feat: add cluster uid derived from kube-system ns

This seems like a simple enough way of uniquely identifying a cluster.
Google searches show that this pattern is used elsewhere.

It seems fair to assume that if the kube-system ns UID changes, it
implies that the cluster changed enough to be considered different
anyway!

This is added to the context so it can be used elsewhere, on the
assumption that it can be determined at startup and won't change
later. We'll use this for "machinehub mode" soon.

Signed-off-by: Ashley Davis <[email protected]>

Author: SgtCoDFish

pkg/agent/run.go

@@ -33,6 +33,7 @@ import (
 
 	"github.com/jetstack/preflight/api"
 	"github.com/jetstack/preflight/pkg/client"
+	"github.com/jetstack/preflight/pkg/clusteruid"
 	"github.com/jetstack/preflight/pkg/datagatherer"
 	"github.com/jetstack/preflight/pkg/datagatherer/k8s"
 	"github.com/jetstack/preflight/pkg/kubeconfig"
@@ -79,6 +80,28 @@ func Run(cmd *cobra.Command, args []string) (returnErr error) {
 		return fmt.Errorf("While evaluating configuration: %v", err)
 	}
 
+	// We need the cluster UID before we progress further so it can be sent along with other data readings
+
+	{
+		restCfg, err := kubeconfig.LoadRESTConfig("")
+		if err != nil {
+			return err
+		}
+
+		clientset, err := kubernetes.NewForConfig(restCfg)
+		if err != nil {
+			return err
+		}
+
+		ctx, err = clusteruid.GetClusterUID(ctx, clientset)
+		if err != nil {
+			return fmt.Errorf("failed to get cluster UID: %v", err)
+		}
+
+		clusterUID := clusteruid.ClusterUIDFromContext(ctx)
+		log.V(logs.Debug).Info("Retrieved cluster UID", "clusterUID", clusterUID)
+	}
+
 	group, gctx := errgroup.WithContext(ctx)
 	defer func() {
 		cancel()

pkg/clusteruid/clusteruid.go

@@ -0,0 +1,45 @@
+package clusteruid
+
+import (
+	"context"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/client-go/kubernetes"
+)
+
+// clusterUIDKey is the context key for storing the cluster UID
+type clusterUIDKey struct{}
+
+// GetClusterUID retrieves the UID of the kube-system namespace using the given Kubernetes clientset.
+// This UID can be used as a unique identifier for the Kubernetes cluster.
+// The UID is stored in the given context for later retrieval; use ClusterUIDFromContext to get it.
+func GetClusterUID(ctx context.Context, clientset kubernetes.Interface) (context.Context, error) {
+	namespace, err := clientset.CoreV1().Namespaces().Get(ctx, "kube-system", metav1.GetOptions{})
+	if err != nil {
+		return ctx, err
+	}
+
+	ctx = withClusterUID(ctx, string(namespace.ObjectMeta.UID))
+	return ctx, nil
+}
+
+// ClusterUIDFromContext retrieves the cluster UID from the context.
+// Panics if the value is not found or if the value is not a string.
+func ClusterUIDFromContext(ctx context.Context) string {
+	value := ctx.Value(clusterUIDKey{})
+	if value == nil {
+		panic("cluster UID not found in context")
+	}
+
+	uid, ok := value.(string)
+	if !ok {
+		panic("cluster UID in context is not a string")
+	}
+
+	return uid
+}
+
+// withClusterUID adds the given cluster UID to the context
+func withClusterUID(ctx context.Context, clusterUID string) context.Context {
+	return context.WithValue(ctx, clusterUIDKey{}, clusterUID)
+}

pkg/clusteruid/clusteruid_test.go

@@ -0,0 +1,40 @@
+package clusteruid
+
+import (
+	"testing"
+
+	"k8s.io/client-go/kubernetes/fake"
+
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/types"
+)
+
+func TestGetClusterUID(t *testing.T) {
+	client := fake.NewSimpleClientset()
+
+	mockUID := "12345678-1234-5678-1234-567812345678"
+
+	kubeSystemNS := &corev1.Namespace{
+		ObjectMeta: metav1.ObjectMeta{
+			Name: "kube-system",
+			UID:  types.UID(mockUID),
+		},
+	}
+
+	_, err := client.CoreV1().Namespaces().Create(t.Context(), kubeSystemNS, metav1.CreateOptions{})
+	if err != nil {
+		t.Fatalf("failed to create kube-system namespace with fake client: %v", err)
+	}
+
+	ctx, err := GetClusterUID(t.Context(), client)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	uid := ClusterUIDFromContext(ctx)
+
+	if uid != mockUID {
+		t.Fatalf("expected to get uid=%v, but got uid=%v", mockUID, uid)
+	}
+}