Merge pull request #18821 from roidelapluie/roidelapluie/k8s-sd-binary-size

discovery/kubernetes: keep SD client from defeating dead-code elimination

discovery/kubernetes/client.go

@@ -0,0 +1,76 @@
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kubernetes
+
+import (
+	"k8s.io/client-go/kubernetes"
+	appsv1client "k8s.io/client-go/kubernetes/typed/apps/v1"
+	batchv1client "k8s.io/client-go/kubernetes/typed/batch/v1"
+	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
+	discoveryv1client "k8s.io/client-go/kubernetes/typed/discovery/v1"
+	networkingv1client "k8s.io/client-go/kubernetes/typed/networking/v1"
+)
+
+// k8sClient exposes only the API-group accessors discovery uses. It is
+// satisfied by both clientAdapter and the fake clientset used in tests.
+type k8sClient interface {
+	CoreV1() corev1client.CoreV1Interface
+	AppsV1() appsv1client.AppsV1Interface
+	BatchV1() batchv1client.BatchV1Interface
+	DiscoveryV1() discoveryv1client.DiscoveryV1Interface
+	NetworkingV1() networkingv1client.NetworkingV1Interface
+}
+
+// clientAdapter captures the used API-group accessors as method-value closures.
+// Keeping the concrete clientset out of an interface-typed field avoids forcing
+// the linker, via reflection, to retain every API group and resource client,
+// which reduces the binary size.
+type clientAdapter struct {
+	coreV1       func() corev1client.CoreV1Interface
+	appsV1       func() appsv1client.AppsV1Interface
+	batchV1      func() batchv1client.BatchV1Interface
+	discoveryV1  func() discoveryv1client.DiscoveryV1Interface
+	networkingV1 func() networkingv1client.NetworkingV1Interface
+}
+
+// newClientAdapter wraps a concrete clientset, exposing only the API groups
+// discovery uses.
+func newClientAdapter(c *kubernetes.Clientset) *clientAdapter {
+	return &clientAdapter{
+		coreV1:       c.CoreV1,
+		appsV1:       c.AppsV1,
+		batchV1:      c.BatchV1,
+		discoveryV1:  c.DiscoveryV1,
+		networkingV1: c.NetworkingV1,
+	}
+}
+
+// CoreV1 returns the core/v1 API-group client.
+func (a *clientAdapter) CoreV1() corev1client.CoreV1Interface { return a.coreV1() }
+
+// AppsV1 returns the apps/v1 API-group client.
+func (a *clientAdapter) AppsV1() appsv1client.AppsV1Interface { return a.appsV1() }
+
+// BatchV1 returns the batch/v1 API-group client.
+func (a *clientAdapter) BatchV1() batchv1client.BatchV1Interface { return a.batchV1() }
+
+// DiscoveryV1 returns the discovery/v1 API-group client.
+func (a *clientAdapter) DiscoveryV1() discoveryv1client.DiscoveryV1Interface {
+	return a.discoveryV1()
+}
+
+// NetworkingV1 returns the networking/v1 API-group client.
+func (a *clientAdapter) NetworkingV1() networkingv1client.NetworkingV1Interface {
+	return a.networkingV1()
+}

discovery/kubernetes/kubernetes.go

@@ -254,7 +254,7 @@ func (c *NamespaceDiscovery) UnmarshalYAML(unmarshal func(any) error) error {
 // targets from Kubernetes.
 type Discovery struct {
 	sync.RWMutex
-	client             kubernetes.Interface
+	client             k8sClient
 	role               Role
 	logger             *slog.Logger
 	namespaceDiscovery *NamespaceDiscovery
@@ -341,7 +341,7 @@ func New(l *slog.Logger, metrics discovery.DiscovererMetrics, conf *SDConfig) (*
 	}
 
 	d := &Discovery{
-		client:             c,
+		client:             newClientAdapter(c),
 		logger:             l,
 		role:               conf.Role,
 		namespaceDiscovery: &conf.NamespaceDiscovery,