metabase: Open(readOnly) moves metabase in RO mode (#3000)

Closes #2889.

CHANGELOG.md

@@ -26,6 +26,7 @@ attribute, which is used for container domain name in NNS contracts (#2954)
 - False negative connection to NeoFS chain in multi-endpoint setup with at least one live node (#2986)
 - Overriding the default container and object attributes only with the appropriate flags (#2985)
 - RPC client reconnection failures leading to complete SN failure (#2797)
+- `meta.DB.Open(readOnly)` moves metabase in RO mode (#3000)
 
 ### Changed
 - `ObjectService`'s `Put` RPC handler caches up to 10K lists of per-object sorted container nodes (#2901)

pkg/local_object_storage/metabase/control.go

@@ -33,6 +33,10 @@ func (db *DB) Open(readOnly bool) error {
 	}
 	db.boltOptions.ReadOnly = readOnly
 
+	if readOnly {
+		db.mode = mode.ReadOnly
+	}
+
 	return db.openBolt()
 }
 

pkg/local_object_storage/metabase/control_test.go

@@ -1,6 +1,7 @@
 package meta_test
 
 import (
+	"path/filepath"
 	"testing"
 
 	"github.com/nspcc-dev/neofs-node/pkg/core/object"
@@ -50,6 +51,43 @@ func TestReset(t *testing.T) {
 	assertExists(addr, false, nil)
 }
 
+func TestOpenRO(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "meta")
+
+	db := meta.New(
+		meta.WithPath(path),
+		meta.WithPermissions(0o600),
+		meta.WithEpochState(epochState{}),
+	)
+
+	require.NoError(t, db.Open(false))
+	require.NoError(t, db.Init())
+
+	obj := generateObject(t)
+	addr := object.AddressOf(obj)
+
+	require.NoError(t, putBig(db, obj))
+	exists, err := metaExists(db, addr)
+	require.NoError(t, err)
+	require.True(t, exists)
+
+	require.NoError(t, db.Close())
+
+	// Open in RO mode
+	require.NoError(t, db.Open(true))
+
+	// we can't write
+	err = putBig(db, obj)
+	require.ErrorIs(t, err, meta.ErrReadOnlyMode)
+
+	// but can read
+	exists, err = metaExists(db, addr)
+	require.NoError(t, err)
+	require.True(t, exists)
+
+	require.NoError(t, db.Close())
+}
+
 func metaExists(db *meta.DB, addr oid.Address) (bool, error) {
 	return db.Exists(addr, false)
 }