Merge pull request #35449 from MrHohn/kubedns-readysignal

Automatic merge from submit-queue

kubedns: use initial resource listing as ready signal

Fix #35140.

Set up the ready signal after the first resource listing finished for both endpoints and services instead of listen on kubernetes service.

@bprashanth @bowei @thockin

**Release note**:
```
```

cmd/kube-dns/app/options/options.go

@@ -23,6 +23,7 @@ import (
 	"net/url"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/spf13/pflag"
 	"k8s.io/kubernetes/pkg/api"
@@ -31,9 +32,10 @@ import (
 )
 
 type KubeDNSConfig struct {
-	ClusterDomain  string
+	ClusterDomain      string
-	KubeConfigFile string
+	KubeConfigFile     string
-	KubeMasterURL  string
+	KubeMasterURL      string
+	InitialSyncTimeout time.Duration
 
 	HealthzPort    int
 	DNSBindAddress string
@@ -47,10 +49,11 @@ type KubeDNSConfig struct {
 
 func NewKubeDNSConfig() *KubeDNSConfig {
 	return &KubeDNSConfig{
-		ClusterDomain:  "cluster.local.",
+		ClusterDomain:      "cluster.local.",
-		HealthzPort:    8081,
+		HealthzPort:        8081,
-		DNSBindAddress: "0.0.0.0",
+		DNSBindAddress:     "0.0.0.0",
-		DNSPort:        53,
+		DNSPort:            53,
+		InitialSyncTimeout: 60 * time.Second,
 
 		Federations: make(map[string]string),
 
@@ -160,4 +163,6 @@ func (s *KubeDNSConfig) AddFlags(fs *pflag.FlagSet) {
 		"config-map name. If empty, then the config-map will not used. Cannot be "+
 			" used in conjunction with federations flag. config-map contains "+
 			"dynamically adjustable configuration.")
+	fs.DurationVar(&s.InitialSyncTimeout, "initial-sync-timeout", s.InitialSyncTimeout,
+		"Timeout for initial resource sync.")
 }

cmd/kube-dns/app/server.go

@@ -47,17 +47,11 @@ type KubeDNSServer struct {
 }
 
 func NewKubeDNSServerDefault(config *options.KubeDNSConfig) *KubeDNSServer {
-	ks := KubeDNSServer{domain: config.ClusterDomain}
-
 	kubeClient, err := newKubeClient(config)
 	if err != nil {
 		glog.Fatalf("Failed to create a kubernetes client: %v", err)
 	}
 
-	ks.healthzPort = config.HealthzPort
-	ks.dnsBindAddress = config.DNSBindAddress
-	ks.dnsPort = config.DNSPort
-
 	var configSync dnsconfig.Sync
 	if config.ConfigMap == "" {
 		glog.V(0).Infof("ConfigMap not configured, using values from command line flags")
@@ -70,9 +64,13 @@ func NewKubeDNSServerDefault(config *options.KubeDNSConfig) *KubeDNSServer {
 			kubeClient, config.ConfigMapNs, config.ConfigMap)
 	}
 
-	ks.kd = kdns.NewKubeDNS(kubeClient, config.ClusterDomain, configSync)
+	return &KubeDNSServer{
-
+		domain:         config.ClusterDomain,
-	return &ks
+		healthzPort:    config.HealthzPort,
+		dnsBindAddress: config.DNSBindAddress,
+		dnsPort:        config.DNSPort,
+		kd:             kdns.NewKubeDNS(kubeClient, config.ClusterDomain, config.InitialSyncTimeout, configSync),
+	}
 }
 
 // TODO: evaluate using pkg/client/clientcmd

hack/verify-flags/known-flags.txt

@@ -276,6 +276,7 @@ image-service-endpoint
 include-extended-apis
 include-extended-apis
 included-types-overrides
+initial-sync-timeout
 input-base
 input-dirs
 insecure-allow-any-token

pkg/dns/dns.go

@@ -24,9 +24,6 @@ import (
 	"sync"
 	"time"
 
