+	var bsExisted common.ExistsPrm
+	bsExisted.Address = addr
+	bsExisted.StorageID = storageID.StorageID()
+	exRes, err := sh.blobStor.Exists(context.Background(), bsExisted)
+	require.NoError(t, err, "failed to check blobstore existance")
+	require.True(t, exRes.Exists, "invalid blobstore existance result")
+
+	//drop from blobstor
+	var bsDeletePrm common.DeletePrm
+	bsDeletePrm.Address = addr
+	bsDeletePrm.StorageID = storageID.StorageID()
+	_, err = sh.blobStor.Delete(bsDeletePrm)
+	require.NoError(t, err, "failed to delete from blobstore")
+
+	//check existance in blobstore
+	exRes, err = sh.blobStor.Exists(context.Background(), bsExisted)
+	require.NoError(t, err, "failed to check blobstore existance")
+	require.False(t, exRes.Exists, "invalid blobstore existance result")
+
+	//get should return object not found
+	_, err = sh.Get(context.Background(), getPrm)
+	require.Error(t, err, "get returned no error")
+	require.True(t, IsErrNotFound(err), "invalid error type")
+}

pkg/local_object_storage/shard/gc_test.go

@@ -2,77 +2,30 @@ package shard_test
 
 import (
 	"context"
-	"path/filepath"
+	"errors"
 	"testing"
 	"time"
 
 	objectV2 "git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/object"
 	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/blobovniczatree"
-	"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"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
-	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	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"
-	"github.com/panjf2000/ants/v2"
+	oidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id/test"
 	"github.com/stretchr/testify/require"
-	"go.uber.org/zap"
 )
 
-func Test_GCDropsLockedExpiredObject(t *testing.T) {
-	var sh *shard.Shard
+func Test_GCDropsLockedExpiredSimpleObject(t *testing.T) {
+	t.Parallel()
 
 	epoch := &epochState{
 		Value: 100,
 	}
 
-	rootPath := t.TempDir()
-	opts := []shard.Option{
-		shard.WithID(shard.NewIDFromBytes([]byte{})),
-		shard.WithLogger(&logger.Logger{Logger: zap.NewNop()}),
-		shard.WithBlobStorOptions(
-			blobstor.WithStorages([]blobstor.SubStorage{
-				{
-					Storage: blobovniczatree.NewBlobovniczaTree(
-						blobovniczatree.WithRootPath(filepath.Join(rootPath, "blob", "blobovnicza")),
-						blobovniczatree.WithBlobovniczaShallowDepth(2),
-						blobovniczatree.WithBlobovniczaShallowWidth(2)),
-					Policy: func(_ *objectSDK.Object, data []byte) bool {
-						return len(data) <= 1<<20
-					},
-				},
-				{
-					Storage: fstree.New(
-						fstree.WithPath(filepath.Join(rootPath, "blob"))),
-				},
-			}),
-		),
-		shard.WithMetaBaseOptions(
-			meta.WithPath(filepath.Join(rootPath, "meta")),
-			meta.WithEpochState(epoch),
-		),
-		shard.WithDeletedLockCallback(func(_ context.Context, addresses []oid.Address) {
-			sh.HandleDeletedLocks(addresses)
-		}),
-		shard.WithExpiredLocksCallback(func(ctx context.Context, epoch uint64, a []oid.Address) {
-			sh.HandleExpiredLocks(ctx, epoch, a)
-		}),
-		shard.WithGCWorkerPoolInitializer(func(sz int) util.WorkerPool {
-			pool, err := ants.NewPool(sz)
-			require.NoError(t, err)
-
-			return pool
-		}),
-	}
-
-	sh = shard.New(opts...)
-	require.NoError(t, sh.Open())
-	require.NoError(t, sh.Init(context.Background()))
+	sh := newCustomShard(t, t.TempDir(), false, nil, nil, []meta.Option{meta.WithEpochState(epoch)})
 
 	t.Cleanup(func() {
 		releaseShard(sh, t)
@@ -120,3 +73,97 @@ func Test_GCDropsLockedExpiredObject(t *testing.T) {
 		return shard.IsErrNotFound(err)
 	}, 3*time.Second, 1*time.Second, "expired object must be deleted")
 }
+
+func Test_GCDropsLockedExpiredComplexObject(t *testing.T) {
+	t.Parallel()
+
+	epoch := &epochState{
+		Value: 100,
+	}
+
+	cnr := cidtest.ID()
+	parentID := oidtest.ID()
+	splitID := objectSDK.NewSplitID()
+
+	var objExpirationAttr objectSDK.Attribute
+	objExpirationAttr.SetKey(objectV2.SysAttributeExpEpoch)
+	objExpirationAttr.SetValue("101")
+
+	var lockExpirationAttr objectSDK.Attribute
+	lockExpirationAttr.SetKey(objectV2.SysAttributeExpEpoch)
+	lockExpirationAttr.SetValue("103")
+
+	parent := testutil.GenerateObjectWithCID(cnr)
+	parent.SetID(parentID)
+	parent.SetPayload(nil)
+	parent.SetAttributes(objExpirationAttr)
+
+	const childCount = 10
+	children := make([]*objectSDK.Object, childCount)
+	childIDs := make([]oid.ID, childCount)
+	for i := range children {
+		children[i] = testutil.GenerateObjectWithCID(cnr)
+		if i != 0 {
+			children[i].SetPreviousID(childIDs[i-1])
+		}
+		if i == len(children)-1 {
+			children[i].SetParent(parent)
+		}
+		children[i].SetSplitID(splitID)
+		children[i].SetPayload([]byte{byte(i), byte(i + 1), byte(i + 2)})
+		childIDs[i], _ = children[i].ID()
+	}
+
+	link := testutil.GenerateObjectWithCID(cnr)
+	link.SetParent(parent)
+	link.SetParentID(parentID)
+	link.SetSplitID(splitID)
+	link.SetChildren(childIDs...)
+
+	linkID, _ := link.ID()
+
+	sh := newCustomShard(t, t.TempDir(), false, nil, nil, []meta.Option{meta.WithEpochState(epoch)})
+
+	t.Cleanup(func() {
+		releaseShard(sh, t)
+	})
+
+	lock := testutil.GenerateObjectWithCID(cnr)
+	lock.SetType(objectSDK.TypeLock)
+	lock.SetAttributes(lockExpirationAttr)
+	lockID, _ := lock.ID()
+
+	var putPrm shard.PutPrm
+
+	for _, child := range children {
+		putPrm.SetObject(child)
+		_, err := sh.Put(putPrm)
+		require.NoError(t, err)
+	}
+
+	putPrm.SetObject(link)
+	_, err := sh.Put(putPrm)
+	require.NoError(t, err)
+
+	err = sh.Lock(cnr, lockID, append(childIDs, parentID, linkID))
+	require.NoError(t, err)
+
+	putPrm.SetObject(lock)
+	_, err = sh.Put(putPrm)
+	require.NoError(t, err)
+
+	var getPrm shard.GetPrm
+	getPrm.SetAddress(objectCore.AddressOf(parent))
+
+	_, err = sh.Get(context.Background(), getPrm)
+	var splitInfoError *objectSDK.SplitInfoError
+	require.True(t, errors.As(err, &splitInfoError), "split info must be provided")
+
+	epoch.Value = 105
+	sh.NotificationChannel() <- shard.EventNewEpoch(epoch.Value)
+
+	require.Eventually(t, func() bool {
+		_, err = sh.Get(context.Background(), getPrm)
+		return shard.IsErrNotFound(err)
+	}, 3*time.Second, 1*time.Second, "expired complex object must be deleted on epoch after lock expires")
+}

pkg/local_object_storage/shard/get.go

@@ -65,6 +65,7 @@ func (r GetRes) HasMeta() bool {
 // Returns an error of type apistatus.ObjectNotFound if the requested object is missing in shard.
 // Returns an error of type apistatus.ObjectAlreadyRemoved if the requested object has been marked as removed in shard.
 // Returns the object.ErrObjectIsExpired if the object is presented but already expired.
+// Returns the ErrShardDisabled if the shard is disabled.
 func (s *Shard) Get(ctx context.Context, prm GetPrm) (GetRes, error) {
 	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.Get",
 		trace.WithAttributes(
@@ -77,6 +78,10 @@ func (s *Shard) Get(ctx context.Context, prm GetPrm) (GetRes, error) {
 	s.m.RLock()
 	defer s.m.RUnlock()
 
+	if s.info.Mode.Disabled() {
+		return GetRes{}, ErrShardDisabled
+	}
+
 	cb := func(stor *blobstor.BlobStor, id []byte) (*objectSDK.Object, error) {
 		var getPrm common.GetPrm
 		getPrm.Address = prm.addr

pkg/local_object_storage/shard/metrics_test.go

@@ -168,7 +168,7 @@ func TestCounters(t *testing.T) {
 		deletedNumber := int(phy / 4)
 		prm.SetAddresses(addrFromObjs(oo[:deletedNumber])...)
 
