k8s driver: use right node selector on old k8s versions

Before kubernetes 1.14 nodes were labeled with the "beta.kubernetes.io/arch"
label instead of the "kubernetes.io/arch".

Current k8s version (v1.15) labels nodes with both labels but it's
deprecated and will removed in future versions.

At driver start get the current k8s api version and choose the right label to
use as node selector based on it.

internal/services/executor/driver/k8s.go

@@ -21,6 +21,8 @@ import (
 	"fmt"
 	"io"
 	"path/filepath"
+	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -62,6 +64,8 @@ const (
 	renewExecutorLeaseInterval = 10 * time.Second
 	staleExecutorLeaseInterval = 1 * time.Minute
 	informerResyncInterval     = 10 * time.Second
+
+	k8sLabelArchBeta = "beta.kubernetes.io/arch"
 )
 
 type K8sDriver struct {
@@ -77,6 +81,7 @@ type K8sDriver struct {
 	podLister        listerscorev1.PodLister
 	cmLister         listerscorev1.ConfigMapLister
 	leaseLister      coordinationlistersv1.LeaseLister
+	k8sLabelArch     string
 }
 
 type K8sPod struct {
@@ -106,12 +111,29 @@ func NewK8sDriver(logger *zap.Logger, executorID, toolboxPath string) (*K8sDrive
 	}
 
 	d := &K8sDriver{
-		log:         logger.Sugar(),
-		restconfig:  kubecfg,
-		client:      kubecli,
-		toolboxPath: toolboxPath,
-		namespace:   namespace,
-		executorID:  executorID,
+		log:          logger.Sugar(),
+		restconfig:   kubecfg,
+		client:       kubecli,
+		toolboxPath:  toolboxPath,
+		namespace:    namespace,
+		executorID:   executorID,
+		k8sLabelArch: corev1.LabelArchStable,
+	}
+
+	serverVersion, err := d.client.Discovery().ServerVersion()
+	if err != nil {
+		return nil, err
+	}
+	sv, err := parseGitVersion(serverVersion.GitVersion)
+	// if server version parsing fails just warn but ignore it
+	if err != nil {
+		d.log.Warnf("failed to parse k8s server version: %v", err)
+	}
+	if sv != nil {
+		// for k8s version < v1.14.x use old arch label
+		if sv.Major == 1 && sv.Minor < 14 {
+			d.k8sLabelArch = k8sLabelArchBeta
+		}
 	}
 
 	lists, err := d.client.Discovery().ServerPreferredResources()
@@ -399,7 +421,7 @@ func (d *K8sDriver) NewPod(ctx context.Context, podConfig *PodConfig, out io.Wri
 
 	if podConfig.Arch != "" {
 		pod.Spec.NodeSelector = map[string]string{
-			corev1.LabelArchStable: string(podConfig.Arch),
+			d.k8sLabelArch: string(podConfig.Arch),
 		}
 	}
 
@@ -736,3 +758,29 @@ func genEnvVars(env map[string]string) []corev1.EnvVar {
 	}
 	return envVars
 }
+
+type serverVersion struct {
+	Major int
+	Minor int
+}
+
+// k8s version is in this format: v0.0.0(-master+$Format:%h$)
+var gitVersionRegex = regexp.MustCompile("v([0-9]+).([0-9]+).[0-9]+.*")
+
+func parseGitVersion(gitVersion string) (*serverVersion, error) {
+	parsedVersion := gitVersionRegex.FindStringSubmatch(gitVersion)
+	if len(parsedVersion) != 3 {
+		return nil, fmt.Errorf("cannot parse git version %s", gitVersion)
+	}
+	sv := &serverVersion{}
+	var err error
+	sv.Major, err = strconv.Atoi(parsedVersion[1])
+	if err != nil {
+		return nil, err
+	}
+	sv.Minor, err = strconv.Atoi(parsedVersion[2])
+	if err != nil {
+		return nil, err
+	}
+	return sv, nil
+}

internal/services/executor/driver/k8s_test.go

@@ -19,6 +19,7 @@ import (
 	"context"
 	"io/ioutil"
 	"os"
+	"reflect"
 	"testing"
 	"time"
 
@@ -253,3 +254,51 @@ func TestK8sPod(t *testing.T) {
 	})
 
 }
+
+func TestParseGitVersion(t *testing.T) {
+	tests := []struct {
+		gitVersion string
+		out        *serverVersion
+		err        bool
+	}{
+		{
+			gitVersion: "v1.8.0",
+			out:        &serverVersion{Major: 1, Minor: 8},
+		},
+		{
+			gitVersion: "v1.12.0",
+			out:        &serverVersion{Major: 1, Minor: 12},
+		},
+		{
+			gitVersion: "v1.12.20",
+			out:        &serverVersion{Major: 1, Minor: 12},
+		},
+		{
+			gitVersion: "v1.12.8-test.10",
+			out:        &serverVersion{Major: 1, Minor: 12},
+		},
+		{
+			gitVersion: "v1.a",
+			err:        true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run("", func(t *testing.T) {
+			sv, err := parseGitVersion(tt.gitVersion)
+			if tt.err {
+				if err == nil {
+					t.Errorf("expected error, got nil error")
+				}
+				return
+			}
+			if err != nil {
+				t.Errorf("unexpected err: %v", err)
+				return
+			}
+			if !reflect.DeepEqual(sv, tt.out) {
+				t.Errorf("expected %v, got %v", tt.out, sv)
+			}
+		})
+	}
+}