code: func (c *controller) backoffEnsureLease() (*coordv1beta1.Lease, bool) {
  	var (
  		lease   *coordv1beta1.Lease
  		created bool
  		err     error
  	)
  	sleep := 100 * time.Millisecond
  	for {
  		lease, created, err = c.ensureLease()
  		if err == nil {
  			break
  		}
  		sleep = minDuration(2*sleep, maxBackoff)
  		klog.Errorf("failed to ensure node lease exists, will retry in %v, error: %v", sleep, err)
  		// backoff wait
  		c.clock.Sleep(sleep)
  	}
  	return lease, created
  }
docs: // backoffEnsureLease attempts to create the lease if it does not exist,
  // and uses exponentially increasing waits to prevent overloading the API server
  // with retries. Returns the lease, and true if this call created the lease,
  // false otherwise.