-		_, err := sh.Delete(prm)
+		_, err := sh.Delete(context.Background(), prm)
 		require.NoError(t, err)
 
 		require.Equal(t, phy-uint64(deletedNumber), mm.objCounters[physical])

pkg/local_object_storage/shard/mode.go

@@ -18,8 +18,8 @@ var ErrDegradedMode = logicerr.New("shard is in degraded mode")
 // Returns any error encountered that did not allow
 // setting shard mode.
 func (s *Shard) SetMode(m mode.Mode) error {
-	s.m.Lock()
-	defer s.m.Unlock()
+	unlock := s.lockExclusive()
+	defer unlock()
 
 	return s.setMode(m)
 }
@@ -55,11 +55,13 @@ func (s *Shard) setMode(m mode.Mode) error {
 		}
 	}
 
+	if !m.Disabled() {
 		for i := range components {
 			if err := components[i].SetMode(m); err != nil {
 				return err
 			}
 		}
+	}
 
 	s.info.Mode = m
 	if s.metricsWriter != nil {

pkg/local_object_storage/shard/mode/mode.go

@@ -57,3 +57,7 @@ func (m Mode) NoMetabase() bool {
 func (m Mode) ReadOnly() bool {
 	return m&ReadOnly != 0
 }
+
+func (m Mode) Disabled() bool {
+	return m == Disabled
+}

pkg/local_object_storage/shard/range.go

@@ -72,6 +72,7 @@ func (r RngRes) HasMeta() bool {
 // Returns an error of type apistatus.ObjectNotFound if the requested object is missing.
 // Returns an error of type apistatus.ObjectAlreadyRemoved if the requested object has been marked as removed in shard.
 // Returns the object.ErrObjectIsExpired if the object is presented but already expired.
+// Returns the ErrShardDisabled if the shard is disabled.
 func (s *Shard) GetRange(ctx context.Context, prm RngPrm) (RngRes, error) {
 	ctx, span := tracing.StartSpanFromContext(ctx, "Shard.GetRange",
 		trace.WithAttributes(
@@ -86,6 +87,10 @@ func (s *Shard) GetRange(ctx context.Context, prm RngPrm) (RngRes, error) {
 	s.m.RLock()
 	defer s.m.RUnlock()
 
+	if s.info.Mode.Disabled() {
+		return RngRes{}, ErrShardDisabled
+	}
+
 	cb := func(stor *blobstor.BlobStor, id []byte) (*object.Object, error) {
 		var getRngPrm common.GetRangePrm
 		getRngPrm.Address = prm.addr

pkg/local_object_storage/shard/range_test.go

@@ -84,7 +84,8 @@ func testShardGetRange(t *testing.T, hasWriteCache bool) {
 				Storage: fstree.New(
 					fstree.WithPath(filepath.Join(t.TempDir(), "blob"))),
 			},
-		})})
+		})},
+		nil)
 	defer releaseShard(sh, t)
 
 	for _, tc := range testCases {

pkg/local_object_storage/shard/shard.go

@@ -3,6 +3,7 @@ package shard
 import (
 	"context"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
@@ -31,6 +32,9 @@ type Shard struct {
 	metaBase *meta.DB
 
 	tsSource TombstoneSource
+
+	gcCancel         atomic.Value
+	setModeRequested atomic.Bool
 }
 
 // Option represents Shard's constructor option.
@@ -209,12 +213,12 @@ func WithWriteCache(use bool) Option {
 }
 
 // hasWriteCache returns bool if write cache exists on shards.
-func (s Shard) hasWriteCache() bool {
+func (s *Shard) hasWriteCache() bool {
 	return s.cfg.useWriteCache
 }
 
 // needRefillMetabase returns true if metabase is needed to be refilled.
-func (s Shard) needRefillMetabase() bool {
+func (s *Shard) needRefillMetabase() bool {
 	return s.cfg.refillMetabase
 }
 

pkg/local_object_storage/shard/shard_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/blobovniczatree"
@@ -12,8 +13,11 @@ 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/writecache"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/panjf2000/ants/v2"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zaptest"
@@ -29,11 +33,13 @@ func (s epochState) CurrentEpoch() uint64 {
 
 func newShard(t testing.TB, enableWriteCache bool) *shard.Shard {
 	return newCustomShard(t, t.TempDir(), enableWriteCache,
+		nil,
 		nil,
 		nil)
 }
 
-func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts []writecache.Option, bsOpts []blobstor.Option) *shard.Shard {
+func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts []writecache.Option, bsOpts []blobstor.Option, metaOptions []meta.Option) *shard.Shard {
+	var sh *shard.Shard
 	if enableWriteCache {
 		rootPath = filepath.Join(rootPath, "wc")
 	} else {
@@ -67,8 +73,9 @@ func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts
 		shard.WithLogger(&logger.Logger{Logger: zap.L()}),
 		shard.WithBlobStorOptions(bsOpts...),
 		shard.WithMetaBaseOptions(
-			meta.WithPath(filepath.Join(rootPath, "meta")),
-			meta.WithEpochState(epochState{}),
+			append([]meta.Option{
+				meta.WithPath(filepath.Join(rootPath, "meta")), meta.WithEpochState(epochState{})},
+				metaOptions...)...,
 		),
 		shard.WithPiloramaOptions(pilorama.WithPath(filepath.Join(rootPath, "pilorama"))),
 		shard.WithWriteCache(enableWriteCache),
@@ -77,9 +84,21 @@ func newCustomShard(t testing.TB, rootPath string, enableWriteCache bool, wcOpts
 				[]writecache.Option{writecache.WithPath(filepath.Join(rootPath, "wcache"))},
 				wcOpts...)...,
 		),
+		shard.WithDeletedLockCallback(func(_ context.Context, addresses []oid.Address) {
+			sh.HandleDeletedLocks(addresses)
+		}),
+		shard.WithExpiredLocksCallback(func(ctx context.Context, epoch uint64, a []oid.Address) {
+			sh.HandleExpiredLocks(ctx, epoch, a)
+		}),
+		shard.WithGCWorkerPoolInitializer(func(sz int) util.WorkerPool {
+			pool, err := ants.NewPool(sz)
+			require.NoError(t, err)
+			return pool
+		}),
+		shard.WithGCRemoverSleepInterval(1 * time.Millisecond),
 	}
 
-	sh := shard.New(opts...)
+	sh = shard.New(opts...)
 
 	require.NoError(t, sh.Open())
 	require.NoError(t, sh.Init(context.Background()))

pkg/local_object_storage/shard/shutdown_test.go

@@ -37,7 +37,7 @@ func TestWriteCacheObjectLoss(t *testing.T) {
 		writecache.WithSmallObjectSize(smallSize),
 		writecache.WithMaxObjectSize(smallSize * 2)}
 
-	sh := newCustomShard(t, dir, true, wcOpts, nil)
+	sh := newCustomShard(t, dir, true, wcOpts, nil, nil)
 
 	var putPrm shard.PutPrm
 
@@ -48,7 +48,7 @@ func TestWriteCacheObjectLoss(t *testing.T) {
 	}
 	require.NoError(t, sh.Close())
 
-	sh = newCustomShard(t, dir, true, wcOpts, nil)
+	sh = newCustomShard(t, dir, true, wcOpts, nil, nil)
 	defer releaseShard(sh, t)
 
 	var getPrm shard.GetPrm

pkg/local_object_storage/shard/tree.go

@@ -155,6 +155,21 @@ func (s *Shard) TreeList(cid cidSDK.ID) ([]string, error) {
 	return s.pilorama.TreeList(cid)
 }
 
+func (s *Shard) TreeHeight(cid cidSDK.ID, treeID string) (uint64, error) {
+	if s.pilorama == nil {
+		return 0, ErrPiloramaDisabled
+	}
+
+	s.m.RLock()
+	defer s.m.RUnlock()
+
+	if s.info.Mode.NoMetabase() {
+		return 0, ErrDegradedMode
+	}
+
+	return s.pilorama.TreeHeight(cid, treeID)
+}
+
 // TreeExists implements the pilorama.Forest interface.
 func (s *Shard) TreeExists(cid cidSDK.ID, treeID string) (bool, error) {
 	if s.pilorama == nil {

pkg/local_object_storage/writecache/flush.go

@@ -32,11 +32,11 @@ const (
 func (c *cache) runFlushLoop() {
 	for i := 0; i < c.workersCount; i++ {
 		c.wg.Add(1)
-		go c.flushWorker(i)
+		go c.workerFlushSmall()
 	}
 
 	c.wg.Add(1)
-	go c.flushBigObjects()
+	go c.workerFlushBig()
 
 	c.wg.Add(1)
 	go func() {
@@ -48,7 +48,7 @@ func (c *cache) runFlushLoop() {
 		for {
 			select {
 			case <-tt.C:
-				c.flushDB()
+				c.flushSmallObjects()
 				tt.Reset(defaultFlushInterval)
 			case <-c.closeCh:
 				return
@@ -57,7 +57,7 @@ func (c *cache) runFlushLoop() {
 	}()
 }
 
-func (c *cache) flushDB() {
+func (c *cache) flushSmallObjects() {
 	var lastKey []byte
 	var m []objectInfo
 	for {
@@ -70,7 +70,7 @@ func (c *cache) flushDB() {
 		m = m[:0]
 
 		c.modeMtx.RLock()
-		if c.readOnly() || !c.initialized.Load() {
+		if c.readOnly() {
 			c.modeMtx.RUnlock()
 			time.Sleep(time.Second)
 			continue
@@ -109,10 +109,6 @@ func (c *cache) flushDB() {
 
 		var count int
 		for i := range m {
-			if c.flushed.Contains(m[i].addr) {
-				continue
-			}
-
 			obj := object.New()
 			if err := obj.Unmarshal(m[i].data); err != nil {
 				continue
@@ -140,7 +136,7 @@ func (c *cache) flushDB() {
 	}
 }
 
-func (c *cache) flushBigObjects() {
+func (c *cache) workerFlushBig() {
 	defer c.wg.Done()
 
 	tick := time.NewTicker(defaultFlushInterval * 10)
@@ -151,9 +147,6 @@ func (c *cache) flushBigObjects() {
 			if c.readOnly() {
 				c.modeMtx.RUnlock()
 				break
-			} else if !c.initialized.Load() {
-				c.modeMtx.RUnlock()
-				continue
 			}
 
 			_ = c.flushFSTree(true)
@@ -181,10 +174,6 @@ func (c *cache) flushFSTree(ignoreErrors bool) error {
 	prm.LazyHandler = func(addr oid.Address, f func() ([]byte, error)) error {
 		sAddr := addr.EncodeToString()
 
-		if _, ok := c.store.flushed.Peek(sAddr); ok {
-			return nil
-		}
-
 		data, err := f()
 		if err != nil {
 			c.reportFlushError("can't read a file", sAddr, err)
@@ -212,9 +201,7 @@ func (c *cache) flushFSTree(ignoreErrors bool) error {
 			return err
 		}
 
-		// mark object as flushed
-		c.flushed.Add(sAddr, false)
-
+		c.deleteFromDisk([]string{sAddr})
 		return nil
 	}
 
@@ -222,8 +209,8 @@ func (c *cache) flushFSTree(ignoreErrors bool) error {
 	return err
 }
 