-	etcd "github.com/coreos/etcd/client"
-	"github.com/miekg/dns"
-	skymsg "github.com/skynetservices/skydns/msg"
 	"k8s.io/kubernetes/pkg/api/v1"
 	"k8s.io/kubernetes/pkg/api/v1/endpoints"
 	metav1 "k8s.io/kubernetes/pkg/apis/meta/v1"
@@ -40,7 +37,10 @@ import (
 	"k8s.io/kubernetes/pkg/util/wait"
 	"k8s.io/kubernetes/pkg/watch"
 
+	etcd "github.com/coreos/etcd/client"
 	"github.com/golang/glog"
+	"github.com/miekg/dns"
+	skymsg "github.com/skynetservices/skydns/msg"
 )
 
 const (
@@ -117,9 +117,12 @@ type KubeDNS struct {
 	configLock sync.RWMutex
 	// configSync manages synchronization of the config map
 	configSync config.Sync
+
+	// Initial timeout for endpoints and services to be synced from APIServer
+	initialSyncTimeout time.Duration
 }
 
-func NewKubeDNS(client clientset.Interface, clusterDomain string, configSync config.Sync) *KubeDNS {
+func NewKubeDNS(client clientset.Interface, clusterDomain string, timeout time.Duration, configSync config.Sync) *KubeDNS {
 	kd := &KubeDNS{
 		kubeClient:          client,
 		domain:              clusterDomain,
@@ -129,6 +132,7 @@ func NewKubeDNS(client clientset.Interface, clusterDomain string, configSync con
 		reverseRecordMap:    make(map[string]*skymsg.Service),
 		clusterIPServiceMap: make(map[string]*v1.Service),
 		domainPath:          util.ReverseArray(strings.Split(strings.TrimRight(clusterDomain, "."), ".")),
+		initialSyncTimeout:  timeout,
 
 		configLock: sync.RWMutex{},
 		configSync: configSync,
@@ -149,38 +153,28 @@ func (kd *KubeDNS) Start() {
 
 	kd.startConfigMapSync()
 
-	// Wait synchronously for the Kubernetes service. This ensures that
+	// Wait synchronously for the initial list operations to be
-	// the Start function returns only after having received Service
+	// complete of endpoints and services from APIServer.
-	// objects from APIServer.
+	kd.waitForResourceSyncedOrDie()
-	//
-	// TODO: we might not have to wait for kubernetes service
-	// specifically. We should just wait for a list operation to be
-	// complete from APIServer.
-	kd.waitForKubernetesService()
 }
 
-func (kd *KubeDNS) waitForKubernetesService() {
+func (kd *KubeDNS) waitForResourceSyncedOrDie() {
-	glog.V(2).Infof("Waiting for Kubernetes service")
+	// Wait for both controllers have completed an initial resource listing
-
+	timeout := time.After(kd.initialSyncTimeout)
-	const kubernetesSvcName = "kubernetes"
+	ticker := time.NewTicker(500 * time.Millisecond)
-	const servicePollInterval = 1 * time.Second
+	defer ticker.Stop()
-
-	name := fmt.Sprintf("%v/%v", v1.NamespaceDefault, kubernetesSvcName)
-	glog.V(2).Infof("Waiting for service: %v", name)
-
 	for {
-		svc, err := kd.kubeClient.Core().Services(v1.NamespaceDefault).Get(kubernetesSvcName)
+		select {
-		if err != nil || svc == nil {
+		case <-timeout:
-			glog.V(3).Infof(
+			glog.Fatalf("Timeout waiting for initialization")
-				"Ignoring error while waiting for service %v: %v. Sleeping %v before retrying.",
+		case <-ticker.C:
-				name, err, servicePollInterval)
+			if kd.endpointsController.HasSynced() && kd.serviceController.HasSynced() {
-			time.Sleep(servicePollInterval)
+				glog.V(0).Infof("Initialized services and endpoints from apiserver")
-			continue
+				return
+			}
+			glog.V(0).Infof("DNS server not ready, retry in 500 milliseconds")
 		}
-		break
 	}
-
-	return
 }
 
 func (kd *KubeDNS) startConfigMapSync() {