Let the applier manage its own discovery cache (#8305)

pkg/applier/applier.go

@@ -9,8 +9,6 @@ import (
 	"os"
 	"path/filepath"
 
-	"github.com/k0sproject/k0s/pkg/kubernetes"
-
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/cli-runtime/pkg/resource"
 
@@ -47,12 +45,11 @@ type Applier struct {
 	Name string
 	Dir  string
 
-	log           *logrus.Entry
-	clientFactory kubernetes.ClientFactoryInterface
+	log     *logrus.Entry
+	clients Clients
 }
 
-// NewApplier creates new Applier
-func NewApplier(dir string, kubeClientFactory kubernetes.ClientFactoryInterface) Applier {
+func NewApplier(dir string, clients Clients) Applier {
 	name := filepath.Base(dir)
 	log := logrus.WithFields(logrus.Fields{
 		"component": "applier",
@@ -60,10 +57,10 @@ func NewApplier(dir string, kubeClientFactory kubernetes.ClientFactoryInterface)
 	})
 
 	return Applier{
-		log:           log,
-		Dir:           dir,
-		Name:          name,
-		clientFactory: kubeClientFactory,
+		log:     log,
+		Dir:     dir,
+		Name:    name,
+		clients: clients,
 	}
 }
 
@@ -81,7 +78,7 @@ func (a *Applier) Apply(ctx context.Context) error {
 	stack := Stack{
 		Name:      a.Name,
 		Resources: resources,
-		Clients:   a.clientFactory,
+		Clients:   a.clients,
 	}
 	a.log.Debug("applying stack")
 	err = stack.Apply(ctx, true)
@@ -96,7 +93,7 @@ func (a *Applier) Apply(ctx context.Context) error {
 
 // Delete deletes the entire stack by applying it with empty set of resources
 func (a *Applier) Delete(ctx context.Context) error {
-	stack := Stack{Name: a.Name, Clients: a.clientFactory}
+	stack := Stack{Name: a.Name, Clients: a.clients}
 	logrus.Debugf("about to delete a stack %s with empty apply", a.Name)
 	return stack.Apply(ctx, true)
 }

pkg/applier/applier_test.go

@@ -76,7 +76,8 @@ spec:
 	require.NoError(t, os.WriteFile(filepath.Join(dir, "test-deploy.yaml"), []byte(templateDeployment), 0400))
 
 	fakes := kubeutil.NewFakeClientFactory()
-	a := applier.NewApplier(dir, fakes)
+	clients := applier.NewClients(fakes)
+	a := applier.NewApplier(dir, clients)
 
 	ctx := t.Context()
 	err := a.Apply(ctx)
@@ -97,7 +98,7 @@ spec:
 	assert.NoError(t, err)
 
 	// Attempt to delete the stack with a different applier
-	a2 := applier.NewApplier(dir, fakes)
+	a2 := applier.NewApplier(dir, clients)
 	assert.NoError(t, a2.Delete(ctx))
 	// Check that the resources are deleted
 	_, err = fakes.DynamicClient.Resource(*gv).Namespace(metav1.NamespaceSystem).Get(ctx, "applier-test", metav1.GetOptions{})

pkg/applier/manager.go

@@ -120,9 +120,10 @@ func (m *Manager) runWatchers(ctx context.Context) {
 	ctx, cancel := context.WithCancelCause(ctx)
 	defer cancel(nil) // satisfy linter, not required for correctness
 	stacks := make(map[string]stack, len(dirs))
+	clients := NewClients(m.KubeClientFactory)
 
 	for _, dir := range dirs {
-		m.createStack(ctx, stacks, filepath.Join(m.bundleDir, dir))
+		m.createStack(ctx, stacks, clients, filepath.Join(m.bundleDir, dir))
 	}
 
 	for {
@@ -135,7 +136,7 @@ func (m *Manager) runWatchers(ctx context.Context) {
 			switch event.Op {
 			case fsnotify.Create:
 				if dir.IsDirectory(event.Name) {
-					m.createStack(ctx, stacks, event.Name)
+					m.createStack(ctx, stacks, clients, event.Name)
 				}
 			case fsnotify.Remove:
 				m.removeStack(ctx, stacks, event.Name)
@@ -152,7 +153,7 @@ func (m *Manager) runWatchers(ctx context.Context) {
 	}
 }
 