-// flushWorker writes objects to the main storage.
-func (c *cache) flushWorker(_ int) {
+// workerFlushSmall writes small objects to the main storage.
+func (c *cache) workerFlushSmall() {
 	defer c.wg.Done()
 
 	var obj *object.Object
@@ -236,9 +223,12 @@ func (c *cache) flushWorker(_ int) {
 		}
 
 		err := c.flushObject(obj, nil)
-		if err == nil {
-			c.flushed.Add(objectCore.AddressOf(obj).EncodeToString(), true)
+		if err != nil {
+			// Error is handled in flushObject.
+			continue
 		}
+
+		c.deleteFromDB([]string{objectCore.AddressOf(obj).EncodeToString()})
 	}
 }
 
@@ -294,10 +284,6 @@ func (c *cache) flush(ignoreErrors bool) error {
 		cs := b.Cursor()
 		for k, data := cs.Seek(nil); k != nil; k, data = cs.Next() {
 			sa := string(k)
-			if _, ok := c.flushed.Peek(sa); ok {
-				continue
-			}
-
 			if err := addr.DecodeString(sa); err != nil {
 				c.reportFlushError("can't decode object address from the DB", sa, err)
 				if ignoreErrors {

pkg/local_object_storage/writecache/flush_test.go

@@ -5,7 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
-	"time"
 
 	objectCore "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/core/object"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor"
@@ -15,7 +14,6 @@ import (
 	"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"
-	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 	cidtest "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id/test"
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
 	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
@@ -109,22 +107,9 @@ func TestFlush(t *testing.T) {
 		require.NoError(t, bs.SetMode(mode.ReadWrite))
 		require.NoError(t, mb.SetMode(mode.ReadWrite))
 
-		wc.(*cache).flushed.Add(objects[0].addr.EncodeToString(), true)
-		wc.(*cache).flushed.Add(objects[1].addr.EncodeToString(), false)
-
 		require.NoError(t, wc.Flush(false))
 
-		for i := 0; i < 2; i++ {
-			var mPrm meta.GetPrm
-			mPrm.SetAddress(objects[i].addr)
-			_, err := mb.Get(mPrm)
-			require.Error(t, err)
-
-			_, err = bs.Get(context.Background(), common.GetPrm{Address: objects[i].addr})
-			require.Error(t, err)
-		}
-
-		check(t, mb, bs, objects[2:])
+		check(t, mb, bs, objects)
 	})
 
 	t.Run("flush on moving to degraded mode", func(t *testing.T) {
@@ -138,23 +123,9 @@ func TestFlush(t *testing.T) {
 		require.NoError(t, wc.SetMode(mode.ReadOnly))
 		require.NoError(t, bs.SetMode(mode.ReadWrite))
 		require.NoError(t, mb.SetMode(mode.ReadWrite))
-
-		wc.(*cache).flushed.Add(objects[0].addr.EncodeToString(), true)
-		wc.(*cache).flushed.Add(objects[1].addr.EncodeToString(), false)
-
 		require.NoError(t, wc.SetMode(mode.Degraded))
 
-		for i := 0; i < 2; i++ {
-			var mPrm meta.GetPrm
-			mPrm.SetAddress(objects[i].addr)
-			_, err := mb.Get(mPrm)
-			require.Error(t, err)
-
-			_, err = bs.Get(context.Background(), common.GetPrm{Address: objects[i].addr})
-			require.Error(t, err)
-		}
-
-		check(t, mb, bs, objects[2:])
+		check(t, mb, bs, objects)
 	})
 
 	t.Run("ignore errors", func(t *testing.T) {
@@ -223,67 +194,6 @@ func TestFlush(t *testing.T) {
 			})
 		})
 	})
-
-	t.Run("on init", func(t *testing.T) {
-		wc, bs, mb := newCache(t)
-		objects := []objectPair{
-			// removed
-			putObject(t, wc, 1),
-			putObject(t, wc, smallSize+1),
-			// not found
-			putObject(t, wc, 1),
-			putObject(t, wc, smallSize+1),
-			// ok
-			putObject(t, wc, 1),
-			putObject(t, wc, smallSize+1),
-		}
-
-		require.NoError(t, wc.Close())
-		require.NoError(t, bs.SetMode(mode.ReadWrite))
-		require.NoError(t, mb.SetMode(mode.ReadWrite))
-
-		for i := range objects {
-			var prm meta.PutPrm
-			prm.SetObject(objects[i].obj)
-			_, err := mb.Put(prm)
-			require.NoError(t, err)
-		}
-
-		var inhumePrm meta.InhumePrm
-		inhumePrm.SetAddresses(objects[0].addr, objects[1].addr)
-		inhumePrm.SetTombstoneAddress(oidtest.Address())
-		_, err := mb.Inhume(inhumePrm)
-		require.NoError(t, err)
-
-		var deletePrm meta.DeletePrm
-		deletePrm.SetAddresses(objects[2].addr, objects[3].addr)
-		_, err = mb.Delete(deletePrm)
-		require.NoError(t, err)
-
-		require.NoError(t, bs.SetMode(mode.ReadOnly))
-		require.NoError(t, mb.SetMode(mode.ReadOnly))
-
-		// Open in read-only: no error, nothing is removed.
-		require.NoError(t, wc.Open(true))
-		initWC(t, wc)
-		for i := range objects {
-			_, err := wc.Get(context.Background(), objects[i].addr)
-			require.NoError(t, err, i)
-		}
-		require.NoError(t, wc.Close())
-
-		// Open in read-write: no error, something is removed.
-		require.NoError(t, wc.Open(false))
-		initWC(t, wc)
-		for i := range objects {
-			_, err := wc.Get(context.Background(), objects[i].addr)
-			if i < 2 {
-				require.ErrorAs(t, err, new(apistatus.ObjectNotFound), i)
-			} else {
-				require.NoError(t, err, i)
-			}
-		}
-	})
 }
 
 func putObject(t *testing.T, c Cache, size int) objectPair {
@@ -321,11 +231,6 @@ func newObject(t *testing.T, size int) (*object.Object, []byte) {
 
 func initWC(t *testing.T, wc Cache) {
 	require.NoError(t, wc.Init())
-
-	require.Eventually(t, func() bool {
-		rawWc := wc.(*cache)
-		return rawWc.initialized.Load()
-	}, 100*time.Second, 1*time.Millisecond)
 }
 
 type dummyEpoch struct{}

pkg/local_object_storage/writecache/get.go

@@ -30,7 +30,6 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 	value, err := Get(c.db, []byte(saddr))
 	if err == nil {
 		obj := objectSDK.New()
-		c.flushed.Get(saddr)
 		return obj, obj.Unmarshal(value)
 	}
 
@@ -39,7 +38,6 @@ func (c *cache) Get(ctx context.Context, addr oid.Address) (*objectSDK.Object, e
 		return nil, logicerr.Wrap(apistatus.ObjectNotFound{})
 	}
 
-	c.flushed.Get(saddr)
 	return res.Object, nil
 }
 

pkg/local_object_storage/writecache/init.go

@@ -1,183 +0,0 @@
-package writecache
-
-import (
-	"context"
-	"errors"
-	"sync"
-
-	"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"
-	meta "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase"
-	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
-	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
-	"go.etcd.io/bbolt"
-	"go.uber.org/zap"
-)
-
-func (c *cache) initFlushMarks() {
-	var localWG sync.WaitGroup
-
-	localWG.Add(1)
-	go func() {
-		defer localWG.Done()
-
-		c.fsTreeFlushMarkUpdate()
-	}()
-
-	localWG.Add(1)
-	go func() {
-		defer localWG.Done()
-
-		c.dbFlushMarkUpdate()
-	}()
-
-	c.initWG.Add(1)
-	c.wg.Add(1)
-	go func() {
-		defer c.wg.Done()
-		defer c.initWG.Done()
-
-		localWG.Wait()
-
-		select {
-		case <-c.stopInitCh:
-			return
-		case <-c.closeCh:
-			return
-		default:
-		}
-
-		c.initialized.Store(true)
-	}()
-}
-
-var errStopIter = errors.New("stop iteration")
-
-func (c *cache) fsTreeFlushMarkUpdate() {
-	c.log.Info("filling flush marks for objects in FSTree")
-
-	var prm common.IteratePrm
-	prm.LazyHandler = func(addr oid.Address, _ func() ([]byte, error)) error {
-		select {
-		case <-c.closeCh:
-			return errStopIter
-		case <-c.stopInitCh:
-			return errStopIter
-		default:
-		}
-
-		flushed, needRemove := c.flushStatus(addr)
-		if flushed {
-			c.store.flushed.Add(addr.EncodeToString(), true)
-			if needRemove {
-				var prm common.DeletePrm
-				prm.Address = addr
-
-				_, err := c.fsTree.Delete(prm)
-				if err == nil {
-					storagelog.Write(c.log,
-						storagelog.AddressField(addr),
-						storagelog.StorageTypeField(wcStorageType),
-						storagelog.OpField("fstree DELETE"),
-					)
-				}
-			}
-		}
-		return nil
-	}
-	_, _ = c.fsTree.Iterate(prm)
-	c.log.Info("finished updating FSTree flush marks")
-}
-
-func (c *cache) dbFlushMarkUpdate() {
-	c.log.Info("filling flush marks for objects in database")
-
-	var m []string
-	var indices []int
-	var lastKey []byte
-	var batchSize = flushBatchSize
-	for {
-		select {
-		case <-c.closeCh:
-			return
-		case <-c.stopInitCh:
-			return
-		default:
-		}
-
-		m = m[:0]
-		indices = indices[:0]
-
-		// We put objects in batches of fixed size to not interfere with main put cycle a lot.
-		_ = c.db.View(func(tx *bbolt.Tx) error {
-			b := tx.Bucket(defaultBucket)
-			cs := b.Cursor()
-			for k, _ := cs.Seek(lastKey); k != nil && len(m) < batchSize; k, _ = cs.Next() {
-				m = append(m, string(k))
-			}
-			return nil
-		})
-
-		var addr oid.Address
-		for i := range m {
-			if err := addr.DecodeString(m[i]); err != nil {
-				continue
-			}
-
-			flushed, needRemove := c.flushStatus(addr)
-			if flushed {
-				c.store.flushed.Add(addr.EncodeToString(), true)
-				if needRemove {
-					indices = append(indices, i)
-				}
-			}
-		}
-
-		if len(m) == 0 {
-			break
-		}
-
-		err := c.db.Batch(func(tx *bbolt.Tx) error {
-			b := tx.Bucket(defaultBucket)
-			for _, j := range indices {
-				if err := b.Delete([]byte(m[j])); err != nil {
-					return err
-				}
-			}
-			return nil
-		})
-		if err == nil {
-			for _, j := range indices {
-				storagelog.Write(c.log,
-					zap.String("address", m[j]),
-					storagelog.StorageTypeField(wcStorageType),
-					storagelog.OpField("db DELETE"),
-				)
-			}
-		}
-		lastKey = append([]byte(m[len(m)-1]), 0)
-	}
-
-	c.log.Info("finished updating flush marks")
-}
-
-// flushStatus returns info about the object state in the main storage.
-// First return value is true iff object exists.
-// Second return value is true iff object can be safely removed.
-func (c *cache) flushStatus(addr oid.Address) (bool, bool) {
-	var existsPrm meta.ExistsPrm
-	existsPrm.SetAddress(addr)
-
-	_, err := c.metabase.Exists(existsPrm)
-	if err != nil {
-		needRemove := errors.Is(err, meta.ErrObjectIsExpired) || errors.As(err, new(apistatus.ObjectAlreadyRemoved))
-		return needRemove, needRemove
-	}
-
-	var prm meta.StorageIDPrm
-	prm.SetAddress(addr)
-
-	mRes, _ := c.metabase.StorageID(prm)
-	res, err := c.blobstor.Exists(context.TODO(), common.ExistsPrm{Address: addr, StorageID: mRes.StorageID()})
-	return err == nil && res.Exists, false
-}

