Remove native sidecar featuregate

.chloggen/fg_native_sidecar_rm.yaml

@@ -0,0 +1,21 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. collector, target allocator, auto-instrumentation, opamp, github action)
+component: operator
+
+# A brief description of the change. Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Remove native sidecar feature gate
+
+# One or more tracking issues related to the change
+issues: [4451]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  The feature gate `operator.sidecarcontainers.native` has been removed.
+  It was introduced in v0.111.0, enabled by default since v0.132.0, and marked as stable in v0.139.0.
+  Native sidecars are now automatically enabled on Kubernetes v1.29+ without requiring a feature gate.
+  If you were explicitly enabling or disabling this feature gate with `--feature-gates=+operator.sidecarcontainers.native`,
+  you must remove that flag.

internal/autodetect/main.go

@@ -26,7 +26,6 @@ import (
 	"github.com/open-telemetry/opentelemetry-operator/internal/autodetect/targetallocator"
 	"github.com/open-telemetry/opentelemetry-operator/internal/config"
 	"github.com/open-telemetry/opentelemetry-operator/internal/rbac"
-	"github.com/open-telemetry/opentelemetry-operator/pkg/featuregate"
 )
 
 var _ AutoDetect = (*autoDetect)(nil)
@@ -266,14 +265,9 @@ func (a *autoDetect) FIPSEnabled(_ context.Context) bool {
 	return fips.IsFipsEnabled()
 }
 
-// CheckNativeSidecarSupport checks if native sidecars are available and enabled.
-// This requires both the operator feature gate to be enabled AND
-// Kubernetes version >= 1.29 (beta support).
+// NativeSidecarSupport checks if native sidecars are available.
+// This requires Kubernetes version >= 1.29 (when native sidecars became stable).
 func (a *autoDetect) NativeSidecarSupport() (bool, error) {
-	if !featuregate.EnableNativeSidecarContainers.IsEnabled() {
-		return false, nil
-	}
-
 	currentVersion, err := a.k8sDetector.GetKubernetesVersion()
 	if err != nil {
 		return false, err

pkg/featuregate/featuregate.go

@@ -14,20 +14,6 @@ const (
 )
 
 var (
-	// EnableNativeSidecarContainers is the feature gate that controls whether a
-	// sidecar should be injected as a native sidecar or the classic way.
-	// Native sidecar containers have been available since kubernetes v1.28 in
-	// alpha and v1.29 in beta.
-	// It needs to be enabled with +featureGate=SidecarContainers.
-	// See:
-	// https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/#feature-gates-for-alpha-or-beta-features
-	EnableNativeSidecarContainers = featuregate.GlobalRegistry().MustRegister(
-		"operator.sidecarcontainers.native",
-		featuregate.StageStable,
-		featuregate.WithRegisterDescription("controls whether the operator supports sidecar containers as init containers. Should only be enabled on k8s v1.29+"),
-		featuregate.WithRegisterFromVersion("v0.111.0"),
-		featuregate.WithRegisterToVersion("v0.140.0"),
-	)
 	// SetGolangFlags is the feature gate that enables automatically setting GOMEMLIMIT and GOMAXPROCS for the
 	// collector, bridge, and target allocator.
 	SetGolangFlags = featuregate.GlobalRegistry().MustRegister(

pkg/sidecar/pod_test.go

@@ -8,30 +8,18 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-	colfeaturegate "go.opentelemetry.io/collector/featuregate"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	logf "sigs.k8s.io/controller-runtime/pkg/log"
 
 	"github.com/open-telemetry/opentelemetry-operator/apis/v1beta1"
 	"github.com/open-telemetry/opentelemetry-operator/internal/config"
 	"github.com/open-telemetry/opentelemetry-operator/internal/naming"
-	"github.com/open-telemetry/opentelemetry-operator/pkg/featuregate"
 )
 
 var logger = logf.Log.WithName("unit-tests")
 
-func enableSidecarFeatureGate(t *testing.T) {
-	originalVal := featuregate.EnableNativeSidecarContainers.IsEnabled()
-	t.Logf("original is: %+v", originalVal)
-	require.NoError(t, colfeaturegate.GlobalRegistry().Set(featuregate.EnableNativeSidecarContainers.ID(), true))
-	t.Cleanup(func() {
-		require.NoError(t, colfeaturegate.GlobalRegistry().Set(featuregate.EnableNativeSidecarContainers.ID(), originalVal))
-	})
-}
-
 func TestAddNativeSidecar(t *testing.T) {
-	enableSidecarFeatureGate(t)
 	// prepare
 	pod := corev1.Pod{
 		Spec: corev1.PodSpec{
@@ -329,8 +317,6 @@ func TestRemoveNonExistingSidecar(t *testing.T) {
 }
 
 func TestExistsIn(t *testing.T) {
-	enableSidecarFeatureGate(t)
-
 	for _, tt := range []struct {
 		desc     string
 		pod      corev1.Pod