Support waiting for kube-apiserver to be ready with timout during NPD startup

cmd/node_problem_detector.go

@@ -26,6 +26,7 @@ import (
 	"github.com/golang/glog"
 	"github.com/spf13/pflag"
 
+	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/node-problem-detector/cmd/options"
 	"k8s.io/node-problem-detector/pkg/custompluginmonitor"
 	"k8s.io/node-problem-detector/pkg/problemclient"
@@ -95,7 +96,25 @@ func main() {
 		startHTTPServer(p, npdo)
 	}
 
+	// This function may be blocked (until a timeout occurs) before
+	// kube-apiserver becomes ready.
+	glog.Infof("Waiting for kube-apiserver to be ready (timeout %v)...", npdo.APIServerWaitTimeout)
+	if err := waitForAPIServerReadyWithTimeout(c, npdo); err != nil {
+		glog.Warningf("kube-apiserver did not become ready: timed out on waiting for kube-apiserver to return the node object: %v", err)
+	}
+
 	if err := p.Run(); err != nil {
 		glog.Fatalf("Problem detector failed with error: %v", err)
 	}
 }
+
+func waitForAPIServerReadyWithTimeout(c problemclient.Client, npdo *options.NodeProblemDetectorOptions) error {
+	return wait.PollImmediate(npdo.APIServerWaitInterval, npdo.APIServerWaitTimeout, func() (done bool, err error) {
+		// If NPD can get the node object from kube-apiserver, the server is
+		// ready and the RBAC permission is set correctly.
+		if _, err := c.GetNode(); err == nil {
+			return true, nil
+		}
+		return false, nil
+	})
+}