-func (m *Manager) createStack(ctx context.Context, stacks map[string]stack, name string) {
+func (m *Manager) createStack(ctx context.Context, stacks map[string]stack, clients Clients, name string) {
 	// safeguard in case the fswatcher would trigger an event for an already existing stack
 	if _, ok := stacks[name]; ok {
 		return
@@ -174,7 +175,7 @@ func (m *Manager) createStack(ctx context.Context, stacks map[string]stack, name
 	ctx, cancel := context.WithCancelCause(ctx)
 	stopped := make(chan struct{})
 
-	stack := stack{cancel, stopped, NewStackApplier(name, m.KubeClientFactory)}
+	stack := stack{cancel, stopped, NewStackApplier(name, clients)}
 	stacks[name] = stack
 
 	go func() {

pkg/applier/stack.go

@@ -18,6 +18,7 @@ import (
 	"github.com/k0sproject/k0s/pkg/kubernetes/watch"
 
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	apiextensionsclientset "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset"
 	apiErrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -25,6 +26,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/discovery/cached/memory"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/restmapper"
 
@@ -33,14 +35,52 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+// Provides the Kubernetes clients required to apply a [Stack].
+type Clients interface {
+	GetDiscoveryClient() (discovery.CachedDiscoveryInterface, error)
+	GetDynamicClient() (dynamic.Interface, error)
+	GetAPIExtensionsClient() (apiextensionsclientset.Interface, error)
+}
+
+// Returns a [Clients] implementation backed by clientFactory. It lazily creates
+// a memory-cached discovery client that lives as long as the returned instance.
+// Hence the lifetime of the returned instance determines the lifetime of the
+// discovery cache.
+func NewClients(clientFactory kubernetes.ClientFactoryInterface) Clients {
+	return &clients{ClientFactoryInterface: clientFactory}
+}
+
+type clients struct {
+	kubernetes.ClientFactoryInterface
+	mu        sync.Mutex
+	discovery discovery.CachedDiscoveryInterface
+}
+
+// GetDiscoveryClient implements [Clients].
+func (c *clients) GetDiscoveryClient() (discovery.CachedDiscoveryInterface, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.discovery == nil {
+		client, err := c.GetClient()
+		if err != nil {
+			return nil, err
+		}
+		c.discovery = memory.NewMemCacheClient(client.Discovery())
+	}
+
+	return c.discovery, nil
+}
+
 func ApplyStack(ctx context.Context, clients kubernetes.ClientFactoryInterface, resources []*unstructured.Unstructured, stackName string) error {
+	applierClients := NewClients(clients)
 	var lastErr error
 	if err := retry.Do(
 		func() error {
 			stack := Stack{
 				Name:      stackName,
 				Resources: resources,
-				Clients:   clients,
+				Clients:   applierClients,
 			}
 			lastErr = stack.Apply(ctx, true)
 			return lastErr
@@ -66,7 +106,7 @@ type Stack struct {
 	Name          string
 	Resources     []*unstructured.Unstructured
 	keepResources []string
-	Clients       kubernetes.ClientFactoryInterface
+	Clients       Clients
 
 	log *logrus.Entry
 }
@@ -76,11 +116,11 @@ type Stack struct {
 func (s *Stack) Apply(ctx context.Context, prune bool) error {
 	s.log = logrus.WithField("stack", s.Name)
 
