[#1143] blobstor: Implement existsSmall check

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

pkg/local_object_storage/blobstor/exists.go

@@ -2,9 +2,12 @@ package blobstor
 
 import (
 	"errors"
+	"path/filepath"
 
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobovnicza"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/blobstor/fstree"
 	addressSDK "github.com/nspcc-dev/neofs-sdk-go/object/address"
+	"go.uber.org/zap"
 )
 
 // ExistsPrm groups the parameters of Exists operation.
@@ -29,20 +32,35 @@ func (r ExistsRes) Exists() bool {
 func (b *BlobStor) Exists(prm *ExistsPrm) (*ExistsRes, error) {
 	// check presence in shallow dir first (cheaper)
 	exists, err := b.existsBig(prm.addr)
-	if !exists {
-		// TODO: #1143 do smth if err != nil
 
-		// check presence in blobovnicza
-		exists, err = b.existsSmall(prm.addr)
+	// If there was an error during existence check below,
+	// it will be returned unless object was found in blobovnicza.
+	// Otherwise, it is logged and the latest error is returned.
+	// FSTree    | Blobovnicza | Behaviour
+	// found     | (not tried) | return true, nil
+	// not found | any result  | return the result
+	// error     | found       | log the error, return true, nil
+	// error     | not found   | return the error
+	// error     | error       | log the first error, return the second
+	if !exists {
+		var smallErr error
+
+		exists, smallErr = b.existsSmall(prm.addr)
+		if err != nil && (smallErr != nil || exists) {
+			b.log.Warn("error occured during object existence checking",
+				zap.Stringer("address", prm.addr),
+				zap.String("error", err.Error()))
+			err = nil
+		}
+		if err == nil {
+			err = smallErr
+		}
 	}
 
 	if err != nil {
 		return nil, err
 	}
-
-	return &ExistsRes{
-		exists: exists,
-	}, err
+	return &ExistsRes{exists: exists}, err
 }
 
 // checks if object is presented in shallow dir.
@@ -55,8 +73,36 @@ func (b *BlobStor) existsBig(addr *addressSDK.Address) (bool, error) {
 	return err == nil, err
 }
 
-// checks if object is presented in blobovnicza.
-func (b *BlobStor) existsSmall(_ *addressSDK.Address) (bool, error) {
-	// TODO: #1143 implement
-	return false, nil
+// existsSmall checks if object is presented in blobovnicza.
+func (b *BlobStor) existsSmall(addr *addressSDK.Address) (bool, error) {
+	return b.blobovniczas.existsSmall(addr)
+}
+
+func (b *blobovniczas) existsSmall(addr *addressSDK.Address) (bool, error) {
+	activeCache := make(map[string]struct{})
+
+	prm := new(blobovnicza.GetPrm)
+	prm.SetAddress(addr)
+
+	var found bool
+	err := b.iterateSortedLeaves(addr, func(p string) (bool, error) {
+		dirPath := filepath.Dir(p)
+
+		_, ok := activeCache[dirPath]
+
+		_, err := b.getObjectFromLevel(prm, p, !ok)
+		if err != nil {
+			if !blobovnicza.IsErrNotFound(err) {
+				b.log.Debug("could not get object from level",
+					zap.String("level", p),
+					zap.String("error", err.Error()))
+			}
+		}
+
+		activeCache[dirPath] = struct{}{}
+		found = err == nil
+		return found, nil
+	})
+
+	return found, err
 }