feat: CNS checks apiserver in healthz

Author: tyler-lloyd

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/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 {