make admission configuration manager retry 5 times if it's not bootstrapped yet

pkg/kubeapiserver/admission/configuration/configuration_manager.go

@@ -26,8 +26,10 @@ import (
 )
 
 const (
-	defaultInterval         = 1 * time.Second
-	defaultFailureThreshold = 5
+	defaultInterval             = 1 * time.Second
+	defaultFailureThreshold     = 5
+	defaultBootstrapRetries     = 5
+	defaultBootstrapGraceperiod = 5 * time.Second
 )
 
 var (
@@ -47,26 +49,43 @@ type poller struct {
 	// a function to consistently read the latest configuration
 	get getFunc
 	// consistent read interval
+	// read-only
 	interval time.Duration
 	// if the number of consecutive read failure equals or exceeds the failureThreshold , the
 	// configuration is regarded as not ready.
+	// read-only
 	failureThreshold int
 	// number of consecutive failures so far.
 	failures int
+	// If the poller has passed the bootstrap phase. The poller is considered
+	// bootstrapped either bootstrapGracePeriod after the first call of
+	// configuration(), or when setConfigurationAndReady() is called, whichever
+	// comes first.
+	bootstrapped bool
+	// configuration() retries bootstrapRetries times if poller is not bootstrapped
+	// read-only
+	bootstrapRetries int
+	// Grace period for bootstrapping
+	// read-only
+	bootstrapGracePeriod time.Duration
+	once                 sync.Once
 	// if the configuration is regarded as ready.
 	ready               bool
 	mergedConfiguration runtime.Object
-	// lock much be hold when reading ready or mergedConfiguration
-	lock    sync.RWMutex
-	lastErr error
+	lastErr             error
+	// lock must be hold when reading/writing the data fields of poller.
+	lock sync.RWMutex
 }
 
 func newPoller(get getFunc) *poller {
-	return &poller{
-		get:              get,
-		interval:         defaultInterval,
-		failureThreshold: defaultFailureThreshold,
+	p := poller{
+		get:                  get,
+		interval:             defaultInterval,
+		failureThreshold:     defaultFailureThreshold,
+		bootstrapRetries:     defaultBootstrapRetries,
+		bootstrapGracePeriod: defaultBootstrapGraceperiod,
 	}
+	return &p
 }
 
 func (a *poller) lastError(err error) {
@@ -81,21 +100,47 @@ func (a *poller) notReady() {
 	a.ready = false
 }
 
+func (a *poller) bootstrapping() {
+	// bootstrapGracePeriod is read-only, so no lock is required
+	timer := time.NewTimer(a.bootstrapGracePeriod)
+	go func() {
+		<-timer.C
+		a.lock.Lock()
+		defer a.lock.Unlock()
+		a.bootstrapped = true
+	}()
+}
+
+// If the poller is not bootstrapped yet, the configuration() gets a few chances
+// to retry. This hides transient failures during system startup.
 func (a *poller) configuration() (runtime.Object, error) {
+	a.once.Do(a.bootstrapping)
 	a.lock.RLock()
 	defer a.lock.RUnlock()
-	if !a.ready {
-		if a.lastErr != nil {
-			return nil, a.lastErr
-		}
-		return nil, ErrNotReady
+	retries := 1
+	if !a.bootstrapped {
+		retries = a.bootstrapRetries
 	}
-	return a.mergedConfiguration, nil
+	for count := 0; count < retries; count++ {
+		if count > 0 {
+			a.lock.RUnlock()
+			time.Sleep(a.interval)
+			a.lock.RLock()
+		}
+		if a.ready {
+			return a.mergedConfiguration, nil
+		}
+	}
+	if a.lastErr != nil {
+		return nil, a.lastErr
+	}
+	return nil, ErrNotReady
 }
 
 func (a *poller) setConfigurationAndReady(value runtime.Object) {
 	a.lock.Lock()
 	defer a.lock.Unlock()
+	a.bootstrapped = true
 	a.mergedConfiguration = value
 	a.ready = true
 	a.lastErr = nil

pkg/kubeapiserver/admission/configuration/configuration_manager_test.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package configuration
+
+import (
+	"fmt"
+	"math"
+	"sync"
+	"testing"
+	"time"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+)
+
+func TestTolerateBootstrapFailure(t *testing.T) {
+	var fakeGetSucceed bool
+	var fakeGetSucceedLock sync.RWMutex
+	fakeGetFn := func() (runtime.Object, error) {
+		fakeGetSucceedLock.RLock()
+		defer fakeGetSucceedLock.RUnlock()
+		if fakeGetSucceed {
+			return nil, nil
+		} else {
+			return nil, fmt.Errorf("this error shouldn't be exposed to caller")
+		}
+	}
+	poller := newPoller(fakeGetFn)
+	poller.bootstrapGracePeriod = 100 * time.Second
+	poller.bootstrapRetries = math.MaxInt32
+	// set failureThreshold to 0 so that one single failure will set "ready" to false.
+	poller.failureThreshold = 0
+	stopCh := make(chan struct{})
+	defer close(stopCh)
+	go poller.Run(stopCh)
+	go func() {
+		// The test might have false negative, but won't be flaky
+		timer := time.NewTimer(2 * time.Second)
+		<-timer.C
+		fakeGetSucceedLock.Lock()
+		defer fakeGetSucceedLock.Unlock()
+		fakeGetSucceed = true
+	}()
+
+	done := make(chan struct{})
+	go func(t *testing.T) {
+		_, err := poller.configuration()
+		if err != nil {
+			t.Errorf("unexpected error: %v", err)
+		}
+		close(done)
+	}(t)
+	<-done
+}
+
+func TestNotTolerateNonbootstrapFailure(t *testing.T) {
+	fakeGetFn := func() (runtime.Object, error) {
+		return nil, fmt.Errorf("this error should be exposed to caller")
+	}
+	poller := newPoller(fakeGetFn)
+	poller.bootstrapGracePeriod = 1 * time.Second
+	poller.interval = 1 * time.Millisecond
+	stopCh := make(chan struct{})
+	defer close(stopCh)
+	go poller.Run(stopCh)
+	// to kick the bootstrap timer
+	go poller.configuration()
+
+	wait.PollInfinite(1*time.Second, func() (bool, error) {
+		poller.lock.Lock()
+		defer poller.lock.Unlock()
+		return poller.bootstrapped, nil
+	})
+
+	_, err := poller.configuration()
+	if err == nil {
+		t.Errorf("unexpected no error")
+	}
+}

