adding support for updating coredns

Signed-off-by: Christopher Hein <me@chrishein.com>

pkg/addons/default/coredns.go

@@ -17,6 +17,8 @@ import (
 	"k8s.io/apimachinery/pkg/watch"
 
 	"github.com/weaveworks/eksctl/pkg/kubernetes"
+	"github.com/weaveworks/eksctl/pkg/printers"
+	k8s "k8s.io/client-go/kubernetes"
 )
 
 const (
@@ -25,6 +27,8 @@ const (
 	// KubeDNS is the name of the kube-dns addon
 	KubeDNS = "kube-dns"
 
+	CoreDNSVersion = "v1.2.2"
+
 	componentLabel = "eks.amazonaws.com/component"
 
 	coreDNSImagePrefix = "602401143452.dkr.ecr."
@@ -153,3 +157,55 @@ func InstallCoreDNS(rawClient kubernetes.RawClientInterface, region string, wait
 	logger.Info("%q is now up-to-date", CoreDNS)
 	return nil
 }
+
+// UpdateCoreDNSImageTag updates image tag for kube-system:deployment/coredns based to match the latest release
+func UpdateCoreDNSImageTag(clientSet k8s.Interface, dryRun bool) error {
+	printer := printers.NewJSONPrinter()
+
+	d, err := clientSet.ExtensionsV1beta1().Deployments(metav1.NamespaceSystem).Get(CoreDNS, metav1.GetOptions{})
+	if err != nil {
+		if apierrs.IsNotFound(err) {
+			logger.Warning("%q was not found", CoreDNS)
+			return nil
+		}
+		return errors.Wrapf(err, "getting %q", CoreDNS)
+	}
+	if numContainers := len(d.Spec.Template.Spec.Containers); !(numContainers >= 1) {
+		return fmt.Errorf("%s has %d containers, expected at least 1", CoreDNS, numContainers)
+	}
+
+	if err := printer.LogObj(logger.Debug, CoreDNS+" [current] = \\\n%s\n", d); err != nil {
+		return err
+	}
+
+	image := &d.Spec.Template.Spec.Containers[0].Image
+	imageParts := strings.Split(*image, ":")
+
+	if len(imageParts) != 2 {
+		return fmt.Errorf("unexpected image format %q for %q", *image, CoreDNS)
+	}
+
+	if imageParts[1] == CoreDNSVersion {
+		logger.Debug("imageParts = %v, desiredTag = %s", imageParts, CoreDNSVersion)
+		logger.Info("%q is already up-to-date", CoreDNS)
+		return nil
+	}
+
+	if dryRun {
+		logger.Critical("%q is not up-to-date", CoreDNS)
+		return nil
+	}
+
+	imageParts[1] = CoreDNSVersion
+	*image = strings.Join(imageParts, ":")
+
+	if err := printer.LogObj(logger.Debug, CoreDNS+" [updated] = \\\n%s\n", d); err != nil {
+		return err
+	}
+	if _, err := clientSet.ExtensionsV1beta1().Deployments(metav1.NamespaceSystem).Update(d); err != nil {
+		return err
+	}
+
+	logger.Info("%q is now up-to-date", CoreDNS)
+	return nil
+}

pkg/addons/default/coredns_test.go

@@ -10,10 +10,11 @@ import (
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/client-go/kubernetes/fake"
 )
 
 var _ = Describe("default addons - coredns", func() {
-	Describe("can update coredns add-on", func() {
+	Describe("can update from kubedns to coredns add-on", func() {
 		var (
 			rawClient *testutils.FakeRawClient
 			ct        *testutils.CollectionTracker
@@ -104,4 +105,42 @@ var _ = Describe("default addons - coredns", func() {
 		})
 
 	})
+
+	Describe("can update coredns", func() {
+		var (
+			clientSet *fake.Clientset
+		)
+
+		check := func(imageTag string) {
+			coreDNS, err := clientSet.ExtensionsV1beta1().Deployments(metav1.NamespaceSystem).Get(CoreDNS, metav1.GetOptions{})
+
+			Expect(err).ToNot(HaveOccurred())
+			Expect(coreDNS).ToNot(BeNil())
+			Expect(coreDNS.Spec.Template.Spec.Containers).To(HaveLen(1))
+
+			Expect(coreDNS.Spec.Template.Spec.Containers[0].Image).To(
+				Equal("602401143452.dkr.ecr.eu-west-1.amazonaws.com/eks/coredns:" + imageTag),
+			)
+		}
+
+		BeforeEach(func() {
+			clientSet, _ = testutils.NewFakeClientSetWithSamples("testdata/sample-1.11.json")
+		})
+
+		It("can load 1.11 sample", func() {
+			check("v1.1.3")
+		})
+
+		It("can update based to latest version", func() {
+			err := UpdateCoreDNSImageTag(clientSet, false)
+			Expect(err).ToNot(HaveOccurred())
+			check("v1.2.2")
+		})
+
+		It("can dry-run update to latest version", func() {
+			err := UpdateCoreDNSImageTag(clientSet, true)
+			Expect(err).ToNot(HaveOccurred())
+			check("v1.1.3")
+		})
+	})
 })