-	discoveryClient, err := s.Clients.GetDiscoveryClient()
+	dynamicClient, err := s.Clients.GetDynamicClient()
 	if err != nil {
 		return err
 	}
-	dynamicClient, err := s.Clients.GetDynamicClient()
+	discoveryClient, err := s.Clients.GetDiscoveryClient()
 	if err != nil {
 		return err
 	}

pkg/applier/stack_test.go

@@ -34,7 +34,7 @@ func TestStack_StripsNamespaceFromClusterScopedResource(t *testing.T) {
 	s := applier.Stack{
 		Name:      "strip-ns",
 		Resources: []*unstructured.Unstructured{resources},
-		Clients:   fakes,
+		Clients:   applier.NewClients(fakes),
 	}
 
 	err = s.Apply(t.Context(), true)
@@ -61,11 +61,12 @@ func TestStack_StackNameChangeTriggersUpdateWithoutChecksumChange(t *testing.T)
 	require.NoError(t, err)
 
 	fakes := testutil.NewFakeClientFactory()
+	clients := applier.NewClients(fakes)
 
 	oldStack := applier.Stack{
 		Name:      "old",
 		Resources: []*unstructured.Unstructured{resources},
-		Clients:   fakes,
+		Clients:   clients,
 	}
 	require.NoError(t, oldStack.Apply(t.Context(), true))
 
@@ -80,7 +81,7 @@ func TestStack_StackNameChangeTriggersUpdateWithoutChecksumChange(t *testing.T)
 	newStack := applier.Stack{
 		Name:      "new",
 		Resources: []*unstructured.Unstructured{resources},
-		Clients:   fakes,
+		Clients:   clients,
 	}
 	require.NoError(t, newStack.Apply(t.Context(), false))
 

pkg/applier/stackapplier.go

@@ -12,7 +12,6 @@ import (
 	"time"
 
 	"github.com/avast/retry-go"
-	"github.com/k0sproject/k0s/pkg/kubernetes"
 
 	"github.com/fsnotify/fsnotify"
 	"github.com/sirupsen/logrus"
@@ -27,9 +26,9 @@ type StackApplier struct {
 }
 
 // NewStackApplier crates new stack applier to manage a stack
-func NewStackApplier(path string, kubeClientFactory kubernetes.ClientFactoryInterface) *StackApplier {
+func NewStackApplier(path string, clients Clients) *StackApplier {
 	var mu sync.Mutex
-	applier := NewApplier(path, kubeClientFactory)
+	applier := NewApplier(path, clients)
 
 	return &StackApplier{
 		log:  logrus.WithField("component", "applier-"+applier.Name),

pkg/component/controller/autopilot.go

@@ -120,7 +120,7 @@ func (a *Autopilot) applyManifests(ctx context.Context) {
 		stack := applier.Stack{
 			Name:      AutopilotStackName,
 			Resources: slices.Concat(crdResources, stackResources),
-			Clients:   a.AdminClientFactory,
+			Clients:   applier.NewClients(a.AdminClientFactory),
 		}
 
 		for {

pkg/component/controller/clusterconfig.go

@@ -240,7 +240,7 @@ func (i *ClusterConfigInitializer) applyAPIConfigStack(ctx context.Context) erro
 	return (&applier.Stack{
 		Name:      ClusterConfigStackName,
 		Resources: []*unstructured.Unstructured{&crd},
-		Clients:   i.clients,
+		Clients:   applier.NewClients(i.clients),
 	}).Apply(ctx, true)
 }
 

pkg/component/controller/crd.go

@@ -80,7 +80,7 @@ func (c *CRDStack) Start(context.Context) error {
 			stack := applier.Stack{
 				Name:      c.stackName,
 				Resources: resources,
-				Clients:   c.clients,
+				Clients:   applier.NewClients(c.clients),
 			}
 
 			for {

pkg/component/controller/workerconfig/reconciler.go

@@ -128,7 +128,7 @@ func (r *Reconciler) Init(context.Context) error {
 	apply := func(ctx context.Context, resources resources) error {
 		return (&applier.Stack{
 			Name:      fmt.Sprintf("k0s-%s-%s", constant.WorkerConfigComponentName, constant.KubernetesMajorMinorVersion),
-			Clients:   clientFactory,
+			Clients:   applier.NewClients(clientFactory),
 			Resources: resources,
 		}).Apply(ctx, true)
 	}