cli: make `linkerd uninstall` fail when injected pods are present (#5642)

* cli: make `linkerd uninstall` fail when injected pods are present

Fixes #5622

This PR updates the `linkerd uninstall` cmd to check if there
are any injected pods and fails if there are any. This also
provides `--force` flag to skip this check.

pods from namespaces with prefix `linkerd` are skipped
so as to not error out for control-plane and extension
pods.

Signed-off-by: Tarun Pothulapati <tarunpothulapati@outlook.com>

cli/cmd/uninstall.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/linkerd/linkerd2/pkg/k8s"
 	"github.com/linkerd/linkerd2/pkg/k8s/resource"
@@ -16,6 +17,7 @@ const (
 )
 
 func newCmdUninstall() *cobra.Command {
+	var force bool
 	cmd := &cobra.Command{
 		Use:   "uninstall",
 		Args:  cobra.NoArgs,
@@ -25,18 +27,41 @@ func newCmdUninstall() *cobra.Command {
 This command provides all Kubernetes namespace-scoped and cluster-scoped resources (e.g services, deployments, RBACs, etc.) necessary to uninstall Linkerd control plane.`,
 		Example: ` linkerd uninstall | kubectl delete -f -`,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			return uninstallRunE(cmd.Context())
+
+			k8sAPI, err := k8s.NewAPI(kubeconfigPath, kubeContext, impersonate, impersonateGroup, 0)
+			if err != nil {
+				return err
+			}
+
+			if !force {
+				podList, err := k8sAPI.CoreV1().Pods("").List(cmd.Context(), metav1.ListOptions{LabelSelector: k8s.ControllerNSLabel})
+				if err != nil {
+					return err
+				}
+
+				var injectedPods []string
+				for _, pod := range podList.Items {
+					// skip core control-plane namespace
+					if pod.Namespace != controlPlaneNamespace {
+						injectedPods = append(injectedPods, fmt.Sprintf("* %s", pod.Name))
+					}
+				}
+
+				if len(injectedPods) > 0 {
+					fmt.Fprintln(os.Stderr, fmt.Sprintf("Please uninject the following pods before uninstalling the control-plane:\n\t%s", strings.Join(injectedPods, "\n\t")))
+					os.Exit(1)
+				}
+			}
+
+			return uninstallRunE(cmd.Context(), k8sAPI)
 		},
 	}
 
+	cmd.Flags().BoolVarP(&force, "force", "f", force, "Force uninstall even if there exist non-control-plane injected pods")
 	return cmd
 }
 
-func uninstallRunE(ctx context.Context) error {
-	k8sAPI, err := k8s.NewAPI(kubeconfigPath, kubeContext, impersonate, impersonateGroup, 0)
-	if err != nil {
-		return err
-	}
+func uninstallRunE(ctx context.Context, k8sAPI *k8s.KubernetesAPI) error {
 
 	resources, err := resource.FetchKubernetesResources(ctx, k8sAPI,
 		metav1.ListOptions{LabelSelector: k8s.ControllerNSLabel},

test/integration/uninstall/uninstall_test.go

@@ -91,8 +91,25 @@ func TestResourcesPostInstall(t *testing.T) {
 }
 
 func TestUninstall(t *testing.T) {
-	args := []string{"uninstall"}
-	out, err := TestHelper.LinkerdRun(args...)
+	var (
+		vizCmd = []string{"viz", "uninstall"}
+	)
+
+	// Uninstall Linkerd Viz Extension
+	out, err := TestHelper.LinkerdRun(vizCmd...)
+	if err != nil {
+		testutil.AnnotatedFatal(t, "'linkerd viz uninstall' command failed", err)
+	}
+
+	args := []string{"delete", "-f", "-"}
+	out, err = TestHelper.Kubectl(out, args...)
+	if err != nil {
+		testutil.AnnotatedFatalf(t, "'kubectl delete' command failed",
+			"'kubectl delete' command failed\n%s", out)
+	}
+
+	args = []string{"uninstall"}
+	out, err = TestHelper.LinkerdRun(args...)
 	if err != nil {
 		testutil.AnnotatedFatal(t, "'linkerd install' command failed", err)
 	}
@@ -100,8 +117,8 @@ func TestUninstall(t *testing.T) {
 	args = []string{"delete", "-f", "-"}
 	out, err = TestHelper.Kubectl(out, args...)
 	if err != nil {
-		testutil.AnnotatedFatalf(t, "'kubectl apply' command failed",
-			"'kubectl apply' command failed\n%s", out)
+		testutil.AnnotatedFatalf(t, "'kubectl delete' command failed",
+			"'kubectl delete' command failed\n%s", out)
 	}
 }
 

viz/cmd/uninstall.go

@@ -34,13 +34,8 @@ func uninstallRunE(ctx context.Context) error {
 		return err
 	}
 
-	vizNs, err := k8sAPI.GetNamespaceWithExtensionLabel(ctx, ExtensionName)
-	if err != nil {
-		return err
-	}
-
 	resources, err := resource.FetchKubernetesResources(ctx, k8sAPI,
-		metav1.ListOptions{LabelSelector: fmt.Sprintf("%s=%s", k8s.LinkerdExtensionLabel, vizNs.Name)},
+		metav1.ListOptions{LabelSelector: fmt.Sprintf("%s=%s", k8s.LinkerdExtensionLabel, ExtensionName)},
 	)
 	if err != nil {
 		return err