Merge pull request #95897 from roycaihw/doc/fake-client-with-informer

Fake client example: document how to handle a race with informer

Kubernetes-commit: 6f8a058e2c29680dccffd9df07765c10e1f69b53

Godeps/Godeps.json

@@ -476,7 +476,7 @@
 		},
 		{
 			"ImportPath": "k8s.io/api",
-			"Rev": "3a2d6b5bb7f8"
+			"Rev": "2824ee61d1ae"
 		},
 		{
 			"ImportPath": "k8s.io/apimachinery",

examples/fake-client/main_test.go

@@ -21,11 +21,13 @@ import (
 	"testing"
 	"time"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/apimachinery/pkg/watch"
 	"k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
+	clienttesting "k8s.io/client-go/testing"
 	"k8s.io/client-go/tools/cache"
 )
 
@@ -34,8 +36,20 @@ func TestFakeClient(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
+	watcherStarted := make(chan struct{})
 	// Create the fake client.
 	client := fake.NewSimpleClientset()
+	// A catch-all watch reactor that allows us to inject the watcherStarted channel.
+	client.PrependWatchReactor("*", func(action clienttesting.Action) (handled bool, ret watch.Interface, err error) {
+		gvr := action.GetResource()
+		ns := action.GetNamespace()
+		watch, err := client.Tracker().Watch(gvr, ns)
+		if err != nil {
+			return false, nil, err
+		}
+		close(watcherStarted)
+		return true, watch, nil
+	})
 
 	// We will create an informer that writes added pods to a channel.
 	pods := make(chan *v1.Pod, 1)
@@ -57,6 +71,15 @@ func TestFakeClient(t *testing.T) {
 	// we send any events to it.
 	cache.WaitForCacheSync(ctx.Done(), podInformer.HasSynced)
 
+	// The fake client doesn't support resource version. Any writes to the client
+	// after the informer's initial LIST and before the informer establishing the
+	// watcher will be missed by the informer. Therefore we wait until the watcher
+	// starts.
+	// Note that the fake client isn't designed to work with informer. It
+	// doesn't support resource version. It's encouraged to use a real client
+	// in an integration/E2E test if you need to test complex behavior with
+	// informer/controllers.
+	<-watcherStarted
 	// Inject an event into the fake client.
 	p := &v1.Pod{ObjectMeta: metav1.ObjectMeta{Name: "my-pod"}}
 	_, err := client.CoreV1().Pods("test-ns").Create(context.TODO(), p, metav1.CreateOptions{})

go.mod

@@ -27,7 +27,7 @@ require (
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
 	golang.org/x/term v0.0.0-20210220032956-6a3ed077a48d
 	golang.org/x/time v0.0.0-20210220033141-f8bda1e9f3ba
-	k8s.io/api v0.0.0-20210323190948-3a2d6b5bb7f8
+	k8s.io/api v0.0.0-20210408212643-2824ee61d1ae
 	k8s.io/apimachinery v0.0.0-20210313025227-57f2a0733447
 	k8s.io/klog/v2 v2.8.0
 	k8s.io/utils v0.0.0-20201110183641-67b214c5f920
@@ -36,6 +36,6 @@ require (
 )
 
 replace (
-	k8s.io/api => k8s.io/api v0.0.0-20210323190948-3a2d6b5bb7f8
+	k8s.io/api => k8s.io/api v0.0.0-20210408212643-2824ee61d1ae
 	k8s.io/apimachinery => k8s.io/apimachinery v0.0.0-20210313025227-57f2a0733447
 )

go.sum

@@ -431,7 +431,7 @@ honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWh
 honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.1-2019.2.3/go.mod h1:a3bituU0lyd329TUQxRnasdCoJDkEUEAqEt0JzvZhAg=
 honnef.co/go/tools v0.0.1-2020.1.3/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
-k8s.io/api v0.0.0-20210323190948-3a2d6b5bb7f8/go.mod h1:7Byi1J8zhqxObDDyvyvJdvEZioXQZDTsNqSFMk4JMMM=
+k8s.io/api v0.0.0-20210408212643-2824ee61d1ae/go.mod h1:7Byi1J8zhqxObDDyvyvJdvEZioXQZDTsNqSFMk4JMMM=
 k8s.io/apimachinery v0.0.0-20210313025227-57f2a0733447/go.mod h1:jbreFvJo3ov9rj7eWT7+sYiRx+qZuCYXwWT1bcDswPY=
 k8s.io/gengo v0.0.0-20200413195148-3a45101e95ac/go.mod h1:ezvh/TsK7cY6rbqRK0oQQ8IAqLxYwwyPxAX1Pzy0ii0=
 k8s.io/klog/v2 v2.0.0/go.mod h1:PBfzABfn139FHAV07az/IF9Wp1bkk3vpT2XSJ76fSDE=