Don't update the mutating webhook if we aren't managing it automatica…

…lly (#344)

* If the webhook is missing from cache, fetch it

I'm not sure under what circumstances the cache will be missing the
webhook config, but it seems to happen sometimes.

* Only fetch the webhook if flagAutoName is used; otherwise we don't know the webhook to patch

* Rename updateWebhook to updateCertificate

* Use Lister instead of using cache directly

subcommand/injector/command.go

@@ -32,6 +32,7 @@ import (
 	"k8s.io/client-go/informers"
 	informerv1 "k8s.io/client-go/informers/core/v1"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/listers/admissionregistration/v1"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/cache"
 )
@@ -357,7 +358,7 @@ func (c *Command) certWatcher(ctx context.Context, ch <-chan cert.Bundle, client
 			<-timer.C
 		}
 
-		err := c.updateWebhook(ctx, clientset, bundle, webhooksCache, leaderElector, log)
+		err := c.updateCertificate(ctx, clientset, bundle, webhooksCache, leaderElector, log)
 		if err != nil {
 			// retry after a delay
 			timer.Reset(expBackoff.NextBackOff())
@@ -368,20 +369,11 @@ func (c *Command) certWatcher(ctx context.Context, ch <-chan cert.Bundle, client
 	}
 }
 
-func (c *Command) updateWebhook(ctx context.Context, clientset *kubernetes.Clientset, bundle cert.Bundle, webhooksCache cache.Store, leaderElector leader.Elector, log hclog.Logger) error {
-	item, exists, err := webhooksCache.GetByKey(c.flagAutoName)
-	if !exists {
-		log.Warn("Could not find webhook config in cache. Trying again...", "item", item)
-		return fmt.Errorf("could not find webhook config in cache")
-	} else if err != nil {
-		log.Warn(fmt.Sprintf("Could not find webhook config in cache: %s. Trying again...", err))
-		return err
-	}
-	config, ok := item.(*adminv1.MutatingWebhookConfiguration)
-	if !ok {
-		log.Error("Got unknown object from cache; expected &MutatingWebhookConfiguration", "item", item)
-	}
+func (c *Command) fetchWebhook(ctx context.Context, clientset *kubernetes.Clientset) (*adminv1.MutatingWebhookConfiguration, error) {
+	return clientset.AdmissionregistrationV1().MutatingWebhookConfigurations().Get(ctx, c.flagAutoName, metav1.GetOptions{})
+}
 
+func (c *Command) updateCertificate(ctx context.Context, clientset *kubernetes.Clientset, bundle cert.Bundle, webhooksCache v1.MutatingWebhookConfigurationLister, leaderElector leader.Elector, log hclog.Logger) error {
 	crt, err := tls.X509KeyPair(bundle.Cert, bundle.Key)
 	if err != nil {
 		log.Warn(fmt.Sprintf("Could not load TLS keypair: %s. Trying again...", err))
@@ -401,6 +393,16 @@ func (c *Command) updateWebhook(ctx context.Context, clientset *kubernetes.Clien
 
 	// If there is an MWC name set, then update the CA bundle.
 	if isLeader && c.flagAutoName != "" && len(bundle.CACert) > 0 {
+		config, err := webhooksCache.Get(c.flagAutoName)
+		if err != nil {
+			log.Warn("Getting webhook config from cache failed", "err", err)
+			config, err = c.fetchWebhook(ctx, clientset)
+			if err != nil {
+				log.Warn("Fetching webhook config directly failed; will try again", "err", err)
+				return err
+			}
+		}
+
 		// Check the current bundles and only update if necessary.
 		if len(config.Webhooks) == 0 || !bytes.Equal(config.Webhooks[0].ClientConfig.CABundle, bundle.CACert) {
 			err = c.updateCABundle(ctx, &bundle, clientset)
@@ -418,7 +420,7 @@ func (c *Command) updateWebhook(ctx context.Context, clientset *kubernetes.Clien
 	return nil
 }
 
-func watchWebhooks(ctx context.Context, clientset *kubernetes.Clientset) (cache.Store, <-chan interface{}, error) {
+func watchWebhooks(ctx context.Context, clientset *kubernetes.Clientset) (v1.MutatingWebhookConfigurationLister, <-chan interface{}, error) {
 	factory := informers.NewSharedInformerFactoryWithOptions(clientset, 0)
 	webhooks := factory.Admissionregistration().V1().MutatingWebhookConfigurations()
 	go webhooks.Informer().Run(ctx.Done())
@@ -427,7 +429,7 @@ func watchWebhooks(ctx context.Context, clientset *kubernetes.Clientset) (cache.
 	}
 	notifyCh := make(webhookWatcher)
 	webhooks.Informer().AddEventHandler(notifyCh)
-	return webhooks.Informer().GetStore(), notifyCh, nil
+	return webhooks.Lister(), notifyCh, nil
 }
 
 type webhookWatcher chan interface{}