[#1549] engine: Disable shard on blobovnicza init failure

There is a need to support working w/o shard if it has problems with
blobovnicza tree.

Make `BlobStor.Init` to return new `ErrInitBlobovniczas` error. Remove
shard from storage engine's shard set if it returned this error from
`Init` call. So if some of the shards (but not all) return this error,
the node will be able to continue working without them.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/blobstor/control.go

@@ -1,5 +1,10 @@
 package blobstor
 
+import (
+	"errors"
+	"fmt"
+)
+
 // Open opens BlobStor.
 func (b *BlobStor) Open() error {
 	b.log.Debug("opening...")
@@ -7,13 +12,23 @@ func (b *BlobStor) Open() error {
 	return nil
 }
 
+// ErrInitBlobovniczas is returned when blobovnicza initialization fails.
+var ErrInitBlobovniczas = errors.New("failure on blobovnicza initialization stage")
+
 // Init initializes internal data structures and system resources.
 //
 // If BlobStor is already initialized, no action is taken.
+//
+// Returns wrapped ErrInitBlobovniczas on blobovnicza tree's initializaiton failure.
 func (b *BlobStor) Init() error {
 	b.log.Debug("initializing...")
 
-	return b.blobovniczas.init()
+	err := b.blobovniczas.init()
+	if err != nil {
+		return fmt.Errorf("%w: %v", ErrInitBlobovniczas, err)
+	}
+
+	return nil
 }
 
 // Close releases all internal resources of BlobStor.

pkg/local_object_storage/engine/control.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
 	"go.uber.org/zap"
 )
@@ -48,10 +49,25 @@ func (e *StorageEngine) Init() error {
 
 	for id, sh := range e.shards {
 		if err := sh.Init(); err != nil {
+			if errors.Is(err, blobstor.ErrInitBlobovniczas) {
+				delete(e.shards, id)
+
+				e.log.Error("shard initialization failure, skipping",
+					zap.String("id", id),
+					zap.Error(err),
+				)
+
+				continue
+			}
+
 			return fmt.Errorf("could not initialize shard %s: %w", id, err)
 		}
 	}
 
+	if len(e.shards) == 0 {
+		return errors.New("failed initialization on all shards")
+	}
+
 	return nil
 }