fix: adjusting SortHosts to sort descending for two-node topologies

internal/bminventory/inventory.go

@@ -1450,10 +1450,10 @@ func (b *bareMetalInventory) InstallClusterInternal(ctx context.Context, params
 	// auto select hosts roles if not selected yet.
 	err = b.db.Transaction(func(tx *gorm.DB) error {
 		var updated bool
-		sortedHosts, canRefreshRoles := host.SortHosts(cluster.Hosts)
+		sortedHosts, canRefreshRoles := host.SortHosts(cluster.Hosts, cluster.ControlPlaneCount)
 		if canRefreshRoles {
 			for i := range sortedHosts {
-				updated, err = b.hostApi.AutoAssignRole(ctx, cluster.Hosts[i], tx)
+				updated, err = b.hostApi.AutoAssignRole(ctx, sortedHosts[i], tx)
 				if err != nil {
 					return err
 				}

internal/host/host_test.go

@@ -3170,6 +3170,49 @@ var _ = Describe("AutoAssignRole", func() {
 		verifyAutoAssignRole(&h, true, true)
 		Expect(hostutil.GetHostFromDB(*h.ID, infraEnvId, db).Role).Should(Equal(models.HostRoleArbiter))
 	})
+
+	It("TNA cluster with day-0 workers having similar resources to arbiter", func() {
+		cluster.ControlPlaneCount = common.MinMasterHostsNeededForInstallationInHaArbiterMode
+		db.Save(cluster)
+
+		hosts := []*models.Host{
+			// 2 intended masters: high resources
+			generateAutoAssignHost(strfmt.UUID(uuid.New().String()), 16, 64, false, "master-capable-1"),
+			generateAutoAssignHost(strfmt.UUID(uuid.New().String()), 16, 64, false, "master-capable-2"),
+			// 1 intended arbiter: lower resources
+			generateAutoAssignHost(strfmt.UUID(uuid.New().String()), 8, 32, false, "arbiter-capable"),
+			// 2 intended workers: similar resources to arbiter
+			generateAutoAssignHost(strfmt.UUID(uuid.New().String()), 8, 32, false, "worker-1"),
+			generateAutoAssignHost(strfmt.UUID(uuid.New().String()), 8, 32, false, "worker-2"),
+		}
+
+		cluster.Hosts = hosts
+
+		sortedHosts, _ := SortHosts(hosts, cluster.ControlPlaneCount)
+
+		var masterCount, arbiterCount, workerCount int
+
+		for _, host := range sortedHosts {
+			Expect(db.Create(host).Error).ShouldNot(HaveOccurred())
+			verifyAutoAssignRole(host, true, true)
+			role := hostutil.GetHostFromDB(*host.ID, infraEnvId, db).Role
+			switch role {
+			case models.HostRoleMaster:
+				// Masters should be the most capable hosts
+				Expect(host.RequestedHostname).To(HavePrefix("master-capable"))
+				masterCount++
+			case models.HostRoleArbiter:
+				arbiterCount++
+			case models.HostRoleWorker:
+				workerCount++
+			}
+		}
+
+		Expect(masterCount).To(Equal(2), "Should have exactly 2 masters")
+		Expect(arbiterCount).To(Equal(1), "Should have exactly 1 arbiter")
+		Expect(workerCount).To(Equal(2), "Should have exactly 2 workers")
+	})
+
 	It("should assign roles based on hardware with GPU weight affecting priority", func() {
 		cluster.ControlPlaneCount = common.MinMasterHostsNeededForInstallationInHaMode
 		hosts := []*models.Host{
@@ -3185,7 +3228,7 @@ var _ = Describe("AutoAssignRole", func() {
 		cluster.Hosts = hosts
 
 		// Sort hosts first (like the real auto-assign logic does)
-		sortedHosts, _ := SortHosts(hosts)
+		sortedHosts, _ := SortHosts(hosts, common.MinMasterHostsNeededForInstallationInHaMode)
 
 		var masterCount, workerCount int
 
@@ -3218,7 +3261,7 @@ var _ = Describe("AutoAssignRole", func() {
 		cluster.Hosts = hosts
 
