Merge pull request kubernetes#94506 from neolit123/1.20-coredns-remove-supported-version-check

kubeadm: remove the CoreDNS check for supported image digests

Author: k8s-ci-robot

cmd/kubeadm/app/phases/addons/dns/BUILD

@@ -46,7 +46,6 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
-        "//staging/src/k8s.io/apimachinery/pkg/util/wait:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/scheme:go_default_library",
         "//vendor/github.com/caddyserver/caddy/caddyfile:go_default_library",

cmd/kubeadm/app/phases/addons/dns/dns.go

@@ -21,9 +21,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net"
-	"regexp"
 	"strings"
-	"time"
 
 	"github.com/caddyserver/caddy/caddyfile"
 	"github.com/coredns/corefile-migration/migration"
@@ -35,7 +33,6 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	kuberuntime "k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
-	"k8s.io/apimachinery/pkg/util/wait"
 	clientset "k8s.io/client-go/kubernetes"
 	clientsetscheme "k8s.io/client-go/kubernetes/scheme"
 	"k8s.io/klog/v2"
@@ -270,22 +267,15 @@ func createCoreDNSAddon(deploymentBytes, serviceBytes, configBytes []byte, clien
 		return errors.Wrap(err, "unable to fetch CoreDNS current installed version and ConfigMap.")
 	}
 
-	canMigrateCorefile, err := isCoreDNSVersionSupported(client)
-	if err != nil {
-		return err
-	}
-
 	corefileMigrationRequired, err := isCoreDNSConfigMapMigrationRequired(corefile, currentInstalledCoreDNSVersion)
 	if err != nil {
 		return err
 	}
 
-	if !canMigrateCorefile {
-		klog.Warningf("the CoreDNS Configuration will not be migrated due to unsupported version of CoreDNS. " +
-			"The existing CoreDNS Corefile configuration and deployment has been retained.")
-	}
+	// Assume that migration is always possible, rely on migrateCoreDNSCorefile() to fail if not.
+	canMigrateCorefile := true
 
-	if corefileMigrationRequired && canMigrateCorefile {
+	if corefileMigrationRequired {
 		if err := migrateCoreDNSCorefile(client, coreDNSConfigMap, corefile, currentInstalledCoreDNSVersion); err != nil {
 			// Errors in Corefile Migration is verified during preflight checks. This part will be executed when a user has chosen
 			// to ignore preflight check errors.
@@ -394,56 +384,6 @@ func isCoreDNSConfigMapMigrationRequired(corefile, currentInstalledCoreDNSVersio
 	return isMigrationRequired, nil
 }
 
-var (
-	// imageDigestMatcher is used to match the SHA256 digest from the ImageID of the CoreDNS pods
-	imageDigestMatcher = regexp.MustCompile(`^.*(?i:sha256:([[:alnum:]]{64}))$`)
-)
-
-func isCoreDNSVersionSupported(client clientset.Interface) (bool, error) {
-	var lastError error
-	var pods []v1.Pod
-
-	pollTimeout := 10 * time.Second
-	err := wait.PollImmediate(kubeadmconstants.APICallRetryInterval, pollTimeout, func() (bool, error) {
-		coreDNSPodList, err := client.CoreV1().Pods(metav1.NamespaceSystem).List(
-			context.TODO(),
-			metav1.ListOptions{
-				LabelSelector: "k8s-app=kube-dns",
-			},
-		)
-		if err != nil {
-			lastError = err
-			return false, nil
-		}
-
-		for _, pod := range coreDNSPodList.Items {
-			if pod.Status.Phase != v1.PodRunning {
-				lastError = errors.New("found non-running CoreDNS pods")
-				return false, nil
-			}
-		}
-		pods = coreDNSPodList.Items
-		return true, nil
-	})
-
-	if err != nil {
-		return false, errors.Wrapf(lastError, "could not list the running CoreDNS pods after %v", pollTimeout)
-	}
-
-	for _, pod := range pods {
-		imageID := imageDigestMatcher.FindStringSubmatch(pod.Status.ContainerStatuses[0].ImageID)
-		if len(imageID) != 2 {
-			return false, errors.Errorf("pod %s unable to match SHA256 digest ID in %q", pod.GetName(), pod.Status.ContainerStatuses[0].ImageID)
-		}
-		// The actual digest should be at imageID[1]
-		if !migration.Released(imageID[1]) {
-			return false, errors.Errorf("unknown digest %q for pod %s", imageID[1], pod.GetName())
-		}
-	}
-
-	return true, nil
-}
-
 func migrateCoreDNSCorefile(client clientset.Interface, cm *v1.ConfigMap, corefile, currentInstalledCoreDNSVersion string) error {
 	// Since the current configuration present is not the default version, try and migrate it.
 	updatedCorefile, err := migration.Migrate(currentInstalledCoreDNSVersion, kubeadmconstants.CoreDNSVersion, corefile, false)