dixudx · December 14, 2017 09:54 · Dec 14, 2017 · Dec 13, 2017 · Dec 13, 2017 · Dec 13, 2017
diff --git a/initailzerconfiguration.yaml b/initailzerconfiguration.yaml
@@ -0,0 +1,16 @@
+apiVersion: admissionregistration.k8s.io/v1alpha1
+kind: InitializerConfiguration
+metadata:
+  name: example-config
+initializers:
+  # the name needs to be fully qualified, i.e., containing at least two "."
+  - name: deployment.example.com
+    rules:
+      # apiGroups, apiVersion, resources all support wildcard "*".
+      # "*" cannot be mixed with non-wildcard.
+      - apiGroups:
+          - "apps"
+        apiVersions:
+          - v1
+        resources:
+          - deployments
diff --git a/deployment_initializer.go b/deployment_initializer.go
@@ -110,7 +110,7 @@ func initializeDeployment(deployment *v1.Deployment, clientset *kubernetes.Clien
 			}
 
 			// Modify the Deployment here
-			initializedDeployment.Annotations["meetup"] = "hosted-by-dockercloud"
+			initializedDeployment.Annotations["k8s-meetup"] = "hosted-by-dockercloud"
 
 			oldData, err := json.Marshal(deployment)
 			if err != nil {

diff --git a/deployment_initializer.yaml → deployment_initializer.go b/deployment_initializer.yaml → deployment_initializer.go
diff --git a/deployment_initializer.yaml b/deployment_initializer.yaml
@@ -0,0 +1,138 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"k8s.io/api/apps/v1"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/fields"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/strategicpatch"
+	"k8s.io/apimachinery/pkg/watch"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/cache"
+)
+
+const (
+	defaultAnnotation      = "initializer.kubernetes.io/abc"
+	defaultInitializerName = "abc.initializer.kubernetes.io"
+)
+
+var (
+	annotation        string
+	initializerName   string
+)
+
+func main() {
+	flag.StringVar(&annotation, "annotation", defaultAnnotation, "The annotation to trigger initialization")
+	flag.StringVar(&initializerName, "initializer-name", defaultInitializerName, "The initializer name")
+	flag.Parse()
+
+	log.Println("Starting the Kubernetes initializer...")
+	log.Printf("Initializer name set to: %s", initializerName)
+
+	clusterConfig, err := rest.InClusterConfig()
+	if err != nil {
+		log.Fatal(err.Error())
+	}
+
+	clientset, err := kubernetes.NewForConfig(clusterConfig)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Watch uninitialized Deployments in all namespaces.
+	restClient := clientset.AppsV1().RESTClient()
+	watchlist := cache.NewListWatchFromClient(restClient, "deployments", corev1.NamespaceAll, fields.Everything())
+
+	// Wrap the returned watchlist to workaround the inability to include
+	// the `IncludeUninitialized` list option when setting up watch clients.
+	includeUninitializedWatchlist := &cache.ListWatch{
+		ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
+			options.IncludeUninitialized = true
+			return watchlist.List(options)
+		},
+		WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
+			options.IncludeUninitialized = true
+			return watchlist.Watch(options)
+		},
+	}
+
+	resyncPeriod := 30 * time.Second
+
+	_, controller := cache.NewInformer(includeUninitializedWatchlist, &v1.Deployment{}, resyncPeriod,
+		cache.ResourceEventHandlerFuncs{
+			AddFunc: func(obj interface{}) {
+				err := initializeDeployment(obj.(*v1.Deployment), clientset)
+				if err != nil {
+					log.Println(err)
+				}
+			},
+		},
+	)
+
+	stop := make(chan struct{})
+	go controller.Run(stop)
+
+	signalChan := make(chan os.Signal, 1)
+	signal.Notify(signalChan, syscall.SIGINT, syscall.SIGTERM)
+	<-signalChan
+
+	log.Println("Shutdown signal received, exiting...")
+	close(stop)
+}
+
+func initializeDeployment(deployment *v1.Deployment, clientset *kubernetes.Clientset) error {
+	if deployment.ObjectMeta.GetInitializers() != nil {
+		pendingInitializers := deployment.ObjectMeta.GetInitializers().Pending
+		if len(pendingInitializers) == 0 {
+			return nil
+		}
+
+		if initializerName == pendingInitializers[0].Name {
+			log.Printf("Initializing deployment: %s", deployment.Name)
+			initializedDeployment := deployment.DeepCopy()
+
+			// Remove self from the list of pending Initializers while preserving ordering.
+			if len(pendingInitializers) == 1 {
+				initializedDeployment.ObjectMeta.Initializers = nil
+			} else {
+				initializedDeployment.ObjectMeta.Initializers.Pending = append(pendingInitializers[:0], pendingInitializers[1:]...)
+			}
+
+			// Modify the Deployment here
+			initializedDeployment.Annotations["meetup"] = "hosted-by-dockercloud"
+
+			oldData, err := json.Marshal(deployment)
+			if err != nil {
+				return err
+			}
+
+			newData, err := json.Marshal(initializedDeployment)
+			if err != nil {
+				return err
+			}
+
+			patchBytes, err := strategicpatch.CreateTwoWayMergePatch(oldData, newData, v1.Deployment{})
+			if err != nil {
+				return err
+			}
+
+			_, err = clientset.AppsV1beta1().Deployments(deployment.Namespace).Patch(deployment.Name, types.StrategicMergePatchType, patchBytes)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
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