refactor(runtime): make maxSkew configurable

Read the TopologySpreadConstraints maxSkew from the YAML config
so we can tune based on cluster/game. By default it will be set to 5.
Using a low value lead to underutilized nodes which impacts in cost

config/config.yaml

@@ -49,6 +49,7 @@ adapters:
       inCluster: false
       masterUrl: "https://127.0.0.1:6443"
       kubeconfig: "./kubeconfig/kubeconfig.yaml"
+      maxSkew: 5
   grpc:
     keepAlive:
       time: 30s

internal/adapters/runtime/kubernetes/game_room.go

@@ -40,7 +40,7 @@ const (
 )
 
 func (k *kubernetes) CreateGameRoomInstance(ctx context.Context, scheduler *entities.Scheduler, gameRoomName string, gameRoomSpec game_room.Spec) (*game_room.Instance, error) {
-	pod, err := convertGameRoomSpec(*scheduler, gameRoomName, gameRoomSpec)
+	pod, err := convertGameRoomSpec(*scheduler, gameRoomName, gameRoomSpec, k.config)
 	if err != nil {
 		return nil, errors.NewErrInvalidArgument("invalid game room spec: %s", err)
 	}

internal/adapters/runtime/kubernetes/game_room_convert.go

@@ -67,7 +67,7 @@ var invalidPodWaitingStates = []string{
 	"RunContainerError",
 }
 
-func convertGameRoomSpec(scheduler entities.Scheduler, gameRoomName string, gameRoomSpec game_room.Spec) (*v1.Pod, error) {
+func convertGameRoomSpec(scheduler entities.Scheduler, gameRoomName string, gameRoomSpec game_room.Spec, config KubernetesConfig) (*v1.Pod, error) {
 	defaultAnnotations := map[string]string{safeToEvictAnnotation: safeToEvictValue}
 	defaultLabels := map[string]string{
 		maestroLabelKey:   maestroLabelValue,
@@ -95,7 +95,7 @@ func convertGameRoomSpec(scheduler entities.Scheduler, gameRoomName string, game
 			// 5. Add a conversion function
 			TopologySpreadConstraints: []v1.TopologySpreadConstraint{
 				{
-					MaxSkew:           1,
+					MaxSkew:           int32(config.MaxSkew),
 					TopologyKey:       "topology.kubernetes.io/zone",
 					WhenUnsatisfiable: v1.ScheduleAnyway,
 					LabelSelector: &metav1.LabelSelector{

internal/adapters/runtime/kubernetes/game_room_convert_test.go

@@ -675,7 +675,7 @@ func TestConvertGameSpec(t *testing.T) {
 			//	Name:        test.scheduler,
 			//	Annotations: test.expectedPod.ObjectMeta.Annotations,
 			//}
-			res, err := convertGameRoomSpec(test.scheduler, test.roomName, test.gameSpec)
+			res, err := convertGameRoomSpec(test.scheduler, test.roomName, test.gameSpec, KubernetesConfig{MaxSkew: 1})
 			if test.withError {
 				require.Error(t, err)
 				return

internal/adapters/runtime/kubernetes/game_room_test.go

@@ -44,7 +44,7 @@ func TestGameRoomCreation(t *testing.T) {
 	ctx := context.Background()
 	gameRoomName := "some-game-room-name"
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("successfully create a room", func(t *testing.T) {
 		t.Parallel()
@@ -98,7 +98,7 @@ func TestGameRoomDeletion(t *testing.T) {
 	ctx := context.Background()
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
 	gameRoomName := "some-game-room"
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("successfully delete a room", func(t *testing.T) {
 		t.Parallel()
@@ -155,7 +155,7 @@ func TestCreateGameRoomName(t *testing.T) {
 	t.Parallel()
 	ctx := context.Background()
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("When scheduler name is greater than max name length minus randomLength", func(t *testing.T) {
 		t.Run("return the name with randomLength", func(t *testing.T) {

