feat: hot reload kubeconfig

internal/wrapper.go

@@ -95,6 +95,28 @@ func RunKubeStateMetricsWrapper(opts *options.Options) {
 		})
 		crcViper.WatchConfig()
 	}
+	if opts.Kubeconfig != "" {
+		kubecfgViper := viper.New()
+		kubecfgViper.SetConfigType("yaml")
+		kubecfgViper.SetConfigFile(opts.Kubeconfig)
+		if err := kubecfgViper.ReadInConfig(); err != nil {
+			if errors.Is(err, viper.ConfigFileNotFoundError{}) {
+				klog.ErrorS(err, "kubeconfig file not found", "file", opts.Kubeconfig)
+			} else {
+				klog.ErrorS(err, "Error reading kubeconfig file", "file", opts.Kubeconfig)
+			}
+			klog.FlushAndExit(klog.ExitFlushTimeout, 1)
+		}
+		kubecfgViper.OnConfigChange(func(e fsnotify.Event) {
+			klog.InfoS("Changes detected", "name", e.Name)
+			cancel()
+			// Wait for the ports to be released.
+			<-time.After(3 * time.Second)
+			ctx, cancel = context.WithCancel(context.Background())
+			go KSMRunOrDie(ctx)
+		})
+		kubecfgViper.WatchConfig()
+	}
 	klog.InfoS("Starting kube-state-metrics")
 	KSMRunOrDie(ctx)
 	select {}

tests/e2e.sh

@@ -209,6 +209,9 @@ go test -race -v ./tests/e2e/discovery_test.go
 echo "running hot-reload tests..."
 go test -v ./tests/e2e/hot-reload_test.go
 
+echo "running hot-reload-kubeconfig tests..."
+go test -v ./tests/e2e/hot-reload-kubeconfig_test.go
+
 output_logs=$(kubectl --namespace=kube-system logs deployment/kube-state-metrics kube-state-metrics)
 if echo "${output_logs}" | grep "^${klog_err}"; then
     echo ""

tests/e2e/hot-reload-kubeconfig_test.go

@@ -0,0 +1,134 @@
+/*
+Copyright 2023 The Kubernetes Authors All rights reserved.
+
+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 e2e
+
+import (
+	"context"
+	"io"
+	"net"
+	"os"
+	"os/exec"
+	"testing"
+	"time"
+
+	"k8s.io/apimachinery/pkg/util/wait"
+
+	"k8s.io/kube-state-metrics/v2/internal"
+	"k8s.io/kube-state-metrics/v2/pkg/options"
+)
+
+func TestKubeConfigHotReload(t *testing.T) {
+
+	// Initialise options.
+	opts := options.NewOptions()
+	cmd := options.InitCommand
+	opts.AddFlags(cmd)
+
+	// Open kubeconfig
+	originalKubeconfig := os.Getenv("KUBECONFIG")
+	if originalKubeconfig == "" {
+		// Assume $HOME is always defined.
+		originalKubeconfig = os.Getenv("HOME") + "/.kube/config"
+	}
+	originalKubeconfigFp, err := os.Open(originalKubeconfig)
+	if err != nil {
+		t.Fatalf("failed to open kubeconfig: %v", err)
+	}
+	defer originalKubeconfigFp.Close()
+
+	// Create temporal kubeconfig based on original one
+	kubeconfigFp, err := os.CreateTemp("", "ksm-hot-reload-kubeconfig")
+	if err != nil {
+		t.Fatalf("failed to create temporal kubeconfig: %v", err)
+	}
+	defer os.Remove(kubeconfigFp.Name())
+
+	if _, err := io.Copy(kubeconfigFp, originalKubeconfigFp); err != nil {
+		t.Fatalf("failed to copy from original kubeconfig to new one: %v", err)
+	}
+	kubeconfig := kubeconfigFp.Name()
+
+	opts.Kubeconfig = kubeconfig
+
+	// Run general validation on options.
+	if err := opts.Parse(); err != nil {
+		t.Fatalf("failed to parse options: %v", err)
+	}
+
+	// Make the process asynchronous.
+	go internal.RunKubeStateMetricsWrapper(opts)
+
+	// Wait for port 8080 to come up.
+	err = wait.PollUntilContextTimeout(context.TODO(), 1*time.Second, 20*time.Second, true, func(ctx context.Context) (bool, error) {
+		conn, err := net.Dial("tcp", "localhost:8080")
+		if err != nil {
+			return false, nil
+		}
+		err = conn.Close()
+		if err != nil {
+			return false, err
+		}
+		return true, nil
+	})
+	if err != nil {
+		t.Fatalf("failed to wait for port 8080 to come up for the first time: %v", err)
+	}
+
+	// Modify config to trigger hot reload.
+	err = exec.Command("kubectl", "config", "set-cluster", "ksm-hot-reload-kubeconfig-test", "--kubeconfig", kubeconfig).Run()
+	if err != nil {
+		t.Fatalf("failed to modify kubeconfig: %v", err)
+	}
+
+	// Revert kubeconfig to original one.
+	defer func() {
+		err := exec.Command("kubectl", "config", "delete-cluster", "ksm-hot-reload-kubeconfig-test", "--kubeconfig", kubeconfig).Run()
+		if err != nil {
+			t.Fatalf("failed to revert kubeconfig: %v", err)
+		}
+	}()
+
+	// Wait for new kubeconfig to be reloaded.
+	time.Sleep(5 * time.Second)
+
+	// Wait for port 8080 to come up.
+	ch := make(chan bool, 1)
+	err = wait.PollUntilContextTimeout(context.TODO(), 1*time.Second, 20*time.Second, true, func(ctx context.Context) (bool, error) {
+		conn, err := net.Dial("tcp", "localhost:8080")
+		if err != nil {
+			return false, nil
+		}
+		err = conn.Close()
+		if err != nil {
+			return false, err
+		}
+		// Indicate that the test has passed.
+		ch <- true
+		return true, nil
+	})
+	if err != nil {
+		t.Fatalf("failed to wait for port 8080 to come up after restarting the process: %v", err)
+	}
+
+	// Wait for process to exit.
+	select {
+	case <-ch:
+		t.Log("test passed successfully")
+	case <-time.After(20 * time.Second):
+		t.Fatal("timed out waiting for test to pass, check the logs for more info")
+	}
+}