pkg/local_object_storage/writecache/iterate.go

@@ -41,9 +41,6 @@ func (c *cache) Iterate(prm IterationPrm) error {
 	err := c.db.View(func(tx *bbolt.Tx) error {
 		b := tx.Bucket(defaultBucket)
 		return b.ForEach(func(k, data []byte) error {
-			if _, ok := c.flushed.Peek(string(k)); ok {
-				return nil
-			}
 			return prm.handler(data)
 		})
 	})
@@ -54,9 +51,6 @@ func (c *cache) Iterate(prm IterationPrm) error {
 	var fsPrm common.IteratePrm
 	fsPrm.IgnoreErrors = prm.ignoreErrors
 	fsPrm.LazyHandler = func(addr oid.Address, f func() ([]byte, error)) error {
-		if _, ok := c.flushed.Peek(addr.EncodeToString()); ok {
-			return nil
-		}
 		data, err := f()
 		if err != nil {
 			if prm.ignoreErrors {

pkg/local_object_storage/writecache/mode.go

@@ -36,19 +36,6 @@ func (c *cache) setMode(m mode.Mode) error {
 		}
 	}
 
-	if !c.initialized.Load() {
-		close(c.stopInitCh)
-
-		c.initWG.Wait()
-		c.stopInitCh = make(chan struct{})
-
-		defer func() {
-			if err == nil && !turnOffMeta {
-				c.initFlushMarks()
-			}
-		}()
-	}
-
 	if c.db != nil {
 		if err = c.db.Close(); err != nil {
 			return fmt.Errorf("can't close write-cache database: %w", err)

pkg/local_object_storage/writecache/put.go

@@ -26,8 +26,6 @@ func (c *cache) Put(prm common.PutPrm) (common.PutRes, error) {
 	defer c.modeMtx.RUnlock()
 	if c.readOnly() {
 		return common.PutRes{}, ErrReadOnly
-	} else if !c.initialized.Load() {
-		return common.PutRes{}, ErrNotInitialized
 	}
 
 	sz := uint64(len(prm.RawData))
@@ -67,7 +65,7 @@ func (c *cache) putSmall(obj objectInfo) error {
 		)
 		c.objCounters.IncDB()
 	}
-	return nil
+	return err
 }
 
 // putBig writes object to FSTree and pushes it to the flush workers queue.

pkg/local_object_storage/writecache/storage.go

@@ -11,8 +11,6 @@ import (
 	"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"
-	lru "github.com/hashicorp/golang-lru/v2"
-	"github.com/hashicorp/golang-lru/v2/simplelru"
 	"go.etcd.io/bbolt"
 	"go.uber.org/zap"
 )
@@ -20,19 +18,7 @@ import (
 // store represents persistent storage with in-memory LRU cache
 // for flushed items on top of it.
 type store struct {
-	maxFlushedMarksCount int
-	maxRemoveBatchSize   int
-
-	// flushed contains addresses of objects that were already flushed to the main storage.
-	// We use LRU cache instead of map here to facilitate removing of unused object in favour of
-	// frequently read ones.
-	// MUST NOT be used inside bolt db transaction because it's eviction handler
-	// removes untracked items from the database.
-	flushed simplelru.LRUCache[string, bool]
 	db *bbolt.DB
-
-	dbKeysToRemove []string
-	fsKeysToRemove []string
 }
 
 const dbName = "small.bolt"
@@ -71,35 +57,9 @@ func (c *cache) openStore(readOnly bool) error {
 		return fmt.Errorf("could not open FSTree: %w", err)
 	}
 
-	// Write-cache can be opened multiple times during `SetMode`.
-	// flushed map must not be re-created in this case.
-	if c.flushed == nil {
-		c.flushed, _ = lru.NewWithEvict[string, bool](c.maxFlushedMarksCount, c.removeFlushed)
-	}
-
-	c.initialized.Store(false)
-
 	return nil
 }
 
-// removeFlushed removes an object from the writecache.
-// To minimize interference with the client operations, the actual removal
-// is done in batches.
-// It is not thread-safe and is used only as an evict callback to LRU cache.
-func (c *cache) removeFlushed(key string, value bool) {
-	fromDatabase := value
-	if fromDatabase {
-		c.dbKeysToRemove = append(c.dbKeysToRemove, key)
-	} else {
-		c.fsKeysToRemove = append(c.fsKeysToRemove, key)
-	}
-
-	if len(c.dbKeysToRemove)+len(c.fsKeysToRemove) >= c.maxRemoveBatchSize {
-		c.dbKeysToRemove = c.deleteFromDB(c.dbKeysToRemove)
-		c.fsKeysToRemove = c.deleteFromDisk(c.fsKeysToRemove)
-	}
-}
-
 func (c *cache) deleteFromDB(keys []string) []string {
 	if len(keys) == 0 {
 		return keys

pkg/local_object_storage/writecache/writecache.go

@@ -12,7 +12,6 @@ import (
 	"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/atomic"
 	"go.uber.org/zap"
 )
 
@@ -52,9 +51,6 @@ type cache struct {
 	mtx sync.RWMutex
 
 	mode    mode.Mode
-	initialized atomic.Bool
-	stopInitCh  chan struct{}  // used to sync initWG initialisation routines and _only_ them
-	initWG      sync.WaitGroup // for initialisation routines only
 	modeMtx sync.RWMutex
 
 	// compressFlags maps address of a big object to boolean value indicating
@@ -97,7 +93,6 @@ func New(opts ...Option) Cache {
 	c := &cache{
 		flushCh: make(chan *object.Object),
 		mode:    mode.ReadWrite,
-		stopInitCh: make(chan struct{}),
 
 		compressFlags: make(map[string]struct{}),
 		options: options{
@@ -116,12 +111,6 @@ func New(opts ...Option) Cache {
 		opts[i](&c.options)
 	}
 
-	// Make the LRU cache contain which take approximately 3/4 of the maximum space.
-	// Assume small and big objects are stored in 50-50 proportion.
-	c.maxFlushedMarksCount = int(c.maxCacheSize/c.maxObjectSize+c.maxCacheSize/c.smallObjectSize) / 2 * 3 / 4
-	// Trigger the removal when the cache is 7/8 full, so that new items can still arrive.
-	c.maxRemoveBatchSize = c.maxFlushedMarksCount / 8
-
 	return c
 }
 
@@ -152,31 +141,27 @@ func (c *cache) Open(readOnly bool) error {
 
 // Init runs necessary services.
 func (c *cache) Init() error {
-	c.initFlushMarks()
 	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()
-	defer c.modeMtx.Unlock()
-
-	// Finish all in-progress operations.
-	if err := c.setMode(mode.ReadOnly); err != nil {
-		return err
-	}
-
 	if c.closeCh != nil {
 		close(c.closeCh)
 	}
+	c.mode = mode.DegradedReadOnly // prevent new operations from being processed
+	c.modeMtx.Unlock()
+
 	c.wg.Wait()
-	if c.closeCh != nil {
+
+	c.modeMtx.Lock()
+	defer c.modeMtx.Unlock()
+
 	c.closeCh = nil
-	}
-
-	c.initialized.Store(false)
-
 	var err error
 	if c.db != nil {
 		err = c.db.Close()

pkg/morph/client/client.go

@@ -57,8 +57,6 @@ type Client struct {
 	acc     *wallet.Account // neo account
 	accAddr util.Uint160    // account's address
 
-	signer *transaction.Signer
-
 	notary *notaryInfo
 
 	cfg cfg
@@ -70,9 +68,6 @@ type Client struct {
 	// on every normal call.
 	switchLock *sync.RWMutex
 
-	notifications chan rpcclient.Notification
-	subsInfo      // protected with switchLock
-
 	// channel for internal stop
 	closeChan chan struct{}
 
@@ -567,26 +562,11 @@ func (c *Client) IsValidScript(script []byte, signers []transaction.Signer) (val
 
