From 5d9ef5feec1c8e6c3a7da4071770d3c34031b02f Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Thu, 28 Jan 2021 14:52:51 +0300
Subject: [PATCH] [#248] netmap: fulfill backup factor for default attribute

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
---
 pkg/netmap/policy_test.go   | 53 +++++++++++++++++++++++++++++++++++++
 pkg/netmap/selector.go      | 12 +++++++++
 pkg/netmap/selector_test.go |  6 ++++-
 3 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/pkg/netmap/policy_test.go b/pkg/netmap/policy_test.go
index 5db6d5b..9fca579 100644
--- a/pkg/netmap/policy_test.go
+++ b/pkg/netmap/policy_test.go
@@ -4,9 +4,62 @@ import (
 	"testing"
 
 	"github.com/nspcc-dev/neofs-api-go/v2/netmap"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+func TestPlacementPolicy_CBFWithEmptySelector(t *testing.T) {
+	nodes := []NodeInfo{
+		nodeInfoFromAttributes("ID", "1", "Attr", "Same"),
+		nodeInfoFromAttributes("ID", "2", "Attr", "Same"),
+		nodeInfoFromAttributes("ID", "3", "Attr", "Same"),
+		nodeInfoFromAttributes("ID", "4", "Attr", "Same"),
+	}
+
+	p1 := newPlacementPolicy(0,
+		[]*Replica{newReplica(2, "")},
+		nil, // selectors
+		nil, // filters
+	)
+
+	p2 := newPlacementPolicy(3,
+		[]*Replica{newReplica(2, "")},
+		nil, // selectors
+		nil, // filters
+	)
+
+	p3 := newPlacementPolicy(3,
+		[]*Replica{newReplica(2, "X")},
+		[]*Selector{newSelector("X", "", ClauseDistinct, 2, "*")},
+		nil, // filters
+	)
+
+	p4 := newPlacementPolicy(3,
+		[]*Replica{newReplica(2, "X")},
+		[]*Selector{newSelector("X", "Attr", ClauseSame, 2, "*")},
+		nil, // filters
+	)
+
+	nm, err := NewNetmap(NodesFromInfo(nodes))
+	require.NoError(t, err)
+
+	v, err := nm.GetContainerNodes(p1, nil)
+	require.NoError(t, err)
+	assert.Len(t, v.Flatten(), 4)
+
+	v, err = nm.GetContainerNodes(p2, nil)
+	require.NoError(t, err)
+	assert.Len(t, v.Flatten(), 4)
+
+	v, err = nm.GetContainerNodes(p3, nil)
+	require.NoError(t, err)
+	assert.Len(t, v.Flatten(), 4)
+
+	v, err = nm.GetContainerNodes(p4, nil)
+	require.NoError(t, err)
+	assert.Len(t, v.Flatten(), 4)
+}
+
 func TestPlacementPolicyFromV2(t *testing.T) {
 	pV2 := new(netmap.PlacementPolicy)
 
diff --git a/pkg/netmap/selector.go b/pkg/netmap/selector.go
index ff83f1b..7a7f297 100644
--- a/pkg/netmap/selector.go
+++ b/pkg/netmap/selector.go
@@ -48,6 +48,7 @@ func GetNodesCount(_ *PlacementPolicy, s *Selector) (int, int) {
 }
 
 // getSelection returns nodes grouped by s.attribute.
+// Last argument specifies if more buckets can be used to fullfill CBF.
 func (c *Context) getSelection(p *PlacementPolicy, s *Selector) ([]Nodes, error) {
 	bucketCount, nodesInBucket := GetNodesCount(p, s)
 	buckets := c.getSelectionBase(s)
@@ -99,6 +100,17 @@ func (c *Context) getSelection(p *PlacementPolicy, s *Selector) ([]Nodes, error)
 		hrw.SortSliceByWeightIndex(nodes, weights, c.pivotHash)
 	}
 
+	if s.Attribute() == "" {
+		nodes, fallback = nodes[:bucketCount], nodes[bucketCount:]
+		for i := range fallback {
+			index := i % bucketCount
+			if len(nodes[index]) >= maxNodesInBucket {
+				break
+			}
+			nodes[index] = append(nodes[index], fallback[i]...)
+		}
+	}
+
 	return nodes[:bucketCount], nil
 }
 
diff --git a/pkg/netmap/selector_test.go b/pkg/netmap/selector_test.go
index 135a7b3..e434821 100644
--- a/pkg/netmap/selector_test.go
+++ b/pkg/netmap/selector_test.go
@@ -54,7 +54,11 @@ func TestPlacementPolicy_Minimal(t *testing.T) {
 		}
 
 		require.NoError(t, err)
-		require.EqualValues(t, rep, len(v.Flatten()))
+		count := int(rep * defaultCBF)
+		if count > len(nm.Nodes) {
+			count = len(nm.Nodes)
+		}
+		require.EqualValues(t, count, len(v.Flatten()))
 	}
 
 	t.Run("REP 1", func(t *testing.T) {