code: func IsMasterNode(nodeName string) bool {
  	// We are trying to capture "master(-...)?$" regexp.
  	// However, using regexp.MatchString() results even in more than 35%
  	// of all space allocations in ControllerManager spent in this function.
  	// That's why we are trying to be a bit smarter.
  	if strings.HasSuffix(nodeName, "master") {
  		return true
  	}
  	if len(nodeName) >= 10 {
  		return strings.HasSuffix(nodeName[:len(nodeName)-3], "master-")
  	}
  	return false
  }
docs: // TODO: find a better way of figuring out if given node is a registered master.