 // NotificationChannel returns channel than receives subscribed
 // notification from the connected RPC node.
-// Channel is closed when connection to the RPC node has been
-// lost without the possibility of recovery.
+// Channel is closed when connection to the RPC node is lost.
 func (c *Client) NotificationChannel() <-chan rpcclient.Notification {
-	return c.notifications
-}
-
-// inactiveMode switches Client to an inactive mode:
-// - notification channel is closed;
-// - all the new RPC request would return ErrConnectionLost;
-// - inactiveModeCb is called if not nil.
-func (c *Client) inactiveMode() {
-	c.switchLock.Lock()
-	defer c.switchLock.Unlock()
-
-	close(c.notifications)
-	c.inactive = true
-
-	if c.cfg.inactiveModeCb != nil {
-		c.cfg.inactiveModeCb()
-	}
+	c.switchLock.RLock()
+	defer c.switchLock.RUnlock()
+	return c.client.Notifications //lint:ignore SA1019 waits for neo-go v0.102.0 https://github.com/nspcc-dev/neo-go/pull/2980
 }
 
 func (c *Client) setActor(act *actor.Actor) {

pkg/morph/client/constructor.go

@@ -9,11 +9,8 @@ import (
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	lru "github.com/hashicorp/golang-lru/v2"
-	"github.com/nspcc-dev/neo-go/pkg/core/block"
-	"github.com/nspcc-dev/neo-go/pkg/core/state"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
-	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
 	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
 	"github.com/nspcc-dev/neo-go/pkg/rpcclient/actor"
 	"github.com/nspcc-dev/neo-go/pkg/util"
@@ -105,17 +102,8 @@ func New(ctx context.Context, key *keys.PrivateKey, opts ...Option) (*Client, er
 		logger:     cfg.logger,
 		acc:        acc,
 		accAddr:    accAddr,
-		signer:        cfg.signer,
 		cfg:        *cfg,
 		switchLock: &sync.RWMutex{},
-		notifications: make(chan rpcclient.Notification),
-		subsInfo: subsInfo{
-			blockRcv:               make(chan *block.Block),
-			notificationRcv:        make(chan *state.ContainedNotificationEvent),
-			notaryReqRcv:           make(chan *result.NotaryRequestEvent),
-			subscribedEvents:       make(map[util.Uint160]string),
-			subscribedNotaryEvents: make(map[util.Uint160]string),
-		},
 		closeChan:  make(chan struct{}),
 	}
 
@@ -145,7 +133,7 @@ func New(ctx context.Context, key *keys.PrivateKey, opts ...Option) (*Client, er
 	}
 	cli.setActor(act)
 
-	go cli.notificationLoop(ctx)
+	go cli.closeWaiter(ctx)
 
 	return cli, nil
 }

pkg/morph/client/multi.go

@@ -5,11 +5,6 @@ import (
 	"sort"
 	"time"
 
-	"github.com/nspcc-dev/neo-go/pkg/core/block"
-	"github.com/nspcc-dev/neo-go/pkg/core/state"
-	"github.com/nspcc-dev/neo-go/pkg/neorpc"
-	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
-	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
 	"go.uber.org/zap"
 )
 
@@ -33,7 +28,8 @@ func (e *endpoints) init(ee []Endpoint) {
 	e.list = ee
 }
 
-func (c *Client) switchRPC(ctx context.Context) bool {
+// SwitchRPC performs reconnection and returns true if it was successful.
+func (c *Client) SwitchRPC(ctx context.Context) bool {
 	c.switchLock.Lock()
 	defer c.switchLock.Unlock()
 
@@ -57,20 +53,8 @@ func (c *Client) switchRPC(ctx context.Context) bool {
 		c.logger.Info("connection to the new RPC node has been established",
 			zap.String("endpoint", newEndpoint))
 
-		subs, ok := c.restoreSubscriptions(ctx, cli, newEndpoint, false)
-		if !ok {
-			// new WS client does not allow
-			// restoring subscription, client
-			// could not work correctly =>
-			// closing connection to RPC node
-			// to switch to another one
-			cli.Close()
-			continue
-		}
-
 		c.client = cli
 		c.setActor(act)
-		c.subsInfo = subs
 
 		if c.cfg.switchInterval != 0 && !c.switchIsActive.Load() &&
 			c.endpoints.list[c.endpoints.curr].Priority != c.endpoints.list[0].Priority {
@@ -81,97 +65,21 @@ func (c *Client) switchRPC(ctx context.Context) bool {
 		return true
 	}
 
+	c.inactive = true
+
+	if c.cfg.inactiveModeCb != nil {
+		c.cfg.inactiveModeCb()
+	}
 	return false
 }
 
-func (c *Client) notificationLoop(ctx context.Context) {
-	var e any
-	var ok bool
-
-	for {
-		c.switchLock.RLock()
-		bChan := c.blockRcv
-		nChan := c.notificationRcv
-		nrChan := c.notaryReqRcv
-		c.switchLock.RUnlock()
-
+func (c *Client) closeWaiter(ctx context.Context) {
 	select {
 	case <-ctx.Done():
-			_ = c.UnsubscribeAll()
-			c.close()
-
-			return
 	case <-c.closeChan:
+	}
 	_ = c.UnsubscribeAll()
 	c.close()
-
-			return
-		case e, ok = <-bChan:
-		case e, ok = <-nChan:
-		case e, ok = <-nrChan:
-		}
-
-		if ok {
-			c.routeEvent(ctx, e)
-			continue
-		}
-
-		if !c.reconnect(ctx) {
-			return
-		}
-	}
-}
-
-func (c *Client) routeEvent(ctx context.Context, e any) {
-	typedNotification := rpcclient.Notification{Value: e}
-
-	switch e.(type) {
-	case *block.Block:
-		typedNotification.Type = neorpc.BlockEventID
-	case *state.ContainedNotificationEvent:
-		typedNotification.Type = neorpc.NotificationEventID
-	case *result.NotaryRequestEvent:
-		typedNotification.Type = neorpc.NotaryRequestEventID
-	}
-
-	select {
-	case c.notifications <- typedNotification:
-	case <-ctx.Done():
-		_ = c.UnsubscribeAll()
-		c.close()
-	case <-c.closeChan:
-		_ = c.UnsubscribeAll()
-		c.close()
-	}
-}
-
-func (c *Client) reconnect(ctx context.Context) bool {
-	if closeErr := c.client.GetError(); closeErr != nil {
-		c.logger.Warn("switching to the next RPC node",
-			zap.String("reason", closeErr.Error()),
-		)
-	} else {
-		// neo-go client was closed by calling `Close`
-		// method, that happens only when a client has
-		// switched to the more prioritized RPC
-		return true
-	}
-
-	if !c.switchRPC(ctx) {
-		c.logger.Error("could not establish connection to any RPC node")
-
-		// could not connect to all endpoints =>
-		// switch client to inactive mode
-		c.inactiveMode()
-
-		return false
-	}
-
-	// TODO(@carpawell): call here some callback retrieved in constructor
-	// of the client to allow checking chain state since during switch
-	// process some notification could be lost
-
-	return true
 }
 
 func (c *Client) switchToMostPrioritized(ctx context.Context) {
@@ -217,7 +125,6 @@ mainLoop:
 					continue
 				}
 
-				if subs, ok := c.restoreSubscriptions(ctx, cli, tryE, true); ok {
 				c.switchLock.Lock()
 
 				// higher priority node could have been
@@ -232,7 +139,6 @@ mainLoop:
 				c.cache.invalidate()
 				c.client = cli
 				c.setActor(act)
-					c.subsInfo = subs
 				c.endpoints.curr = i
 
 				c.switchLock.Unlock()
@@ -242,18 +148,13 @@ mainLoop:
 
 				return
 			}
-
-				c.logger.Warn("could not restore side chain subscriptions using node",
-					zap.String("endpoint", tryE),
-					zap.Error(err),
-				)
-			}
 		}
 	}
 }
 
 // close closes notification channel and wrapped WS client.
 func (c *Client) close() {
-	close(c.notifications)
+	c.switchLock.RLock()
+	defer c.switchLock.RUnlock()
 	c.client.Close()
 }

pkg/morph/client/nns.go

@@ -208,8 +208,8 @@ func (c *Client) SetGroupSignerScope() error {
 		return err
 	}
 
-	c.signer.Scopes = transaction.CustomGroups
-	c.signer.AllowedGroups = []*keys.PublicKey{pub}
+	c.cfg.signer.Scopes = transaction.CustomGroups
+	c.cfg.signer.AllowedGroups = []*keys.PublicKey{pub}
 	return nil
 }
 

pkg/morph/client/notary.go

@@ -596,18 +596,18 @@ func (c *Client) notaryCosigners(invokedByAlpha bool, ir []*keys.PublicKey, comm
 
 	s = append(s, transaction.Signer{
 		Account:          hash.Hash160(multisigScript),
-		Scopes:           c.signer.Scopes,
-		AllowedContracts: c.signer.AllowedContracts,
-		AllowedGroups:    c.signer.AllowedGroups,
+		Scopes:           c.cfg.signer.Scopes,
+		AllowedContracts: c.cfg.signer.AllowedContracts,
+		AllowedGroups:    c.cfg.signer.AllowedGroups,
 	})
 
 	if !invokedByAlpha {
 		// then we have invoker signature
 		s = append(s, transaction.Signer{
 			Account:          hash.Hash160(c.acc.GetVerificationScript()),
-			Scopes:           c.signer.Scopes,
-			AllowedContracts: c.signer.AllowedContracts,
-			AllowedGroups:    c.signer.AllowedGroups,
+			Scopes:           c.cfg.signer.Scopes,
+			AllowedContracts: c.cfg.signer.AllowedContracts,
+			AllowedGroups:    c.cfg.signer.AllowedGroups,
 		})
 	}
 

pkg/morph/client/notifications.go

@@ -1,15 +1,11 @@
 package client
 
 import (
-	"context"
-
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
 	"github.com/nspcc-dev/neo-go/pkg/neorpc"
 	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
-	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
 	"github.com/nspcc-dev/neo-go/pkg/util"
-	"go.uber.org/zap"
 )
 
 // Close closes connection to the remote side making
@@ -23,71 +19,46 @@ func (c *Client) Close() {
 	close(c.closeChan)
 }
 
-// SubscribeForExecutionNotifications adds subscription for notifications
-// generated during contract transaction execution to this instance of client.
+// ReceiveExecutionNotifications performs subscription for notifications
+// generated during contract execution. Events are sent to the specified channel.
 //
 // Returns ErrConnectionLost if client has not been able to establish
 // connection to any of passed RPC endpoints.
-func (c *Client) SubscribeForExecutionNotifications(contract util.Uint160) error {
+func (c *Client) ReceiveExecutionNotifications(contract util.Uint160, ch chan<- *state.ContainedNotificationEvent) (string, error) {
 	c.switchLock.Lock()
 	defer c.switchLock.Unlock()
 
 	if c.inactive {
-		return ErrConnectionLost
+		return "", ErrConnectionLost
 	}
 
-	_, subscribed := c.subscribedEvents[contract]
-	if subscribed {
-		// no need to subscribe one more time
-		return nil
+	return c.client.ReceiveExecutionNotifications(&neorpc.NotificationFilter{Contract: &contract}, ch)
 }
 
