[#156] netmap: Use default value for CBF if unset

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

pkg/netmap/netmap.go

@@ -6,6 +6,8 @@ import (
 	"github.com/nspcc-dev/hrw"
 )
 
+const defaultCBF = 3
+
 // Netmap represents netmap which contains preprocessed nodes.
 type Netmap struct {
 	Nodes Nodes
@@ -49,6 +51,10 @@ func (m *Netmap) GetContainerNodes(p *PlacementPolicy, pivot []byte) (ContainerN
 	c := NewContext(m)
 	c.setPivot(pivot)
 
+	if p.ContainerBackupFactor() == 0 {
+		p.SetContainerBackupFactor(defaultCBF)
+	}
+
 	if err := c.processFilters(p); err != nil {
 		return nil, err
 	}

pkg/netmap/selector_test.go

@@ -31,6 +31,29 @@ func TestPlacementPolicy_UnspecifiedClause(t *testing.T) {
 	require.Equal(t, 4, len(v.Flatten()))
 }
 
+func TestPlacementPolicy_DefaultCBF(t *testing.T) {
+	p := newPlacementPolicy(0,
+		[]*Replica{
+			newReplica(1, "EU"),
+		},
+		[]*Selector{
+			newSelector("EU", "Location", ClauseSame, 1, "*"),
+		},
+		nil)
+	nodes := []NodeInfo{
+		nodeInfoFromAttributes("Location", "Europe", "Country", "RU", "City", "St.Petersburg"),
+		nodeInfoFromAttributes("Location", "Europe", "Country", "RU", "City", "Moscow"),
+		nodeInfoFromAttributes("Location", "Europe", "Country", "DE", "City", "Berlin"),
+		nodeInfoFromAttributes("Location", "Europe", "Country", "FR", "City", "Paris"),
+	}
+
+	nm, err := NewNetmap(NodesFromInfo(nodes))
+	require.NoError(t, err)
+	v, err := nm.GetContainerNodes(p, nil)
+	require.NoError(t, err)
+	require.Equal(t, defaultCBF, len(v.Flatten()))
+}
+
 func TestPlacementPolicy_GetPlacementVectors(t *testing.T) {
 	p := newPlacementPolicy(2,
 		[]*Replica{