Name  string `xml:"Name"`
	Value string `xml:"Value"`
}

func (filter FilterRule) isEmpty() bool {
	return filter.Name == "" && filter.Value == ""
}

// MarshalXML implements a custom marshaller to support `omitempty` feature.
func (filter FilterRule) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if filter.isEmpty() {
		return nil
	}
	type filterRuleWrapper FilterRule

	LoggerWebhookSubSys,
	AuditWebhookSubSys,
	AuditKafkaSubSys,
	StorageClassSubSys,
	CacheSubSys,
	ILMSubSys,
	BatchSubSys,
	BrowserSubSys,
)

// SubSystemsSingleTargets - subsystems which only support single target.
var SubSystemsSingleTargets = set.CreateStringSet(
	SiteSubSys,
	RegionSubSys,
	EtcdSubSys,
	CacheSubSys,
	APISubSys,
	StorageClassSubSys,
	CompressionSubSys,
	PolicyOPASubSys,