 		// Sort hosts first (like the real auto-assign logic does)
-		sortedHosts, _ := SortHosts(hosts)
+		sortedHosts, _ := SortHosts(hosts, common.MinMasterHostsNeededForInstallationInHaMode)
 
 		var masterCount, workerCount int
 
@@ -4410,7 +4453,7 @@ var _ = Describe("sortHost by hardware", func() {
 	}
 
 	It("verify host order", func() {
-		sorted, _ := SortHosts(generateHosts())
+		sorted, _ := SortHosts(generateHosts(), common.MinMasterHostsNeededForInstallationInHaMode)
 		expected := []string{
 			"insufficient for both master and worker",
 			"minimal worker with 3 disks (total of 120 GB)",
@@ -4428,6 +4471,26 @@ var _ = Describe("sortHost by hardware", func() {
 			Expect(h.RequestedHostname).To(Equal(expected[i]))
 		}
 	})
+	It("verify host order for two-node topology", func() {
+		sorted, _ := SortHosts(generateHosts(), common.MinMasterHostsNeededForInstallationInHaArbiterMode)
+		expected := []string{
+			"odf worker with 3 disks (total of 120 GB)",
+			"odf worker with 3 disks (total of 80 GB)",
+			"insufficient for both master and worker",
+			"odf worker with 1 disk of 40 GB",
+			"odf master with 3 disks (total of 120 GB)",
+			"sno master with 3 disks (total of 120 GB)",
+			"minimal master with 3 disks (total of 120 GB)",
+			"minimal master with 3 disks (total of 80 GB)",
+			"minimal master with no disks",
+			"minimal worker with 3 disks (total of 120 GB)",
+			// GPU hosts still last
+			"host with minimal hardware to be either master/worker, with GPU",
+		}
+		for i, h := range sorted {
+			Expect(h.RequestedHostname).To(Equal(expected[i]))
+		}
+	})
 })
 
 var _ = Describe("update node labels", func() {

internal/host/monitor.go

@@ -68,7 +68,7 @@ func (m *Manager) initMonitoringQueryGenerator() {
 	}
 }
 
-func SortHosts(hosts []*models.Host) ([]*models.Host, bool) {
+func SortHosts(hosts []*models.Host, controlPlaneCount int64) ([]*models.Host, bool) {
 	diskCapacityGiB := func(disks []*models.Disk) int64 {
 		return funk.Reduce(disks, func(acc int64, d *models.Disk) int64 {
 			if d.InstallationEligibility.Eligible {
@@ -116,6 +116,9 @@ func SortHosts(hosts []*models.Host) ([]*models.Host, bool) {
 		}
 	}
 
+	isTwoNodeTopology := controlPlaneCount >= common.MinMasterHostsNeededForInstallationInHaArbiterMode &&
+		controlPlaneCount < common.MinMasterHostsNeededForInstallationInHaMode
+
 	sortByWeight := func(hostList []*models.Host) {
 		sort.SliceStable(hostList, func(i, j int) bool {
 			inventory_i, _ := common.UnmarshalInventory(hostList[i].Inventory)
@@ -137,6 +140,10 @@ func SortHosts(hosts []*models.Host) ([]*models.Host, bool) {
 				HostWeightMemWeight*(float64(memInGib(inventory_j))-HostWeightMinimumMemGib) +
 				HostWeightDiskWeight*(float64(diskCapacityGiB(inventory_j.Disks))-HostWeightMinimumDiskCapacityGib)
 
+			if isTwoNodeTopology {
+				return wi > wj
+			}
+
 			return wi < wj
 		})
 	}
@@ -150,6 +157,17 @@ func SortHosts(hosts []*models.Host) ([]*models.Host, bool) {
 	result = append(result, hostsWithoutGPU...)
 	result = append(result, hostsWithGPU...)
 
+	// for TNA, move the least capable non-GPU host (last in the non-GPU
+	// descending section) to the arbiter position so that the greedy algorithm
+	// in selectRole assings it as a arbiter instead of a more capable worker.
+	if isTwoNodeTopology && len(hostsWithoutGPU) > int(controlPlaneCount) {
+		lastNonGPUIdx := len(hostsWithoutGPU) - 1
+		leastCapable := result[lastNonGPUIdx]
+		arbiterPos := int(controlPlaneCount)
+		copy(result[arbiterPos+1:], result[arbiterPos:lastNonGPUIdx])
+		result[arbiterPos] = leastCapable
+	}
+
 	return result, allHostsHasInventory
 }
 
@@ -202,7 +220,7 @@ func (m *Manager) clusterHostMonitoring() {
 
 		for _, c := range clusters {
 			inventoryCache := make(InventoryCache)
-			sortedHosts, canRefreshRoles := SortHosts(c.Hosts)
+			sortedHosts, canRefreshRoles := SortHosts(c.Hosts, c.ControlPlaneCount)
 
 			log = log.WithField("cluster", c.ID.String())