Dynamic Kubelet Configuration

Alpha implementation of the Dynamic Kubelet Configuration feature.
See the proposal doc in #29459.

pkg/apis/componentconfig/validation/validation.go

@@ -0,0 +1,56 @@
+/*
+Copyright 2017 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 validation
+
+import (
+	"fmt"
+
+	"k8s.io/kubernetes/pkg/apis/componentconfig"
+	containermanager "k8s.io/kubernetes/pkg/kubelet/cm"
+)
+
+// MaxCrashLoopThreshold is the maximum allowed KubeletConfiguraiton.CrashLoopThreshold
+const MaxCrashLoopThreshold = 10
+
+// ValidateKubeletConfiguration validates `kc` and returns an error if it is invalid
+func ValidateKubeletConfiguration(kc *componentconfig.KubeletConfiguration) error {
+	// restrict crashloop threshold to between 0 and `maxCrashLoopThreshold`, inclusive
+	// more than `maxStartups=maxCrashLoopThreshold` adds unnecessary bloat to the .startups.json file,
+	// and negative values would be silly.
+	if kc.CrashLoopThreshold < 0 || kc.CrashLoopThreshold > MaxCrashLoopThreshold {
+		return fmt.Errorf("field `CrashLoopThreshold` must be between 0 and %d, inclusive", MaxCrashLoopThreshold)
+	}
+
+	if !kc.CgroupsPerQOS && len(kc.EnforceNodeAllocatable) > 0 {
+		return fmt.Errorf("node allocatable enforcement is not supported unless Cgroups Per QOS feature is turned on")
+	}
+	if kc.SystemCgroups != "" && kc.CgroupRoot == "" {
+		return fmt.Errorf("invalid configuration: system container was specified and cgroup root was not specified")
+	}
+	for _, val := range kc.EnforceNodeAllocatable {
+		switch val {
+		case containermanager.NodeAllocatableEnforcementKey:
+		case containermanager.SystemReservedEnforcementKey:
+		case containermanager.KubeReservedEnforcementKey:
+			continue
+		default:
+			return fmt.Errorf("invalid option %q specified for EnforceNodeAllocatable setting. Valid options are %q, %q or %q",
+				val, containermanager.NodeAllocatableEnforcementKey, containermanager.SystemReservedEnforcementKey, containermanager.KubeReservedEnforcementKey)
+		}
+	}
+	return nil
+}