Auto-create system critical prioity classes at API server startup

pkg/apis/scheduling/types.go

@@ -23,9 +23,17 @@ const (
 	// that do not specify any priority class and there is no priority class
 	// marked as default.
 	DefaultPriorityWhenNoDefaultClassExists = 0
+	// HighestUserDefinablePriority is the highest priority for user defined priority classes. Priority values larger than 1 billion are reserved for Kubernetes system use.
+	HighestUserDefinablePriority = int32(1000000000)
+	// SystemCriticalPriority is the beginning of the range of priority values for critical system components.
+	SystemCriticalPriority = 2 * HighestUserDefinablePriority
 	// SystemPriorityClassPrefix is the prefix reserved for system priority class names. Other priority
 	// classes are not allowed to start with this prefix.
 	SystemPriorityClassPrefix = "system-"
+	// NOTE: In order to avoid conflict of names with user-defined priority classes, all the names must
+	// start with SystemPriorityClassPrefix.
+	SystemClusterCritical = SystemPriorityClassPrefix + "cluster-critical"
+	SystemNodeCritical    = SystemPriorityClassPrefix + "node-critical"
 )
 
 // +genclient

pkg/apis/scheduling/validation/validation.go

@@ -17,8 +17,6 @@ limitations under the License.
 package validation
 
 import (
-	"strings"
-
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	apivalidation "k8s.io/kubernetes/pkg/apis/core/validation"
 	"k8s.io/kubernetes/pkg/apis/scheduling"
@@ -26,12 +24,7 @@ import (
 
 // ValidatePriorityClassName checks whether the given priority class name is valid.
 func ValidatePriorityClassName(name string, prefix bool) []string {
-	var allErrs []string
-	if strings.HasPrefix(name, scheduling.SystemPriorityClassPrefix) {
-		allErrs = append(allErrs, "priority class names with '"+scheduling.SystemPriorityClassPrefix+"' prefix are reserved for system use only")
-	}
-	allErrs = append(allErrs, apivalidation.NameIsDNSSubdomain(name, prefix)...)
-	return allErrs
+	return apivalidation.NameIsDNSSubdomain(name, prefix)
 }
 
 // ValidatePriorityClass tests whether required fields in the PriorityClass are

pkg/apis/scheduling/validation/validation_test.go

@@ -53,10 +53,6 @@ func TestValidatePriorityClass(t *testing.T) {
 			ObjectMeta: metav1.ObjectMeta{Name: "tier&1", Namespace: ""},
 			Value:      100,
 		},
-		"invalid system name": {
-			ObjectMeta: metav1.ObjectMeta{Name: scheduling.SystemPriorityClassPrefix + "test"},
-			Value:      100,
-		},
 	}
 
 	for k, v := range errorCases {