test/e2e_node: add e2e test for Kubeletconfig drop-in dir

Signed-off-by: Sohan Kunkerkar <sohank2602@gmail.com>
Co-authored-by: Peter Hunt <pehunt@redhat.com>

test/e2e_node/kubelet_config_dir_test.go

@@ -0,0 +1,113 @@
+/*
+Copyright 2023 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 e2enode
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"time"
+
+	"github.com/onsi/ginkgo/v2"
+	"github.com/onsi/gomega"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	kubeletconfig "k8s.io/kubernetes/pkg/kubelet/apis/config"
+	"k8s.io/kubernetes/test/e2e/framework"
+	"k8s.io/kubernetes/test/e2e/nodefeature"
+)
+
+var _ = SIGDescribe("Kubelet Config", framework.WithSlow(), framework.WithSerial(), framework.WithDisruptive(), nodefeature.KubeletConfigDropInDir, func() {
+	f := framework.NewDefaultFramework("kubelet-config-drop-in-dir-test")
+	ginkgo.Context("when merging drop-in configs", func() {
+		var oldcfg *kubeletconfig.KubeletConfiguration
+		ginkgo.BeforeEach(func(ctx context.Context) {
+			var err error
+			oldcfg, err = getCurrentKubeletConfig(ctx)
+			framework.ExpectNoError(err)
+		})
+		ginkgo.AfterEach(func(ctx context.Context) {
+			files, err := filepath.Glob(filepath.Join(framework.TestContext.KubeletConfigDropinDir, "*"+".conf"))
+			framework.ExpectNoError(err)
+			for _, file := range files {
+				err := os.Remove(file)
+				framework.ExpectNoError(err)
+			}
+			updateKubeletConfig(ctx, f, oldcfg, true)
+		})
+		ginkgo.It("should merge kubelet configs correctly", func(ctx context.Context) {
+			// Get the initial kubelet configuration
+			initialConfig, err := getCurrentKubeletConfig(ctx)
+			framework.ExpectNoError(err)
+
+			ginkgo.By("Stopping the kubelet")
+			restartKubelet := stopKubelet()
+
+			// wait until the kubelet health check will fail
+			gomega.Eventually(ctx, func() bool {
+				return kubeletHealthCheck(kubeletHealthCheckURL)
+			}, f.Timeouts.PodStart, f.Timeouts.Poll).Should(gomega.BeFalse())
+
+			configDir := framework.TestContext.KubeletConfigDropinDir
+
+			contents := []byte(`apiVersion: kubelet.config.k8s.io/v1beta1
+kind: KubeletConfiguration
+port: 10255
+readOnlyPort: 10257
+clusterDNS:
+- 192.168.1.10
+systemReserved:
+  memory: 1Gi`)
+			framework.ExpectNoError(os.WriteFile(filepath.Join(configDir, "10-kubelet.conf"), contents, 0755))
+			contents = []byte(`apiVersion: kubelet.config.k8s.io/v1beta1
+kind: KubeletConfiguration
+clusterDNS:
+- 192.168.1.1
+- 192.168.1.5
+- 192.168.1.8
+port: 8080
+cpuManagerReconcilePeriod: 0s
+systemReserved:
+  memory: 2Gi`)
+			framework.ExpectNoError(os.WriteFile(filepath.Join(configDir, "20-kubelet.conf"), contents, 0755))
+			ginkgo.By("Restarting the kubelet")
+			restartKubelet()
+			// wait until the kubelet health check will succeed
+			gomega.Eventually(ctx, func() bool {
+				return kubeletHealthCheck(kubeletHealthCheckURL)
+			}, f.Timeouts.PodStart, f.Timeouts.Poll).Should(gomega.BeTrue())
+
+			mergedConfig, err := getCurrentKubeletConfig(ctx)
+			framework.ExpectNoError(err)
+
+			// Replace specific fields in the initial configuration with expectedConfig values
+			initialConfig.Port = int32(8080)                  // not overridden by second file, should be retained.
+			initialConfig.ReadOnlyPort = int32(10257)         // overridden by second file.
+			initialConfig.SystemReserved = map[string]string{ // overridden by map in second file.
+				"memory": "2Gi",
+			}
+			initialConfig.ClusterDNS = []string{"192.168.1.1", "192.168.1.5", "192.168.1.8"} // overridden by slice in second file.
+			// This value was explicitly set in the drop-in, make sure it is retained
+			initialConfig.CPUManagerReconcilePeriod = metav1.Duration{Duration: time.Duration(0)}
+			// Meanwhile, this value was not explicitly set, but could have been overridden by a "default" of 0 for the type.
+			// Ensure the true default persists.
+			initialConfig.CPUCFSQuotaPeriod = metav1.Duration{Duration: time.Duration(100000000)}
+			// Compare the expected config with the merged config
+			gomega.Expect(initialConfig).To(gomega.BeComparableTo(mergedConfig), "Merged kubelet config does not match the expected configuration.")
+		})
+	})
+
+})