-	id, err := c.client.ReceiveExecutionNotifications(&neorpc.NotificationFilter{Contract: &contract}, c.notificationRcv)
-	if err != nil {
-		return err
-	}
-
-	c.subscribedEvents[contract] = id
-
-	return nil
-}
-
-// SubscribeForNewBlocks adds subscription for new block events to this
-// instance of client.
+// ReceiveBlocks performs subscription for new block events. Events are sent
+// to the specified channel.
 //
 // Returns ErrConnectionLost if client has not been able to establish
 // connection to any of passed RPC endpoints.
-func (c *Client) SubscribeForNewBlocks() error {
+func (c *Client) ReceiveBlocks(ch chan<- *block.Block) (string, error) {
 	c.switchLock.Lock()
 	defer c.switchLock.Unlock()
 
 	if c.inactive {
-		return ErrConnectionLost
+		return "", ErrConnectionLost
 	}
 
-	if c.subscribedToBlocks {
-		// no need to subscribe one more time
-		return nil
+	return c.client.ReceiveBlocks(nil, ch)
 }
 
-	_, err := c.client.ReceiveBlocks(nil, c.blockRcv)
-	if err != nil {
-		return err
-	}
-
-	c.subscribedToBlocks = true
-
-	return nil
-}
-
-// SubscribeForNotaryRequests adds subscription for notary request payloads
+// ReceiveNotaryRequests performsn subscription for notary request payloads
 // addition or removal events to this instance of client. Passed txSigner is
 // used as filter: subscription is only for the notary requests that must be
-// signed by txSigner.
+// signed by txSigner. Events are sent to the specified channel.
 //
 // Returns ErrConnectionLost if client has not been able to establish
 // connection to any of passed RPC endpoints.
-func (c *Client) SubscribeForNotaryRequests(txSigner util.Uint160) error {
+func (c *Client) ReceiveNotaryRequests(txSigner util.Uint160, ch chan<- *result.NotaryRequestEvent) (string, error) {
 	if c.notary == nil {
 		panic(notaryNotEnabledPanicMsg)
 	}
@@ -96,30 +67,17 @@ func (c *Client) SubscribeForNotaryRequests(txSigner util.Uint160) error {
 	defer c.switchLock.Unlock()
 
 	if c.inactive {
-		return ErrConnectionLost
+		return "", ErrConnectionLost
 	}
 
-	_, subscribed := c.subscribedNotaryEvents[txSigner]
-	if subscribed {
-		// no need to subscribe one more time
-		return nil
+	return c.client.ReceiveNotaryRequests(&neorpc.TxFilter{Signer: &txSigner}, ch)
 }
 
-	id, err := c.client.ReceiveNotaryRequests(&neorpc.TxFilter{Signer: &txSigner}, c.notaryReqRcv)
-	if err != nil {
-		return err
-	}
-
-	c.subscribedNotaryEvents[txSigner] = id
-
-	return nil
-}
-
-// UnsubscribeContract removes subscription for given contract event stream.
+// Unsubscribe performs unsubscription for the given subscription ID.
 //
 // Returns ErrConnectionLost if client has not been able to establish
 // connection to any of passed RPC endpoints.
-func (c *Client) UnsubscribeContract(contract util.Uint160) error {
+func (c *Client) Unsubscribe(subID string) error {
 	c.switchLock.Lock()
 	defer c.switchLock.Unlock()
 
@@ -127,55 +85,7 @@ func (c *Client) UnsubscribeContract(contract util.Uint160) error {
 		return ErrConnectionLost
 	}
 
-	_, subscribed := c.subscribedEvents[contract]
-	if !subscribed {
-		// no need to unsubscribe contract
-		// without subscription
-		return nil
-	}
-
-	err := c.client.Unsubscribe(c.subscribedEvents[contract])
-	if err != nil {
-		return err
-	}
-
-	delete(c.subscribedEvents, contract)
-
-	return nil
-}
-
-// UnsubscribeNotaryRequest removes subscription for given notary requests
-// signer.
-//
-// Returns ErrConnectionLost if client has not been able to establish
-// connection to any of passed RPC endpoints.
-func (c *Client) UnsubscribeNotaryRequest(signer util.Uint160) error {
-	if c.notary == nil {
-		panic(notaryNotEnabledPanicMsg)
-	}
-
-	c.switchLock.Lock()
-	defer c.switchLock.Unlock()
-
-	if c.inactive {
-		return ErrConnectionLost
-	}
-
-	_, subscribed := c.subscribedNotaryEvents[signer]
-	if !subscribed {
-		// no need to unsubscribe signer's
-		// requests without subscription
-		return nil
-	}
-
-	err := c.client.Unsubscribe(c.subscribedNotaryEvents[signer])
-	if err != nil {
-		return err
-	}
-
-	delete(c.subscribedNotaryEvents, signer)
-
-	return nil
+	return c.client.Unsubscribe(subID)
 }
 
 // UnsubscribeAll removes all active subscriptions of current client.
@@ -190,163 +100,10 @@ func (c *Client) UnsubscribeAll() error {
 		return ErrConnectionLost
 	}
 
-	// no need to unsubscribe if there are
-	// no active subscriptions
-	if len(c.subscribedEvents) == 0 && len(c.subscribedNotaryEvents) == 0 &&
-		!c.subscribedToBlocks {
-		return nil
-	}
-
 	err := c.client.UnsubscribeAll()
 	if err != nil {
 		return err
 	}
 
-	c.subscribedEvents = make(map[util.Uint160]string)
-	c.subscribedNotaryEvents = make(map[util.Uint160]string)
-	c.subscribedToBlocks = false
-
 	return nil
 }
-
-// subsInfo includes channels for ws notifications;
-// cached subscription information.
-type subsInfo struct {
-	blockRcv        chan *block.Block
-	notificationRcv chan *state.ContainedNotificationEvent
-	notaryReqRcv    chan *result.NotaryRequestEvent
-
-	subscribedToBlocks     bool
-	subscribedEvents       map[util.Uint160]string
-	subscribedNotaryEvents map[util.Uint160]string
-}
-
-// restoreSubscriptions restores subscriptions according to cached
-// information about them.
-//
-// If it is NOT a background operation switchLock MUST be held.
-// Returns a pair: the second is a restoration status and the first
-// one contains subscription information applied to the passed cli
-// and receivers for the updated subscriptions.
-// Does not change Client instance.
-func (c *Client) restoreSubscriptions(ctx context.Context, cli *rpcclient.WSClient, endpoint string, background bool) (si subsInfo, ok bool) {
-	var (
-		err error
-		id  string
-	)
-
-	stopCh := make(chan struct{})
-	defer close(stopCh)
-
-	blockRcv := make(chan *block.Block)
-	notificationRcv := make(chan *state.ContainedNotificationEvent)
-	notaryReqRcv := make(chan *result.NotaryRequestEvent)
-
-	c.startListen(ctx, stopCh, blockRcv, notificationRcv, notaryReqRcv, background)
-
-	if background {
-		c.switchLock.RLock()
-		defer c.switchLock.RUnlock()
-	}
-
-	si.subscribedToBlocks = c.subscribedToBlocks
-	si.subscribedEvents = copySubsMap(c.subscribedEvents)
-	si.subscribedNotaryEvents = copySubsMap(c.subscribedNotaryEvents)
-	si.blockRcv = blockRcv
-	si.notificationRcv = notificationRcv
-	si.notaryReqRcv = notaryReqRcv
-
-	// new block events restoration
-	if si.subscribedToBlocks {
-		_, err = cli.ReceiveBlocks(nil, blockRcv)
-		if err != nil {
-			c.logger.Error("could not restore block subscription after RPC switch",
-				zap.String("endpoint", endpoint),
-				zap.Error(err),
-			)
-
-			return
-		}
-	}
-
-	// notification events restoration
-	for contract := range si.subscribedEvents {
-		contract := contract // See https://github.com/nspcc-dev/neo-go/issues/2890
-		id, err = cli.ReceiveExecutionNotifications(&neorpc.NotificationFilter{Contract: &contract}, notificationRcv)
-		if err != nil {
-			c.logger.Error("could not restore notification subscription after RPC switch",
-				zap.String("endpoint", endpoint),
-				zap.Error(err),
-			)
-
-			return
-		}
-
-		si.subscribedEvents[contract] = id
-	}
-
-	// notary notification events restoration
-	if c.notary != nil {
-		for signer := range si.subscribedNotaryEvents {
-			signer := signer // See https://github.com/nspcc-dev/neo-go/issues/2890
-			id, err = cli.ReceiveNotaryRequests(&neorpc.TxFilter{Signer: &signer}, notaryReqRcv)
-			if err != nil {
-				c.logger.Error("could not restore notary notification subscription after RPC switch",
-					zap.String("endpoint", endpoint),
-					zap.Error(err),
-				)
-
-				return
-			}
-
-			si.subscribedNotaryEvents[signer] = id
-		}
-	}
-
-	return si, true
-}
-
-func (c *Client) startListen(ctx context.Context, stopCh <-chan struct{}, blockRcv <-chan *block.Block,
-	notificationRcv <-chan *state.ContainedNotificationEvent, notaryReqRcv <-chan *result.NotaryRequestEvent, background bool) {
-	// neo-go WS client says to _always_ read notifications
-	// from its channel. Subscribing to any notification
-	// while not reading them in another goroutine may
-	// lead to a dead-lock, thus that async side notification
-	// listening while restoring subscriptions
-
-	go func() {
-		var e any
-		var ok bool
-
-		for {
-			select {
-			case <-stopCh:
-				return
-			case e, ok = <-blockRcv:
-			case e, ok = <-notificationRcv:
-			case e, ok = <-notaryReqRcv:
-			}
-
-			if !ok {
-				return
-			}
-
-			if background {
-				// background client (test) switch, no need to send
-				// any notification, just preventing dead-lock
-				continue
-			}
-
-			c.routeEvent(ctx, e)
-		}
-	}()
-}
-
-func copySubsMap(m map[util.Uint160]string) map[util.Uint160]string {
-	newM := make(map[util.Uint160]string, len(m))
-	for k, v := range m {
-		newM[k] = v
-	}
-
-	return newM
-}

pkg/morph/subscriber/subscriber.go

@@ -10,8 +10,8 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
-	"github.com/nspcc-dev/neo-go/pkg/neorpc"
 	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
 	"github.com/nspcc-dev/neo-go/pkg/util"
 	"go.uber.org/zap"
 )
@@ -35,16 +35,27 @@ type (
 		Close()
 	}
 
