[#1204] shard: Save ID in the metabase

`AddShard` must return shard id, so we temporarily open metabase
there.

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

pkg/local_object_storage/engine/control_test.go

@@ -3,8 +3,10 @@ package engine
 import (
 	"errors"
 	"os"
+	"path/filepath"
 	"testing"
 
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
 	cidtest "github.com/nspcc-dev/neofs-sdk-go/container/id/test"
 	"github.com/stretchr/testify/require"
 )
@@ -48,3 +50,38 @@ func TestExecBlocks(t *testing.T) {
 	// try to resume
 	require.Error(t, e.ResumeExecution())
 }
+
+func TestPersistentShardID(t *testing.T) {
+	dir, err := os.MkdirTemp("", "*")
+	require.NoError(t, err)
+
+	e, _, id := newEngineWithErrorThreshold(t, dir, 1)
+
+	checkShardState(t, e, id[0], shard.ModeReadWrite)
+	require.NoError(t, e.Close())
+
+	e, _, newID := newEngineWithErrorThreshold(t, dir, 1)
+	require.Equal(t, id, newID)
+	require.NoError(t, e.Close())
+
+	p1 := e.shards[id[0].String()].DumpInfo().MetaBaseInfo.Path
+	p2 := e.shards[id[1].String()].DumpInfo().MetaBaseInfo.Path
+	tmp := filepath.Join(dir, "tmp")
+	require.NoError(t, os.Rename(p1, tmp))
+	require.NoError(t, os.Rename(p2, p1))
+	require.NoError(t, os.Rename(tmp, p2))
+
+	e, _, newID = newEngineWithErrorThreshold(t, dir, 1)
+	require.Equal(t, id[1], newID[0])
+	require.Equal(t, id[0], newID[1])
+	require.NoError(t, e.Close())
+
+}
+
+func checkShardState(t *testing.T, e *StorageEngine, id *shard.ID, mode shard.Mode) {
+	e.mtx.RLock()
+	sh := e.shards[id.String()]
+	e.mtx.RUnlock()
+
+	require.Equal(t, mode, sh.GetMode())
+}

pkg/local_object_storage/engine/shards.go

@@ -25,26 +25,34 @@ func (e *StorageEngine) AddShard(opts ...shard.Option) (*shard.ID, error) {
 	e.mtx.Lock()
 	defer e.mtx.Unlock()
 
-	id, err := generateShardID()
-	if err != nil {
-		return nil, fmt.Errorf("could not generate shard ID: %w", err)
-	}
-
 	pool, err := ants.NewPool(int(e.shardPoolSize), ants.WithNonblocking(true))
 	if err != nil {
 		return nil, err
 	}
 
-	strID := id.String()
+	id, err := generateShardID()
+	if err != nil {
+		return nil, fmt.Errorf("could not generate shard ID: %w", err)
+	}
 
-	e.shards[strID] = shard.New(append(opts,
+	sh := shard.New(append(opts,
 		shard.WithID(id),
 		shard.WithExpiredObjectsCallback(e.processExpiredTombstones),
 	)...)
 
+	if err := sh.UpdateID(); err != nil {
+		return nil, fmt.Errorf("could not open shard: %w", err)
+	}
+
+	strID := sh.ID().String()
+	if _, ok := e.shards[strID]; ok {
+		return nil, fmt.Errorf("shard with id %s was already added", strID)
+	}
+
+	e.shards[strID] = sh
 	e.shardPools[strID] = pool
 
-	return id, nil
+	return sh.ID(), nil
 }
 
 func generateShardID() (*shard.ID, error) {

pkg/local_object_storage/metabase/shard_id.go

@@ -0,0 +1,36 @@
+package meta
+
+import (
+	"github.com/nspcc-dev/neo-go/pkg/util/slice"
+	"go.etcd.io/bbolt"
+)
+
+var (
+	shardInfoBucket = []byte(invalidBase58String + "i")
+	shardIDKey      = []byte("id")
+)
+
+// ReadShardID reads shard id from db.
+// If id is missing, returns nil, nil.
+func (db *DB) ReadShardID() ([]byte, error) {
+	var id []byte
+	err := db.boltDB.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(shardInfoBucket)
+		if b != nil {
+			id = slice.Copy(b.Get(shardIDKey))
+		}
+		return nil
+	})
+	return id, err
+}
+
+// WriteShardID writes shard it to db.
+func (db *DB) WriteShardID(id []byte) error {
+	return db.boltDB.Update(func(tx *bbolt.Tx) error {
+		b, err := tx.CreateBucketIfNotExists(shardInfoBucket)
+		if err != nil {
+			return err
+		}
+		return b.Put(shardIDKey, id)
+	})
+}

pkg/local_object_storage/shard/control.go

@@ -26,7 +26,6 @@ func (s *Shard) Open() error {
 			return fmt.Errorf("could not open %T: %w", component, err)
 		}
 	}
-
 	return nil
 }
 

pkg/local_object_storage/shard/id.go

@@ -23,3 +23,25 @@ func (id ID) String() string {
 func (s *Shard) ID() *ID {
 	return s.info.ID
 }
+
+// UpdateID reads shard ID saved in the metabase and updates it if it is missing.
+func (s *Shard) UpdateID() (err error) {
+	if err = s.metaBase.Open(); err != nil {
+		return err
+	}
+	defer func() {
+		cErr := s.metaBase.Close()
+		if err == nil {
+			err = cErr
+		}
+	}()
+	id, err := s.metaBase.ReadShardID()
+	if err != nil {
+		return err
+	}
+	if len(id) != 0 {
+		s.info.ID = NewIDFromBytes(id)
+		return nil
+	}
+	return s.metaBase.WriteShardID(*s.info.ID)
+}

pkg/local_object_storage/shard/shard.go

@@ -96,7 +96,7 @@ func New(opts ...Option) *Shard {
 	return s
 }
 
-// WithID returns option to set shard identifier.
+// WithID returns option to set the default shard identifier.
 func WithID(id *ID) Option {
 	return func(c *cfg) {
 		c.info.ID = id