feat: CNS checks apiserver in healthz

cns/healthserver/healthz.go

@@ -0,0 +1,54 @@
+package healthserver
+
+import (
+	"net/http"
+
+	"github.com/Azure/azure-container-networking/crd/nodenetworkconfig/api/v1alpha"
+	"github.com/pkg/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/healthz"
+)
+
+var schema = runtime.NewScheme()
+
+func init() {
+	utilruntime.Must(v1alpha.AddToScheme(schema))
+}
+
+func NewHealthzHandlerWithChecks() http.Handler {
+	cfg, err := ctrl.GetConfig()
+	if err != nil {
+		panic(err)
+	}
+	cli, err := client.New(cfg, client.Options{
+		Scheme: schema,
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	checks := map[string]healthz.Checker{
+		"nnc": func(req *http.Request) error {
+			ctx := req.Context()
+			// we just care that we're allowed to List NNCs so set limit to 1 to minimize
+			// additional load on apiserver
+			if err := cli.List(ctx, &v1alpha.NodeNetworkConfigList{}, &client.ListOptions{
+				Namespace: metav1.NamespaceSystem,
+				Limit:     int64(1),
+			}); err != nil {
+				return errors.Wrap(err, "failed to list NodeNetworkConfig")
+			}
+			return nil
+		},
+	}
+
+	// strip prefix so that it runs through all checks registered on the handler.
+	// otherwise it will look for a check named "healthz" and return a 404 if not there.
+	return http.StripPrefix("/healthz", &healthz.Handler{
+		Checks: checks,
+	})
+}

cns/healthserver/server.go

@@ -12,6 +12,7 @@ import (
 func Start(log *zap.Logger, addr string, healthz, readyz http.Handler) {
 	e := echo.New()
 	e.HideBanner = true
+
 	e.GET("/healthz", echo.WrapHandler(http.StripPrefix("/healthz", healthz)))
 	e.GET("/readyz", echo.WrapHandler(http.StripPrefix("/readyz", readyz)))
 	e.GET("/metrics", echo.WrapHandler(promhttp.HandlerFor(metrics.Registry, promhttp.HandlerOpts{

cns/service/main.go

@@ -642,7 +642,8 @@ func main() {
 			return nil
 		}),
 	}
-	go healthserver.Start(z, cnsconfig.MetricsBindAddress, &healthz.Handler{}, readyChecker)
+	healthzHandler := healthserver.NewHealthzHandlerWithChecks()
+	go healthserver.Start(z, cnsconfig.MetricsBindAddress, healthzHandler, readyChecker)
 
 	nmaConfig, err := nmagent.NewConfig(cnsconfig.WireserverIP)
 	if err != nil {