fix balance fallback replica placement (#8824)

weed/worker/tasks/balance/replica_placement_test.go

@@ -3,6 +3,8 @@ package balance
 import (
 	"testing"
 
+	"github.com/seaweedfs/seaweedfs/weed/admin/topology"
+	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
 	"github.com/seaweedfs/seaweedfs/weed/storage/super_block"
 	"github.com/seaweedfs/seaweedfs/weed/worker/types"
 )
@@ -125,3 +127,112 @@ func TestIsGoodMove_NilReplicaPlacement(t *testing.T) {
 		t.Error("nil replica placement should allow any move")
 	}
 }
+
+func TestCalculateBalanceScore_ReplicationAware(t *testing.T) {
+	disk := func(dc, rack string) *topology.DiskInfo {
+		return &topology.DiskInfo{
+			DataCenter: dc,
+			Rack:       rack,
+			DiskInfo:   &master_pb.DiskInfo{MaxVolumeCount: 100, VolumeCount: 50},
+		}
+	}
+
+	// 001: same-rack replication — should prefer same rack and same DC
+	rp001 := rp(t, "001")
+	sameRack := calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, rp001)
+	diffRack := calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp001)
+	diffDC := calculateBalanceScore(disk("dc2", "r2"), "r1", "dc1", 0, rp001)
+	if sameRack <= diffRack {
+		t.Errorf("001: same-rack score (%v) should exceed different-rack score (%v)", sameRack, diffRack)
+	}
+	if sameRack <= diffDC {
+		t.Errorf("001: same-rack score (%v) should exceed different-DC score (%v)", sameRack, diffDC)
+	}
+
+	// 010: different-rack replication — should prefer different rack, same DC
+	rp010 := rp(t, "010")
+	sameRack = calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, rp010)
+	diffRack = calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp010)
+	if diffRack <= sameRack {
+		t.Errorf("010: different-rack score (%v) should exceed same-rack score (%v)", diffRack, sameRack)
+	}
+
+	// 100: different-DC replication — should prefer different DC
+	rp100 := rp(t, "100")
+	sameDC := calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, rp100)
+	diffDCScore := calculateBalanceScore(disk("dc2", "r2"), "r1", "dc1", 0, rp100)
+	if diffDCScore <= sameDC {
+		t.Errorf("100: different-DC score (%v) should exceed same-DC score (%v)", diffDCScore, sameDC)
+	}
+
+	// nil rp: should prefer cross-rack/DC (default behavior)
+	sameRack = calculateBalanceScore(disk("dc1", "r1"), "r1", "dc1", 0, nil)
+	diffRack = calculateBalanceScore(disk("dc1", "r2"), "r1", "dc1", 0, nil)
+	if diffRack <= sameRack {
+		t.Errorf("nil rp: different-rack score (%v) should exceed same-rack score (%v)", diffRack, sameRack)
+	}
+}
+
+func TestPlanBalanceDestination_ChoosesBestValidCompositeDestination(t *testing.T) {
+	servers := []serverSpec{
+		{id: "node-a", diskType: "hdd", diskID: 1, dc: "dc1", rack: "rack1"},
+		{id: "node-b", diskType: "hdd", diskID: 2, dc: "dc1", rack: "rack3"},
+		{id: "node-c", diskType: "hdd", diskID: 3, dc: "dc1", rack: "rack1"},
+	}
+	volumes := makeVolumesWith("node-a", "hdd", "dc1", "rack1", "c1", 1, 1, withReplicas(11))
+	replicas := []types.ReplicaLocation{
+		loc("dc1", "rack1", "node-a"),
+		loc("dc1", "rack1", "node-d"),
+		loc("dc1", "rack2", "node-e"),
+	}
+
+	plan, err := planBalanceDestination(buildTopology(servers, volumes), volumes[0], rp(t, "011"), replicas, map[string]int{
+		"node-b": 0,
+		"node-c": 0,
+	})
+	if err != nil {
+		t.Fatalf("planBalanceDestination failed: %v", err)
+	}
+	if plan.TargetNode != "node-c" {
+		t.Fatalf("expected valid same-rack destination node-c, got %s", plan.TargetNode)
+	}
+	if plan.TargetRack != "rack1" {
+		t.Fatalf("expected rack1 destination, got %s", plan.TargetRack)
+	}
+}
+
+func TestCreateBalanceTask_FallbackSelectsValidCompositeDestination(t *testing.T) {
+	servers := []serverSpec{
+		{id: "node-a", diskType: "hdd", diskID: 1, dc: "dc1", rack: "rack1"},
+		{id: "node-b", diskType: "hdd", diskID: 2, dc: "dc1", rack: "rack3"},
+		{id: "node-c", diskType: "hdd", diskID: 3, dc: "dc1", rack: "rack1"},
+	}
+	volumes := makeVolumesWith("node-a", "hdd", "dc1", "rack1", "c1", 1, 1, withReplicas(11))
+	clusterInfo := &types.ClusterInfo{
+		ActiveTopology: buildTopology(servers, volumes),
+		VolumeReplicaMap: map[uint32][]types.ReplicaLocation{
+			1: {
+				loc("dc1", "rack1", "node-a"),
+				loc("dc1", "rack1", "node-d"),
+				loc("dc1", "rack2", "node-e"),
+			},
+		},
+	}
+
+	task, destination := createBalanceTask("hdd", volumes[0], clusterInfo, "node-b", map[string]int{
+		"node-b": 0,
+		"node-c": 0,
+	})
+	if task == nil {
+		t.Fatal("expected a balance task")
+	}
+	if destination != "node-c" {
+		t.Fatalf("expected fallback destination node-c, got %s", destination)
+	}
+	if len(task.TypedParams.Targets) != 1 {
+		t.Fatalf("expected 1 target, got %d", len(task.TypedParams.Targets))
+	}
+	if got := task.TypedParams.Targets[0].Node; got != "node-c:8080" {
+		t.Fatalf("expected target node-c:8080, got %s", got)
+	}
+}