[kubelet] Allow priority to be set for kubelet process on Windows

cmd/kubelet/app/init_others.go

@@ -18,6 +18,6 @@ limitations under the License.
 
 package app
 
-func initForOS(service bool) error {
+func initForOS(service bool, priorityClass string) error {
 	return nil
 }

cmd/kubelet/app/init_windows.go

@@ -19,6 +19,10 @@ limitations under the License.
 package app
 
 import (
+	"fmt"
+
+	"golang.org/x/sys/windows"
+	"k8s.io/klog/v2"
 	"k8s.io/kubernetes/pkg/windows/service"
 )
 
@@ -26,7 +30,33 @@ const (
 	serviceName = "kubelet"
 )
 
-func initForOS(windowsService bool) error {
+// getPriorityValue returns the value associated with a Windows process priorityClass
+// Ref: https://docs.microsoft.com/en-us/windows/win32/cimwin32prov/setpriority-method-in-class-win32-process
+func getPriorityValue(priorityClassName string) uint32 {
+	var priorityClassMap = map[string]uint32{
+		"IDLE_PRIORITY_CLASS":         uint32(64),
+		"BELOW_NORMAL_PRIORITY_CLASS": uint32(16384),
+		"NORMAL_PRIORITY_CLASS":       uint32(32),
+		"ABOVE_NORMAL_PRIORITY_CLASS": uint32(32768),
+		"HIGH_PRIORITY_CLASS":         uint32(128),
+		"REALTIME_PRIORITY_CLASS":     uint32(256),
+	}
+	return priorityClassMap[priorityClassName]
+}
+
+func initForOS(windowsService bool, windowsPriorityClass string) error {
+	priority := getPriorityValue(windowsPriorityClass)
+	if priority == 0 {
+		return fmt.Errorf("unknown priority class %s, valid ones are available at "+
+			"https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities", windowsPriorityClass)
+	}
+	kubeletProcessHandle := windows.CurrentProcess()
+	// Set the priority of the kubelet process to given priority
+	klog.Infof("Setting the priority of kubelet process to %s", windowsPriorityClass)
+	if err := windows.SetPriorityClass(kubeletProcessHandle, priority); err != nil {
+		return err
+	}
+
 	if windowsService {
 		return service.InitService(serviceName)
 	}

cmd/kubelet/app/init_windows_test.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package app
+
+import "testing"
+
+func TestIsValidPriorityClass(t *testing.T) {
+	testCases := []struct {
+		description           string
+		priorityClassName     string
+		expectedPriorityValue uint32
+	}{
+		{
+			description:           "Invalid Priority Class",
+			priorityClassName:     "myPriorityClass",
+			expectedPriorityValue: 0,
+		},
+		{
+			description:           "Valid Priority Class",
+			priorityClassName:     "IDLE_PRIORITY_CLASS",
+			expectedPriorityValue: uint32(64),
+		},
+	}
+	for _, test := range testCases {
+		actualPriorityValue := getPriorityValue(test.priorityClassName)
+		if test.expectedPriorityValue != actualPriorityValue {
+			t.Fatalf("unexpected error for %s", test.description)
+		}
+	}
+}

cmd/kubelet/app/options/options.go

@@ -111,6 +111,13 @@ type KubeletFlags struct {
 	// Its corresponding flag only gets registered in Windows builds.
 	WindowsService bool
 
+	// WindowsPriorityClass sets the priority class associated with the Kubelet process
+	// Its corresponding flag only gets registered in Windows builds
+	// The default priority class associated with any process in Windows is NORMAL_PRIORITY_CLASS. Keeping it as is
+	// to maintain backwards compatibility.
+	// Source: https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities
+	WindowsPriorityClass string
+
 	// remoteRuntimeEndpoint is the endpoint of remote runtime service
 	RemoteRuntimeEndpoint string
 	// remoteImageEndpoint is the endpoint of remote image service

cmd/kubelet/app/options/osflags_windows.go

@@ -24,4 +24,10 @@ import (
 
 func (f *KubeletFlags) addOSFlags(fs *pflag.FlagSet) {
 	fs.BoolVar(&f.WindowsService, "windows-service", f.WindowsService, "Enable Windows Service Control Manager API integration")
+	// The default priority class associated with any process in Windows is NORMAL_PRIORITY_CLASS. Keeping it as is
+	// to maintain backwards compatibility.
+	// Source: https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities
+	fs.StringVar(&f.WindowsPriorityClass, "windows-priorityclass", "NORMAL_PRIORITY_CLASS",
+		"Set the PriorityClass associated with kubelet process, the default ones are available at "+
+			"https://docs.microsoft.com/en-us/windows/win32/procthread/scheduling-priorities")
 }

cmd/kubelet/app/server.go

@@ -414,7 +414,7 @@ func Run(ctx context.Context, s *options.KubeletServer, kubeDeps *kubelet.Depend
 	logOption.Apply()
 	// To help debugging, immediately log version
 	klog.Infof("Version: %+v", version.Get())
-	if err := initForOS(s.KubeletFlags.WindowsService); err != nil {
+	if err := initForOS(s.KubeletFlags.WindowsService, s.KubeletFlags.WindowsPriorityClass); err != nil {
 		return fmt.Errorf("failed OS init: %v", err)
 	}
 	if err := run(ctx, s, kubeDeps, featureGate); err != nil {