fix: keep aggregator volume order stable to avoid rollout on operator upgrade

internal/vector/aggregator/deployment.go

@@ -197,26 +197,12 @@ func (ctrl *Controller) generateVectorAggregatorVolume() []corev1.Volume {
 			Name:         "config",
 			VolumeSource: configVolumeSource,
 		},
-		{
-			Name: "procfs",
-			VolumeSource: corev1.VolumeSource{
-				HostPath: &corev1.HostPathVolumeSource{
-					Path: "/proc",
-				},
-			},
-		},
-		{
-			Name: "sysfs",
-			VolumeSource: corev1.VolumeSource{
-				HostPath: &corev1.HostPathVolumeSource{
-					Path: "/sys",
-				},
-			},
-		},
 	}
 
 	// In persistent mode the data volume comes from the StatefulSet volume claim
 	// template, so only add the hostPath data volume for the Deployment path.
+	// Keep it right after "config": reordering the volume list changes the pod
+	// template and rolls every non-persistent aggregator on operator upgrade.
 	if !ctrl.persistenceEnabled() {
 		requiredVolumes = append(requiredVolumes, corev1.Volume{
 			Name: dataVolumeName,
@@ -228,6 +214,25 @@ func (ctrl *Controller) generateVectorAggregatorVolume() []corev1.Volume {
 		})
 	}
 
+	requiredVolumes = append(requiredVolumes,
+		corev1.Volume{
+			Name: "procfs",
+			VolumeSource: corev1.VolumeSource{
+				HostPath: &corev1.HostPathVolumeSource{
+					Path: "/proc",
+				},
+			},
+		},
+		corev1.Volume{
+			Name: "sysfs",
+			VolumeSource: corev1.VolumeSource{
+				HostPath: &corev1.HostPathVolumeSource{
+					Path: "/sys",
+				},
+			},
+		},
+	)
+
 	// Only add volumes that don't already exist
 	for _, reqVol := range requiredVolumes {
 		if !existingVolumes[reqVol.Name] {

internal/vector/aggregator/deployment_test.go

@@ -0,0 +1,25 @@
+package aggregator
+
+import (
+	"testing"
+
+	. "github.com/onsi/gomega"
+
+	vectorv1alpha1 "github.com/kaasops/vector-operator/api/v1alpha1"
+)
+
+func TestGenerateVolumesKeepsPreUpgradeOrderWhenNotPersistent(t *testing.T) {
+	g := NewWithT(t)
+
+	ctrl := createTestController("test", "default", &vectorv1alpha1.VectorAggregatorCommon{}, false)
+
+	volumes := ctrl.generateVectorAggregatorVolume()
+
+	names := make([]string, 0, len(volumes))
+	for _, v := range volumes {
+		names = append(names, v.Name)
+	}
+	// The exact order v0.4.1 generated: a reordered (even if semantically equal)
+	// pod template rolls every aggregator Deployment on operator upgrade.
+	g.Expect(names).To(Equal([]string{"config", "data", "procfs", "sysfs"}))
+}