kubernetes: replace klog.Fatal and os.Exit for defer funcs

Hello, team 👋

What happened:

The defer function will not be called if os.Exit(1). https://play.golang.org/p/f7IjXeb62dd

deferred functions are not run. https://golang.org/pkg/os/#Exit

Now, the entry points of some Kubernetes components use defer functions to flush logs.

For example, kube-scheduler https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-scheduler/scheduler.go#L41

func main() {
	rand.Seed(time.Now().UnixNano())

	pflag.CommandLine.SetNormalizeFunc(cliflag.WordSepNormalizeFunc)

	command := app.NewSchedulerCommand()

	logs.InitLogs()
	defer logs.FlushLogs()

	if err := command.Execute(); err != nil {
		os.Exit(1)
	}
}

When command.Execute() returns an error, logs are not flushed. Is this an expected behavior?

How to fix

We can ensure that defer is executed by separating the functions as follows.

func main() {
  if err := realmain(); err != nil {
    os.Exit(1)
  }
}

func realmain() error {
	rand.Seed(time.Now().UnixNano())

	pflag.CommandLine.SetNormalizeFunc(cliflag.WordSepNormalizeFunc)

	command := app.NewSchedulerCommand()

	logs.InitLogs()
	defer logs.FlushLogs()

	if err := command.Execute(); err != nil {
		return err
	}
       return nil
}

can I pick this issue? /assign

Edit (October 23)

For entry points, https://github.com/kubernetes/kubernetes/pull/105076 resolves the issue. But it is better to delete all klog.Fatal and os.Exit as much as possible. They can be replaced by returning error/nil. And in some case, we may be able to use panic() (defer funcs are executed when panic ref)