add unit tests for version compatibility check

pkg/descheduler/descheduler.go

@@ -18,12 +18,14 @@ package descheduler
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"math"
 	"strconv"
 	"strings"
 	"time"
 
+	"k8s.io/client-go/discovery"
 	componentbaseconfig "k8s.io/component-base/config"
 	"k8s.io/klog/v2"
 
@@ -88,7 +90,9 @@ func Run(ctx context.Context, rs *options.DeschedulerServer) error {
 	}
 
 	// Add k8s compatibility warnings to logs
-	versionCompatibilityCheck(rs)
+	if err := validateVersionCompatibility(rs.Client.Discovery(), version.Get()); err != nil {
+		klog.Warning(err.Error())
+	}
 
 	evictionPolicyGroupVersion, err := eutils.SupportEviction(rs.Client)
 	if err != nil || len(evictionPolicyGroupVersion) == 0 {
@@ -104,7 +108,7 @@ func Run(ctx context.Context, rs *options.DeschedulerServer) error {
 	}
 
 	if rs.LeaderElection.LeaderElect && rs.DryRun {
-		klog.V(1).InfoS("Warning: DryRun is set to True. You need to disable it to use Leader Election.")
+		klog.V(1).Info("Warning: DryRun is set to True. You need to disable it to use Leader Election.")
 	}
 
 	if rs.LeaderElection.LeaderElect && !rs.DryRun {
@@ -117,27 +121,34 @@ func Run(ctx context.Context, rs *options.DeschedulerServer) error {
 	return runFn()
 }
 
-func versionCompatibilityCheck(rs *options.DeschedulerServer) {
-	serverVersion, serverErr := rs.Client.Discovery().ServerVersion()
+func validateVersionCompatibility(discovery discovery.DiscoveryInterface, versionInfo version.Info) error {
+	serverVersion, serverErr := discovery.ServerVersion()
 	if serverErr != nil {
-		klog.V(1).InfoS("Warning: Get Kubernetes server version fail")
-		return
+		return errors.New("failed to get Kubernetes server version")
 	}
 
-	deschedulerMinorVersion := strings.Split(version.Get().Minor, ".")[0]
+	deschedulerMinorVersion := strings.Split(versionInfo.Minor, ".")[0]
 	deschedulerMinorVersionFloat, err := strconv.ParseFloat(deschedulerMinorVersion, 64)
 	if err != nil {
-		klog.Warning("Warning: Convert Descheduler minor version to float fail")
+		return errors.New("failed to convert Descheduler minor version to float")
 	}
 
 	kubernetesMinorVersionFloat, err := strconv.ParseFloat(serverVersion.Minor, 64)
 	if err != nil {
-		klog.Warning("Warning: Convert Kubernetes server minor version to float fail")
+		return errors.New("failed to convert Kubernetes server minor version to float")
 	}
 
 	if math.Abs(deschedulerMinorVersionFloat-kubernetesMinorVersionFloat) > 3 {
-		klog.Warningf("Warning: Descheduler minor version %v is not supported on your version of Kubernetes %v.%v. See compatibility docs for more info: https://github.com/kubernetes-sigs/descheduler#compatibility-matrix", deschedulerMinorVersion, serverVersion.Major, serverVersion.Minor)
+		return fmt.Errorf(
+			"descheduler minor version %v is not supported on your version of Kubernetes %v.%v. "+
+				"See compatibility docs for more info: https://github.com/kubernetes-sigs/descheduler#compatibility-matrix",
+			deschedulerMinorVersion,
+			serverVersion.Major,
+			serverVersion.Minor,
+		)
 	}
+
+	return nil
 }
 
 func cachedClient(

pkg/descheduler/descheduler_test.go

@@ -11,6 +11,8 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/conversion"
 	"k8s.io/apimachinery/pkg/runtime"
+	apiversion "k8s.io/apimachinery/pkg/version"
+	fakediscovery "k8s.io/client-go/discovery/fake"
 	fakeclientset "k8s.io/client-go/kubernetes/fake"
 	core "k8s.io/client-go/testing"
 	"sigs.k8s.io/descheduler/cmd/descheduler/app/options"
@@ -19,6 +21,7 @@ import (
 	"sigs.k8s.io/descheduler/pkg/framework/pluginregistry"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/removeduplicates"
 	"sigs.k8s.io/descheduler/pkg/framework/plugins/removepodsviolatingnodetaints"
+	deschedulerversion "sigs.k8s.io/descheduler/pkg/version"
 	"sigs.k8s.io/descheduler/test"
 )
 
@@ -240,6 +243,63 @@ func TestRootCancelWithNoInterval(t *testing.T) {
 	}
 }
 
+func TestValidateVersionCompatibility(t *testing.T) {
+	type testCase struct {
+		name             string
+		deschedulerMinor string
+		serverMinor      string
+		expectError      bool
+	}
+	testCases := []testCase{
+		{
+			name:             "no error when descheduler minor equals to server minor",
+			deschedulerMinor: "26",
+			serverMinor:      "26",
+			expectError:      false,
+		},
+		{
+			name:             "no error when descheduler minor is 3 behind server minor",
+			deschedulerMinor: "23",
+			serverMinor:      "26",
+			expectError:      false,
+		},
+		{
+			name:             "no error when descheduler minor is 3 ahead of server minor",
+			deschedulerMinor: "26",
+			serverMinor:      "23",
+			expectError:      false,
+		},
+		{
+			name:             "error when descheduler minor is 4 behind server minor",
+			deschedulerMinor: "22",
+			serverMinor:      "26",
+			expectError:      true,
+		},
+		{
+			name:             "error when descheduler minor is 4 ahead of server minor",
+			deschedulerMinor: "26",
+			serverMinor:      "22",
+			expectError:      true,
+		},
+	}
+	client := fakeclientset.NewSimpleClientset()
+	fakeDiscovery, _ := client.Discovery().(*fakediscovery.FakeDiscovery)
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			fakeDiscovery.FakedServerVersion = &apiversion.Info{Major: "1", Minor: tc.serverMinor}
+			deschedulerVersion := deschedulerversion.Info{Major: "0", Minor: tc.deschedulerMinor}
+			err := validateVersionCompatibility(fakeDiscovery, deschedulerVersion)
+
+			hasError := err != nil
+			if tc.expectError != hasError {
+				t.Error("unexpected version compatibility behavior")
+			}
+		})
+	}
+}
+
 func podEvictionReactionFuc(evictedPods *[]string) func(action core.Action) (bool, runtime.Object, error) {
 	return func(action core.Action) (bool, runtime.Object, error) {
 		if action.GetSubresource() == "eviction" {