+	subChannels struct {
+		NotifyChan chan *state.ContainedNotificationEvent
+		BlockChan  chan *block.Block
+		NotaryChan chan *result.NotaryRequestEvent
+	}
+
 	subscriber struct {
 		*sync.RWMutex
 		log    *logger.Logger
 		client *client.Client
 
 		notifyChan chan *state.ContainedNotificationEvent
-
 		blockChan  chan *block.Block
-
 		notaryChan chan *result.NotaryRequestEvent
+
+		current subChannels
+
+		// cached subscription information
+		subscribedEvents       map[util.Uint160]bool
+		subscribedNotaryEvents map[util.Uint160]bool
+		subscribedToNewBlocks  bool
 	}
 
 	// Params is a group of Subscriber constructor parameters.
@@ -75,22 +86,28 @@ func (s *subscriber) SubscribeForNotification(contracts ...util.Uint160) error {
 	s.Lock()
 	defer s.Unlock()
 
-	notifyIDs := make(map[util.Uint160]struct{}, len(contracts))
+	notifyIDs := make([]string, 0, len(contracts))
 
 	for i := range contracts {
+		if s.subscribedEvents[contracts[i]] {
+			continue
+		}
 		// subscribe to contract notifications
-		err := s.client.SubscribeForExecutionNotifications(contracts[i])
+		id, err := s.client.ReceiveExecutionNotifications(contracts[i], s.current.NotifyChan)
 		if err != nil {
 			// if there is some error, undo all subscriptions and return error
-			for hash := range notifyIDs {
-				_ = s.client.UnsubscribeContract(hash)
+			for _, id := range notifyIDs {
+				_ = s.client.Unsubscribe(id)
 			}
 
 			return err
 		}
 
 		// save notification id
-		notifyIDs[contracts[i]] = struct{}{}
+		notifyIDs = append(notifyIDs, id)
+	}
+	for i := range contracts {
+		s.subscribedEvents[contracts[i]] = true
 	}
 
 	return nil
@@ -109,82 +126,34 @@ func (s *subscriber) Close() {
 }
 
 func (s *subscriber) BlockNotifications() error {
-	if err := s.client.SubscribeForNewBlocks(); err != nil {
+	s.Lock()
+	defer s.Unlock()
+	if s.subscribedToNewBlocks {
+		return nil
+	}
+	if _, err := s.client.ReceiveBlocks(s.current.BlockChan); err != nil {
 		return fmt.Errorf("could not subscribe for new block events: %w", err)
 	}
 
+	s.subscribedToNewBlocks = true
+
 	return nil
 }
 
 func (s *subscriber) SubscribeForNotaryRequests(mainTXSigner util.Uint160) error {
-	if err := s.client.SubscribeForNotaryRequests(mainTXSigner); err != nil {
+	s.Lock()
+	defer s.Unlock()
+	if s.subscribedNotaryEvents[mainTXSigner] {
+		return nil
+	}
+	if _, err := s.client.ReceiveNotaryRequests(mainTXSigner, s.current.NotaryChan); err != nil {
 		return fmt.Errorf("could not subscribe for notary request events: %w", err)
 	}
 
+	s.subscribedNotaryEvents[mainTXSigner] = true
 	return nil
 }
 
-func (s *subscriber) routeNotifications(ctx context.Context) {
-	notificationChan := s.client.NotificationChannel()
-
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case notification, ok := <-notificationChan:
-			if !ok {
-				s.log.Warn("remote notification channel has been closed")
-				close(s.notifyChan)
-				close(s.blockChan)
-				close(s.notaryChan)
-
-				return
-			}
-
-			switch notification.Type {
-			case neorpc.NotificationEventID:
-				notifyEvent, ok := notification.Value.(*state.ContainedNotificationEvent)
-				if !ok {
-					s.log.Error("can't cast notify event value to the notify struct",
-						zap.String("received type", fmt.Sprintf("%T", notification.Value)),
-					)
-					continue
-				}
-
-				s.log.Debug("new notification event from sidechain",
-					zap.String("name", notifyEvent.Name),
-				)
-
-				s.notifyChan <- notifyEvent
-			case neorpc.BlockEventID:
-				b, ok := notification.Value.(*block.Block)
-				if !ok {
-					s.log.Error("can't cast block event value to block",
-						zap.String("received type", fmt.Sprintf("%T", notification.Value)),
-					)
-					continue
-				}
-
-				s.blockChan <- b
-			case neorpc.NotaryRequestEventID:
-				notaryRequest, ok := notification.Value.(*result.NotaryRequestEvent)
-				if !ok {
-					s.log.Error("can't cast notify event value to the notary request struct",
-						zap.String("received type", fmt.Sprintf("%T", notification.Value)),
-					)
-					continue
-				}
-
-				s.notaryChan <- notaryRequest
-			default:
-				s.log.Debug("unsupported notification from the chain",
-					zap.Uint8("type", uint8(notification.Type)),
-				)
-			}
-		}
-	}
-}
-
 // New is a constructs Neo:Morph event listener and returns Subscriber interface.
 func New(ctx context.Context, p *Params) (Subscriber, error) {
 	switch {
@@ -208,16 +177,170 @@ func New(ctx context.Context, p *Params) (Subscriber, error) {
 		notifyChan: make(chan *state.ContainedNotificationEvent),
 		blockChan:  make(chan *block.Block),
 		notaryChan: make(chan *result.NotaryRequestEvent),
-	}
 
-	// Worker listens all events from neo-go websocket and puts them
-	// into corresponding channel. It may be notifications, transactions,
-	// new blocks. For now only notifications.
+		current: newSubChannels(),
+
+		subscribedEvents:       make(map[util.Uint160]bool),
+		subscribedNotaryEvents: make(map[util.Uint160]bool),
+	}
+	// Worker listens all events from temporary NeoGo channel and puts them
+	// into corresponding permanent channels.
 	go sub.routeNotifications(ctx)
 
 	return sub, nil
 }
 
+func (s *subscriber) routeNotifications(ctx context.Context) {
+	var (
+		// TODO: not needed after nspcc-dev/neo-go#2980.
+		cliCh             = s.client.NotificationChannel()
+		restoreCh         = make(chan bool)
+		restoreInProgress bool
+	)
+
+routeloop:
+	for {
+		var connLost bool
+		s.RLock()
+		curr := s.current
+		s.RUnlock()
+		select {
+		case <-ctx.Done():
+			break routeloop
+		case ev, ok := <-curr.NotifyChan:
+			if ok {
+				s.notifyChan <- ev
+			} else {
+				connLost = true
+			}
+		case ev, ok := <-curr.BlockChan:
+			if ok {
+				s.blockChan <- ev
+			} else {
+				connLost = true
+			}
+		case ev, ok := <-curr.NotaryChan:
+			if ok {
+				s.notaryChan <- ev
+			} else {
+				connLost = true
+			}
+		case _, ok := <-cliCh:
+			connLost = !ok
+		case ok := <-restoreCh:
+			restoreInProgress = false
+			if !ok {
+				connLost = true
+			}
+		}
+		if connLost {
+			if !restoreInProgress {
+				restoreInProgress, cliCh = s.switchEndpoint(ctx, restoreCh)
+				if !restoreInProgress {
+					break routeloop
+				}
+				curr.drain()
+			} else { // Avoid getting additional !ok events.
+				s.Lock()
+				s.current.NotifyChan = nil
+				s.current.BlockChan = nil
+				s.current.NotaryChan = nil
+				s.Unlock()
+			}
+		}
+	}
+	close(s.notifyChan)
+	close(s.blockChan)
+	close(s.notaryChan)
+}
+
+func (s *subscriber) switchEndpoint(ctx context.Context, finishCh chan<- bool) (bool, <-chan rpcclient.Notification) {
+	s.log.Info("RPC connection lost, attempting reconnect")
+	if !s.client.SwitchRPC(ctx) {
+		s.log.Error("can't switch RPC node")
+		return false, nil
+	}
+
+	cliCh := s.client.NotificationChannel()
+
+	s.Lock()
+	chs := newSubChannels()
+	go func() {
+		finishCh <- s.restoreSubscriptions(chs.NotifyChan, chs.BlockChan, chs.NotaryChan)
+	}()
+	s.current = chs
+	s.Unlock()
+
+	return true, cliCh
+}
+
+func newSubChannels() subChannels {
+	return subChannels{
+		NotifyChan: make(chan *state.ContainedNotificationEvent),
+		BlockChan:  make(chan *block.Block),
+		NotaryChan: make(chan *result.NotaryRequestEvent),
+	}
+}
+
+func (s *subChannels) drain() {
+drainloop:
+	for {
+		select {
+		case _, ok := <-s.NotifyChan:
+			if !ok {
+				s.NotifyChan = nil
+			}
+		case _, ok := <-s.BlockChan:
+			if !ok {
+				s.BlockChan = nil
+			}
+		case _, ok := <-s.NotaryChan:
+			if !ok {
+				s.NotaryChan = nil
+			}
+		default:
+			break drainloop
+		}
+	}
+}
+
+// restoreSubscriptions restores subscriptions according to
+// cached information about them.
+func (s *subscriber) restoreSubscriptions(notifCh chan<- *state.ContainedNotificationEvent,
+	blCh chan<- *block.Block, notaryCh chan<- *result.NotaryRequestEvent) bool {
+	var err error
+
+	// new block events restoration
+	if s.subscribedToNewBlocks {
+		_, err = s.client.ReceiveBlocks(blCh)
+		if err != nil {
+			s.log.Error("could not restore block subscription after RPC switch", zap.Error(err))
+			return false
+		}
+	}
+
+	// notification events restoration
+	for contract := range s.subscribedEvents {
+		contract := contract // See https://github.com/nspcc-dev/neo-go/issues/2890
+		_, err = s.client.ReceiveExecutionNotifications(contract, notifCh)
+		if err != nil {
+			s.log.Error("could not restore notification subscription after RPC switch", zap.Error(err))
+			return false
+		}
+	}
+
+	// notary notification events restoration
+	for signer := range s.subscribedNotaryEvents {
+		signer := signer // See https://github.com/nspcc-dev/neo-go/issues/2890
+		_, err = s.client.ReceiveNotaryRequests(signer, notaryCh)
+		if err != nil {
+			s.log.Error("could not restore notary notification subscription after RPC switch", zap.Error(err))
+			return false
+		}
+	}
+	return true
+}
+
 // awaitHeight checks if remote client has least expected block height and
 // returns error if it is not reached that height after timeout duration.
 // This function is required to avoid connections to unsynced RPC nodes, because

pkg/services/object/put/pool.go

@@ -4,7 +4,10 @@ import (
 	"sync"
 )
 
