[#965] policer: Implement continuous replication

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/services/policer/queue.go

@@ -1,8 +1,9 @@
 package policer
 
 import (
+	"fmt"
+
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/engine"
-	"github.com/nspcc-dev/neofs-node/pkg/util/rand"
 	"github.com/nspcc-dev/neofs-sdk-go/object"
 )
 
@@ -10,23 +11,15 @@ type jobQueue struct {
 	localStorage *engine.StorageEngine
 }
 
-func (q *jobQueue) Select(limit int) ([]*object.Address, error) {
-	// TODO: optimize the logic for selecting objects
-	// We can prioritize objects for migration, newly arrived objects, etc.
-	// It is recommended to make changes after updating the metabase
+func (q *jobQueue) Select(cursor *engine.Cursor, count uint32) ([]*object.Address, *engine.Cursor, error) {
+	prm := new(engine.ListWithCursorPrm)
+	prm.WithCursor(cursor)
+	prm.WithCount(count)
 
-	res, err := engine.List(q.localStorage, 0) // consider some limit
+	res, err := q.localStorage.ListWithCursor(prm)
 	if err != nil {
-		return nil, err
+		return nil, nil, fmt.Errorf("cannot list objects in engine: %w", err)
 	}
 
-	rand.New().Shuffle(len(res), func(i, j int) {
-		res[i], res[j] = res[j], res[i]
-	})
-
-	if len(res) < limit {
-		return res, nil
-	}
-
-	return res[:limit], nil
+	return res.AddressList(), res.Cursor(), nil
 }