[#56] node: Allow reading expired locked object

Signed-off-by: Pavel Karpy <p.karpy@yadro.com>

CHANGELOG.md

@@ -20,6 +20,7 @@ Changelog for FrostFS Node
 - Pilorama now can merge multiple batches into one (#2231)
 - Storage engine now can start even when some shard components are unavailable (#2238)
 - `neofs-cli` buffer for object put increased from 4 KiB to 3 MiB (#2243)
+- Expired locked object is available for reading (#56)
 
 ### Fixed
 - Increase payload size metric on shards' `put` operation (#1794)

pkg/local_object_storage/metabase/exists.go

@@ -100,6 +100,11 @@ func (db *DB) exists(tx *bbolt.Tx, addr oid.Address, currEpoch uint64) (exists b
 //   - 2 if object is covered with tombstone;
 //   - 3 if object is expired.
 func objectStatus(tx *bbolt.Tx, addr oid.Address, currEpoch uint64) uint8 {
+	// locked object could not be removed/marked with GC/expired
+	if objectLocked(tx, addr.Container(), addr.Object()) {
+		return 0
+	}
+
 	// we check only if the object is expired in the current
 	// epoch since it is considered the only corner case: the
 	// GC is expected to collect all the objects that have

pkg/local_object_storage/metabase/lock_test.go

@@ -169,6 +169,27 @@ func TestDB_Lock(t *testing.T) {
 	})
 }
 
+func TestDB_Lock_Expired(t *testing.T) {
+	es := &epochState{e: 123}
+
+	db := newDB(t, meta.WithEpochState(es))
+
+	// put an object
+	addr := putWithExpiration(t, db, object.TypeRegular, 124)
+
+	// expire the obj
+	es.e = 125
+	_, err := metaGet(db, addr, false)
+	require.ErrorIs(t, err, meta.ErrObjectIsExpired)
+
+	// lock the obj
+	require.NoError(t, db.Lock(addr.Container(), oidtest.ID(), []oid.ID{addr.Object()}))
+
+	// object is expired but locked, thus, must be available
+	_, err = metaGet(db, addr, false)
+	require.NoError(t, err)
+}
+
 func TestDB_IsLocked(t *testing.T) {
 	db := newDB(t)