-const defaultAllocSize = 1024
+const (
+	defaultAllocSize = 1024
+	poolSliceMaxSize = 128 * 1024
+)
 
 type payload struct {
 	Data []byte
@@ -19,6 +22,9 @@ func getPayload() *payload {
 }
 
 func putPayload(p *payload) {
+	if cap(p.Data) > poolSliceMaxSize {
+		return
+	}
 	p.Data = p.Data[:0]
 	putBytesPool.Put(p)
 }

pkg/services/object/put/prm.go

@@ -40,6 +40,14 @@ func (p *PutInitPrm) WithObject(v *object.Object) *PutInitPrm {
 	return p
 }
 
+func (p *PutInitPrm) WithCopyNumber(v uint32) *PutInitPrm {
+	if p != nil {
+		p.traverseOpts = append(p.traverseOpts, placement.SuccessAfter(v))
+	}
+
+	return p
+}
+
 func (p *PutInitPrm) WithRelay(f func(client.NodeInfo, client.MultiAddressClient) error) *PutInitPrm {
 	if p != nil {
 		p.relay = f

pkg/services/object/put/v2/util.go

@@ -24,7 +24,8 @@ func (s *streamer) toInitPrm(part *objectV2.PutObjectPartInit, req *objectV2.Put
 			object.NewFromV2(oV2),
 		).
 		WithRelay(s.relayRequest).
-		WithCommonPrm(commonPrm), nil
+		WithCommonPrm(commonPrm).
+		WithCopyNumber(part.GetCopiesNumber()), nil
 }
 
 func toChunkPrm(req *objectV2.PutObjectPartChunk) *putsvc.PutChunkPrm {

pkg/services/tree/cache.go

@@ -27,7 +27,7 @@ type cacheItem struct {
 }
 
 const (
-	defaultClientCacheSize      = 10
+	defaultClientCacheSize      = 32
 	defaultClientConnectTimeout = time.Second * 2
 	defaultReconnectInterval    = time.Second * 15
 )
@@ -36,7 +36,9 @@ var errRecentlyFailed = errors.New("client has recently failed")
 
 func (c *clientCache) init() {
 	l, _ := simplelru.NewLRU[string, cacheItem](defaultClientCacheSize, func(_ string, value cacheItem) {
-		_ = value.cc.Close()
+		if conn := value.cc; conn != nil {
+			_ = conn.Close()
+		}
 	})
 	c.LRU = *l
 }

pkg/services/tree/service.go

@@ -13,6 +13,7 @@ import (
 	cidSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
 	netmapSDK "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/netmap"
 	"github.com/panjf2000/ants/v2"
+	"go.uber.org/atomic"
 	"go.uber.org/zap"
 )
 
@@ -31,6 +32,8 @@ type Service struct {
 	syncChan chan struct{}
 	syncPool *ants.Pool
 
+	initialSyncDone atomic.Bool
+
 	// cnrMap contains existing (used) container IDs.
 	cnrMap map[cidSDK.ID]struct{}
 	// cnrMapMtx protects cnrMap
@@ -89,6 +92,10 @@ func (s *Service) Shutdown() {
 }
 
 func (s *Service) Add(ctx context.Context, req *AddRequest) (*AddResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -137,6 +144,10 @@ func (s *Service) Add(ctx context.Context, req *AddRequest) (*AddResponse, error
 }
 
 func (s *Service) AddByPath(ctx context.Context, req *AddByPathRequest) (*AddByPathResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -197,6 +208,10 @@ func (s *Service) AddByPath(ctx context.Context, req *AddByPathRequest) (*AddByP
 }
 
 func (s *Service) Remove(ctx context.Context, req *RemoveRequest) (*RemoveResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -246,6 +261,10 @@ func (s *Service) Remove(ctx context.Context, req *RemoveRequest) (*RemoveRespon
 // Move applies client operation to the specified tree and pushes in queue
 // for replication on other nodes.
 func (s *Service) Move(ctx context.Context, req *MoveRequest) (*MoveResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -294,6 +313,10 @@ func (s *Service) Move(ctx context.Context, req *MoveRequest) (*MoveResponse, er
 }
 
 func (s *Service) GetNodeByPath(ctx context.Context, req *GetNodeByPathRequest) (*GetNodeByPathResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -370,6 +393,10 @@ func (s *Service) GetNodeByPath(ctx context.Context, req *GetNodeByPathRequest)
 }
 
 func (s *Service) GetSubTree(req *GetSubTreeRequest, srv TreeService_GetSubTreeServer) error {
+	if !s.initialSyncDone.Load() {
+		return ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -499,6 +526,10 @@ func (s *Service) Apply(_ context.Context, req *ApplyRequest) (*ApplyResponse, e
 }
 
 func (s *Service) GetOpLog(req *GetOpLogRequest, srv TreeService_GetOpLogServer) error {
+	if !s.initialSyncDone.Load() {
+		return ErrAlreadySyncing
+	}
+
 	b := req.GetBody()
 
 	var cid cidSDK.ID
@@ -531,9 +562,13 @@ func (s *Service) GetOpLog(req *GetOpLogRequest, srv TreeService_GetOpLogServer)
 	}
 
 	h := b.GetHeight()
+	lastHeight, err := s.forest.TreeHeight(cid, b.GetTreeId())
+	if err != nil {
+		return err
+	}
 	for {
 		lm, err := s.forest.TreeGetOpLog(cid, b.GetTreeId(), h)
-		if err != nil || lm.Time == 0 {
+		if err != nil || lm.Time == 0 || lastHeight < lm.Time {
 			return err
 		}
 
@@ -555,6 +590,10 @@ func (s *Service) GetOpLog(req *GetOpLogRequest, srv TreeService_GetOpLogServer)
 }
 
 func (s *Service) TreeList(ctx context.Context, req *TreeListRequest) (*TreeListResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	var cid cidSDK.ID
 
 	err := cid.Decode(req.GetBody().GetContainerId())
@@ -638,5 +677,9 @@ func (s *Service) getContainerInfo(cid cidSDK.ID, pub []byte) ([]netmapSDK.NodeI
 }
 
 func (s *Service) Healthcheck(context.Context, *HealthcheckRequest) (*HealthcheckResponse, error) {
+	if !s.initialSyncDone.Load() {
+		return nil, ErrAlreadySyncing
+	}
+
 	return new(HealthcheckResponse), nil
 }

pkg/services/tree/sync.go

@@ -203,24 +203,29 @@ func (s *Service) synchronizeSingle(ctx context.Context, cid cid.ID, treeID stri
 	rawCID := make([]byte, sha256.Size)
 	cid.Encode(rawCID)
 
+	errG, ctx := errgroup.WithContext(ctx)
+	errG.SetLimit(1024)
+
 	for {
-		newHeight := height
 		req := &GetOpLogRequest{
 			Body: &GetOpLogRequest_Body{
 				ContainerId: rawCID,
 				TreeId:      treeID,
-				Height:      newHeight,
+				Height:      height,
 			},
 		}
 		if err := SignMessage(req, s.key); err != nil {
-			return newHeight, err
+			_ = errG.Wait()
+			return height, err
 		}
 
 		c, err := treeClient.GetOpLog(ctx, req)
 		if err != nil {
-			return newHeight, fmt.Errorf("can't initialize client: %w", err)
+			_ = errG.Wait()
+			return height, fmt.Errorf("can't initialize client: %w", err)
 		}
 
+		lastApplied := height
 		res, err := c.Recv()
 		for ; err == nil; res, err = c.Recv() {
 			lm := res.GetBody().GetOperation()
@@ -229,21 +234,28 @@ func (s *Service) synchronizeSingle(ctx context.Context, cid cid.ID, treeID stri
 				Child:  lm.ChildId,
 			}
 			if err := m.Meta.FromBytes(lm.Meta); err != nil {
-				return newHeight, err
+				_ = errG.Wait()
+				return height, err
 			}
-			if err := s.forest.TreeApply(cid, treeID, m, true); err != nil {
-				return newHeight, err
+			if lastApplied < m.Meta.Time {
+				lastApplied = m.Meta.Time
 			}
-			if m.Time > newHeight {
-				newHeight = m.Time + 1
-			} else {
-				newHeight++
+			errG.Go(func() error {
+				return s.forest.TreeApply(cid, treeID, m, true)
+			})
 		}
+
+		// First check local errors: if everything is ok, we can update starting height,
+		// because everything was applied.
+		applyErr := errG.Wait()
+		if applyErr != nil {
+			return height, applyErr
 		}
-		if height == newHeight || err != nil && !errors.Is(err, io.EOF) {
-			return newHeight, err
+
+		height = lastApplied
+		if err != nil && !errors.Is(err, io.EOF) {
+			return height, err
 		}
-		height = newHeight
 	}
 }
 
@@ -288,7 +300,7 @@ func (s *Service) syncLoop(ctx context.Context) {
 			cnrs, err := s.cfg.cnrSource.List()
 			if err != nil {
 				s.log.Error("could not fetch containers", zap.Error(err))
-				continue
+				break
 			}
 
 			newMap, cnrsToSync := s.containersToSync(cnrs)
@@ -299,6 +311,7 @@ func (s *Service) syncLoop(ctx context.Context) {
 
 			s.log.Debug("trees have been synchronized")
 		}
+		s.initialSyncDone.Store(true)
 	}
 }