client-go/tools/cache: add APIs with context parameter

The context is used for cancellation and to support contextual logging.

In most cases, alternative *WithContext APIs get added, except for
NewIntegerResourceVersionMutationCache where code searches indicate that the
API is not used downstream.

An API break around SharedInformer couldn't be avoided because the
alternative (keeping the interface unchanged and adding a second one with
the new method) would have been worse. controller-runtime needs to be updated
because it implements that interface in a test package. Downstream consumers of
controller-runtime will work unless they use those test package.

Converting Kubernetes to use the other new alternatives will follow. In the
meantime, usage of the new alternatives cannot be enforced via logcheck
yet (see https://github.com/kubernetes/kubernetes/issues/126379 for the
process).

Passing context through and checking it for cancellation is tricky for event
handlers. A better approach is to map the context cancellation to the normal
removal of an event handler via a helper goroutine. Thanks to the new
HandleErrorWithLogr and HandleCrashWithLogr, remembering the logger is
sufficient for handling problems at runtime.

Kubernetes-commit: 4638ba971661497b147906b8977ae206c9dd6e44

examples/workqueue/main.go

@@ -17,6 +17,8 @@ limitations under the License.
 package main
 
 import (
+	"context"
+	"errors"
 	"flag"
 	"fmt"
 	"time"
@@ -116,30 +118,30 @@ func (c *Controller) handleErr(err error, key string) {
 }
 
 // Run begins watching and syncing.
-func (c *Controller) Run(workers int, stopCh chan struct{}) {
-	defer runtime.HandleCrash()
+func (c *Controller) Run(ctx context.Context, workers int) {
+	defer runtime.HandleCrashWithContext(ctx)
 
 	// Let the workers stop when we are done
 	defer c.queue.ShutDown()
 	klog.Info("Starting Pod controller")
 
-	go c.informer.Run(stopCh)
+	go c.informer.RunWithContext(ctx)
 
 	// Wait for all involved caches to be synced, before processing items from the queue is started
-	if !cache.WaitForCacheSync(stopCh, c.informer.HasSynced) {
+	if !cache.WaitForNamedCacheSyncWithContext(ctx, c.informer.HasSynced) {
 		runtime.HandleError(fmt.Errorf("Timed out waiting for caches to sync"))
 		return
 	}
 
 	for i := 0; i < workers; i++ {
-		go wait.Until(c.runWorker, time.Second, stopCh)
+		go wait.UntilWithContext(ctx, c.runWorker, time.Second)
 	}
 
-	<-stopCh
+	<-ctx.Done()
 	klog.Info("Stopping Pod controller")
 }
 
-func (c *Controller) runWorker() {
+func (c *Controller) runWorker(ctx context.Context) {
 	for c.processNextItem() {
 	}
 }
@@ -164,6 +166,8 @@ func main() {
 		klog.Fatal(err)
 	}
 
+	ctx := context.Background()
+
 	// create the pod watcher
 	podListWatcher := cache.NewListWatchFromClient(clientset.CoreV1().RESTClient(), "pods", v1.NamespaceDefault, fields.Everything())
 
@@ -211,9 +215,9 @@ func main() {
 	})
 
 	// Now let's start the controller
-	stop := make(chan struct{})
-	defer close(stop)
-	go controller.Run(1, stop)
+	cancelCtx, cancel := context.WithCancelCause(ctx)
+	defer cancel(errors.New("time to stop because main has completed"))
+	go controller.Run(cancelCtx, 1)
 
 	// Wait forever
 	select {}