Merge pull request #701 from nirmata/700_bug

add kubernetes server version check

cmd/initContainer/main.go

@@ -6,6 +6,8 @@ package main
 import (
 	"flag"
 	"os"
+	"regexp"
+	"strconv"
 	"sync"
 	"time"
 
@@ -44,6 +46,11 @@ func main() {
 		glog.Fatalf("Error creating client: %v\n", err)
 	}
 
+	// Exit for unsupported version of kubernetes cluster
+	// https://github.com/nirmata/kyverno/issues/700
+	// - supported from v1.12.7+
+	isVersionSupported(client)
+
 	requests := []request{
 		// Resource
 		{validatingWebhookConfigKind, config.ValidatingWebhookConfigurationName},
@@ -206,3 +213,32 @@ func merge(done <-chan struct{}, stopCh <-chan struct{}, processes ...<-chan err
 	}()
 	return out
 }
+
+func isVersionSupported(client *client.Client) {
+	serverVersion, err := client.DiscoveryClient.GetServerVersion()
+	if err != nil {
+		glog.Fatalf("Failed to get kubernetes server version: %v\n", err)
+	}
+	exp := regexp.MustCompile(`v(\d*).(\d*).(\d*)`)
+	groups := exp.FindAllStringSubmatch(serverVersion.String(), -1)
+	if len(groups) != 1 || len(groups[0]) != 4 {
+		glog.Fatalf("Failed to extract kubernetes server version: %v.err %v\n", serverVersion, err)
+	}
+	// convert string to int
+	// assuming the version are always intergers
+	major, err := strconv.Atoi(groups[0][1])
+	if err != nil {
+		glog.Fatalf("Failed to extract kubernetes major server version: %v.err %v\n", serverVersion, err)
+	}
+	minor, err := strconv.Atoi(groups[0][2])
+	if err != nil {
+		glog.Fatalf("Failed to extract kubernetes minor server version: %v.err %v\n", serverVersion, err)
+	}
+	sub, err := strconv.Atoi(groups[0][3])
+	if err != nil {
+		glog.Fatalf("Failed to extract kubernetes sub minor server version:%v. err %v\n", serverVersion, err)
+	}
+	if major <= 1 && minor <= 12 && sub < 7 {
+		glog.Fatalf("Unsupported kubernetes server version %s. Kyverno is supported from version v1.12.7+", serverVersion)
+	}
+}

pkg/dclient/client.go

@@ -16,6 +16,7 @@ import (
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	patchTypes "k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/discovery/cached/memory"
 	"k8s.io/client-go/dynamic"
@@ -213,6 +214,7 @@ func convertToCSR(obj *unstructured.Unstructured) (*certificates.CertificateSign
 //IDiscovery provides interface to mange Kind and GVR mapping
 type IDiscovery interface {
 	GetGVRFromKind(kind string) schema.GroupVersionResource
+	GetServerVersion() (*version.Info, error)
 }
 
 // SetDiscovery sets the discovery client implementation
@@ -265,6 +267,11 @@ func (c ServerPreferredResources) GetGVRFromKind(kind string) schema.GroupVersio
 	return gvr
 }
 
+//GetServerVersion returns the server version of the cluster
+func (c ServerPreferredResources) GetServerVersion() (*version.Info, error) {
+	return c.cachedClient.ServerVersion()
+}
+
 func loadServerResources(k string, cdi discovery.CachedDiscoveryInterface) (schema.GroupVersionResource, error) {
 	serverresources, err := cdi.ServerPreferredResources()
 	emptyGVR := schema.GroupVersionResource{}

pkg/dclient/utils.go

@@ -6,6 +6,7 @@ import (
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/version"
 	"k8s.io/client-go/dynamic/fake"
 	kubernetesfake "k8s.io/client-go/kubernetes/fake"
 )
@@ -64,6 +65,10 @@ func (c *fakeDiscoveryClient) getGVR(resource string) schema.GroupVersionResourc
 	return schema.GroupVersionResource{}
 }
 
+func (c *fakeDiscoveryClient) GetServerVersion() (*version.Info, error) {
+	return nil, nil
+}
+
 func (c *fakeDiscoveryClient) GetGVRFromKind(kind string) schema.GroupVersionResource {
 	resource := strings.ToLower(kind) + "s"
 	return c.getGVR(resource)