internal/adapters/runtime/kubernetes/game_room_watcher_test.go

@@ -45,7 +45,7 @@ func TestGameRoomsWatch(t *testing.T) {
 		t.Parallel()
 		ctx := context.Background()
 		client := test.GetKubernetesClientSet(t, kubernetesContainer)
-		kubernetesRuntime := New(client)
+		kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 		scheduler := &entities.Scheduler{Name: "watch-room-addition"}
 		err := kubernetesRuntime.CreateScheduler(ctx, scheduler)
@@ -96,7 +96,7 @@ func TestGameRoomsWatch(t *testing.T) {
 		t.Parallel()
 		ctx := context.Background()
 		client := test.GetKubernetesClientSet(t, kubernetesContainer)
-		kubernetesRuntime := New(client)
+		kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 		scheduler := &entities.Scheduler{Name: "watch-room-ready"}
 		err := kubernetesRuntime.CreateScheduler(ctx, scheduler)
@@ -158,7 +158,7 @@ func TestGameRoomsWatch(t *testing.T) {
 		t.Parallel()
 		ctx := context.Background()
 		client := test.GetKubernetesClientSet(t, kubernetesContainer)
-		kubernetesRuntime := New(client)
+		kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 		scheduler := &entities.Scheduler{Name: "watch-room-error"}
 		err := kubernetesRuntime.CreateScheduler(ctx, scheduler)
@@ -213,7 +213,7 @@ func TestGameRoomsWatch(t *testing.T) {
 		t.Parallel()
 		ctx := context.Background()
 		client := test.GetKubernetesClientSet(t, kubernetesContainer)
-		kubernetesRuntime := New(client)
+		kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 		scheduler := &entities.Scheduler{Name: "watch-room-delete"}
 		err := kubernetesRuntime.CreateScheduler(ctx, scheduler)

internal/adapters/runtime/kubernetes/kubernetes.go

@@ -35,16 +35,27 @@ import (
 
 var _ ports.Runtime = (*kubernetes)(nil)
 
+const DefaultMaxSkew = 5
+
+type KubernetesConfig struct {
+	MaxSkew int
+}
+
 type kubernetes struct {
 	clientSet     kube.Interface
 	logger        *zap.Logger
 	eventRecorder record.EventRecorder
+	config        KubernetesConfig
 }
 
-func New(clientSet kube.Interface) *kubernetes {
+func New(clientSet kube.Interface, config KubernetesConfig) *kubernetes {
+	if config.MaxSkew <= 0 {
+		config.MaxSkew = DefaultMaxSkew
+	}
 	k := &kubernetes{
 		clientSet: clientSet,
 		logger:    zap.L().With(zap.String(logs.LogFieldRuntime, "kubernetes")),
+		config:    config,
 	}
 
 	eventBroadcaster := record.NewBroadcaster()

internal/adapters/runtime/kubernetes/scheduler_test.go

@@ -41,7 +41,7 @@ import (
 func TestSchedulerCreation(t *testing.T) {
 	ctx := context.Background()
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("create single scheduler", func(t *testing.T) {
 		scheduler := &entities.Scheduler{Name: "single-scheduler-test", PdbMaxUnavailable: "5%"}
@@ -66,7 +66,7 @@ func TestSchedulerCreation(t *testing.T) {
 func TestSchedulerDeletion(t *testing.T) {
 	ctx := context.Background()
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("delete scheduler", func(t *testing.T) {
 		scheduler := &entities.Scheduler{Name: "delete-scheduler-test", PdbMaxUnavailable: "5%"}
@@ -92,7 +92,7 @@ func TestSchedulerDeletion(t *testing.T) {
 func TestPDBCreationAndDeletion(t *testing.T) {
 	ctx := context.Background()
 	client := test.GetKubernetesClientSet(t, kubernetesContainer)
-	kubernetesRuntime := New(client)
+	kubernetesRuntime := New(client, KubernetesConfig{MaxSkew: 1})
 
 	t.Run("create pdb from scheduler without autoscaling", func(t *testing.T) {
 		if !kubernetesRuntime.isPDBSupported() {

internal/service/adapters.go

@@ -74,6 +74,7 @@ const (
 	runtimeKubernetesInClusterPath  = "adapters.runtime.kubernetes.inCluster"
 	runtimeKubernetesQPS            = "adapters.runtime.kubernetes.qps"
 	runtimeKubernetesBurst          = "adapters.runtime.kubernetes.burst"
+	runtimeKubernetesMaxSkew        = "adapters.runtime.kubernetes.maxSkew"
 	// Redis operation storage
 	operationStorageRedisURLPath      = "adapters.operationStorage.redis.url"
 	operationLeaseStorageRedisURLPath = "adapters.operationLeaseStorage.redis.url"
@@ -146,7 +147,9 @@ func NewRuntimeKubernetes(c config.Config) (ports.Runtime, error) {
 		return nil, fmt.Errorf("failed to initialize Kubernetes runtime: %w", err)
 	}
 
-	return kubernetesRuntime.New(clientSet), nil
+	return kubernetesRuntime.New(clientSet, kubernetesRuntime.KubernetesConfig{
+		MaxSkew: c.GetInt(runtimeKubernetesMaxSkew),
+	}), nil
 }
 
 // NewOperationStorageRedis instantiates redis as operation storage.