Merge pull request #57932 from atlassian/cancellable-leader-election

Automatic merge from submit-queue (batch tested with PRs 65256, 64236, 64919, 64879, 57932). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Cancellable leader election

**What this PR does / why we need it**:
Adds ability to cancel leader election. Useful in integration tests where the whole app is started and stopped in each test.

**Special notes for your reviewer**:
I used the `context` package - it is impossible/hard to achieve the same behaviour with just channels without spawning additional goroutines but it is trivial with `context`. See `acquire()` and `renew()` methods.

**Release note**:

```release-note
NONE
```
/kind enhancement
/sig api-machinery

cmd/kube-controller-manager/app/controllermanager.go

@@ -21,6 +21,7 @@ limitations under the License.
 package app
 
 import (
+	"context"
 	"fmt"
 	"io/ioutil"
 	"math/rand"
@@ -144,7 +145,7 @@ func Run(c *config.CompletedConfig) error {
 		}
 	}
 
-	run := func(stop <-chan struct{}) {
+	run := func(ctx context.Context) {
 		rootClientBuilder := controller.SimpleControllerClientBuilder{
 			ClientConfig: c.Kubeconfig,
 		}
@@ -164,24 +165,24 @@ func Run(c *config.CompletedConfig) error {
 		} else {
 			clientBuilder = rootClientBuilder
 		}
-		ctx, err := CreateControllerContext(c, rootClientBuilder, clientBuilder, stop)
+		controllerContext, err := CreateControllerContext(c, rootClientBuilder, clientBuilder, ctx.Done())
 		if err != nil {
 			glog.Fatalf("error building controller context: %v", err)
 		}
 		saTokenControllerInitFunc := serviceAccountTokenControllerStarter{rootClientBuilder: rootClientBuilder}.startServiceAccountTokenController
 
-		if err := StartControllers(ctx, saTokenControllerInitFunc, NewControllerInitializers(ctx.LoopMode)); err != nil {
+		if err := StartControllers(controllerContext, saTokenControllerInitFunc, NewControllerInitializers(controllerContext.LoopMode)); err != nil {
 			glog.Fatalf("error starting controllers: %v", err)
 		}
 
-		ctx.InformerFactory.Start(ctx.Stop)
-		close(ctx.InformersStarted)
+		controllerContext.InformerFactory.Start(controllerContext.Stop)
+		close(controllerContext.InformersStarted)
 
 		select {}
 	}
 
 	if !c.ComponentConfig.GenericComponent.LeaderElection.LeaderElect {
-		run(wait.NeverStop)
+		run(context.TODO())
 		panic("unreachable")
 	}
 
@@ -204,7 +205,7 @@ func Run(c *config.CompletedConfig) error {
 		glog.Fatalf("error creating lock: %v", err)
 	}
 
-	leaderelection.RunOrDie(leaderelection.LeaderElectionConfig{
+	leaderelection.RunOrDie(context.TODO(), leaderelection.LeaderElectionConfig{
 		Lock:          rl,
 		LeaseDuration: c.ComponentConfig.GenericComponent.LeaderElection.LeaseDuration.Duration,
 		RenewDeadline: c.ComponentConfig.GenericComponent.LeaderElection.RenewDeadline.Duration,