pkg/kubeapiserver/admission/init_test.go

@@ -22,7 +22,6 @@ import (
 
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/authorization/authorizer"
-	"k8s.io/kubernetes/pkg/apis/admissionregistration"
 )
 
 // TestAuthorizer is a testing struct for testing that fulfills the authorizer interface.
@@ -123,26 +122,3 @@ func TestWantsClientCert(t *testing.T) {
 		t.Errorf("plumbing fail - %v %v", ccw.gotCert, ccw.gotKey)
 	}
 }
-
-type fakeHookSource struct{}
-
-func (f *fakeHookSource) List() ([]admissionregistration.ExternalAdmissionHook, error) {
-	return nil, nil
-}
-
-type hookSourceWanter struct {
-	doNothingAdmission
-	got WebhookSource
-}
-
-func (s *hookSourceWanter) SetWebhookSource(w WebhookSource) { s.got = w }
-
-func TestWantsWebhookSource(t *testing.T) {
-	hsw := &hookSourceWanter{}
-	fhs := &fakeHookSource{}
-	i := &PluginInitializer{}
-	i.SetWebhookSource(fhs).Initialize(hsw)
-	if got, ok := hsw.got.(*fakeHookSource); !ok || got != fhs {
-		t.Errorf("plumbing fail - %v %v#", ok, got)
-	}
-}

pkg/kubeapiserver/admission/initializer.go

@@ -22,7 +22,6 @@ import (
 	"k8s.io/apimachinery/pkg/api/meta"
 	"k8s.io/apiserver/pkg/admission"
 	"k8s.io/apiserver/pkg/authorization/authorizer"
-	"k8s.io/kubernetes/pkg/apis/admissionregistration"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/clientset"
 	"k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
 	informers "k8s.io/kubernetes/pkg/client/informers/informers_generated/internalversion"
@@ -83,23 +82,12 @@ type WantsClientCert interface {
 	SetClientCert(cert, key []byte)
 }
 
-// WantsWebhookSource defines a function that accepts a webhook lister for the
-// dynamic webhook plugin.
-type WantsWebhookSource interface {
-	SetWebhookSource(WebhookSource)
-}
-
 // ServiceResolver knows how to convert a service reference into an actual
 // location.
 type ServiceResolver interface {
 	ResolveEndpoint(namespace, name string) (*url.URL, error)
 }
 
-// WebhookSource can list dynamic webhook plugins.
-type WebhookSource interface {
-	List() ([]admissionregistration.ExternalAdmissionHook, error)
-}
-
 type PluginInitializer struct {
 	internalClient  internalclientset.Interface
 	externalClient  clientset.Interface
@@ -109,7 +97,6 @@ type PluginInitializer struct {
 	restMapper      meta.RESTMapper
 	quotaRegistry   quota.Registry
 	serviceResolver ServiceResolver
-	webhookSource   WebhookSource
 
 	// for proving we are apiserver in call-outs
 	clientCert []byte
@@ -155,13 +142,6 @@ func (i *PluginInitializer) SetClientCert(cert, key []byte) *PluginInitializer {
 	return i
 }
 
-// SetWebhookSource sets the webhook source-- admittedly this is probably
-// specific to the external admission hook plugin.
-func (i *PluginInitializer) SetWebhookSource(w WebhookSource) *PluginInitializer {
-	i.webhookSource = w
-	return i
-}
-
 // Initialize checks the initialization interfaces implemented by each plugin
 // and provide the appropriate initialization data
 func (i *PluginInitializer) Initialize(plugin admission.Interface) {
@@ -206,11 +186,4 @@ func (i *PluginInitializer) Initialize(plugin admission.Interface) {
 		}
 		wants.SetClientCert(i.clientCert, i.clientKey)
 	}
-
-	if wants, ok := plugin.(WantsWebhookSource); ok {
-		if i.webhookSource == nil {
-			panic("An admission plugin wants a webhook source, but it was not provided.")
-		}
-		wants.SetWebhookSource(i.webhookSource)
-	}
 }