enable karmada-scheduler health check endpoint /healthz (#163)

Signed-off-by: changzhen <changzhen5@huawei.com>

artifacts/deploy/karmada-scheduler.yaml

@@ -26,6 +26,8 @@ spec:
           command:
             - /bin/karmada-scheduler
             - --kubeconfig=/etc/kubeconfig
+            - --bind-address=0.0.0.0
+            - --secure-port=10351
           volumeMounts:
             - name: kubeconfig
               subPath: kubeconfig

cmd/scheduler/app/options/options.go

@@ -9,6 +9,11 @@ import (
 	componentbaseconfig "k8s.io/component-base/config"
 )
 
+const (
+	defaultBindAddress = "0.0.0.0"
+	defaultPort        = 10351
+)
+
 var (
 	defaultElectionLeaseDuration = metav1.Duration{Duration: 15 * time.Second}
 	defaultElectionRenewDeadline = metav1.Duration{Duration: 10 * time.Second}
@@ -20,6 +25,10 @@ type Options struct {
 	LeaderElection componentbaseconfig.LeaderElectionConfiguration
 	KubeConfig     string
 	Master         string
+	// BindAddress is the IP address on which to listen for the --secure-port port.
+	BindAddress string
+	// SecurePort is the port that the server serves at.
+	SecurePort int
 }
 
 // NewOptions builds an default scheduler options.
@@ -45,4 +54,6 @@ func (o *Options) AddFlags(fs *pflag.FlagSet) {
 	fs.StringVar(&o.LeaderElection.ResourceNamespace, "lock-namespace", "", "Define the namespace of the lock object.")
 	fs.StringVar(&o.KubeConfig, "kubeconfig", o.KubeConfig, "Path to a KubeConfig. Only required if out-of-cluster.")
 	fs.StringVar(&o.Master, "master", o.Master, "The address of the Kubernetes API server. Overrides any value in KubeConfig. Only required if out-of-cluster.")
+	fs.StringVar(&o.BindAddress, "bind-address", defaultBindAddress, "The IP address on which to listen for the --secure-port port.")
+	fs.IntVar(&o.SecurePort, "secure-port", defaultPort, "The secure port on which to serve HTTPS.")
 }

cmd/scheduler/app/scheduler.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"net/http"
 	"os"
 
 	"github.com/google/uuid"
@@ -42,6 +43,8 @@ func NewSchedulerCommand(stopChan <-chan struct{}) *cobra.Command {
 }
 
 func run(opts *options.Options, stopChan <-chan struct{}) error {
+	go serveHealthz(fmt.Sprintf("%s:%d", opts.BindAddress, opts.SecurePort))
+
 	resetConfig, err := clientcmd.BuildConfigFromFlags(opts.Master, opts.KubeConfig)
 	if err != nil {
 		return fmt.Errorf("error building kubeconfig: %s", err.Error())
@@ -101,3 +104,12 @@ func run(opts *options.Options, stopChan <-chan struct{}) error {
 
 	return nil
 }
+
+func serveHealthz(address string) {
+	http.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("ok"))
+	})
+
+	klog.Fatal(http.ListenAndServe(address, nil))
+}